Jump to content

Europa (moon)

From Wikipedia, the free encyclopedia
(Redirected from Life on Europa)
"Jupiter II" redirects here. For the spaceship in the 1960s television series Lost in Space, see Jupiter 2.
For the asteroid, see 52 Europa.

Europa
Surface predominantly white, with a prominent brown oval on the lower right named Callanish crater
Europa, as imaged by the Juno spacecraft, October 2023.[1] Numerous dark lineae criss-cross its geologically young surface.
Discovery
Discovered byGalileo Galilei
Simon Marius
Discovery date8 January 1610[2]
Designations
Pronunciation/jʊˈroʊpə/[3]
Named after
Ευρώπη Eurōpē
Jupiter II
AdjectivesEuropan /jʊˈroʊpən/[4][5]
Orbital characteristics[6]
Epoch 8 January 2004
Periapsis664862 km[a]
Apoapsis676938 km[b]
Mean orbit radius
670900 km[7]
Eccentricity0.009[7]
3.551181 d[7]
13743.36 m/s[8]
Inclination0.470° (to Jupiter's equator)
1.791° (to the ecliptic)[7]
Satellite ofJupiter
GroupGalilean moon
Physical characteristics
1560.8±0.5 km
(0.245 Earths)[9]
3.09×107 km2
(0.061 Earths)[c]
Volume1.593×1010 km3
(0.015 Earths)[d]
Mass4.79984×1022 kg
(0.008 Earths)[9]
Mean density
3.013±0.005 g/cm3
(0.546 Earths)[9]
1.314 m/s2
(0.134 g)[e]
0.346±0.005[10] (estimate)
2.025 km/s[f]
Synchronous[11]
0.1°[12] (to Jupiter)
North pole right ascension
268.08° [13]
North pole declination
64.51° [13]
Albedo0.67 ± 0.03[9]
Surface temp. min mean max
Surface ≈ 50 K[14] 102 K (−171 °C) 125 K
5.29 (opposition)[9]
Atmosphere
Surface pressure
0.1 μPa (10−12 bar)[15]

Europa /jʊˈroʊpə/ ⓘ, or Jupiter II, is the smallest of the four Galilean moons orbiting Jupiter, and the sixth-closest to the planet of all the 95 known moons of Jupiter. It is also the sixth-largest moon in the Solar System. Europa was discovered independently by Simon Marius and Galileo Galilei[2] and was named (by Marius) after Europa, the Phoenician mother of King Minos of Crete and lover of Zeus (the Greek equivalent of the Roman god Jupiter).

Slightly smaller than Earth's Moon, Europa is made of silicate rock and has a water-ice crust[16] and probably an iron–nickel core. It has a very thin atmosphere, composed primarily of oxygen. Its geologically young white-beige surface is striated by light tan cracks and streaks, with very few impact craters. In addition to Earth-bound telescope observations, Europa has been examined by a succession of space-probe flybys, the first occurring in the early 1970s. In September 2022, the Juno spacecraft flew within about 320 km (200 miles) of Europa for a more recent close-up view.[17]

Europa has the smoothest surface of any known solid object in the Solar System. The apparent youth and smoothness of the surface is due to a water ocean beneath the surface, which could conceivably harbor extraterrestrial life, although such life would most likely be that of single celled organisms and bacteria-like creatures.[18] The predominant model suggests that heat from tidal flexing causes the ocean to remain liquid and drives ice movement similar to plate tectonics, absorbing chemicals from the surface into the ocean below.[19][20] Sea salt from a subsurface ocean may be coating some geological features on Europa, suggesting that the ocean is interacting with the sea floor. This may be important in determining whether Europa could be habitable.[21] In addition, the Hubble Space Telescope detected water vapor plumes similar to those observed on Saturn's moon Enceladus, which are thought to be caused by erupting cryogeysers.[22] In May 2018, astronomers provided supporting evidence of water plume activity on Europa, based on an updated analysis of data obtained from the Galileo space probe, which orbited Jupiter from 1995 to 2003. Such plume activity could help researchers in a search for life from the subsurface Europan ocean without having to land on the moon.[23][24][25][26] In March 2024, astronomers reported that the surface of Europa may have much less oxygen than previously inferred.[27][28]

The Galileo mission, launched in 1989, provides the bulk of current data on Europa. No spacecraft has yet landed on Europa, although there have been several proposed exploration missions. The European Space Agency's Jupiter Icy Moon Explorer (JUICE) is a mission to Ganymede launched on 14 April 2023, that will include two flybys of Europa.[29][30] NASA's Europa Clipper was launched on 14 October 2024,[31][32] with a complementary lander possible based on its findings.

Discovery and naming

[edit]

Europa, along with Jupiter's three other large moons, Io, Ganymede, and Callisto, was discovered by Galileo Galilei on 8 January 1610,[2] and possibly independently by Simon Marius. On 7 January, Galileo had observed Io and Europa together using a 20×-magnification refracting telescope at the University of Padua, but the low resolution could not separate the two objects. The following night, he saw Io and Europa for the first time as separate bodies.[2]

The moon is the namesake of Europa, in Greek mythology the daughter of the Phoenician king of Tyre. Like all the Galilean satellites, Europa is named after a lover of Zeus, the Greek counterpart of Jupiter. Europa was courted by Zeus and became the queen of Crete.[33] The naming scheme was suggested by Simon Marius,[34] who attributed the proposal to Johannes Kepler:[34][35]

Jupiter is much blamed by the poets on account of his irregular loves. Three maidens are especially mentioned as having been clandestinely courted by Jupiter with success. Io, daughter of the River Inachus, Callisto of Lycaon, Europa of Agenor. Then there was Ganymede, the handsome son of King Tros, whom Jupiter, having taken the form of an eagle, transported to heaven on his back, as poets fabulously tell... I think, therefore, that I shall not have done amiss if the First is called by me Io, the Second Europa, the Third, on account of its majesty of light, Ganymede, the Fourth Callisto...[36][37]

The names fell out of favor for a considerable time and were not revived in general use until the mid-20th century.[38] In much of the earlier astronomical literature, Europa is simply referred to by its Roman numeral designation as Jupiter II (a system also introduced by Galileo) or as the "second satellite of Jupiter". In 1892, the discovery of Amalthea, whose orbit lay closer to Jupiter than those of the Galilean moons, pushed Europa to the third position. The Voyager probes discovered three more inner satellites in 1979, so Europa is now counted as Jupiter's sixth satellite, though it is still referred to as Jupiter II.[38] The adjectival form has stabilized as Europan.[5][39]

Orbit and rotation

[edit]
Animation of the Laplace resonance of Io, Europa and Ganymede (conjunctions are highlighted by color changes)

Europa orbits Jupiter in just over three and a half days, with an orbital radius of about 670,900 km. With an orbital eccentricity of only 0.009, the orbit itself is nearly circular, and the orbital inclination relative to Jupiter's equatorial plane is small, at 0.470°.[40] Like its fellow Galilean satellites, Europa is tidally locked to Jupiter, with one hemisphere of Europa constantly facing Jupiter. Because of this, there is a sub-Jovian point on Europa's surface, from which Jupiter would appear to hang directly overhead. Europa's prime meridian is a line passing through this point.[41] Research suggests that tidal locking may not be full, as a non-synchronous rotation has been proposed: Europa spins faster than it orbits, or at least did so in the past. This suggests an asymmetry in internal mass distribution and that a layer of subsurface liquid separates the icy crust from the rocky interior.[11]

The slight eccentricity of Europa's orbit, maintained by gravitational disturbances from the other Galileans, causes Europa's sub-Jovian point to oscillate around a mean position. As Europa comes slightly nearer to Jupiter, Jupiter's gravitational attraction increases, causing Europa to elongate towards and away from it. As Europa moves slightly away from Jupiter, Jupiter's gravitational force decreases, causing Europa to relax back into a more spherical shape, and creating tides in its ocean. The orbital eccentricity of Europa is continuously pumped by its mean-motion resonance with Io.[42] Thus, the tidal flexing kneads Europa's interior and gives it a source of heat, possibly allowing its ocean to stay liquid while driving subsurface geological processes.[19][42] The ultimate source of this energy is Jupiter's rotation, which is tapped by Io through the tides it raises on Jupiter and is transferred to Europa and Ganymede by the orbital resonance.[42][43]

Analysis of the unique cracks lining Europa yielded evidence that it likely spun around a tilted axis at some point in time. If correct, this would explain many of Europa's features. Europa's immense network of crisscrossing cracks serves as a record of the stresses caused by massive tides in its global ocean. Europa's tilt could influence calculations of how much of its history is recorded in its frozen shell, how much heat is generated by tides in its ocean, and even how long the ocean has been liquid. Its ice layer must stretch to accommodate these changes. When there is too much stress, it cracks. A tilt in Europa's axis could suggest that its cracks may be much more recent than previously thought. The reason for this is that the direction of the spin pole may change by as much as a few degrees per day, completing one precession period over several months. A tilt could also affect estimates of the age of Europa's ocean. Tidal forces are thought to generate the heat that keeps Europa's ocean liquid, and a tilt in the spin axis would cause more heat to be generated by tidal forces. Such additional heat would have allowed the ocean to remain liquid for a longer time. However, it has not yet been determined when this hypothesized shift in the spin axis might have occurred.[44]

Physical characteristics

[edit]
Size comparison of Europa (lower left) with the Moon (top left) and Earth (right)

Europa is slightly smaller than the Earth's moon. At just over 3,100 kilometres (1,900 mi) in diameter, it is the sixth-largest moon and fifteenth-largest object in the Solar System. Though by a wide margin the least massive of the Galilean satellites, it is nonetheless more massive than all known moons in the Solar System smaller than itself combined.[45] Its bulk density suggests that it is similar in composition to terrestrial planets, being primarily composed of silicate rock.[46]

Internal structure

[edit]

It is estimated that Europa has an outer layer of water around 100 km (62 mi) thick – a part frozen as its crust and a part as a liquid ocean underneath the ice. Recent magnetic-field data from the Galileo orbiter showed that Europa has an induced magnetic field through interaction with Jupiter's, which suggests the presence of a subsurface conductive layer.[47] This layer is likely to be a salty liquid-water ocean. Portions of the crust are estimated to have undergone a rotation of nearly 80°, nearly flipping over (see true polar wander), which would be unlikely if the ice were solidly attached to the mantle.[48] Europa probably contains a metallic iron core.[49][50]

Surface features

[edit]
Map of Europa, by the United States Geological Survey

Europa is the smoothest known object in the Solar System, lacking large-scale features such as mountains and craters.[51] The prominent markings crisscrossing Europa appear to be mainly albedo features that emphasize low topography. There are few craters on Europa, because its surface is tectonically too active and therefore young.[52][53] Its icy crust has an albedo (light reflectivity) of 0.64, one of the highest of any moon.[40][53] This indicates a young and active surface: based on estimates of the frequency of cometary bombardment that Europa experiences, the surface is about 20 to 180 million years old.[54] There is no scientific consensus about the explanation for Europa's surface features.[55]

