Climate of Mars: Difference between revisions
Content deleted Content added
m Undid revision 645474738 by 204.83.240.120 (talk) |
mars climet Tag: repeating characters |
||
| Line 1: | Line 1: | ||
haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris |
|||
{{Use mdy dates|date=September 2014}} |
|||
{{Further|Atmosphere of Mars}} |
|||
[[File:Mars Valles Marineris.jpeg|thumb|right|250px|Mosaic image of [[Mars]] as seen by [[Viking 1]], February 22, 1980]] |
|||
The '''climate of Mars''' has been an issue of scientific curiosity for centuries, not least because [[Mars]] is the only [[terrestrial planet]] whose surface can be directly observed in detail from the [[Earth]] with help from a [[telescope]]. |
|||
Although Mars is smaller at 11% of Earth's [[mass]] and 50% farther from the [[Sun]] than the Earth, its climate has important similarities, such as the [[polar ice cap]]s, [[season]]al changes and the observable presence of [[weather]] patterns. It has attracted sustained study from [[planetology|planetologists]] and [[climatology|climatologists]]. Although Mars's climate has similarities to Earth's, including seasons and periodic [[ice age]]s, there are also important differences such as the absence of liquid water (though frozen water exists) and much lower [[Volumetric heat capacity#Thermal inertia|thermal inertia]]. Mars' atmosphere has a [[scale height]] of approximately {{convert|11|km|ft|abbr=on}}, 60% greater than that on Earth. The climate is of considerable relevance to the question of whether life is or was present on the planet. The climate briefly received more interest in the news due to NASA measurements indicating increased [[sublimation (phase transition)|sublimation]] of the south polar icecap leading to some popular press speculation that Mars was undergoing a parallel bout of [[global warming]],<ref>{{cite web | url=http://www.astronomy.com/asy/default.aspx?c=a&id=3503 | title=MGS sees changing face of Mars | date=September 23, 2005 | publisher=Astronomy Magazine | author=Francis Reddy | accessdate=September 6, 2007}}</ref> though global average temperature has actually [[Climate of Mars#Temperature|cooled in recent decades]]. |
|||
Mars has been studied by Earth-based instruments since as early as the 17th century but it is only since the [[exploration of Mars]] began in the mid-1960s that close-range observation has been possible. Flyby and orbital spacecraft have provided data from above, while direct measurements of atmospheric conditions have been provided by a number of landers and rovers. Advanced Earth orbital instruments today continue to provide some useful "big picture" observations of relatively large weather phenomena. |
|||
The first Martian flyby mission was [[Mariner 4]] which arrived in 1965. That quick two day pass (July 14–15, 1965) was limited and crude in terms of its contribution to the state of knowledge of Martian climate. Later Mariner missions ([[Mariner 6]], and [[Mariner 7]]) filled in some of the gaps in basic climate information. Data based climate studies started in earnest with the [[Viking program]] in 1975 and continues with such probes as the [[Mars Reconnaissance Orbiter]]. |
|||
This observational work has been complemented by a type of scientific computer simulation called the [[Mars General Circulation Model]].<ref>{{cite web | title = Mars General Circulation Modeling |
|||
| author = NASA |
|||
| publisher = NASA |
|||
| url = http://www-mgcm.arc.nasa.gov/MGCM.html |
|||
| accessdate = February 22, 2007}}</ref> Several different iterations of MGCM have led to an increased understanding of Mars as well as the limits of such models. Models are limited in their ability to represent atmospheric physics that occurs at a smaller scale than their resolution. They also may be based on inaccurate or unrealistic assumptions about how Mars works and certainly suffer from the quality and limited density in time and space of climate data from Mars. |
|||
== Historical climate observations == |
|||
[[Giancomo Miraldi]] determined in 1704 that the southern cap is not centered on the rotational pole of Mars.<ref name=mars1700>[http://www.exploringmars.com/history/1700.html Exploring Mars in the 1700s]</ref> During the opposition of 1719, Miraldi observed both polar caps and temporal variability in their extent. |
|||
[[William Herschel]] was the first to deduce the low density of the Martian atmosphere in his 1784 paper entitled ''On the remarkable appearances at the polar regions on the planet Mars, the inclination of its axis, the position of its poles, and its spheroidal figure; with a few hints relating to its real diameter and atmosphere''. When two faint stars passed close to Mars with no effect on their brightness, Herschel correctly concluded that this meant that there was little atmosphere around Mars to interfere with their light.<ref name=mars1700 /> |
|||
[[Honore Flaugergues]] 1809 discovery of "yellow clouds" on the surface of Mars is the first known observation of Martian dust storms.<ref>[http://www.exploringmars.com/history/1800.html Exploring Mars in the 1800s]</ref> Flaugergues also observed in 1813 significant polar ice waning during Martian springtime. His speculation that this meant that Mars was warmer than earth proved inaccurate. |
|||
== Martian paleoclimatology == |
|||
Prior to any serious examination of Martian paleoclimatology one has to agree on terms, especially broad terms of planetary ages. There are [[Geology of Mars#Timeline|two dating systems]] now in use for Martian geological time. One is based on crater density and has three ages: [[Noachian]], [[Hesperian]], and [[Amazonian (Mars)|Amazonian]]. The other is a mineralogical timeline, also having three ages: Phyllocian, Theikian, and Siderikian. |
|||
Recent observations and modeling are producing information not only about the present climate and atmospheric conditions on Mars but also about its past. The Noachian-era Martian atmosphere had long been theorized to be [[carbon dioxide]] rich. Recent spectral observations of deposits of clay minerals on Mars and modeling of clay mineral formation conditions<ref>{{cite web | url=http://www.sciencedaily.com/upi/index.php?feed=Science&article=UPI-1-20070719-14530900-bc-us-mars.xml | title=Clay studies might alter Mars theories | publisher=Science Daily | date=July 19, 2007 | accessdate=September 6, 2007 |archiveurl = http://web.archive.org/web/20070930201205/http://www.sciencedaily.com/upi/index.php?feed=Science&article=UPI-1-20070719-14530900-bc-us-mars.xml |archivedate = September 30, 2007}}</ref> have found that there is little to no carbonate present in clay of that era. Clay formation in a carbon dioxide rich environment is always accompanied by carbonate formation, though the carbonate may later be dissolved by volcanic acidity. |
|||
The discovery of water-formed minerals on Mars including [[hematite]] and [[jarosite]], by the Opportunity rover and [[goethite]] by the Spirit rover, has led to the conclusion that climatic conditions in the distant past allowed for free-flowing water on Mars. The morphology of some crater impacts on Mars indicate that the ground was wet at the time of impact.<ref>Carr, M.H., et al. (1977), Martian impact craters and emplacement of ejecta by surface flow, J. Geophys. Res., 82, 4055-65.</ref> Geomorphic observations of both landscape erosion rates<ref>Golombek, M.P., and Bridges, N.T. (2000), Erosion rates on Mars and implications for climate change: constraints from the Pathfinder landing site, J. Geophys. Res., 105(E1), 1841–1853</ref> and Martian [[Valley networks (Mars)|valley networks]]<ref>Craddock, R.A., and Howard, A.D. (2002), The case for rainfall on a warm, wet early Mars, J. Geophys. Res., 107(E11), {{DOI|10.1029/2001JE001505}}</ref> also strongly imply warmer, wetter conditions on [[Noachian]]-era Mars (earlier than about 4 billion years ago). However, chemical analysis of [[Martian meteorite]] samples suggests that the ambient near-surface temperature of Mars has most likely been below 0 °C for the last four billion years.<ref name=science309_5734>{{cite journal | title=Martian Surface Paleotemperatures from Thermochronology of Meteorites | author=Shuster, David L.; Weiss, Benjamin P. | journal=Science | date=July 22, 2005 | volume=309 | issue=5734 | pages=594–600 | doi=10.1126/science.1113077 | pmid=16040703 |bibcode = 2005Sci...309..594S }}</ref> |
|||