It has been postulated Europa's equator may be covered in icy spikes called penitentes, which may be up to 15 meters high. Their formation is due to direct overhead sunlight near the equator causing the ice to sublime, forming vertical cracks.[56][57][58] Although the imaging available from the Galileo orbiter does not have the resolution for confirmation, radar and thermal data are consistent with this speculation.[58]

The ionizing radiation level at Europa's surface is equivalent to a daily dose of about 5.4 Sv (540 rem),[59] an amount that would cause severe illness or death in human beings exposed for a single Earth day (24 hours).[60] A Europan day is about 3.5 times as long as an Earth day.[61]

Lineae

[edit]
See also: List of lineae on Europa
True color mosaic of Europa's numerous lineae. The region of lineae at the center of this image is the Annwn Regio.[62][63]

Europa's most striking surface features are a series of dark streaks crisscrossing the entire globe, called lineae (English: lines). Close examination shows that the edges of Europa's crust on either side of the cracks have moved relative to each other. The larger bands are more than 20 km (12 mi) across, often with dark, diffuse outer edges, regular striations, and a central band of lighter material.[64]

The most likely hypothesis is that the lineae on Europa were produced by a series of eruptions of warm ice as Europa's crust slowly spreads open to expose warmer layers beneath.[65] The effect would have been similar to that seen on Earth's oceanic ridges. These various fractures are thought to have been caused in large part by the tidal flexing exerted by Jupiter. Because Europa is tidally locked to Jupiter, and therefore always maintains approximately the same orientation towards Jupiter, the stress patterns should form a distinctive and predictable pattern. However, only the youngest of Europa's fractures conform to the predicted pattern; other fractures appear to occur at increasingly different orientations the older they are. This could be explained if Europa's surface rotates slightly faster than its interior, an effect that is possible due to the subsurface ocean mechanically decoupling Europa's surface from its rocky mantle and the effects of Jupiter's gravity tugging on Europa's outer ice crust.[66] Comparisons of Voyager and Galileo spacecraft photos serve to put an upper limit on this hypothetical slippage. A full revolution of the outer rigid shell relative to the interior of Europa takes at least 12,000 years.[67] Studies of Voyager and Galileo images have revealed evidence of subduction on Europa's surface, suggesting that, just as the cracks are analogous to ocean ridges,[68][69] so plates of icy crust analogous to tectonic plates on Earth are recycled into the molten interior. This evidence of both crustal spreading at bands[68] and convergence at other sites[69] suggests that Europa may have active plate tectonics, similar to Earth.[20] However, the physics driving these plate tectonics are not likely to resemble those driving terrestrial plate tectonics, as the forces resisting potential Earth-like plate motions in Europa's crust are significantly stronger than the forces that could drive them.[70]

Chaos and lenticulae

[edit]
See also: List of geological features on Europa
Left: surface features indicative of tidal flexing: lineae, lenticulae and the Conamara Chaos region (close-up, right) where craggy, 250 m high peaks and smooth plates are jumbled together

Other features present on Europa are circular and elliptical lenticulae (Latin for "freckles"). Many are domes, some are pits and some are smooth, dark spots. Others have a jumbled or rough texture. The dome tops look like pieces of the older plains around them, suggesting that the domes formed when the plains were pushed up from below.[71]

One hypothesis states that these lenticulae were formed by diapirs of warm ice rising up through the colder ice of the outer crust, much like magma chambers in Earth's crust.[71] The smooth, dark spots could be formed by meltwater released when the warm ice breaks through the surface. The rough, jumbled lenticulae (called regions of "chaos"; for example, Conamara Chaos) would then be formed from many small fragments of crust, embedded in hummocky, dark material, appearing like icebergs in a frozen sea.[72]

An alternative hypothesis suggests that lenticulae are actually small areas of chaos and that the claimed pits, spots and domes are artefacts resulting from the over-interpretation of early, low-resolution Galileo images. The implication is that the ice is too thin to support the convective diapir model of feature formation.[73][74]

In November 2011, a team of researchers, including researchers at University of Texas at Austin, presented evidence suggesting that many "chaos terrain" features on Europa sit atop vast lakes of liquid water.[75][76] These lakes would be entirely encased in Europa's icy outer shell and distinct from a liquid ocean thought to exist farther down beneath the ice shell. Full confirmation of the lakes' existence will require a space mission designed to probe the ice shell either physically or indirectly, e.g. using radar.[76] Chaos features may also be a result of increased melting of the ice shell and deposition of marine ice at low latitudes as a result of heterogeneous heating.[77]

Work published by researchers from Williams College suggests that chaos terrain may represent sites where impacting comets penetrated through the ice crust and into an underlying ocean.[78][79]

Subsurface ocean

[edit]
Model of Europa's possible interior structure, with a thin ice crust and a subsurface ocean atop a rocky mantle and metallic core

The scientific consensus is that a layer of liquid water exists beneath Europa's surface, and that heat from tidal flexing allows the subsurface ocean to remain liquid.[19][80] Europa's surface temperature averages about 110 K (−160 °C; −260 °F) at the equator and only 50 K (−220 °C; −370 °F) at the poles, keeping Europa's icy crust as hard as granite.[14] The first hints of a subsurface ocean came from theoretical considerations of tidal heating (a consequence of Europa's slightly eccentric orbit and orbital resonance with the other Galilean moons). Galileo imaging team members argue for the existence of a subsurface ocean from analysis of Voyager and Galileo images.[80] The most dramatic example is "chaos terrain", a common feature on Europa's surface that some interpret as a region where the subsurface ocean has melted through the icy crust. This interpretation is controversial. Most geologists who have studied Europa favor what is commonly called the "thick ice" model, in which the ocean has rarely, if ever, directly interacted with the present surface.[81] The best evidence for the thick-ice model is a study of Europa's large craters. The largest impact structures are surrounded by concentric rings and appear to be filled with relatively flat, fresh ice; based on this and on the calculated amount of heat generated by Europan tides, it is estimated that the outer crust of solid ice is approximately 10 to 30 km (6 to 20 mi) thick,[82] including a ductile "warm ice" layer, which could mean that the liquid ocean underneath may be about 100 km (60 mi) deep.[83] This leads to a volume of Europa's oceans of 3×1018m3, between two or three times the volume of Earth's oceans.[84][85]

The thin-ice model suggests that Europa's ice shell may be only a few kilometers thick. However, most planetary scientists conclude that this model considers only those topmost layers of Europa's crust that behave elastically when affected by Jupiter's tides.[86] One example is flexure analysis, in which Europa's crust is modeled as a plane or sphere weighted and flexed by a heavy load. Models such as this suggest the outer elastic portion of the ice crust could be as thin as 200 metres (660 ft). If the ice shell of Europa is really only a few kilometers thick, this "thin ice" model would mean that regular contact of the liquid interior with the surface could occur through open ridges, causing the formation of areas of chaotic terrain.[86] Large impacts going fully through the ice crust would also be a way that the subsurface ocean could be exposed.[78][79]

Composition

[edit]
Closeup views of Europa obtained on 26 September 1998; images clockwise from upper left show locations from north to south as indicated at lower left.

The Galileo orbiter found that Europa has a weak magnetic moment, which is induced by the varying part of the Jovian magnetic field. The field strength at the magnetic equator (about 120 nT) created by this magnetic moment is about one-sixth the strength of Ganymede's field and six times the value of Callisto's.[87] The existence of the induced moment requires a layer of a highly electrically conductive material in Europa's interior. The most plausible candidate for this role is a large subsurface ocean of liquid saltwater.[49]

Europa Closeups
29 September 2022
9 September 2022

Since the Voyager spacecraft flew past Europa in 1979, scientists have worked to understand the composition of the reddish-brown material that coats fractures and other geologically youthful features on Europa's surface.[88] Spectrographic evidence suggests that the darker, reddish streaks and features on Europa's surface may be rich in salts such as magnesium sulfate, deposited by evaporating water that emerged from within.[89] Sulfuric acid hydrate is another possible explanation for the contaminant observed spectroscopically.[90] In either case, because these materials are colorless or white when pure, some other material must also be present to account for the reddish color, and sulfur compounds are suspected.[91]

NIR image of Europa by the James Webb Space Telescope, confirming the presence of carbon dioxide on the moon[92]

Another hypothesis for the colored regions is that they are composed of abiotic organic compounds collectively called tholins.[93][94][95] The morphology of Europa's impact craters and ridges is suggestive of fluidized material welling up from the fractures where pyrolysis and radiolysis take place. In order to generate colored tholins on Europa, there must be a source of materials (carbon, nitrogen, and water) and a source of energy to make the reactions occur. Impurities in the water ice crust of Europa are presumed both to emerge from the interior as cryovolcanic events that resurface the body, and to accumulate from space as interplanetary dust.[93] Tholins bring important astrobiological implications, as they may play a role in prebiotic chemistry and abiogenesis.[96][97][98]

The presence of sodium chloride in the internal ocean has been suggested by a 450 nm absorption feature, characteristic of irradiated NaCl crystals, that has been spotted in HST observations of the chaos regions, presumed to be areas of recent subsurface upwelling.[99] The subterranean ocean of Europa contains carbon[100] and was observed on the surface ice as a concentration of carbon dioxide within Tara Regio, a geologically recently resurfaced terrain.[101]

A series of images of Europa in different wavelengths by the James Webb Space Telescope. The different wavelengths show the presence of different forms of carbon dioxide on Europa.

Sources of heat

[edit]

Europa receives thermal energy from tidal heating, which occurs through the tidal friction and tidal flexing processes caused by tidal acceleration: orbital and rotational energy are dissipated as heat in the core of the moon, the internal ocean, and the ice crust.[102]

Tidal friction
[edit]

Ocean tides are converted to heat by frictional losses in the oceans and their interaction with the solid bottom and with the top ice crust. In late 2008, it was suggested Jupiter may keep Europa's oceans warm by generating large planetary tidal waves on Europa because of its small but non-zero obliquity. This generates so-called Rossby waves that travel quite slowly, at just a few kilometers per day, but can generate significant kinetic energy. For the current axial tilt estimate of 0.1 degree, the resonance from Rossby waves would contain 7.3×1018 J of kinetic energy, which is two thousand times larger than that of the flow excited by the dominant tidal forces.[103][104] Dissipation of this energy could be the principal heat source of Europa's ocean.[103][104]

Tidal flexing
[edit]

Tidal flexing kneads Europa's interior and ice shell, which becomes a source of heat.[105] Depending on the amount of tilt, the heat generated by the ocean flow could be 100 to thousands of times greater than the heat generated by the flexing of Europa's rocky core in response to the gravitational pull from Jupiter and the other moons circling that planet.[106] Europa's seafloor could be heated by the moon's constant flexing, driving hydrothermal activity similar to undersea volcanoes in Earth's oceans.[102]

Experiments and ice modeling published in 2016, indicate that tidal flexing dissipation can generate one order of magnitude more heat in Europa's ice than scientists had previously assumed.[107][108] Their results indicate that most of the heat generated by the ice actually comes from the ice's crystalline structure (lattice) as a result of deformation, and not friction between the ice grains.[107][108] The greater the deformation of the ice sheet, the more heat is generated.

Radioactive decay
[edit]

In addition to tidal heating, the interior of Europa could also be heated by the decay of radioactive material (radiogenic heating) within the rocky mantle.[102][109] But the models and values observed are one hundred times higher than those that could be produced by radiogenic heating alone,[110] thus implying that tidal heating has a leading role in Europa.[111]

Plumes

[edit]
Photo composite of suspected water plumes on Europa[112]

The Hubble Space Telescope acquired an image of Europa in 2012 that was interpreted to be a plume of water vapour erupting from near its south pole.[113][112] The image suggests the plume may be 200 km (120 mi) high, or more than 20 times the height of Mt. Everest.,[22][114][115] though recent observations and modeling suggest that typical Europan plumes may be much smaller.[116][117][118] It has been suggested that if plumes exist, they are episodic[119] and likely to appear when Europa is at its farthest point from Jupiter, in agreement with tidal force modeling predictions.[120] Additional imaging evidence from the Hubble Space Telescope was presented in September 2016.[121][122]

In May 2018, astronomers provided supporting evidence of water plume activity on Europa, based on an updated critical analysis of data obtained from the Galileo space probe, which orbited Jupiter between 1995 and 2003. Galileo flew by Europa in 1997 within 206 km (128 mi) of the moon's surface and the researchers suggest it may have flown through a water plume.[23][24][25][26] Such plume activity could help researchers in a search for life from the subsurface Europan ocean without having to land on the moon.[23]

The tidal forces are about 1,000 times stronger than the Moon's effect on Earth. The only other moon in the Solar System exhibiting water vapor plumes is Enceladus.[22] The estimated eruption rate at Europa is about 7000 kg/s[120] compared to about 200 kg/s for the plumes of Enceladus.[123][124] If confirmed, it would open the possibility of a flyby through the plume and obtain a sample to analyze in situ without having to use a lander and drill through kilometres of ice.[121][125][126]

In November 2020, a study was published in the peer-reviewed scientific journal Geophysical Research Letters suggesting that the plumes may originate from water within the crust of Europa as opposed to its subsurface ocean. The study's model, using images from the Galileo space probe, proposed that a combination of freezing and pressurization may result in at least some of the cryovolcanic activity. The pressure generated by migrating briny water pockets would thus, eventually, burst through the crust, thereby creating these plumes. The hypothesis that cryovolcanism on Europa could be triggered by freezing and pressurization of liquid pockets in the icy crust was first proposed by Sarah Fagents at the University of Hawai'i at Mānoa, who in 2003, was the first to model and publish work on this process.[127] A press release from NASA's Jet Propulsion Laboratory referencing the November 2020 study suggested that plumes sourced from migrating liquid pockets could potentially be less hospitable to life. This is due to a lack of substantial energy for organisms to thrive off, unlike proposed hydrothermal vents on the subsurface ocean floor.[128][129]

Atmosphere

[edit]
Diagram of how Europa's atmosphere is created by bombardment from ionized particles

The atmosphere of Europa can be categorized as thin and tenuous (often called an exosphere), primarily composed of oxygen and trace amounts of water vapor.[130] However, this quantity of oxygen is produced in a non-biological manner. Given that Europa's surface is icy, and subsequently very cold; as solar ultraviolet radiation and charged particles (ions and electrons) from the Jovian magnetospheric environment collide with Europa's surface, water vapor is created and instantaneously separated into oxygen and hydrogen constituents. As it continues to move, the hydrogen is light enough to pass through the surface gravity of the atmosphere leaving behind only oxygen.[131] The surface-bounded atmosphere forms through radiolysis, the dissociation of molecules through radiation.[132] This accumulated oxygen atmosphere can get to a height of 190 km (120 mi) above the surface of Europa. Molecular oxygen is the densest component of the atmosphere because it has a long lifetime; after returning to the surface, it does not stick (freeze) like a water or hydrogen peroxide molecule but rather desorbs from the surface and starts another ballistic arc. Molecular hydrogen never reaches the surface, as it is light enough to escape Europa's surface gravity.[133][134] Europa is one of the few moons in our solar system with a quantifiable atmosphere, along with Titan, Io, Triton, Ganymede and Callisto.[135] Europa is also one of several moons in our solar system with very large quantities of ice (volatiles), otherwise known as "icy moons".[136]

Magnetic field around Europa. The red line shows a trajectory of the Galileo spacecraft during a typical flyby (E4 or E14).

Europa is also considered to be geologically active due to the constant release of hydrogen-oxygen mixtures into space. As a result of the moon's particle venting, the atmosphere requires continuous replenishment.[131] Europa also contains a small magnetosphere (approximately 25% of Ganymede's). However, this magnetosphere varies in size as Europa orbits through Jupiter's magnetic field. This confirms that a conductive element, such as a large ocean, likely lies below its icy surface.[137] As multiple studies have been conducted over Europa's atmosphere, several findings conclude that not all oxygen molecules are released into the atmosphere. This unknown percentage of oxygen may be absorbed into the surface and sink into the subsurface. Because the surface may interact with the subsurface ocean (considering the geological discussion above), this molecular oxygen may make its way to the ocean, where it could aid in biological processes.[138][139] One estimate suggests that, given the turnover rate inferred from the apparent ~0.5 Gyr maximum age of Europa's surface ice, subduction of radiolytically generated oxidizing species might well lead to oceanic free oxygen concentrations that are comparable to those in terrestrial deep oceans.[140]

Through the slow release of oxygen and hydrogen, a neutral torus around Europa's orbital plane is formed. This "neutral cloud" has been detected by both the Cassini and Galileo spacecraft, and has a greater content (number of atoms and molecules) than the neutral cloud surrounding Jupiter's inner moon Io.[141] This torus was officially confirmed using Energetic Neutral Atom (ENA) imaging. Europa's torus ionizes through the process of neutral particles exchanging electrons with its charged particles. Since Europa's magnetic field rotates faster than its orbital velocity, these ions are left in the path of its magnetic field trajectory, forming a plasma. It has been hypothesized that these ions are responsible for the plasma within Jupiter's magnetosphere.[142]

On 4 March 2024, astronomers reported that the surface of Europa may have much less oxygen than previously inferred.[27][28]

Discovery of atmosphere

[edit]

The atmosphere of Europa was first discovered in 1995 by astronomers D. T. Hall and collaborators using the Goddard High Resolution Spectrograph instrument of the Hubble Space Telescope.[143] This observation was further supported in 1997 by the Galileo orbiter during its mission within the Jovian system. The Galileo orbiter performed three radio occultation events of Europa, where the probe's radio contact with Earth was temporarily blocked by passing behind Europa. By analyzing the effects Europa's sparse atmosphere had on the radio signal just before and after the occultation, for a total of six events, a team of astronomers led by A. J. Kliore established the presence of an ionized layer in Europa's atmosphere.[144]

Climate and weather

[edit]

Despite the presence of a gas torus, Europa has no weather producing clouds. As a whole, Europa has no wind, precipitation, or presence of sky color as its gravity is too low to hold an atmosphere substantial enough for those features. Europa's gravity is approximately 13% of Earth's. The temperature on Europa varies from −160 °C at the equator, to −220 °C at either of its poles.[145] Europa's subsurface ocean is thought to be significantly[clarification needed] warmer however. It is hypothesized that because of radioactive and tidal heating (as mentioned in the sections above), there are points in the depths of Europa's ocean that may be only slightly cooler than Earth's oceans. Studies have also concluded that Europa's ocean would have been rather acidic at first, with large concentrations of sulfate, calcium, and carbon dioxide. But over the course of 4.5 billion years, it became full[clarification needed] of chloride, thus resembling our 1.94% chloride oceans on Earth.

Exploration

[edit]
In 1973 Pioneer 10 made the first closeup images of Europa. The probe was too far away to obtain more detailed images.
Europa seen in detail in 1979 by Voyager 2

Exploration of Europa began with the Jupiter flybys of Pioneer 10 and 11 in 1973 and 1974, respectively. The first closeup photos were of low resolution compared to later missions. The two Voyager probes traveled through the Jovian system in 1979, providing more-detailed images of Europa's icy surface. The images caused many scientists to speculate about the possibility of a liquid ocean underneath. Starting in 1995, the Galileo space probe orbited Jupiter for eight years, until 2003, and provided the most detailed examination of the Galilean moons to date. It included the "Galileo Europa Mission" and "Galileo Millennium Mission", with numerous close flybys of Europa.[146] In 2007, New Horizons imaged Europa, as it flew by the Jovian system while on its way to Pluto.[147] In 2022, the Juno orbiter flew by Europa at a distance of 352 km (219 mi).[17][148]

In 2012, Jupiter Icy Moons Explorer (JUICE) was selected by the European Space Agency (ESA) as a planned mission.[30][149] That mission includes two flybys of Europa, but is more focused on Ganymede.[150] It was launched in 2023, and is expected to reach Jupiter in July 2031 after four gravity assists and eight years of travel.[151]

In 2011, a Europa mission was recommended by the U.S. Planetary Science Decadal Survey.[152] In response, NASA commissioned concept studies of a Europa lander in 2011, along with concepts for a Europa flyby (Europa Clipper), and a Europa orbiter.[153][154] The orbiter element option concentrates on the "ocean" science, while the multiple-flyby element (Clipper) concentrates on the chemistry and energy science. On 13 January 2014, the House Appropriations Committee announced a new bipartisan bill that includes $80 million in funding to continue the Europa mission concept studies.[155][156]

In July 2013 an updated concept for a flyby Europa mission called Europa Clipper was presented by the Jet Propulsion Laboratory (JPL) and the Applied Physics Laboratory (APL).[157] In May 2015, NASA announced that it had accepted development of the Europa Clipper mission, and revealed the instruments it would use.[158] The aim of Europa Clipper is to explore Europa in order to investigate its habitability, and to aid in selecting sites for a future lander. The Europa Clipper would not orbit Europa, but instead orbit Jupiter and conduct 45 low-altitude flybys of Europa during its envisioned mission. The probe would carry an ice-penetrating radar, short-wave infrared spectrometer, topographical imager, and an ion- and neutral-mass spectrometer. The mission was launched on 14 October 2024 aboard a Falcon Heavy.[159]

Future missions

[edit]

Conjectures regarding extraterrestrial life have ensured a high profile for Europa and have led to steady lobbying for future missions.[160][161] The aims of these missions have ranged from examining Europa's chemical composition to searching for extraterrestrial life in its hypothesized subsurface oceans.[162][163] Robotic missions to Europa need to endure the high-radiation environment around Jupiter.[161] Because it is deeply embedded within Jupiter's magnetosphere, Europa receives about 5.40 Sv of radiation per day.[164]

  • Europa Lander is a recent NASA concept mission under study. 2018 research suggests Europa may be covered in tall, jagged ice spikes, presenting a problem for any potential landing on its surface.[165][166]

Old proposals

[edit]
Artist's concept of the cryobot and its deployed "hydrobot" submersible

In the early 2000s, Jupiter Europa Orbiter led by NASA and the Jupiter Ganymede Orbiter led by the ESA were proposed together as an Outer Planet Flagship Mission to Jupiter's icy moons called Europa Jupiter System Mission, with a planned launch in 2020.[167] In 2009 it was given priority over Titan Saturn System Mission.[168] At that time, there was competition from other proposals.[169] Japan proposed Jupiter Magnetospheric Orbiter.