Some scientists maintain that the great mass of the [[Tharsis]] volcanoes has had a major influence on the climate of Mars. Erupting volcanoes give off great amounts of gas, mainly water vapor and CO<sub>2</sub>. Enough gas may have been released by volcanoes to have made the earlier Martian atmosphere thicker than Earth's. The volcanoes could also have emitted enough H<sub>2</sub>O to cover the whole Martian surface to a depth of {{convert|120|m|ft|abbr=on}}. CO<sub>2</sub> is a [[greenhouse gas]] that raises the temperature of a planet: it traps heat by absorbing [[infrared radiation]]. So Tharsis volcanoes, by giving off CO<sub>2</sub>, could have made Mars more Earth-like in the past. Mars may have once had a much thicker and warmer atmosphere, and oceans and/or lakes may have been present.<ref>Hartmann, W. 2003. A Traveler's Guide to Mars. Workman Publishing. NY NY.</ref> It has, however, proven extremely difficult to construct convincing [[global climate models]] for Mars which produce temperatures above 0 °C at any point in its history,<ref>aberle, R.M. (1998), Early Climate Models, J. Geophys. Res., 103(E12),28467-79</ref> though this may simply reflect problems in accurately calibrating such models. |
|||
== Weather == |
|||
[[File:PIA17940-MartianMorningClouds-VikingOrbiter1-1976-20140212.jpg|thumb|right|Martian Morning Clouds - [[Viking 1#Orbiter|Viking Orbiter 1]] (taken in 1976) - (February 12, 2014).]] |
|||
Mars' temperature and circulation vary from year to year (as expected for any planet with an atmosphere). Mars lacks oceans, a source of much inter-annual variation on Earth.{{clarify|date=May 2013}} [[Mars Orbiter Camera]] data beginning in March 1999 and covering 2.5 Martian years<ref>{{cite web | url=http://www.msss.com/mars_images/moc/mer_weather/ | title=Weather at the Mars Exploration Rover and Beagle 2 Landing Sites | publisher=[[Malin Space Science Systems]] | accessdate=September 8, 2007}}</ref> show that Martian weather tends to be more repeatable and hence more predictable than that of Earth. If an event occurs at a particular time of year in one year, the available data (sparse as it is) indicate that it is fairly likely to repeat the next year at nearly the same location give or take a week. |
|||
On September 29, 2008, the [[Phoenix (spacecraft)|Phoenix lander]] took pictures of snow falling from clouds 4.5 km above its [[Green Valley (Mars)|landing site]] near [[Heimdall (Martian crater)|Heimdall crater]]. The precipitation vaporized before reaching the ground, a phenomenon called [[virga]].<ref>{{cite web|url=http://www.nasa.gov/mission_pages/phoenix/news/phoenix-20080929.html|title=NASA Mars Lander Sees Falling Snow, Soil Data Suggest Liquid Past|accessdate=October 3, 2008|date=September 29, 2008}}</ref> |
|||
== Clouds == |
|||
{{Expand section|date=January 2010}} |
|||
[[File:Ice Clouds in Martian Arctic.gif|frame|right|Animation of ice clouds moving above the [[Phoenix (spacecraft)|Phoenix]] landing site over a period of ten minutes (August 29, 2008).]] |
|||
Mars' dust storms can kick up fine particles in the atmosphere around which clouds can form. These clouds can form very high up, up to {{convert|100|km|mi|abbr=on}} above the planet.<ref>[http://www.space.com/scienceastronomy/060828_mars_clouds.html Mars Clouds Higher Than Any On Earth]</ref> The clouds are very faint and can only be seen reflecting sunlight against the darkness of the night sky. In that respect, they look similar to the mesospheric clouds, also known as [[noctilucent clouds]] on Earth, which occur about {{convert|80|km|mi|abbr=on}} above our planet. |
|||
== Temperature == |
|||
Martian temperatures have been measured by various means: |
|||
Measurements of Martian temperature predate the "Space Age." However, early instrumentation and techniques of [[radio astronomy]] produced crude, differing results.<ref>{{cite journal | title= Radiation Measures on the Planet Mars | journal= Publications of the Astronomical Society of the Pacific | last=Pettit et al. | first=E. | volume=36 | issue=9 | date= September 1924 | pages=269–272|jstor=40693334|bibcode=1924PASP...36..269P}}</ref><ref>{{cite journal | title= Temperature Estimates of the Planet Mars | journal=Astronomische Nachrichten | last=Coblentz | first= W. | volume=224 | date=June 1925 | pages=361 | doi=10.1002/asna.19252242202}}</ref> |
|||
Early flyby probes ([[Mariner 4]]) and later orbiters used [[radio occultation]] to perform [[aeronomy]]. With chemical composition already deduced from [[spectroscopy]], temperature and pressure could then be derived. Nevertheless, flyby occultations can only measure properties along two [[transects]], at their trajectories' entries and exits from Mars' disk as seen from Earth. This results in weather "snapshots" at a particular area, at a particular time. Orbiters then increase the number of radio transects. |
|||
Later missions, starting with the dual [[Mariner 6]] and [[Mariner 7|7]] flybys, plus the Soviet [[Mars 2]] and [[Mars 2|3]], carried infrared detectors to measure radiant energy. Mariner 9 was the first to place an infrared radiometer and spectrometer in Mars orbit in 1971, along with its other instruments and radio transmitter. [[Viking 1]] and [[Viking 2|2]] followed, with not merely Infrared Thermal Mappers (IRTM).<ref>{{cite web | url=http://nssdc.gsfc.nasa.gov/nmc/experimentDisplay.do?id=1975-075A-02 | title=National Space Science Data Center: Infrared Thermal Mapper (IRTM) | accessdate=September 14, 2014}}</ref> The missions could also [[Corroborating evidence|corroborate]] these remote sensing datasets with not only their ''[[in situ]]'' lander metrology booms,<ref>{{cite web | url=http://nssdc.gsfc.nasa.gov/nmc/experimentDisplay.do?id=1975-075C-07 | title=National Space Science Data Center: Meteorology | accessdate=September 14, 2014}}</ref> but with higher-altitude temperature and pressure sensors for their descent.<ref>{{cite web | url=http://nssdc.gsfc.nasa.gov/nmc/experimentDisplay.do?id=1975-075C-02 | title=National Space Science Data Center: Atmospheric Structure | accessdate=September 14, 2014}}</ref> |
|||
Differing ''in situ'' values have been reported for the average temperature on Mars,<ref>{{cite web|url=http://hypertextbook.com/facts/2001/AlbertEydelman.shtml|title=Temperature on the Surface of Mars|work=The Physics Factbook|date=2001|first=Albert|last=Eydelman}}</ref> with a common value being {{convert|−55|C|K F}}.<ref>{{cite web | url=http://www.marsnews.com/focus/mars/ | title=Focus Sections :: The Planet Mars | publisher=MarsNews.com | accessdate=September 8, 2007}}</ref> Surface temperatures may reach a high of about {{convert|20|C|K F}} at noon, at the equator, and a low of about {{convert|−153|C|K F}} at the poles.<ref>{{cite web | url = http://quest.nasa.gov/aero/planetary/mars.html | title = Mars Facts | accessdate = June 20, 2013 | publisher = NASA}}</ref> Actual temperature measurements at the Viking landers' site range from {{convert|−17.2|C|K F}} to {{convert|−107|C|K F}}. The warmest soil temperature on the Mars surface estimated by the Viking Orbiter was {{convert|27|C|K F}}.<ref>James E. Tillman [http://www-k12.atmos.washington.edu/k12/resources/mars_data-information/temperature_overview.html Mars – Temperature Overview]</ref> The Spirit rover recorded a maximum daytime air temperature in the shade of {{convert|35|C|K F}}, and regularly recorded temperatures well above {{convert|0|C|K F}}, except in winter.<ref>[http://marsrover.nasa.gov/spotlight/20070612.html Extreme Planet Takes its Toll] ''Jet Propulsion Laboratory Featured Story, June 12, 2007''.</ref> |
|||
It has been reported that "On the basis of the nightime air temperature data, every northern spring and early northern summer yet observed were identical to within the level of experimental error (to within ±1 °C)" but that the "daytime data, however, suggest a somewhat different story, with temperatures varying from year-to-year by up to 6 °C in this season.<ref>{{cite journal | url=http://www.gfdl.gov/~gth/netscape/2003/liu0301.pdf | title=An assessment of the global, seasonal, and interannual spacecraft record of Martian climate in the thermal infrared | journal=[[Journal of Geophysical Research]] | last=Liu | first=Junjun |author2=Mark I. Richardson |author3=R. J. Wilson | volume=108 | issue=5089 | doi=10.1029/2002JE001921 | date=15 August 2003 | accessdate=September 8, 2007 | pages=5089 | format=– <sup>[http://scholar.google.co.uk/scholar?hl=en&lr=&q=author%3ALiu+intitle%3AAn+assessment+of+the+global%2C+seasonal%2C+and+interannual+spacecraft+record+of+Martian+climate+in+the+thermal+infrared&as_publication=%5B%5BJournal+of+Geophysical+Research%5D%5D&as_ylo=&as_yhi=&btnG=Search Scholar search]</sup> | bibcode=2003JGRE..108.5089L}} {{Dead link|date=April 2009}}</ref> This day-night discrepancy is unexpected and not understood". In southern spring and summer, variance is dominated by dust storms which increase the value of the night low temperature and decrease the daytime peak temperature.<ref name="Sheehan-13">William Sheehan, ''The Planet Mars: A History of Observation and Discovery,'' Chapter 13 ([http://www.uapress.arizona.edu/onlinebks/mars/chap13.htm available on the web])</ref> This results in a small (20 °C) decrease in average surface temperature, and a moderate (30 °C) increase in upper atmosphere temperature.<ref name="Gurwell">Mark A. Gurwell, Edwin A. Bergin, Gary J. Melnick and Volker Tolls, "Mars surface and atmospheric temperature during the 2001 global dust storm," ''Icarus, Volume 175, Issue 1, May 2005, Pages 23-3, {{DOI|10.1016/j.icarus.2004.10.009}}</ref> |