Jovian Europa Orbiter was an ESA Cosmic Vision concept study from 2007. Another concept was Ice Clipper,[170] which would have used an impactor similar to the Deep Impact mission—it would make a controlled crash into the surface of Europa, generating a plume of debris that would then be collected by a small spacecraft flying through the plume.[170][171]

Jupiter Icy Moons Orbiter (JIMO) was a partially developed fission-powered spacecraft with ion thrusters that was cancelled in 2006.[161][172] It was part of Project Prometheus.[172] The Europa Lander Mission proposed a small nuclear-powered Europa lander for JIMO.[173] It would travel with the orbiter, which would also function as a communication relay to Earth.[173]

Europa Orbiter – Its objective would be to characterize the extent of the ocean and its relation to the deeper interior. Instrument payload could include a radio subsystem, laser altimeter, magnetometer, Langmuir probe, and a mapping camera.[174][175] The Europa Orbiter received the go-ahead in 1999 but was canceled in 2002. This orbiter featured a special ice-penetrating radar that would allow it to scan below the surface.[51]

More ambitious ideas have been put forward including an impactor in combination with a thermal drill to search for biosignatures that might be frozen in the shallow subsurface.[176][177]

Another proposal put forward in 2001 calls for a large nuclear-powered "melt probe" (cryobot) that would melt through the ice until it reached an ocean below.[161][178] Once it reached the water, it would deploy an autonomous underwater vehicle (hydrobot) that would gather information and send it back to Earth.[179] Both the cryobot and the hydrobot would have to undergo some form of extreme sterilization to prevent detection of Earth organisms instead of native life and to prevent contamination of the subsurface ocean.[180] This suggested approach has not yet reached a formal conceptual planning stage.[181]

Habitability

[edit]
Europa – possible effect of radiation on biosignature chemicals

So far, there is no evidence that life exists on Europa, but the moon has emerged as one of the most likely locations in the Solar System for potential habitability.[140][182] Life could exist in its under-ice ocean, perhaps in an environment similar to Earth's deep-ocean hydrothermal vents.[162][183] Even if Europa lacks volcanic hydrothermal activity, a 2016 NASA study found that Earth-like levels of hydrogen and oxygen could be produced through processes related to serpentinization and ice-derived oxidants, which do not directly involve volcanism.[184] In 2015, scientists announced that salt from a subsurface ocean may likely be coating some geological features on Europa, suggesting that the ocean is interacting with the seafloor. This may be important in determining if Europa could be habitable.[21][185] The likely presence of liquid water in contact with Europa's rocky mantle has spurred calls to send a probe there.[186]

The energy provided by tidal forces drives active geological processes within Europa's interior, just as they do to a far more obvious degree on its sister moon Io. Although Europa, like the Earth, may possess an internal energy source from radioactive decay, the energy generated by tidal flexing would be several orders of magnitude greater than any radiological source.[187] Life on Europa could exist clustered around hydrothermal vents on the ocean floor, or below the ocean floor, where endoliths are known to inhabit on Earth. Alternatively, it could exist clinging to the lower surface of Europa's ice layer, much like algae and bacteria in Earth's polar regions, or float freely in Europa's ocean.[188] Should Europa's oceans be too cold, biological processes similar to those known on Earth could not occur; too salty, only extreme halophiles could survive in that environment.[188] In 2010, a model proposed by Richard Greenberg of the University of Arizona proposed that irradiation of ice on Europa's surface could saturate its crust with oxygen and peroxide, which could then be transported by tectonic processes into the interior ocean. Such a process could render Europa's ocean as oxygenated as our own within just 12 million years, allowing the existence of complex, multicellular lifeforms.[189]

Evidence suggests the existence of lakes of liquid water entirely encased in Europa's icy outer shell and distinct from a liquid ocean thought to exist farther down beneath the ice shell,[190][76] as well as pockets of water that form M-shaped ice ridges when the water freezes on the surface – as in Greenland.[191] If confirmed, the lakes and pockets of water could be yet another potential habitat for life. Evidence suggests that hydrogen peroxide is abundant across much of the surface of Europa.[192] Because hydrogen peroxide decays into oxygen and water when combined with liquid water, the authors argue that it could be an important energy supply for simple life forms. Nonetheless, on 4 March 2024, astronomers reported that the surface of Europa may have much less oxygen than previously inferred.[27][28]

Clay-like minerals (specifically, phyllosilicates), often associated with organic matter on Earth, have been detected on the icy crust of Europa.[193] The presence of the minerals may have been the result of a collision with an asteroid or comet.[193] Some scientists have speculated that life on Earth could have been blasted into space by asteroid collisions and arrived on the moons of Jupiter in a process called lithopanspermia.[194]

See also

[edit]

Notes

[edit]
  1. ^ Periapsis is derived from the semimajor axis (a) and eccentricity (e): a(1 − e).
  2. ^ Apoapsis is derived from the semimajor axis (a) and eccentricity (e): a(1 + e).
  3. ^ Surface area derived from the radius (r): 4πr 2.
  4. ^ Volume derived from the radius (r): 4/3πr 3.
  5. ^ Surface gravity derived from the mass (m), the gravitational constant (G) and the radius (r): Gm/r2.
  6. ^ Escape velocity derived from the mass (m), the gravitational constant (G) and the radius (r): .