|||
'' |
|||
Before and after the Viking missions, newer, more advanced Martian temperatures were determined from Earth via microwave spectroscopy. As the microwave beam, of under 1 arcminute, is larger than the disk of the planet, the results are global averages.<ref>{{cite journal | title=Global Changes in the 0-70 km Thermal Structure of the Mars Atmosphere Derived from 1975 to 1989 Microwave CO Spectra | journal=Journal of Geophysical Research | last=Clancy |first=R. | volume=95 | issue=9 | date=August 30, 1990 | pages=14,543-14,554}}</ref> Later, the [[Mars Global Surveyor]]'s [[Thermal Emission Spectrometer]] and to a lesser extent [[2001 Mars Odyssey]]'s [[Thermal Emission Imaging System|THEMIS]] could not merely [[Reproducibility|reproduce]] infrared measurements but [[Sensor fusion|intercompare]] lander, rover, and Earth microwave data. The [[Mars Reconnaissance Orbiter]]'s [[Mars Climate Sounder]] can similarly [[Atmospheric sounding|derive atmospheric profiles]]. |
|||
The datasets "suggest generally colder atmospheric temperatures and lower dust loading in recent decades on Mars than during the Viking Mission,"<ref name="Bell et al.">{{cite journal | title=Mars Reconnaissance Orbiter Mars Color Imager (MARCI): Instrument Description, Calibration, and Performance | journal=Journal of Geophysical Research | author=Bell, J et al. | volume=114 | issue=8 | date=August 28, 2009}}</ref> though Viking data had previously been revised downward.<ref>{{cite journal | title=The Martian Atmosphere During the Viking I Mission, I: Infrared Measurements of Atmospheric Temperatures Revisited | journal= Icarus | author=Wilson, R. | author2=Richardson, M. | volume=145 | date=2000 | pages=555–579 | doi=10.1006/icar.2000.6378}}</ref> The TES data indicates "Much colder (10-20 K) global atmospheric temperatures were observed during the 1997 versus 1977 perihelion periods" and "that the global aphelion atmosphere of Mars is colder, less dusty, and cloudier than indicated by the established Viking climatology," again, taking into account the Wilson and Richardson revisions to Viking data.<ref name="Clancy et al 2000">{{cite journal | title=An intercomparison of ground-based millimeter, MGS TES, and Viking atmospheric temperature measurements: Seasonal and interannual variability of temperatures and dust loading in the global Mars atmosphere | journal=Journal of Geophysical Research | last=Clancy |first=R. | volume=105 | issue=4 | date=April 25, 2000 | pages=9553–9571}}</ref> |
|||
A later comparison, while admitting "it is the microwave record of air temperatures which is the most representative," attempted to merge the discontinuous spacecraft record. No measurable trend in global average temperature between Viking IRTM and MGS TES was visible. "Viking and MGS air temperatures are essentially indistinguishable for this period, suggesting that the Viking and MGS eras are characterized by essentially the same climatic state." It found "a [[Martian dichotomy|strong dichotomy]]" between the northern and southern hemispheres, a "very asymmetric paradigm for the Martian annual cycle: a northern spring and summer which is relatively cool, not very dusty, and relatively rich in water vapor and ice clouds; and a southern summer rather similar to that observed by Viking with warmer air temperatures, less water vapor and water ice, and higher levels of atmospheric dust."<ref>{{cite journal | author=Liu, J., Richardson, M. | title=An assessment of the global, seasonal, and interannual spacecraft record of Martian climate in the thermal infrared | journal=Journal of Geophysical Research | volume=108 | issue= 8 |date=August 2003 }}</ref> |
|||
The [[Mars Reconnaissance Orbiter]] MCS (Mars Climate Sounder) instrument was, upon arrival, able to operate jointly with MGS for a brief period; the less-capable Mars Odyssey THEMIS and Mars Express SPICAM datasets may also be used to span a single, well-calibrated record. While MCS and TES temperatures are generally consistent,<ref>{{cite journal | author=Kleinböhl, A., et al. | title=Mars Climate Sounder Limb Profile Retrieval of Atmospheric Temperature, Pressure, and Dust and Water Ice Opacity | journal=Journal of Geophysical Research | volume=114 | issue= E10 | date=Oct 2009 }}</ref> investigators report possible cooling below the analytical precision. "After accounting for this modeled cooling, MCS MY 28 temperatures are an average of 0.9 (daytime) and 1.7 K (night- time) cooler than TES MY 24 measurements".<ref>{{cite journal | author=Bandfield, J. L. et al. | title=Radiometric Comparision of Mars Climate Sounder and Thermal Emission Spectrometer Measurements | journal=Icarus | volume=225 | date=2013 | pages=28–39 | doi=10.1016/j.icarus.2013.03.007}}</ref> |
|||
== Atmospheric properties and processes == |
|||
[[File:PIA16460-Mars-AtmophereGases-20121102.jpg|thumb|left|300px|[[Mars|Planet Mars]] – [[Atmosphere of Mars|most abundant gases]] – ([[Curiosity rover]], [[Sample Analysis at Mars]] device, October 2012).]] |
|||
=== Low atmospheric pressure === |
|||
The [[Atmosphere of Mars|Martian atmosphere]] is composed mainly of [[carbon dioxide]] and has a mean [[surface pressure]] of about 600 [[pascal (unit)|pascals]] (Pa), much lower than the Earth's 101,000 Pa. One effect of this is that Mars' atmosphere can react much more quickly to a given energy input than that of Earth's atmosphere.<ref>{{cite web | title = Mars' low surface pressure. | author = [[Mars General Circulation Model]]ing Group | publisher = NASA | url = http://www-mgcm.arc.nasa.gov/mgcm/HTML/WEATHER/pressure.html | accessdate = February 22, 2007}}</ref> As a consequence, Mars is subject to strong thermal tides produced by solar heating rather than a gravitational influence. These tides can be significant, being up to 10% of the total atmospheric pressure (typically about 50 Pa). Earth's atmosphere experiences similar diurnal and semidiurnal tides but their effect is less noticeable because of Earth's much greater atmospheric mass. |
|||
Although the temperature on Mars can reach above freezing ({{convert|0|C|K F|abbr=on}}), liquid water is unstable over much of the planet, as the atmospheric pressure is below water's [[triple point]] and water ice [[Sublimation (phase transition)|sublimes]] into water vapor. Exceptions to this are the low-lying areas of the planet, most notably in the [[Hellas Planitia]] impact basin, the largest such crater on Mars. It is so deep that the atmospheric pressure at the bottom reaches 1155 Pa, which is above the triple point, so if the temperature exceeded 0 °C liquid water could exist there.{{Citation needed|date=August 2012}} |
|||
=== Wind === |
|||
[[File:PIA16813-MarsCuriosityRover-ParachuteFlapsInWind-20120812to20130113.gif|thumb|right|''[[Curiosity (rover)|Curiosity rover's]]'' parachute flapping in the Martian wind ([[HiRISE]]/[[Mars Reconnaissance Orbiter|MRO]]) (August 12, 2012 to January 13, 2013).]] |
|||
The surface of Mars has a very low [[thermal inertia]], which means it heats quickly when the sun shines on it. Typical daily temperature swings, away from the polar regions, are around 100 K. On Earth, winds often develop in areas where thermal inertia changes suddenly, such as from sea to land. There are no seas on Mars, but there are areas where the thermal inertia of the soil changes, leading to morning and evening winds akin to the sea breezes on Earth.<ref>{{cite web | title = Mars' desert surface. | author = [[Mars General Circulation Model]]ing Group | publisher = NASA |
|||
| url = http://www-mgcm.arc.nasa.gov/mgcm/HTML/WEATHER/surface.html | accessdate = February 25, 2007}}</ref> The Antares project "Mars Small-Scale Weather" (MSW) has recently identified some minor weaknesses in current global climate models (GCMs) due to the GCMs' more primitive soil modeling "heat admission to the ground and back is quite important in Mars, so soil schemes have to be quite accurate. "<ref>[http://websrv2.tekes.fi/opencms/opencms/OhjelmaPortaali/Paattyneet/Antares/en/Dokumenttiarkisto/Viestinta_ja_aktivointi/Lehdistotiedotteet/Press/fallpress2003.htx.i1948.doc Antares project "Mars Small-Scale Weather" (MSW)]</ref> Those weaknesses are being corrected and should lead to more accurate future assessments, but make continued reliance on older predictions of modeled Martian climate somewhat problematic. |