References

[edit]
  1. ^ "JunoCam Image of Europa from Flyby". Jet Propulsion Laboratory.
  2. ^ a b c d Blue, Jennifer (9 November 2009). "Planet and Satellite Names and Discoverers". USGS. Archived from the original on 25 August 2009. Retrieved 14 January 2010.
  3. ^ "Europa". Lexico UK English Dictionary. Oxford University Press. Archived from the original on 22 March 2020.
    "Europa". Merriam-Webster.com Dictionary. Merriam-Webster.
  4. ^ Lucchita, B. K.; Soderblom, L. A. (1982). Morrison, David; Matthews, Mildred Shapley (eds.). Satellites of Jupiter (PDF). Space science series. Tucson, Ariz: University of Arizona Press. ISBN 978-0-8165-0762-7.
  5. ^ a b Greenberg (2005) Europa: the ocean moon
  6. ^ "JPL HORIZONS solar system data and ephemeris computation service". Solar System Dynamics. NASA, Jet Propulsion Laboratory. Archived from the original on 7 October 2012. Retrieved 10 August 2007.
  7. ^ a b c d "Overview of Europa Facts". NASA. Archived from the original on 26 March 2014. Retrieved 27 December 2007.
  8. ^ "By the Numbers | Europa". NASA Solar System Exploration. Archived from the original on 6 May 2021. Retrieved 6 May 2021.
  9. ^ a b c d e Yeomans, Donald K. (13 July 2006). "Planetary Satellite Physical Parameters". JPL Solar System Dynamics. Archived from the original on 14 August 2009. Retrieved 5 November 2007.
  10. ^ Showman, A. P.; Malhotra, R. (1 October 1999). "The Galilean Satellites". Science. 286 (5437): 77–84. doi:10.1126/science.286.5437.77. PMID 10506564. S2CID 9492520.
  11. ^ a b Geissler, P. E.; Greenberg, R.; Hoppa, G.; Helfenstein, P.; McEwen, A.; Pappalardo, R.; Tufts, R.; Ockert-Bell, M.; Sullivan, R.; Greeley, R.; Belton, M. J. S.; Denk, T.; Clark, B. E.; Burns, J.; Veverka, J. (1998). "Evidence for non-synchronous rotation of Europa". Nature. 391 (6665): 368–70. Bibcode:1998Natur.391..368G. doi:10.1038/34869. PMID 9450751. S2CID 4426840.
  12. ^ Bills, Bruce G. (2005). "Free and forced obliquities of the Galilean satellites of Jupiter". Icarus. 175 (1): 233–247. Bibcode:2005Icar..175..233B. doi:10.1016/j.icarus.2004.10.028. Archived from the original on 27 July 2020. Retrieved 29 June 2019.
  13. ^ a b Archinal, B. A.; Acton, C. H.; A'Hearn, M. F.; Conrad, A.; Consolmagno, G. J.; Duxbury, T.; Hestroffer, D.; Hilton, J. L.; Kirk, R. L.; Klioner, S. A.; McCarthy, D.; Meech, K.; Oberst, J.; Ping, J.; Seidelmann, P. K. (2018). "Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements: 2015". Celestial Mechanics and Dynamical Astronomy. 130 (3): 22. Bibcode:2018CeMDA.130...22A. doi:10.1007/s10569-017-9805-5. ISSN 0923-2958.
  14. ^ a b McFadden, Lucy-Ann; Weissman, Paul; Johnson, Torrence (2007). The Encyclopedia of the Solar System. Elsevier. p. 432. ISBN 978-0-12-226805-2.
  15. ^ McGrath (2009). "Atmosphere of Europa". In Pappalardo, Robert T.; McKinnon, William B.; Khurana, Krishan K. (eds.). Europa. University of Arizona Press. ISBN 978-0-8165-2844-8.
  16. ^ Chang, Kenneth (12 March 2015). "Suddenly, It Seems, Water Is Everywhere in Solar System". The New York Times. Archived from the original on 9 May 2020. Retrieved 13 March 2015.
  17. ^ a b Chang, Kenneth (30 September 2022). "New Europa Pictures Beamed Home by NASA's Juno Spacecraft - The space probe has been studying Jupiter since 2016 and just flew within about 200 miles of the surface of the ice-covered ocean moon". The New York Times. Archived from the original on 30 September 2022. Retrieved 30 September 2022.
  18. ^ Tritt, Charles S. (2002). "Possibility of Life on Europa". Milwaukee School of Engineering. Archived from the original on 9 June 2007. Retrieved 10 August 2007.
  19. ^ a b c "Tidal Heating". geology.asu.edu. Archived from the original on 29 March 2006.
  20. ^ a b Dyches, Preston; Brown, Dwayne; Buckley, Michael (8 September 2014). "Scientists Find Evidence of 'Diving' Tectonic Plates on Europa". NASA. Archived from the original on 4 April 2019. Retrieved 8 September 2014.
  21. ^ a b Dyches, Preston; Brown, Dwayne (12 May 2015). "NASA Research Reveals Europa's Mystery Dark Material Could Be Sea Salt". NASA. Archived from the original on 15 May 2015. Retrieved 12 May 2015.
  22. ^ a b c Cook, Jia-Rui C.; Gutro, Rob; Brown, Dwayne; Harrington, J. D.; Fohn, Joe (12 December 2013). "Hubble Sees Evidence of Water Vapor at Jupiter Moon". NASA. Archived from the original on 15 December 2013. Retrieved 12 December 2013.
  23. ^ a b c Jia, Xianzhe; Kivelson, Margaret G.; Khurana, Krishan K.; Kurth, William S. (14 May 2018). "Evidence of a plume on Europa from Galileo magnetic and plasma wave signatures". Nature Astronomy. 2 (6): 459–464. Bibcode:2018NatAs...2..459J. doi:10.1038/s41550-018-0450-z. S2CID 134370392.
  24. ^ a b McCartney, Gretchen; Brown, Dwayne; Wendel, JoAnna (14 May 2018). "Old Data Reveal New Evidence of Europa Plumes". Jet Propulsion Laboratory. Archived from the original on 17 June 2019. Retrieved 14 May 2018.
  25. ^ a b Chang, Kenneth (14 May 2018). "NASA Finds Signs of Plumes From Europa, Jupiter's Ocean Moon". The New York Times. Archived from the original on 14 May 2018. Retrieved 14 May 2018.
  26. ^ a b Wall, Mike (14 May 2018). "This May Be the Best Evidence Yet of a Water Plume on Jupiter's Moon Europa". Space.com. Archived from the original on 14 May 2018. Retrieved 14 May 2018.
  27. ^ a b c Miller, Katrina (4 March 2024). "An Ocean Moon Thought to Be Habitable May Be Oxygen-Starved - A new study suggests that the amount of the element on the moon of Jupiter is on the lower end of previous estimates". The New York Times. Archived from the original on 5 March 2024. Retrieved 5 March 2024.
  28. ^ a b c Szalay, J.R.; et al. (4 March 2024). "Oxygen production from dissociation of Europa's water-ice surface". Nature Astronomy. 8 (5): 567–576. Bibcode:2024NatAs...8..567S. doi:10.1038/s41550-024-02206-x. PMC 11111413. PMID 38798715.
  29. ^ "ESA Science & Technology - JUICE". ESA. 8 November 2021. Archived from the original on 21 September 2019. Retrieved 10 November 2021.
  30. ^ a b Amos, Jonathan (2 May 2012). "Esa selects 1bn-euro Juice probe to Jupiter". BBC News Online. Archived from the original on 11 May 2020. Retrieved 2 May 2012.
  31. ^ "NASA's Europa Clipper". NASA. 9 April 2023. Archived from the original on 4 April 2023. Retrieved 9 April 2023.
  32. ^ Borenstein, Seth (4 March 2014). "NASA plots daring flight to Jupiter's watery moon". Associated Press. Archived from the original on 5 March 2014. Retrieved 5 March 2014.
  33. ^ Arnett, Bill (October 2005). "Europa". Nine Planets. Archived from the original on 28 March 2014. Retrieved 27 April 2014.
  34. ^ a b Marius, S.; (1614) Mundus Iovialis anno M.DC.IX Detectus Ope Perspicilli Belgici [1] Archived 29 September 2019 at the Wayback Machine, where he attributes the suggestion Archived 1 November 2019 at the Wayback Machine to Johannes Kepler
  35. ^ "Simon Marius (January 20, 1573 – December 26, 1624)". Students for the Exploration and Development of Space. University of Arizona. Archived from the original on 13 July 2007. Retrieved 9 August 2007.
  36. ^ Van Helden, Albert (August 1994). "Naming the Satellites of Jupiter and Saturn" (PDF). The Newsletter of the Historical Astronomy Division of the American Astronomical Society (32). Archived (PDF) from the original on 7 December 2022. Retrieved 10 March 2023.
  37. ^ Marius, SImon (1614). Mundus Iovialis: anno MDCIX detectus ope perspicilli Belgici, hoc est, quatuor Jovialium planetarum, cum theoria, tum tabulæ. Nuremberg: Sumptibus & Typis Iohannis Lauri. p. B2, recto and verso (images 35 and 36), with erratum on last page (image 78). Archived from the original on 2 July 2020. Retrieved 30 June 2020.
  38. ^ a b Marazzini, Claudio (2005). "I nomi dei satelliti di Giove: da Galileo a Simon Marius" [The names of Jupiter's satellites: from Galileo to Simon Marius]. Lettere Italiane (in Italian). 57 (3): 391–407. JSTOR 26267017.
  39. ^ US National Research Council (2000) A Science Strategy for the Exploration of Europa
  40. ^ a b "Europa, a Continuing Story of Discovery". Project Galileo. NASA, Jet Propulsion Laboratory. Archived from the original on 5 January 1997. Retrieved 9 August 2007.
  41. ^ "Planetographic Coordinates". Wolfram Research. 2010. Archived from the original on 1 March 2009. Retrieved 29 March 2010.
  42. ^ a b c Showman, Adam P.; Malhotra, Renu (May 1997). "Tidal Evolution into the Laplace Resonance and the Resurfacing of Ganymede". Icarus. 127 (1): 93–111. Bibcode:1997Icar..127...93S. doi:10.1006/icar.1996.5669. S2CID 55790129.
  43. ^ Moore, W. B. (2003). "Tidal heating and convection in Io". Journal of Geophysical Research. 108 (E8): 5096. Bibcode:2003JGRE..108.5096M. CiteSeerX 10.1.1.558.6924. doi:10.1029/2002JE001943.
  44. ^ Cook, Jia-Rui C. (18 September 2013) Long-stressed Europa Likely Off-kilter at One Time Archived 17 August 2014 at the Wayback Machine. jpl.nasa.gov
  45. ^ Mass of Europa: 48×1021 kg. Mass of Triton plus all smaller moons: 39.5×1021 kg (see note k here)
  46. ^ Kargel, Jeffrey S.; Kaye, Jonathan Z.; Head, James W.; Marion, Giles M.; Sassen, Roger; Crowley, James K.; Ballesteros, Olga Prieto; Grant, Steven A.; Hogenboom, David L. (November 2000). "Europa's Crust and Ocean: Origin, Composition, and the Prospects for Life". Icarus. 148 (1): 226–265. Bibcode:2000Icar..148..226K. doi:10.1006/icar.2000.6471. Archived from the original on 31 July 2020. Retrieved 10 January 2020.
  47. ^ Phillips, Cynthia B.; Pappalardo, Robert T. (20 May 2014). "Europa Clipper Mission Concept". Eos, Transactions American Geophysical Union. 95 (20): 165–167. Bibcode:2014EOSTr..95..165P. doi:10.1002/2014EO200002.
  48. ^ Cowen, Ron (7 June 2008). "A Shifty Moon". Science News. Archived from the original on 4 November 2011. Retrieved 29 May 2008.
  49. ^ a b Kivelson, Margaret G.; Khurana, Krishan K.; Russell, Christopher T.; Volwerk, Martin; Walker, Raymond J.; Zimmer, Christophe (2000). "Galileo Magnetometer Measurements: A Stronger Case for a Subsurface Ocean at Europa". Science. 289 (5483): 1340–1343. Bibcode:2000Sci...289.1340K. doi:10.1126/science.289.5483.1340. PMID 10958778. S2CID 44381312.
  50. ^ Bhatia, G.K.; Sahijpal, S. (2017). "Thermal evolution of trans-Neptunian objects, icy satellites, and minor icy planets in the early solar system". Meteoritics & Planetary Science. 52 (12): 2470–2490. Bibcode:2017M&PS...52.2470B. doi:10.1111/maps.12952. S2CID 133957919.