|||
[[File:MarsDustDevi-AmazonisPlanitia-MGS-MOC-20010401-E03-00938.gif|thumb|left|200px|[[Dust devil tracks|Martian Dust Devil]] – in [[Amazonis Planitia]] (April 10, 2001) ([http://www.nasa.gov/mission_pages/MRO/multimedia/pia15116.html also]) ([http://www.youtube.com/watch?v=0t0LWFHB8Qo video (02:19)]).]] |
|||
At low latitudes the [[Hadley circulation]] dominates, and is essentially the same as the process which on Earth generates the [[trade winds]]. At higher latitudes a series of high and low pressure areas, called [[baroclinic]] pressure waves, dominate the weather. Mars is dryer and colder than Earth, and in consequence dust raised by these winds tends to remain in the atmosphere longer than on Earth as there is no precipitation to wash it out (excepting CO<sub>2</sub> snowfall).<ref name="François Forget">{{cite web | title = Alien Weather at the Poles of Mars |
|||
| author = François Forget |
|||
| publisher = [[Science (journal)|Science]] |
|||
| url = http://www-mars.lmd.jussieu.fr/mars/publi/forget_science2004.pdf |
|||
| accessdate = February 25, 2007}}</ref> One such [[cyclone|cyclonic]] storm was recently captured by the Hubble space telescope (pictured below). |
|||
One of the major differences between Mars' and Earth's Hadley circulations is their speed<ref>{{cite web | title = The Martian tropics... |
|||
| author = [[Mars General Circulation Model]]ing Group |
|||
| publisher = [[NASA]] |
|||
| url = http://www-mgcm.arc.nasa.gov/mgcm/HTML/WEATHER/tropics.html |
|||
| accessdate=September 8, 2007}}</ref> which is measured on an [[overturning timescale]]. The overturning timescale on Mars is about 100 [[Timekeeping on Mars|Martian days]] while on Earth, it is over a year. |
|||
=== Effect of dust storms === |
|||
{{See also|Martian soil#Atmospheric dust}} |
|||
[[File:hellas basin.gif|thumb|200px|right|2001 Hellas Basin dust storm]] |
|||
[[File:Mars dust opacities MER-B Sol 1205 to 1235.jpg|thumb|200px|right|Time-lapse composite of Martian horizon during Sols 1205 (0.94), 1220 (2.9), 1225 (4.1), 1233 (3.8), 1235 (4.7) shows how much sunlight the July 2007 dust storms blocked; Tau of 4.7 indicates 99% blocked.]] |
|||
{{multiple image |
|||
|align=left |
|||
|direction=vertical |
|||
|width=200 |
|||
|image1=PIA16450-MarsDustStorm-20121118.jpg |
|||
|image2=PIA16454-MarsDustStorm-20121125.jpg |
|||
|caption1=November 18, 2012 |
|||
|caption2=November 25, 2012 |
|||
|header=[[Dust Storm]] on Mars. |
|||
|footer=Locations of [[Opportunity rover|Opportunity]] and [[Curiosity rover|Curiosity]] rovers are noted ([[Mars Reconnaissance Orbiter|MRO]]).}} |
|||
When the [[Mariner 9]] probe arrived at [[Mars]] in 1971, the world expected to see crisp new pictures of surface detail. Instead they saw a near planet-wide dust storm<ref>{{cite web |title=Planet Gobbling Dust Storms |author=NASA |publisher=NASA |url=http://science.nasa.gov/headlines/y2001/ast16jul_1.htm |accessdate=February 22, 2007 }}</ref> with only the giant volcano [[Olympus Mons]] showing above the haze. The storm lasted for a month, an occurrence scientists have since learned is quite common on Mars. |
|||
As observed by the Viking spacecraft from the surface,<ref name="Sheehan-13" /> "during a global dust storm the diurnal temperature range narrowed sharply, from fifty degrees to only about ten degrees, and the wind speeds picked up considerably—indeed, within only an hour of the storm's arrival they had increased to {{convert|17|m/s|km/h|abbr=on}}, with gusts up to {{convert|26|m/s|km/h|abbr=on}}. Nevertheless, no actual transport of material was observed at either site, only a gradual brightening and loss of contrast of the surface material as dust settled onto it." |
|||
On June 26, 2001, the Hubble Space Telescope spotted a dust storm brewing in [[Hellas Basin]] on Mars (pictured right). A day later the storm "exploded" and became a global event. Orbital measurements showed that this dust storm reduced the average temperature of the surface and raised the temperature of the atmosphere of Mars by 30 °C.<ref name="Gurwell" /> The low density of the Martian atmosphere means that winds of {{convert|18|to|22|m/s|km/h|abbr=on}} are needed to lift dust from the surface, but since Mars is so dry, the dust can stay in the atmosphere far longer than on Earth, where it is soon washed out by rain. The season following that dust storm had daytime temperatures 4 °C below average. This was attributed to the global covering of light-colored dust that settled out of the dust storm, temporarily increasing Mars' [[albedo]].<ref name=Fenton /> |
|||
In mid-2007 a planet-wide dust storm posed a serious threat to the solar-powered Spirit and Opportunity [[Mars Exploration Rover]]s by reducing the amount of energy provided by the solar panels and necessitating the shut-down of most science experiments while waiting for the storms to clear.<ref>[http://marsrovers.jpl.nasa.gov/newsroom/pressreleases/20070731a.html Mars Exploration Rover Status Report Concern Increasing About Opportunity]</ref> Following the dust storms, the rovers had significantly reduced power due to settling of dust on the arrays. |
|||
Dust storms are most common during [[perihelion]], when the planet receives 40 percent more sunlight than during [[aphelion]]. During aphelion water ice clouds form in the atmosphere, interacting with the dust particles and affecting the temperature of the planet.<ref>{{cite web | title = Duststorms on Mars |publisher = whfreeman.com | url = http://www.whfreeman.com/ENVIRONMENTALGEOLOGY/EXMOD36/F3614.HTM |accessdate=February 22, 2007}}</ref> |
|||
It has been suggested that dust storms on Mars could play a role in storm formation similar to that of water clouds on Earth.{{Citation needed|date=February 2007}} Observation since the 1950s has shown that the chances of a planet-wide dust storm in a particular Martian year are approximately one in three.<ref>{{cite journal |title=Interannual variability of planet-encircling dust storms on Mars | last1=Zurek | first1=Richard W. |first2=Leonard J. |last2=Martin |publisher=[[Journal of Geophysical Research]] |date=1993 | volume=98 | issue=E2 | journal = Journal of Geophysical Research | pages=3247–3259 | url=http://www.agu.org/pubs/crossref/1993/92JE02936.shtml | accessdate=March 16, 2007 |bibcode=1993JGR....98.3247Z |doi = 10.1029/92JE02936}}</ref> |
|||
==== Saltation ==== |
|||
The process of [[Saltation (geology)|geological saltation]] is quite important on Mars as a mechanism for adding particulates to the atmosphere. Saltating sand particles have been observed on the MER Spirit rover.<ref>G. Landis, et al., "Dust and Sand Deposition on the MER Solar Arrays as Viewed by the Microscopic Imager," 37th Lunar and Planetary Science Conference, Houston TX, March 13–17, 2006. [http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1932.pdf pdf file] (also summarized in NASA Glenn [http://www.grc.nasa.gov/WWW/RT/2006/RP/RPV-landis2.html Research and Technology 2006] report)</ref> Theory and real world observations have not agreed with each other, classical theory missing up to half of real-world saltating particles.<ref>{{cite journal |last=Kok |first=Jasper F. |authorlink= |author2=Renno, Nilton O. |date=2008 |title= Electrostatics in Wind-Blown Sand |journal=[[Physical Review Letters]] |volume=100 |issue= 1|pages=014501 |doi=10.1103/PhysRevLett.100.014501 |url= |accessdate= |quote= |pmid=18232774 |bibcode=2008PhRvL.100a4501K|arxiv = 0711.1341 }}</ref> A new model more closely in accord with real world observations demonstrates that saltating particles create an electrical field that increases the saltation effect. Mars grains saltate in 100 times higher and longer trajectories and reach 5-10 times higher velocities than Earth grains do.<ref>{{cite journal |last=Almeida |first=Murilo P. |authorlink= |date=2008 |title=Giant saltation on Mars |journal=[[Proceedings of the National Academy of Sciences|PNAS]] |volume=105 |issue= 17|pages=6222–6226 |doi=10.1073/pnas.0800202105 |url= |accessdate= |quote= |pmid=18443302 |pmc=2359785 |bibcode = 2008PNAS..105.6222A |display-authors=1 |last2=Parteli |first2=E. J. R. |last3=Andrade |first3=J. S. |last4=Herrmann |first4=H. J. }}</ref> |
|||
=== Repeating northern annular cloud === |
|||
[[File:Mars cyclone.jpg|thumb|right|Hubble view of the colossal polar cloud on Mars]] |
|||
A large doughnut shaped cloud appears in North polar region of Mars around the same time every Martian year and of about the same size.<ref name=mgs>[http://mpfwww.jpl.nasa.gov/mgs/gallery/20050912-repeatNPWIC.html Mars Global Surveyor - "8 Year Anniversary"]</ref> It forms in the morning, dissipates by the Martian afternoon.<ref name=mgs /> The outer diameter of the cloud is roughly {{convert|1000|mi|km|disp=flip|abbr=on}}, and the inner hole or eye is {{convert|320|km|mi|abbr=on}} across.<ref name=cornell /> The cloud is thought to be composed of water-ice,<ref name=cornell /> so it is white in color, unlike the more common dust storms. |