  51. ^ a b "Europa: Another Water World?". Project Galileo: Moons and Rings of Jupiter. NASA, Jet Propulsion Laboratory. 2001. Archived from the original on 21 July 2011. Retrieved 9 August 2007.
  52. ^ Arnett, Bill (7 November 1996) Europa Archived 4 September 2011 at the Wayback Machine. astro.auth.gr
  53. ^ a b Hamilton, Calvin J. "Jupiter's Moon Europa". solarviews.com. Archived from the original on 24 January 2012. Retrieved 27 February 2007.
  54. ^ Schenk, Paul M.; Chapman, Clark R.; Zahnle, Kevin; and Moore, Jeffrey M. (2004) "Chapter 18: Ages and Interiors: the Cratering Record of the Galilean Satellites" Archived 24 December 2016 at the Wayback Machine, pp. 427 ff. in Bagenal, Fran; Dowling, Timothy E.; and McKinnon, William B., editors; Jupiter: The Planet, Satellites and Magnetosphere, Cambridge University Press, ISBN 0-521-81808-7.
  55. ^ "High Tide on Europa". Astrobiology Magazine. astrobio.net. 2007. Archived from the original on 29 September 2007. Retrieved 20 October 2007.{{cite web}}: CS1 maint: unfit URL (link)
  56. ^ Rincon, Paul (20 March 2013). "Ice blades threaten Europa landing". BBC News. Archived from the original on 7 November 2018. Retrieved 21 June 2018.
  57. ^ Europa may have towering ice spikes on its surface Archived 21 January 2021 at the Wayback Machine. Paul Scott Anderson, Earth and Sky. 20 October 2018.
  58. ^ a b Hobley, Daniel E. J.; Moore, Jeffrey M.; Howard, Alan D.; Umurhan, Orkan M. (8 October 2018). "Formation of metre-scale bladed roughness on Europa's surface by ablation of ice" (PDF). Nature Geoscience. 11 (12): 901–904. Bibcode:2018NatGe..11..901H. doi:10.1038/s41561-018-0235-0. S2CID 134294079. Archived (PDF) from the original on 31 July 2020. Retrieved 11 January 2020.
  59. ^ Frederick A. Ringwald (29 February 2000). "SPS 1020 (Introduction to Space Sciences)". California State University, Fresno. Archived from the original on 25 July 2008. Retrieved 4 July 2009.
  60. ^ The Effects of Nuclear Weapons, Revised ed., US DOD 1962, pp. 592–593
  61. ^ "Europa: Facts about Jupiter's Moon, Europa • The Planets". The Planets. Archived from the original on 11 January 2021. Retrieved 9 January 2021.
  62. ^ "Planetary Names".
  63. ^ "Europa Nomenclature" (PDF). asc-planetarynames. Retrieved 25 February 2024.
  64. ^ Geissler, P.E.; Greenberg, R.; Hoppa, G.; McEwen, A.; Tufts, R.; Phillips, C.; Clark, B.; Ockert-Bell, M.; Helfenstein, P.; Burns, J.; Veverka, J.; Sullivan, R.; Greeley, R.; Pappalardo, R.T.; Head, J.W.; Belton, M.J.S.; Denk, T. (September 1998). "Evolution of Lineaments on Europa: Clues from Galileo Multispectral Imaging Observations". Icarus. 135 (1): 107–126. Bibcode:1998Icar..135..107G. doi:10.1006/icar.1998.5980. S2CID 15375333.
  65. ^ Figueredo, Patricio H.; Greeley, Ronald (February 2004). "Resurfacing history of Europa from pole-to-pole geological mapping". Icarus. 167 (2): 287–312. Bibcode:2004Icar..167..287F. doi:10.1016/j.icarus.2003.09.016.
  66. ^ Hurford, T.A.; Sarid, A.R.; Greenberg, R. (January 2007). "Cycloidal cracks on Europa: Improved modeling and non-synchronous rotation implications". Icarus. 186 (1): 218–233. Bibcode:2007Icar..186..218H. doi:10.1016/j.icarus.2006.08.026.
  67. ^ Kattenhorn, Simon A. (2002). "Nonsynchronous Rotation Evidence and Fracture History in the Bright Plains Region, Europa". Icarus. 157 (2): 490–506. Bibcode:2002Icar..157..490K. doi:10.1006/icar.2002.6825.
  68. ^ a b Schenk, Paul M.; McKinnon, William B. (May 1989). "Fault offsets and lateral crustal movement on Europa: Evidence for a mobile ice shell". Icarus. 79 (1): 75–100. Bibcode:1989Icar...79...75S. doi:10.1016/0019-1035(89)90109-7.
  69. ^ a b Kattenhorn, Simon A.; Prockter, Louise M. (7 September 2014). "Evidence for subduction in the ice shell of Europa". Nature Geoscience. 7 (10): 762–767. Bibcode:2014NatGe...7..762K. doi:10.1038/ngeo2245.
  70. ^ Howell, Samuel M.; Pappalardo, Robert T. (1 April 2019). "Can Earth-like plate tectonics occur in ocean world ice shells?". Icarus. 322: 69–79. Bibcode:2019Icar..322...69H. doi:10.1016/j.icarus.2019.01.011. S2CID 127545679.
  71. ^ a b Sotin, Christophe; Head, James W.; Tobie, Gabriel (April 2002). "Europa: Tidal heating of upwelling thermal plumes and the origin of lenticulae and chaos melting" (PDF). Geophysical Research Letters. 29 (8): 74-1–74-4. Bibcode:2002GeoRL..29.1233S. doi:10.1029/2001GL013844. S2CID 14413348. Archived (PDF) from the original on 31 July 2020. Retrieved 12 April 2020.
  72. ^ Goodman, Jason C. (2004). "Hydrothermal plume dynamics on Europa: Implications for chaos formation". Journal of Geophysical Research. 109 (E3): E03008. Bibcode:2004JGRE..109.3008G. doi:10.1029/2003JE002073. hdl:1912/3570.
  73. ^ O'Brien, David P.; Geissler, Paul; Greenberg, Richard (October 2000). "Tidal Heat in Europa: Ice Thickness and the Plausibility of Melt-Through". Bulletin of the American Astronomical Society. 30: 1066. Bibcode:2000DPS....32.3802O.
  74. ^ Greenberg, Richard (2008). Unmasking Europa. Copernicus. Springer + Praxis Publishing. pp. 205–215, 236. ISBN 978-0-387-09676-6. Archived from the original on 22 January 2010. Retrieved 28 August 2017.
  75. ^ Schmidt, B. E.; Blankenship, D. D.; Patterson, G. W.; Schenk, P. M. (November 2011). "Active formation of 'chaos terrain' over shallow subsurface water on Europa". Nature. 479 (7374): 502–505. Bibcode:2011Natur.479..502S. doi:10.1038/nature10608. ISSN 1476-4687. PMID 22089135.
  76. ^ a b c Airhart, Marc (2011). "Scientists Find Evidence for "Great Lake" on Europa and Potential New Habitat for Life". Jackson School of Geosciences. Archived from the original on 18 December 2013. Retrieved 16 November 2011.
  77. ^ Soderlund, K. M.; Schmidt, B. E.; Wicht, J.; Blankenship, D. D. (January 2014). "Ocean-driven heating of Europa's icy shell at low latitudes". Nature Geoscience. 7 (1): 16–19. Bibcode:2014NatGe...7...16S. doi:10.1038/ngeo2021. ISSN 1752-0894.
  78. ^ a b Cox, Rónadh; Bauer, Aaron W. (October 2015). "Impact breaching of Europa's ice: Constraints from numerical modeling: IMPACT BREACHING OF EUROPA'S ICE". Journal of Geophysical Research: Planets. 120 (10): 1708–1719. doi:10.1002/2015JE004877. S2CID 17563282.
  79. ^ a b Cox, Rónadh; Ong, Lissa C. F.; Arakawa, Masahiko; Scheider, Kate C. (December 2008). "Impact penetration of Europa's ice crust as a mechanism for formation of chaos terrain". Meteoritics & Planetary Science. 43 (12): 2027–2048. Bibcode:2008M&PS...43.2027C. doi:10.1111/j.1945-5100.2008.tb00659.x. S2CID 129700548. Archived from the original on 1 October 2021. Retrieved 12 January 2021.
  80. ^ a b Greenberg, Richard (2005). Europa: The Ocean Moon: Search for an Alien Biosphere. Springer Praxis Books. Springer + Praxis. pp. 7 ff. doi:10.1007/b138547. ISBN 978-3-540-27053-9.
  81. ^ Greeley, Ronald; et al. (2004) "Chapter 15: Geology of Europa", pp. 329 ff. in Bagenal, Fran; Dowling, Timothy E.; and McKinnon, William B., editors; Jupiter: The Planet, Satellites and Magnetosphere, Cambridge University Press, ISBN 0-521-81808-7.
  82. ^ Park, Ryan S.; Bills, Bruce; Buffington, Brent B. (July 2015). "Improved detection of tides at Europa with radiometric and optical tracking during flybys". Planetary and Space Science. 112: 10–14. Bibcode:2015P&SS..112...10P. doi:10.1016/j.pss.2015.04.005.
  83. ^ Adamu, Zaina (1 October 2012). "Water near surface of a Jupiter moon only temporary". CNN News. Archived from the original on 5 October 2012. Retrieved 2 October 2012.
  84. ^ Nemiroff, R.; Bonnell, J., eds. (24 May 2012). "All the Water on Europa". Astronomy Picture of the Day. NASA. Retrieved 8 March 2016.
  85. ^ Williams, Matt (15 September 2015). "Jupiter's Moon Europa". Universe Today. Archived from the original on 10 March 2016. Retrieved 9 March 2016.
  86. ^ a b Billings, Sandra E.; Kattenhorn, Simon A. (2005). "The great thickness debate: Ice shell thickness models for Europa and comparisons with estimates based on flexure at ridges". Icarus. 177 (2): 397–412. Bibcode:2005Icar..177..397B. doi:10.1016/j.icarus.2005.03.013.
  87. ^ Zimmer, C (October 2000). "Subsurface Oceans on Europa and Callisto: Constraints from Galileo Magnetometer Observations". Icarus. 147 (2): 329–347. Bibcode:2000Icar..147..329Z. CiteSeerX 10.1.1.366.7700. doi:10.1006/icar.2000.6456.
  88. ^ "Europa Mission to Probe Magnetic Field and Chemistry". Jet Propulsion Laboratory. 27 May 2015. Archived from the original on 2 December 2020. Retrieved 29 May 2015.
  89. ^ McCord, Thomas B.; Hansen, Gary B.; et al. (1998). "Salts on Europa's Surface Detected by Galileo's Near Infrared Mapping Spectrometer". Science. 280 (5367): 1242–1245. Bibcode:1998Sci...280.1242M. doi:10.1126/science.280.5367.1242. PMID 9596573.
  90. ^ Carlson, R. W.; Anderson, M. S.; Mehlman, R.; Johnson, R. E. (2005). "Distribution of hydrate on Europa: Further evidence for sulfuric acid hydrate". Icarus. 177 (2): 461. Bibcode:2005Icar..177..461C. doi:10.1016/j.icarus.2005.03.026.
  91. ^ Calvin, Wendy M.; Clark, Roger N.; Brown, Robert H.; Spencer, John R. (1995). "Spectra of the ice Galilean satellites from 0.2 to 5 μm: A compilation, new observations, and a recent summary". Journal of Geophysical Research. 100 (E9): 19, 041–19, 048. Bibcode:1995JGR...10019041C. doi:10.1029/94JE03349.
  92. ^ "NASA's Webb Finds Carbon Source on Surface of Jupiter's Moon Europa - NASA". 21 September 2023.
  93. ^ a b Borucki, Jerome G.; Khare, Bishun; Cruikshank, Dale P. (2002). "A new energy source for organic synthesis in Europa's surface ice". Journal of Geophysical Research: Planets. 107 (E11): 24–1–24–5. Bibcode:2002JGRE..107.5114B. doi:10.1029/2002JE001841.
  94. ^ Whalen, Kelly; Lunine, Jonathan I.; Blaney, Diana L. (2017). MISE: A Search for Organics on Europa. American Astronomical Society Meeting Abstracts #229. Vol. 229. p. 138.04. Bibcode:2017AAS...22913804W.
  95. ^ "Europa Mission to Probe Magnetic Field and Chemistry". Jet Propulsion Laboratory. 27 May 2015. Archived from the original on 2 December 2020. Retrieved 23 October 2017.
  96. ^ Trainer, MG (2013). "Atmospheric Prebiotic Chemistry and Organic Hazes". Curr Org Chem. 17 (16): 1710–1723. doi:10.2174/13852728113179990078. PMC 3796891. PMID 24143126.
  97. ^ Coll, Patrice; Szopa, Cyril; Buch, Arnaud; Carrasco, Nathalie; Ramirez, Sandra I.; Quirico, Eric; Sternberg, Robert; Cabane, Michel; Navarro-Gonzalez, Rafael; Raulin, Francois; Israel, G.; Poch, O.; Brasse, C. (2010). Prebiotic chemistry on Titan ? The nature of Titan's aerosols and their potential evolution at the satellite surface. 38th Cospar Scientific Assembly. Vol. 38. p. 11. Bibcode:2010cosp...38..777C.