|||
It looks like a cyclonic storm, similar to a hurricane, but it does not rotate.<ref name=mgs /> The cloud appears during the northern summer and at high latitude. Speculation is that this is due to unique climate conditions near the northern pole.<ref name=cornell>{{cite web | url=http://www.news.cornell.edu/releases/May99/mars.cyclone.deb.html | title=Colossal cyclone swirling near Martian north pole is observed by Cornell-led team on Hubble telescope | publisher=Cornell News | author=David Brand and Ray Villard | date=May 19, 1999 | accessdate=September 6, 2007}}</ref> Cyclone-like storms were first detected during the Viking orbital mapping program, but the northern annular cloud is nearly three times larger.<ref name=cornell /> The cloud has also been detected by various probes and telescopes including the [[Hubble Space Telescope|Hubble]] and [[Mars Global Surveyor]].<ref name=mgs /><ref name=cornell /> |
|||
Other repeating events are dust storms and [[Dust devil tracks|dust devils]].<ref name=cornell /> |
|||
=== Methane presence === |
|||
{{See also|Atmosphere of Mars#Methane}} |
|||
[[File:Martian Methane Map.jpg|thumb|right|Methane map]] |
|||
Although [[methane]] is a greenhouse gas on Earth, the small amounts that have been claimed to be present on Mars would have little effect on the Martian global climate. Trace amounts of [[methane]] (CH<sub>4</sub>) at concentration of several parts per billion (ppb), were first reported in the [[Atmosphere of Mars#Methane|atmosphere of Mars]] by a team at the NASA Goddard Space Flight Center in 2003.<ref name="methane3">Mumma, M. J.; Novak, R. E.; DiSanti, M. A.; Bonev, B. P., [http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2003DPS....35.1418M&db_key=AST&data_type=HTML&format= "A Sensitive Search for Methane on Mars"] (abstract only). American Astronomical Society, DPS meeting #35, #14.18.</ref><ref name="repeat1">{{cite web|title=Mars Methane Boosts Chances for Life|author=Michael J. Mumma|publisher=Skytonight.com|url=http://www-mgcm.arc.nasa.gov/MGCM.html|accessdate=February 23, 2007| archiveurl= http://web.archive.org/web/20070220100252/http://www-mgcm.arc.nasa.gov/MGCM.html| archivedate= February 20, 2007 | deadurl= no}}</ref> |
|||
In March 2004 the [[Mars Express Orbiter]]<ref name="Formisano">{{cite journal|title=Detection of Methane in the Atmosphere of Mars|author=V. Formisano, S. Atreya T. Encrenaz, N. Ignatiev, M. Giuranna|journal=Science|volume=306|issue=5702|pages=1758–1761|date=2004|url=|doi=10.1126/science.1101732|pmid=15514118|bibcode = 2004Sci...306.1758F }}</ref><ref>{{cite web | url=http://www.astronomy.com/asy/default.aspx?c=a&id=4009 | publisher=Astronomy Magazine | title=Titan, Mars methane may be on ice | author=Francis Reddy | date=March 7, 2006 | accessdate=September 6, 2007}}</ref><ref name="methane-me">{{cite journal | author= V. Formisano, S. Atreya, T. Encrenaz, N. Ignatiev, M. Giuranna | title= Detection of Methane in the Atmosphere of Mars | journal = [[Science (journal)|Science]] | date= 2004 | volume= 306 | pages= 1758–1761 |doi= 10.1126/science.1101732 | pmid= 15514118 | issue= 5702|bibcode = 2004Sci...306.1758F }}</ref><ref name="methane">{{cite news | date = March 30, 2004 | title = Mars Express confirms methane in the Martian atmosphere | publisher = [[ESA]] | url = http://www.esa.int/SPECIALS/Mars_Express/SEMZ0B57ESD_0.html | accessdate = August 19, 2008 }}</ref> and ground based observations from [[Canada-France-Hawaii Telescope]]<ref name="Krasnopolskya">{{cite journal|title=Detection of methane in the Martian atmosphere: evidence for life?|author=V. A. Krasnopolskya, J. P. Maillard, T. C. Owen|journal=Icarus|volume=172|issue=2|pages=537–547|date=2004|url=|doi=10.1016/j.icarus.2004.07.004|bibcode=2004Icar..172..537K}}</ref> also suggested the presence of methane in the atmosphere with a mole fraction of about 10 nmol/mol.<ref name="methane">{{cite web|title=Mars Express confirms methane in the Martian atmosphere|author=[[ESA]] Press release|publisher=[[ESA]]|url=http://www.esa.int/SPECIALS/Mars_Express/SEMZ0B57ESD_0.html|accessdate=March 17, 2006| archiveurl= http://web.archive.org/web/20060224102528/http://www.esa.int/SPECIALS/Mars_Express/SEMZ0B57ESD_0.html| archivedate= February 24, 2006 | deadurl= no}}</ref> However, the complexity of these observations has sparked discussion as to the reliability of the results.<ref name="Zahnle11">Zahnle, Kevin; Freedman, Richard S.; Catling, David C., [http://adsabs.harvard.edu/abs/2011Icar..212..493Z] (abstract only). Icarus, Volume 212, Issue 2, p. 493-503.</ref> |
|||
[[File:PIA19088-MarsCuriosityRover-MethaneSource-20141216.png|thumb|left|300px|[[Atmosphere of Mars#Methane|Methane]] (CH<sub>4</sub>) on Mars - potential sources and sinks.]] |
|||
Since breakup of that much methane by ultraviolet light would only take 350 years under current Martian conditions, if methane is present some sort of active source must be replenishing the gas.<ref>{{cite journal | author=Martin Baucom | title=Life on Mars? | journal=[[American Scientist]] | date=2006 | volume=94 | issue=2 | url=http://www.americanscientist.org/template/AssetDetail/assetid/49613|accessdate = February 26, 2007 |archiveurl = http://web.archive.org/web/20060223045353/http://www.americanscientist.org/template/AssetDetail/assetid/49613 |archivedate = February 23, 2006}}</ref> |
|||
[[Clathrate hydrates]],<ref>{{cite journal|title=Variability of the methane trapping in Martian subsurface clathrate hydrates|journal=Planetary and Space Science|date=January 2009|first=Caroline|last=Thomas|author2=et al.|volume=57|issue=1|pages=42–47|doi=10.1016/j.pss.2008.10.003|url=http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V6T-4TPHRT5-2&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=e64bf861e4ef71f5336823d5dc1b9e12|format=|accessdate=August 2, 2009|bibcode = 2009P&SS...57...42T |arxiv = 0810.4359 }}</ref> or water-rock reactions<ref name="Tazaz13">Tazaz, Amanda M.; Bebout, Brad M.; Kelley, Cheryl A.; Poole, Jennifer; Chanton, Jeffrey P. [http://adsabs.harvard.edu/abs/2013Icar..224..268T] (abstract only). Icarus, Volume 224, Issue 2, p. 268-275.</ref> could be possible geological sources of methane but there is presently no consensus on the source or existence of Martian methane. |
|||
The [[Curiosity rover]] landed on Mars in August 2012. It is able to make precise abundance measurements and also distinguish between different isotopologues of methane.<ref>{{cite web|url=http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=2765&mode=thread&order=0&thold=0|title=Making Sense of Mars Methane|accessdate=October 8, 2008|last=Tenenbaum|first=David|date=June 9, 2008|work=Astrobiology Magazine|archiveurl= http://web.archive.org/web/20080923195833/http://astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=2765&mode=thread&order=0&thold=0| archivedate= September 23, 2008 | deadurl= no}}</ref> The first measurements with the [[Sample Analysis at Mars|Tunable Laser Spectrometer (TLS)]] indicate that there is less than 5 ppb of methane at the landing site.<ref>{{cite web |url=http://www.ustream.tv/nasajpl |title=Mars Curiosity Rover News Telecon -November 2, 2012}}</ref><ref name="Science-20121102">{{cite web |last=Kerr |first=Richard A.|title=Curiosity Finds Methane on Mars, or Not|url=http://news.sciencemag.org/sciencenow/2012/11/curiosity-finds-methane-on-mars-.html |date=November 2, 2012|publisher=[[Science (journal)]] |accessdate=November 3, 2012 }}</ref><ref name="Space-20121102">{{cite web|last=Wall |first=Mike |title=Curiosity Rover Finds No Methane on Mars —Yet|url=http://www.space.com/18333-mars-rover-curiosity-methane-measurements.html |date=November 2, 2012|publisher=[[Space.com]] |accessdate=November 3, 2012 }}</ref><ref name="NYT-20121102">{{cite news|last=Chang|first=Kenneth |title=Hope of Methane on Mars Fades|url=http://www.nytimes.com/2012/11/03/science/space/hopes-for-methane-on-mars-deflated.html |date=November 2, 2012 |publisher=[[New York Times]] |accessdate=November 3, 2012 }}</ref> On September 19, 2013 NASA scientists used further measurements from Curiosity to report a non-detection of [[atmospheric methane]] with a measured value of {{val|0.18|0.67}} ppbv corresponding to an upper limit of 1.3 ppbv (95% confidence limit).<ref name="SJ-20130919">{{cite journal |last1=Webster |first1=Christopher R. |last2=Mahaffy |first2=Paul R. |last3=Atreya |first3=Sushil K. |last4=Flesch |first4=Gregory J. |last5=Farley |first5=Kenneth A. |title=Low Upper Limit to Methane Abundance on Mars |url=http://www.sciencemag.org/content/early/2013/09/18/science.1242902.abstract |date=September 19, 2013 |journal=[[Science (journal)|Science]] |doi=10.1126/science.1242902 |accessdate=September 19, 2013 }}</ref> |
|||
On 16 December 2014, NASA reported the ''Curiosity'' rover detected a "tenfold spike", likely localized, in the amount of [[methane]] in the [[Atmosphere of Mars|Martian atmosphere]]. Sample measurements taken "a dozen times over 20 months" showed increases in late 2013 and early 2014, averaging "7 parts of methane per billion in the atmosphere." Before and after that, readings averaged around one-tenth that level.<ref name="NASA-20141216-GW">{{cite web |last=Webster |first=Guy |last2=Jones |first2=Nancy Neal |last3=Brown |first3=Dwayne |title=NASA Rover Finds Active and Ancient Organic Chemistry on Mars |url=http://www.jpl.nasa.gov/news/news.php?release=2014-432 |date=December 16, 2014 |work=[[NASA]] |accessdate=December 16, 2014 }}</ref><ref name="NYT-20141216-KC">{{cite news |last=Chang |first=Kenneth |title=‘A Great Moment’: Rover Finds Clue That Mars May Harbor Life |url=http://www.nytimes.com/2014/12/17/science/a-new-clue-in-the-search-for-life-on-mars.html |date=December 16, 2014 |work=[[New York Times]] |accessdate=December 16, 2014 }}</ref> |
|||
The Indian [[Mars Orbiter Mission]], launched in November 5, 2013, will attempt to detect and map the sources of methane, if they exist.<ref name="ISSDC-201209">{{cite web |author=Staff |title=Mangalyaan -Mission Objectives |url=http://www.isro.org/pslv-c25/mission-objective.aspx |date=September 2012 |work=Indian Space Science Data Centre |accessdate=October 8, 2013}}</ref> The [[ExoMars Trace Gas Orbiter]] planned to launch in 2016 would further study the methane,<ref>{{Cite news|first=Paul|last=Rincon|authorlink=|title=Agencies outline Mars initiative|date=July 9, 2009|publisher=|url=http://news.bbc.co.uk/2/hi/science/nature/8130393.stm|work=BBC News|pages=|accessdate=July 26, 2009|language=}}</ref><ref>{{Cite news| first=| last=| authorlink=| title=NASA orbiter to hunt for source of Martian methane in 2016|date=March 6, 2009|publisher=| url=http://www.thaindian.com/newsportal/health/nasa-orbiter-to-hunt-for-source-of-martian-methane-in-2016_100163335.html| work=Thaindian News| pages=| accessdate=July 26, 2009| language=}}</ref> as well as its decomposition products such as [[formaldehyde]] and [[methanol]]. |
|||
=== Carbon dioxide carving === |
|||
[[Mars Reconnaissance Orbiter]] images suggest an unusual erosion effect occurs based on Mars' unique climate. Spring warming in certain areas leads to CO<sub>2</sub> ice subliming and flowing upwards, creating highly unusual erosion patterns called "spider gullies".<ref name="nyt20071212">{{cite news| url=http://www.nytimes.com/2007/12/12/science/space/12mars.html?ex=1355202000&en=c42725b421422007&ei=5124&partner=permalink&exprod=permalink | work=The New York Times | title=Mars Rover Finding Suggests Once Habitable Environment | first=Kenneth | last=Chang | date=December 12, 2007 | accessdate=April 30, 2010}}</ref> Translucent CO<sub>2</sub> ice forms over winter and as the spring sunlight warms the surface, it vaporizes the CO<sub>2</sub> to gas which flows uphill under the translucent CO<sub>2</sub> ice. Weak points in that ice lead to CO<sub>2</sub> geysers.<ref name="nyt20071212" /> |
|||
== Mountains == |
|||
[[File:PIA16463-MarsVolatiles-20121102.jpg|thumb|250px|left|[[Mars|Planet Mars]] – [[Atmosphere of Mars|volatile gases]] – ([[Curiosity rover]], October 2012).]] |
|||
Martian storms are significantly affected by Mars' large mountain ranges.<ref>{{cite web | title=The Martian mountain ranges... | author=[[Mars General Circulation Model]]ing Group | publisher=[[NASA]] | url=http://www-mgcm.arc.nasa.gov/mgcm/HTML/WEATHER/mountains.html | accessdate = September 8, 2007}}</ref> [[List of mountains on Mars|Individual mountains]] like record holding [[Olympus Mons]] ({{convert|27|km|ft|abbr=on}}) can affect local weather but larger weather effects are due to the larger collection of volcanoes in the [[Tharsis]] region. |
|||
One unique repeated weather phenomena involving Mountains is a spiral dust cloud that forms over [[Arsia Mons]]. The spiral dust cloud over Arsia Mons can tower {{convert|15|to|30|km|ft|abbr=on}} above the volcano.<ref>{{cite web | url=http://photojournal.jpl.nasa.gov/catalog/PIA04294 | title=PIA04294: Repeated Clouds over Arsia Mons | publisher=[[NASA]] | accessdate=September 8, 2007}}</ref> Clouds are present around Arsia Mons throughout the Martian year, peaking in late summer.<ref name=icarus>{{cite journal|journal=[[Icarus (journal)|Icarus]]|title=Interannual variability of water ice clouds over major martian volcanoes observed by MOC|date=2006|author=Benson|volume=184|pages=365–371|doi=10.1016/j.icarus.2006.03.014|last2=James|first2=P|last3=Cantor|first3=B|last4=Remigio|first4=R|bibcode=2006Icar..184..365B|display-authors=1|issue=2}}</ref> |
|||
Clouds surrounding mountains display a seasonal variability. Clouds at Olympus Mons and Ascreaus Mons appear in northern hemisphere spring and summer, reaching a total maximum area of approximately 900,000 km<sup>2</sup> and 1,000,000 km<sup>2</sup> respectively in late spring. Clouds around [[Alba Patera]] and [[Pavonis Mons]] show an additional, smaller peak in late summer. Very few clouds were observed in winter. Predictions from the Mars General Circulation Model are consistent with these observations.<ref name=icarus /> |
|||
== Polar caps == |
|||
[[File:Mars Ice Age PIA04933 modest.jpg|200px|thumb|right|An illustration of what Mars might have looked like during an [[ice age]] between 2.1 million and 400,000 years ago, when Mars's axial tilt is believed to have been much larger than today.]] |
|||
[[File:PIA11858 Starburst Spider.jpg|200px|thumb|right|[[HiRISE]] image of "dark dune spots" and fans formed by eruptions of CO<sub>2</sub> gas [[Geysers on Mars|geysers on Mars']] south polar ice sheet.]] |
|||
Mars has ice caps at its north pole and south pole, which mainly consist of water ice; however, there is frozen carbon dioxide ([[dry ice]]) present on their surfaces. Dry ice accumulates in the north polar region ([[Planum Boreum]]) in winter only, subliming completely in summer, while the south polar region additionally has a permanent dry ice cover up to eight meters (25 feet) thick.<ref>{{cite web |
|||
| last = Darling | first = David |
|||
| title = Mars, polar caps, ENCYCLOPEDIA OF ASTROBIOLOGY, ASTRONOMY, AND SPACEFLIGHT |
|||
| url = http://www.daviddarling.info/encyclopedia/M/Marspoles.html |
|||
| accessdate = February 26, 2007}}</ref> This difference is due to the higher elevation of the south pole. |
|||
So much of the atmosphere can condense at the winter pole that the atmospheric pressure can vary by up to a third of its mean value. This condensation and evaporation will cause the proportion of the noncondensable gases in the atmosphere to change inversely.<ref name="François Forget" /> The eccentricity of Mars's orbit affects this cycle, as well as other factors. In the spring and autumn wind due to the carbon dioxide sublimation process is so strong that it can be a cause of the global dust storms mentioned above.<ref>{{cite web | title = Mars' dry ice polar caps... |
|||
| author = [[Mars General Circulation Model]]ing Group |
|||
| publisher = NASA |
|||
| url = http://www-mgcm.arc.nasa.gov/mgcm/HTML/WEATHER/ice.html |
|||
| accessdate = February 22, 2007}}</ref> |
|||
The northern polar cap has a diameter of approximately 1,000 km during the northern Mars summer,<ref>{{cite web | title = MIRA's Field Trips to the Stars Internet Education Program |
|||
| author = |
|||
| publisher = Mira.org |
|||
| url = http://www.mira.org/fts0/planets/097/text/txt002x.htm |
|||
| accessdate = February 26, 2007}}</ref> |
|||
and contains about 1.6 million cubic kilometres of ice, which if spread evenly on the cap would be 2 km thick.<ref name="brown">{{cite journal | last = Carr | first = Michael H. |title=Oceans on Mars: An assessment of the observational evidence and possible fate | journal=Journal of Geophysical Research | date=2003 | volume=108 | issue=5042 | pages=24 | doi=10.1029/2002JE001963 | bibcode=2003JGRE..108.5042C}}</ref> (This compares to a volume of 2.85 million cubic kilometres for the [[Greenland ice sheet]].) The southern polar cap has a diameter of 350 km and a maximum thickness of 3 km.<ref name="nasa">{{cite web |
|||
| last = Phillips |
|||
| first = Tony |
|||
| title = Mars is Melting, Science at NASA |
|||
| url = http://science.nasa.gov/headlines/y2003/07aug_southpole.htm |
|||