  98. ^ Ruiz-Bermejo, Marta; Rivas, Luis A.; Palacín, Arantxa; Menor-Salván, César; Osuna-Esteban, Susana (16 December 2010). "Prebiotic Synthesis of Protobiopolymers Under Alkaline Ocean Conditions". Origins of Life and Evolution of Biospheres. 41 (4): 331–345. Bibcode:2011OLEB...41..331R. doi:10.1007/s11084-010-9232-z. PMID 21161385. S2CID 19283373.
  99. ^ Trumbo, Samantha K.; Brown, Michael E.; Hand, Kevin P. (12 June 2019). "Sodium chloride on the surface of Europa". Science Advances. 5 (6): eaaw7123. Bibcode:2019SciA....5.7123T. doi:10.1126/sciadv.aaw7123. PMC 6561749. PMID 31206026.
  100. ^ Devlin, Hannah (21 September 2023). "Scientists excited to find ocean of one of Jupiter's moons contains carbon". The Guardian.
  101. ^ Trumbo, Samantha (September 2023). "The distribution of CO2 on Europa indicates an internal source of carbon". Science. 381 (6664): 1308–1311. arXiv:2309.11684. doi:10.1126/science.adg4155. PMID 37733851.
  102. ^ a b c "Frequently Asked Questions about Europa". NASA. 2012. Archived from the original on 28 April 2016. Retrieved 18 April 2016.
  103. ^ a b Zyga, Lisa (12 December 2008). "Scientist Explains Why Jupiter's Moon Europa Could Have Energetic Liquid Oceans". PhysOrg.com. Archived from the original on 17 February 2009. Retrieved 28 July 2009.
  104. ^ a b Tyler, Robert H. (11 December 2008). "Strong ocean tidal flow and heating on moons of the outer planets". Nature. 456 (7223): 770–772. Bibcode:2008Natur.456..770T. doi:10.1038/nature07571. PMID 19079055. S2CID 205215528.
  105. ^ "Europa: Energy". NASA. 2012. Archived from the original on 28 April 2016. Retrieved 18 April 2016. Tidal flexing of the ice shell could create slightly warmer pockets of ice that rise slowly upward to the surface, carrying material from the ocean below.
  106. ^ Tyler, Robert (15 December 2008). "Jupiter's Moon Europa Does The Wave To Generate Heat". University of Washington. Science Daily. Archived from the original on 14 May 2016. Retrieved 18 April 2016.
  107. ^ a b Stacey, Kevin (14 April 2016). "Europa's heaving ice might make more heat than scientists thought". Brown University. Archived from the original on 21 April 2016. Retrieved 18 April 2016.
  108. ^ a b McCarthy, Christine; Cooper, Reid F. (1 June 2016). "Tidal dissipation in creeping ice and the thermal evolution of Europa". Earth and Planetary Science Letters. 443: 185–194. Bibcode:2016E&PSL.443..185M. doi:10.1016/j.epsl.2016.03.006.
  109. ^ Barr, Amy C.; Showman, Adam P. (2009). "Heat transfer in Europa's icy shell". In Pappalardo, Robert T.; McKinnon, William B.; Khurana, Krishan (eds.). Europa. University of Arizona Press. pp. 405–430. Bibcode:2009euro.book..405B. CiteSeerX 10.1.1.499.6279. ISBN 978-0-8165-2844-8.
  110. ^ Lowell, Robert P.; DuBosse, Myesha (9 March 2005). "Hydrothermal systems on Europa". Geophysical Research Letters. 32 (5): L05202. Bibcode:2005GeoRL..32.5202L. doi:10.1029/2005GL022375. S2CID 129270513.
  111. ^ Ruiz, Javier (October 2005). "The heat flow of Europa" (PDF). Icarus. 177 (2): 438–446. Bibcode:2005Icar..177..438R. doi:10.1016/j.icarus.2005.03.021. Archived (PDF) from the original on 9 October 2022.
  112. ^ a b "Photo composite of suspected water plumes on Europa". www.spacetelescope.org. Archived from the original on 9 October 2016. Retrieved 6 October 2016.
  113. ^ "Hubble discovers water vapour venting from Jupiter's moon Europa". www.spacetelescope.org. Hubble Space Telescope/European Space Agency. 12 December 2013. Archived from the original on 16 April 2019. Retrieved 16 April 2019.
  114. ^ Fletcher, Leigh (12 December 2013). "The Plumes of Europa". The Planetary Society. Archived from the original on 15 December 2013. Retrieved 17 December 2013.
  115. ^ Choi, Charles Q. (12 December 2013). "Jupiter Moon Europa May Have Water Geysers Taller Than Everest". Space.com. Archived from the original on 15 December 2013. Retrieved 17 December 2013.
  116. ^ Fagents, Sarah A.; Greeley, Ronald; Sullivan, Robert J.; Pappalardo, Robert T.; Prockter, Louise M. (30 June 1999). "Cryomagmatic Mechanisms for the Formation of Rhadamanthys Linea, Triple Band Margins, and Other Low-Albedo Features on Europa". Icarus. 144 (1): 54–88. doi:10.1006/icar.1999.6254. Archived from the original on 16 June 2022. Retrieved 16 June 2022.
  117. ^ Quick, Lynnae C.; Barnouin, Olivier S.; Prockter, Louise; Patterson, G. Wesley (15 September 2013). "Constraints on the Detection of Cryovolcanic Plumes on Europa". Planetary and Space Science. 86 (1): 1–9. doi:10.1006/icar.1999.6254. Archived from the original on 16 June 2022. Retrieved 16 June 2022.
  118. ^ Paganini, L.; Villanueva, G.L.; Mandell, A.M.; Hurford, T.A.; Retherford, K.D.; Mumma, M.A. (18 November 2019). "CA measurement of water vapour amid a largely quiescent environment on Europa". Nature Astronomy. 4 (3): 266–272. doi:10.1038/s41550-019-0933-6. S2CID 210278335. Archived from the original on 18 June 2022. Retrieved 16 June 2022.
  119. ^ Dyches, Preston (30 July 2015). "Signs of Europa Plumes Remain Elusive in Search of Cassini Data". NASA. Archived from the original on 16 April 2016. Retrieved 18 April 2016.
  120. ^ a b Roth, L.; Saur, J.; Retherford, K. D.; Strobel, D. F.; Feldman, P. D.; McGrath, M. A.; Nimmo, F. (12 December 2013). "Transient Water Vapor at Europa's South Pole". Science. 343 (6167): 171–174. Bibcode:2014Sci...343..171R. doi:10.1126/science.1247051. PMID 24336567. S2CID 27428538.
  121. ^ a b Berger, Eric (26 September 2016). "Hubble finds additional evidence of water vapor plumes on Europa". NASA. ARS Technica. Archived from the original on 26 September 2016. Retrieved 26 September 2016.
  122. ^ Amos, Jonathan (26 September 2016). "Europa moon 'spewing water jets'". BBC News. Archived from the original on 26 September 2016. Retrieved 26 September 2016.
  123. ^ Hansen, C. J.; Esposito, L.; Stewart, A. I.; Colwell, J.; Hendrix, A.; Pryor, W.; Shemansky, D.; West, R. (10 March 2006). "Enceladus' Water Vapor Plume". Science. 311 (5766): 1422–1425. Bibcode:2006Sci...311.1422H. doi:10.1126/science.1121254. PMID 16527971. S2CID 2954801.
  124. ^ Spencer, J. R.; Nimmo, F. (May 2013). "Enceladus: An Active Ice World in the Saturn System". Annual Review of Earth and Planetary Sciences. 41 (1): 693. Bibcode:2013AREPS..41..693S. doi:10.1146/annurev-earth-050212-124025. S2CID 140646028.
  125. ^ O'Neill, Ian (22 September 2016). "NASA: Activity Spied on Europa, But It's 'NOT Aliens'". Discovery News. Space. Archived from the original on 23 September 2016. Retrieved 23 September 2016.
  126. ^ Huybrighs, Hans; Futaana, Yoshifumi; Barabash, Stas; Wieser, Martin; Wurz, Peter; Krupp, Norbert; Glassmeier, Karl-Heinz; Vermeersen, Bert (June 2017). "On the in-situ detectability of Europa's water vapour plumes from a flyby mission". Icarus. 289: 270–280. arXiv:1704.00912. Bibcode:2017Icar..289..270H. doi:10.1016/j.icarus.2016.10.026. S2CID 119470009.
  127. ^ Fagents, Sarah A. (27 December 2003). "Considerations for effusive cryovolcanism on Europa:The post-Galileo perspective". Icarus. 108 (E12): 5139. Bibcode:2003JGRE..108.5139F. doi:10.1029/2003JE002128. Archived from the original on 16 June 2022. Retrieved 16 June 2022.
  128. ^ McCartney, Gretchen; Hautaluoma, Grey; Johnson, Alana; Tucker, Danielle (13 November 2020). "Potential Plumes on Europa Could Come From Water in the Crust". Jet Propulsion Laboratory. Archived from the original on 13 November 2020. Retrieved 13 November 2020.
  129. ^ Steinbrügge, G.; Voigt, J. R. C.; Wolfenbarger, N. S.; Hamilton, C. W.; Soderlund, K. M.; Young D., D. A.; Blankenship, D.; Vance D., S. D.; Schroeder, M. (5 November 2020). "Brine Migration and Impact-Induced Cryovolcanism on Europa". Geophysical Research Letters. 47 (21): {e2020GL090797}. Bibcode:2020GeoRL..4790797S. doi:10.1029/2020GL090797. S2CID 228890686.
  130. ^ "Life Beyond Earth - The Habitable Zone - Europa". www.pbs.org. Archived from the original on 13 May 2022. Retrieved 13 May 2022.
  131. ^ a b "Hubble Finds Oxygen Atmosphere on Jupiter's Moon, Europa". HubbleSite.org. Archived from the original on 16 April 2023. Retrieved 13 May 2022.
  132. ^ Johnson, Robert E.; Lanzerotti, Louis J.; Brown, Walter L. (1982). "Planetary applications of ion induced erosion of condensed-gas frosts". Nuclear Instruments and Methods in Physics Research. 198 (1): 147. Bibcode:1982NIMPR.198..147J. doi:10.1016/0167-5087(82)90066-7.
  133. ^ Liang, Mao-Chang (2005). "Atmosphere of Callisto". Journal of Geophysical Research. 110 (E2): E02003. Bibcode:2005JGRE..110.2003L. doi:10.1029/2004JE002322. S2CID 8162816. Archived from the original on 16 April 2023. Retrieved 15 July 2022.
  134. ^ Smyth, W. H.; Marconi, M. L. (2007). Processes Shaping Galilean Satellite Atmospheres from the Surface to the Magnetosphere. Workshop on Ices. Vol. 1357. p. 131. Bibcode:2007LPICo1357..131S.
  135. ^ "Hubble Finds Oxygen Atmosphere On Jupiter's Moon Europa". solarviews.com. Archived from the original on 2 October 2022. Retrieved 13 May 2022.
  136. ^ Cartier, Kimberly M. S. (14 December 2020). "Do Uranus's Moons Have Subsurface Oceans?". Eos. Archived from the original on 16 May 2022. Retrieved 13 May 2022.
  137. ^ "Europa". NASA Solar System Exploration. Archived from the original on 14 May 2022. Retrieved 13 May 2022.
  138. ^ Chyba, C. F.; Hand, K. P. (2001). "PLANETARY SCIENCE: Enhanced: Life Without Photosynthesis". Science. 292 (5524): 2026–2027. doi:10.1126/science.1060081. PMID 11408649. S2CID 30589825.
  139. ^ Chyba, Christopher F.; Hand, Kevin P. (15 June 2001). "Life Without Photosynthesis". Science. 292 (5524): 2026–2027. doi:10.1126/science.1060081. ISSN 0036-8075. PMID 11408649. S2CID 30589825. Archived from the original on 13 May 2022. Retrieved 13 May 2022.
  140. ^ a b Hand, Kevin P.; Carlson, Robert W.; Chyba, Christopher F. (December 2007). "Energy, Chemical Disequilibrium, and Geological Constraints on Europa". Astrobiology. 7 (6): 1006–1022. Bibcode:2007AsBio...7.1006H. CiteSeerX 10.1.1.606.9956. doi:10.1089/ast.2007.0156. PMID 18163875.
  141. ^ Smyth, William H.; Marconi, Max L. (2006). "Europa's atmosphere, gas tori, and magnetospheric implications". Icarus. 181 (2): 510. Bibcode:2006Icar..181..510S. doi:10.1016/j.icarus.2005.10.019.
  142. ^ Smith, Howard Todd; Mitchell, Donald G.; Johnson, Robert E.; Mauk, Barry H.; Smith, Jacob E. (22 January 2019). "Europa Neutral Torus Confirmation and Characterization Based on Observations and Modeling". The Astrophysical Journal. 871 (1): 69. Bibcode:2019ApJ...871...69S. doi:10.3847/1538-4357/aaed38. ISSN 1538-4357. S2CID 126922049.
  143. ^ Hall, D. T.; Strobel, D. F.; Feldman, P. D.; McGrath, M. A.; Weaver, H. A. (23 February 1995). "Detection of an oxygen atmosphere on Jupiter's moon Europa". Nature. 373 (6516): 677–679. Bibcode:1995Natur.373..677H. doi:10.1038/373677a0. PMID 7854447.
  144. ^ Kliore, A. J.; Hinson, D. P.; Flaser, F. M.; Nagy, A. F.; Cravens, T. E. (18 July 1997). "The Ionosphere of Europa from Galileo Radio Occultations". Science. 277 (5324): 355–358. Bibcode:1997Sci...277..355K. doi:10.1126/science.277.5324.355. PMID 9219689.
  145. ^ Elizabeth Howell (22 March 2018). "Europa: Facts About Jupiter's Icy Moon and Its Ocean". Space.com. Archived from the original on 13 May 2022. Retrieved 13 May 2022.
  146. ^ The Journey to Jupiter: Extended Tours – GEM and the Millennium Mission. Solarsystem.nasa.gov. Retrieved on 23 July 2013.
  147. ^ "PIA09246: Europa". NASA photojournal. 2 April 2007. Archived from the original on 6 March 2016. Retrieved 9 March 2016.
  148. ^ "NASA's Juno Shares First Image From Flyby of Jupiter's Moon Europa". NASA. 29 September 2022. Archived from the original on 1 October 2022. Retrieved 30 September 2022.
  149. ^ Selection of the L1 mission Archived 16 October 2015 at the Wayback Machine. ESA, 17 April 2012. (PDF). Retrieved on 23 July 2013.
  150. ^ "JUICE – Science objectives". European Space Agency. 16 March 2012. Archived from the original on 8 June 2013. Retrieved 20 April 2012.
  151. ^ "Juice's journey and Jupiter system tour". ESA. 29 March 2022. Archived from the original on 24 September 2022. Retrieved 3 April 2022.
  152. ^ Zabarenko, Deborah (7 March 2011). "Lean U.S. missions to Mars, Jupiter moon recommended". Reuters. Archived from the original on 7 September 2020. Retrieved 5 July 2021.
  153. ^ "Europa Lander". NASA. Archived from the original on 16 January 2014. Retrieved 15 January 2014.
  154. ^ March 2012 OPAG Meeting Archived 3 March 2016 at the Wayback Machine. Lunar and Planetary Institute, NASA. Retrieved on 23 July 2013.
  155. ^ Khan, Amina (15 January 2014). "NASA gets some funding for Mars 2020 rover in federal spending bill". Los Angeles Times. Archived from the original on 21 April 2014. Retrieved 16 January 2014.
  156. ^ Girardot, Frank C. (14 January 2014). "JPL's Mars 2020 rover benefits from spending bill". Pasadena Star-News. Archived from the original on 31 July 2017. Retrieved 15 January 2014.
  157. ^ Pappalardo, Robert; Cooke, Brian; Goldstein, Barry; Prockter, Louise; Senske, Dave; Magner, Tom (2013). "The Europa Clipper – OPAG Update" (PDF). JPL/APL. Archived (PDF) from the original on 25 January 2021. Retrieved 13 December 2013.
  158. ^ "NASA's Europa Mission Begins with Selection of Science Instruments". NASA. 26 May 2015. Archived from the original on 5 July 2015. Retrieved 3 July 2015.
  159. ^ Potter, Sean (23 July 2021). "NASA Awards Launch Services Contract for the Europa Clipper Mission" (Press release). NASA. Archived from the original on 24 July 2021. Retrieved 23 July 2021. Public Domain This article incorporates text from this source, which is in the public domain.
  160. ^ David, Leonard (7 February 2006). "Europa Mission: Lost In NASA Budget". Space.com. Archived from the original on 24 December 2010. Retrieved 25 February 2007.
  161. ^ a b c d Friedman, Louis (14 December 2005). "Projects: Europa Mission Campaign; Campaign Update: 2007 Budget Proposal". The Planetary Society. Archived from the original on 11 August 2011.
  162. ^ a b Chandler, David L. (20 October 2002). "Thin ice opens lead for life on Europa". New Scientist. Archived from the original on 14 May 2008. Retrieved 27 August 2017.
  163. ^ Muir, Hazel (22 May 2002) Europa has raw materials for life Archived 16 April 2008 at the Wayback Machine, New Scientist.
  164. ^ Ringwald, Frederick A. (29 February 2000) SPS 1020 (Introduction to Space Sciences) Course Notes Archived 25 July 2008 at the Wayback Machine, California State University, csufresno.edu.
  165. ^ Grush, Loren (8 October 2018). "Future spacecraft landing on Jupiter's moon Europa may have to navigate jagged blades of ice". The Verge. Archived from the original on 28 March 2019. Retrieved 16 April 2019.
  166. ^ Guarino, Ben (8 October 2018). "Jagged ice spikes cover Jupiter's moon Europa, study suggests". The Washington Post. Archived from the original on 16 April 2019. Retrieved 15 April 2019.
  167. ^ "NASA and ESA Prioritize Outer Planet Missions". NASA. 2009. Archived from the original on 25 August 2011. Retrieved 26 July 2009.
  168. ^ Rincon, Paul (20 February 2009). "Jupiter in space agencies' sights". BBC News. Archived from the original on 21 February 2009. Retrieved 20 February 2009.
  169. ^ "Cosmic Vision 2015–2025 Proposals". ESA. 21 July 2007. Archived from the original on 2 September 2011. Retrieved 20 February 2009.
  170. ^ a b McKay, C. P. (2002). "Planetary protection for a Europa surface sample return: The Ice Clipper mission". Advances in Space Research. 30 (6): 1601–1605. Bibcode:2002AdSpR..30.1601M. doi:10.1016/S0273-1177(02)00480-5. Archived from the original on 31 July 2020. Retrieved 29 June 2019.
  171. ^ Goodman, Jason C. (9 September 1998) Re: Galileo at Europa Archived 1 March 2012 at the Wayback Machine, MadSci Network forums.
  172. ^ a b Berger, Brian; NASA 2006 Budget Presented: Hubble, Nuclear Initiative Suffer Archived 2 June 2009 at the Wayback Machine Space.com (7 February 2005)
  173. ^ a b Abelson & Shirley – Small RPS-Enabled Europa Lander Mission (2005). . (PDF). Retrieved on 23 July 2013.
  174. ^ 2012 Europa Mission Studies Archived 3 June 2013 at the Wayback Machine. OPAG 29 March 2012 (PDF). Lunar and Planetary Institute, NASA. Retrieved on 23 July 2013.
  175. ^ Europa Study Team (1 May 2012), "Europa Study 2012 Report" (PDF), Europa Orbiter Mission (PDF), JPL – NASA, archived from the original (PDF) on 2 February 2014, retrieved 17 January 2014
  176. ^ Weiss, P.; Yung, K. L.; Kömle, N.; Ko, S. M.; Kaufmann, E.; Kargl, G. (2011). "Thermal drill sampling system onboard high-velocity impactors for exploring the subsurface of Europa". Advances in Space Research. 48 (4): 743. Bibcode:2011AdSpR..48..743W. doi:10.1016/j.asr.2010.01.015. hdl:10397/12621.
  177. ^ Hsu, J. (15 April 2010). "Dual Drill Designed for Europa's Ice". Astrobiology Magazine. Archived from the original on 18 April 2010.{{cite web}}: CS1 maint: unfit URL (link)
  178. ^ Knight, Will (14 January 2002). "Ice-melting robot passes Arctic test". New Scientist. Archived from the original on 17 March 2008. Retrieved 27 August 2017.
  179. ^ Bridges, Andrew (10 January 2000). "Latest Galileo Data Further Suggest Europa Has Liquid Ocean". Space.com. Archived from the original on 8 February 2009.
  180. ^ Preventing the Forward Contamination of Europa. Washington (DC): National Academy Press. 2000. ISBN 978-0-309-57554-6. Archived from the original on 13 February 2008.
  181. ^ Powell, Jesse; Powell, James; Maise, George; Paniagua, John (2005). "NEMO: A mission to search for and return to Earth possible life forms on Europa". Acta Astronautica. 57 (2–8): 579–593. Bibcode:2005AcAau..57..579P. doi:10.1016/j.actaastro.2005.04.003.
  182. ^ Schulze-Makuch, Dirk; Irwin, Louis N. (2001). "Alternative energy sources could support life on Europa". Eos, Transactions American Geophysical Union. 82 (13): 150. Bibcode:2001EOSTr..82..150S. doi:10.1029/EO082i013p00150. S2CID 140714995.
  183. ^ Jones, Nicola (11 December 2001). "Bacterial explanation for Europa's rosy glow". New Scientist. Archived from the original on 27 February 2015. Retrieved 26 September 2016.
  184. ^ "Europa's Ocean May Have An Earthlike Chemical Balance", Jpl.nasa.gov, archived from the original on 18 May 2016, retrieved 18 May 2016
  185. ^ Wall, Mike (9 June 2015). "NASA Aiming for Multiple Missions to Jupiter Moon Europa". Space.com. Archived from the original on 11 June 2015. Retrieved 10 June 2015.
  186. ^ Phillips, Cynthia (28 September 2006) Time for Europa Archived 25 November 2006 at the Wayback Machine, Space.com.
  187. ^ Wilson, Colin P. (March 2007). Tidal Heating on Io and Europa and its Implications for Planetary Geophysics. Northeastern Section – 42nd Annual Meeting. Archived from the original on 5 September 2008. Retrieved 21 December 2007.
  188. ^ a b Marion, Giles M.; Fritsen, Christian H.; Eicken, Hajo; Payne, Meredith C. (2003). "The Search for Life on Europa: Limiting Environmental Factors, Potential Habitats, and Earth Analogues". Astrobiology. 3 (4): 785–811. Bibcode:2003AsBio...3..785M. doi:10.1089/153110703322736105. PMID 14987483. S2CID 23880085.
  189. ^ Richard Greenberg (May 2010). "Transport Rates of Radiolytic Substances into Europa's Ocean: Implications for the Potential Origin and Maintenance of Life". Astrobiology. 10 (3): 275–283. Bibcode:2010AsBio..10..275G. doi:10.1089/ast.2009.0386. PMID 20446868.
  190. ^ Schmidt, Britney; Blankenship, Don; Patterson, Wes; Schenk, Paul (24 November 2011). "Active formation of 'chaos terrain' over shallow subsurface water on Europa". Nature. 479 (7374): 502–505. Bibcode:2011Natur.479..502S. doi:10.1038/nature10608. PMID 22089135. S2CID 4405195.
  191. ^ Icy Europa's mysterious double ridges may hint at hidden pockets of water Archived 22 April 2022 at the Wayback Machine Rahul Rao, Space.com. 21 April 2022
  192. ^ NASA – Mapping the Chemistry Needed for Life at Europa. Archived 8 April 2013 at the Wayback Machine. Nasa.gov (4 April 2013). Retrieved on 23 July 2013.
  193. ^ a b Cook, Jia-Rui C. (11 December 2013). "Clay-Like Minerals Found on Icy Crust of Europa". NASA. Archived from the original on 30 January 2020. Retrieved 11 December 2013.
  194. ^ Choi, Charles Q. (8 December 2013). "Life Could Have Hitched a Ride to Outer Planet Moons". Astrobiology Magazine. Astrobiology Web. Archived from the original on 12 December 2013. Retrieved 12 December 2013.

Further reading

[edit]
[edit]
Wikimedia Commons has media related to Europa (moon).
Retrieved from "https://en.wikipedia.org/w/index.php?title=Europa_(moon)&oldid=1257158573#Habitability"