| accessdate = February 26, 2007 }}</ref> Both polar caps show spiral troughs, which were formerly believed to form as a result of differential solar heating, coupled with the sublimation of ice and condensation of water vapor.<ref>{{cite journal | title=How do spiral troughs form on Mars? | last=Pelletier | first=J. D. | journal=Geology | volume=32 | date=2004 | pages=365–367| url=http://www.gsajournals.org/perlserv/?request=get-abstract&doi=10.1130%2FG20228.2|accessdate=February 27, 2007 | doi=10.1130/G20228.2|bibcode = 2004Geo....32..365P | issue=4 }}</ref><ref>{{cite web|url=http://www.marstoday.com/viewpr.html?pid=13914|publisher=Mars Today|title=Mars Polar Cap Mystery Solved|date=March 25, 2004|accessdate=January 23, 2007}}</ref> Recent analysis of ice penetrating radar data from [[SHARAD]] has demonstrated that the spiral troughs are formed from a unique situation in which high density [[katabatic wind]]s descend from the polar high to transport ice and create large wavelength bedforms.<ref>{{cite journal | title=Onset and migration of spiral troughs on Mars revealed by orbital radar | author=Smith, Isaac B.; Holt, J. W. | journal=Nature | volume=465 | date=2010 | pages=450–453| url=http://www.nature.com/nature/journal/v465/n7297/full/nature09049.html | doi=10.1038/nature09049|bibcode = 2010Nature....32..450P | issue=4 }}</ref><ref>{{cite web|url=http://www.space.com/8494-mystery-spirals-mars-finally-explained.html|publisher=Space.com|title=Mystery Spirals on Mars Finally Explained|date=May 26, 2010|accessdate=May 26, 2010}}</ref> The spiral shape comes from [[Coriolis effect]] forcing of the winds, much like winds on earth spiral to form a hurricane. The troughs did not form with either ice cap, instead they began to form between 2.4 million and 500,000 years ago, after three fourths of the ice cap was in place. This suggests that a climatic shift allowed for their onset. Both polar caps shrink and regrow following the temperature fluctuation of the Martian seasons; there are also [[Climate of Mars#Evidence for recent climatic change|longer-term trends]] that are not fully understood. |
|||
During the southern hemisphere spring, solar heating of dry ice deposits at the south pole leads in places to accumulation of pressurized CO<sub>2</sub> gas below the surface of the semitransparent ice, warmed by absorption of radiation by the darker substrate. After attaining the necessary pressure, the gas bursts through the ice in geyser-like plumes. While the eruptions have not been directly observed, they leave evidence in the form of "dark dune spots" and lighter fans atop the ice, representing sand and dust carried aloft by the eruptions, and a spider-like pattern of grooves created below the ice by the outrushing gas.<ref name="THEMIS">{{cite web |
|||
| last = Burnham |
|||
| first = Robert |
|||
| authorlink = |
|||
| title = Gas jet plumes unveil mystery of 'spiders' on Mars |
|||
| work = [[Arizona State University]] web site |
|||
| publisher = |
|||
| date = August 16, 2006 |
|||
| url = http://www.asu.edu/news/stories/200608/20060818_marsplumes.htm |
|||
| doi = |
|||
| accessdate = August 29, 2009}}</ref><ref name="Kieffer">{{cite journal |
|||
| last1 = Kieffer |
|||
| first1 = Hugh H. |
|||
| last2 = Christensen |first2=Philip R. |last3=Titus |first3=Timothy N. |
|||
| title = CO<sub>2</sub> jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap |
|||
| journal = [[Nature (journal)|Nature]] |
|||
| volume = 442 |
|||
| issue =7104 |
|||
| pages = 793–796 |
|||
| publisher = [[Nature Publishing Group]] |
|||
| location = |
|||
| date = August 17, 2006 |
|||
| url = http://www.nature.com/nature/journal/v442/n7104/full/nature04945.html |
|||
| issn = |
|||
| doi = 10.1038/nature04945 |
|||
| id = |
|||
| accessdate = August 31, 2009 |
|||
| pmid = 16915284|bibcode = 2006Natur.442..793K }}</ref> (see [[Geysers on Mars]].) Eruptions of [[nitrogen]] gas observed by ''[[Voyager 2]]'' on [[Triton (moon)|Triton]] are thought to occur by a similar mechanism. |
|||
== Solar wind == |
|||
Mars lost most of its magnetic field about four billion years ago. As a result, [[solar wind]] and [[cosmic radiation]] interacts directly with the Martian ionosphere. This keeps the atmosphere thinner than it would otherwise be by solar wind action constantly stripping away atoms from the outer atmospheric layer.<ref>[http://science.nasa.gov/headlines/y2001/ast31jan_1.htm The Solar Wind at Mars<!-- Bot generated title -->]</ref> Most of the historical atmospheric loss on Mars can be traced back to this solar wind effect. Current theory posits a weakening solar wind and thus today's atmosphere stripping effects are much less than those in the past when the solar wind was stronger.{{Citation needed|date=August 2011}} |
|||
== Seasons == |
|||
{{See also|Astronomy on Mars#Seasons}} |
|||
[[File:Sublimation Of Ice In Martian Spring.jpg|thumb|In spring, [[Sublimation (phase transition)|sublimation]] of ice causes sand from below the ice layer to form fan-shaped deposits on top of the seasonal ice.]] |
|||
[[Mars]] has an [[axial tilt]] of 25.2°. This means that there are seasons on Mars, just as on Earth. The [[Orbital eccentricity|eccentricity]] of Mars' orbit is 0.1, much greater than the Earth's present orbital eccentricity of about 0.02. The large eccentricity causes the [[insolation]] on Mars to vary as the planet orbits the Sun (the Martian year lasts 687 days, roughly 2 Earth years). As on Earth, Mars' [[obliquity]] dominates the seasons but, because of the large eccentricity, winters in the southern hemisphere are long and cold while those in the North are short and warm. |
|||
It is now widely believed that ice accumulated when Mars' orbital tilt was very different from what it is now (the axis the planet spins on has considerable "wobble," meaning its angle changes over time).<ref>Madeleine, J. et al. 2007. Mars: A proposed climatic scenario for northern mid-latitude glaciation. Lunar Planet. Sci. 38. Abstract 1778.</ref><ref>Madeleine, J. et al. 2009. Amazonian northern mid-latitude glaciation on Mars: A proposed climate scenario. Icarus: 203. 300-405.</ref><ref>Mischna, M. et al. 2003. On the orbital forcing of martian water and CO2 cycles: A general circulation model study with simplified volatile schemes. J. Geophys. Res. 108. (E6). 5062.</ref> A few million years ago, the tilt of the axis of Mars was 45 degrees instead of its present 25 degrees. Its tilt, also called obliquity, varies greatly because its two tiny moons cannot stabilize it like our moon. |
|||
Many features on Mars, especially in the Ismenius Lacus quadrangle, are believed to contain large amounts of ice. The most popular model for the origin of the ice is climate change from large changes in the tilt of the planet's rotational axis. At times the tilt has even been greater than 80 degrees<ref>Touma J. and J. Wisdom. 1993. The Chaotic Obliquity of Mars" ''Science'' 259, 1294–1297.</ref><ref>Laskar, J., A. Correia, M. Gastineau, F. Joutel, B. Levrard, and P. Robutel. 2004. Long term evolution and chaotic diffusion of the insolation quantities of Mars" ''Icarus'' 170, 343-364.</ref> Large changes in the tilt explains many ice-rich features on Mars. |
|||
Studies have shown that when the tilt of Mars reaches 45 degrees from its current 25 degrees, ice is no longer stable at the poles.<ref>Levy, J., J. Head, D. Marchant, D. Kowalewski. 2008. Identification of sublimation-type thermal contraction crack polygons at the proposed NASA Phoenix landing site: Implications for substrate properties and climate-driven morphological evolution. Geophys. Res. Lett. 35. {{DOI|10.1029/2007GL032813}}</ref> Furthermore, at this high tilt, stores of solid carbon dioxide (dry ice) sublimate, thereby increasing the atmospheric pressure. This increased pressure allows more dust to be held in the atmosphere. Moisture in the atmosphere will fall as snow or as ice frozen onto dust grains. Calculations suggest this material will concentrate in the mid-latitudes.<ref>Levy, J., J. Head, D. Marchant. 2009a. Thermal contraction crack polygons on Mars: Classification, distribution, and climate implications from HiRISE observations. J. Geophys. Res. 114. {{DOI|10.1029/2008JE003273}}</ref><ref>Hauber, E., D. Reiss, M. Ulrich, F. Preusker, F. Trauthan, M. Zanetti, H. Hiesinger, R. Jaumann, L. Johansson, A. Johnsson, S. Van Gaselt, M. Olvmo. 2011. Landscape evolution in Martian mid-latitude regions: insights from analogous periglacial landforms in Svalbard. In: Balme, M., A. Bargery, C. Gallagher, S. Guta (eds). Martian Geomorphology. Geological Society, London. Special Publications: 356. 111-131</ref> General circulation models of the Martian atmosphere predict accumulations of ice-rich dust in the same areas where ice-rich features are found.<ref>Laskar, J., A. Correia, M. Gastineau, F. Joutel, B. Levrard, and P. Robutel. 2004. Long term evolution and chaotic diffusion of the insolation quantities of Mars" ''Icarus'' 170, 343-364.</ref> |
|||
When the tilt begins to return to lower values, the ice sublimates (turns directly to a gas) and leaves behind a lag of dust.<ref name="Mellon, M. 1995">Mellon, M., B. Jakosky. 1995. The distribution and behavior of Martian ground ice during past and present epochs" ''J. Geophys. Res.'' 100, 11781–11799.</ref><ref name="Mellon, M. 1995"/><ref>Schorghofer, N., 2007. Dynamics of ice ages on Mars" ''Nature'' 449, 192–194.</ref> The lag deposit caps the underlying material so with each cycle of high tilt levels, some ice-rich mantle remains behind.<ref>Madeleine, J., F. Forget, J. Head, B. Levrard, F. Montmessin. 2007. Exploring the northern mid-latitude glaciation with a general circulation model. In: Seventh International Conference on Mars. Abstract 3096.</ref> Note, that the smooth surface mantle layer probably represents only relative recent material. |
|||
The seasons present unequal lengths are as follows: |
|||
{| class="wikitable" |
|||
!Season !! Sols<br />(on Mars) !! Days<br />(on Earth) |
|||
|- |
|||
| Northern Spring, Southern Autumn: || 193.30 || 92.764 |
|||
|- |
|||
| Northern Summer, Southern Winter: || 178.64 || 93.647 |
|||
|- |
|||
| Northern Autumn, Southern Spring: || 142.70 || 89.836 |
|||
|- |
|||
| Northern Winter, Southern Summer: || 153.95 || 88.997 |
|||
|} |
|||
[[Axial precession (astronomy)|Precession]] in the alignment of the obliquity and eccentricity lead to global warming and cooling ('great' summers and winters) with a period of 170,000 years.<ref name="repeat">{{cite web | title = Global warming on Mars? | author = Steinn Sigurðsson|publisher= RealClimate | url = http://www.realclimate.org/index.php?p=192 | accessdate = February 21, 2007}}</ref> |
|||
Like Earth, the [[obliquity]] of Mars undergoes periodic changes which can lead to long-lasting changes in climate. Once again, the effect is more pronounced on Mars because it lacks the stabilizing influence of a large moon. As a result the obliquity can alter by as much as 45°. Jacques Laskar, of France's National Centre for Scientific Research, argues that the effects of these periodic climate changes can be seen in the layered nature of the ice cap at the Martian north pole.<ref>{{cite news | title = Martian 'wobbles' shift climate |
|||
| author = Jacques Laskar |
|||
| publisher = [[BBC]] |
|||
| url = http://news.bbc.co.uk/1/hi/sci/tech/2280991.stm |
|||
| accessdate = February 24, 2007 | date=September 25, 2002}}</ref> Current research suggests that Mars is in a warm interglacial period which has lasted more than 100,000 years.<ref>{{cite web | title = Titan, Mars methane may be on ice |
|||
| author = Francis Reddy |
|||
| publisher = [[Astronomy Magazine]] |
|||
| url = http://www.astronomy.com/asy/default.aspx?c=a&id=4009 |
|||
| accessdate = March 16, 2007}}</ref> |
|||
Because the [[Mars Global Surveyor]] was able to observe Mars for 4 Martian years, it was found that Martian weather was similar from year to year. Any differences were directly related to changes in the solar energy that reached Mars. Scientists were even able to accurately predict dust storms that would occur during the landing of [[Beagle 2]]. Regional dust storms were discovered to be closely related to where dust was available.<ref name="marsjournal.org">Malin, M. et al. 2010. An overview of the 1985–2006 Mars Orbiter Camera science investigation. MARS INFORMATICS. http://marsjournal.org</ref> |
|||
== Evidence for recent climatic change == |
|||
[[File:mars pits 1999.gif|thumb|right|370px|Pits in south polar ice cap, MGS 1999, NASA]] |
|||
There have been regional changes around the south pole ([[Planum Australe]]) over the past few Martian years. In 1999 the [[Mars Global Surveyor]] photographed pits in the layer of frozen carbon dioxide at the Martian south pole. Because of their striking shape and orientation these pits have become known as [[swiss cheese features]]. In 2001 the craft photographed the same pits again and found that they had grown larger, retreating about 3 meters in one Martian year.<ref>{{cite web | title = MOC Observes Changes in the South Polar Cap| author = | publisher = Malin Space Science Systems | url = http://mars.jpl.nasa.gov/mgs/msss/camera/images/CO2_Science_rel/index.html| accessdate = February 22, 2007}}</ref> These features are caused by the sublimation of the dry ice layer, thereby exposing the inert water ice layer. More recent observations indicate that the ice at Mars' south pole is continuing to sublime.<ref>{{cite web | title = Evaporating ice | author = | publisher = Astronomy.com| url = http://www.astronomy.com/asy/default.aspx?c=a&id=3503 | accessdate = February 22, 2007}}</ref> |
|||
The pits in the ice continue to grow by about 3 meters per Martian year. Malin states that conditions on Mars are not currently conducive to the formation of new ice. A [[NASA]] press release has suggested that this indicates a "climate change in progress"<ref>[http://mpfwww.jpl.nasa.gov/mgs/newsroom/20050920a.html Orbiter's Long Life Helps Scientists Track Changes on Mars]</ref> on [[Mars]]. In a summary of observations with the Mars Orbiter Camera, researchers speculated that some dry ice may have been deposited between the [[Mariner 9]] and the [[Mars Global Surveyor]] mission. Based on the current rate of loss, the deposits of today may be gone in a hundred years.<ref name="marsjournal.org" /> |
|||
Elsewhere on the planet, low latitude areas have more water ice than they should have given current climatic conditions.<ref>[http://www.space.com/scienceastronomy/mars_ice-age_031208.html Mars Emerging from Ice Age, Data Suggest]</ref> Mars Odyssey "is giving us indications of recent global climate change in Mars," said Jeffrey Plaut, project scientist for the mission at NASA's Jet Propulsion Laboratory, in non-peer reviewed published work in 2003. |
|||
=== Attribution theories === |
|||
==== Polar changes ==== |
|||
Colaprete et al. conducted simulations with the Mars General Circulation Model which show that the local climate around the Martian south pole may currently be in an unstable period. The simulated instability is rooted in the geography of the region, leading the authors to speculate that the sublimation of the polar ice is a local phenomenon rather than a global one.<ref>{{cite journal |
|||
| authorlink = |
|||
| title = Albedo of the South Pole of Mars. |
|||
| journal = Nature |
|||
| volume = 435 |
|||
| pages = 184–188 |
|||
| date = May 12, 2005 |
|||
| publisher = |
|||
| pmid = 15889086 |
|||
| last1 = Colaprete |
|||
| first1 = A |
|||
| last2 = Barnes |
|||
| first2 = JR |
|||
| last3 = Haberle |
|||
| first3 = RM |
|||
| last4 = Hollingsworth |
|||
| first4 = JL |
|||
| last5 = Kieffer |
|||
| first5 = HH |
|||
| last6 = Titus |
|||
| first6 = TN |
|||
| issue = 7039 |
|||
| doi = 10.1038/nature03561|bibcode = 2005Natur.435..184C }}</ref> The researchers showed that even with a constant solar luminosity the poles were capable of jumping between states of depositing or losing ice. The trigger for a change of states could be either increased dust loading in the atmosphere or an albedo change due to deposition of water ice on the polar cap.<ref>{{cite journal |
|||
| authorlink = |
|||
| title = Year-to-year instability of the Mars Polar Cap |
|||
| journal = J.Geophys Res |
|||
| volume = 95 |
|||
| pages = 1359–1365 |
|||
| date = 1990 |
|||
| publisher = |
|||
| doi = 10.1029/JB095iB02p01359 |
|||
| author = Jakosky, Bruce M. |
|||
| last2 = Haberle |
|||
| first2 = Robert M. |
|||
| bibcode=1990JGR....95.1359J}}</ref> This theory is somewhat problematic due to the lack of ice depositation after the 2001 global dust storm.<ref name=Fenton /> Another issue is that the accuracy of the Mars General Circulation Model decreases as the scale of the phenomenon becomes more local. |
|||
It has been argued that "observed regional changes in south polar ice cover are almost certainly due to a regional climate transition, not a global phenomenon, and are demonstrably unrelated to external forcing."<ref name="repeat" /> Writing in a ''Nature'' news story, Chief News and Features Editor Oliver Morton said "The warming of other solar bodies has been seized upon by climate sceptics. On Mars, the warming seems to be down to dust blowing around and uncovering big patches of black basaltic rock that heat up in the day."<ref name=Fenton>{{cite journal | first=Lori K. | last=Fenton | first2=Paul E. | last2=Geissler | first3=Robert M. | last3=Haberle | title=Global warming and climate forcing by recent albedo changes on Mars | date=2007 | journal=[[Nature (journal)|Nature]] | volume=446 | doi=10.1038/nature05718 | url=http://humbabe.arc.nasa.gov/~fenton/pdf/fenton/nature05718.pdf | pages=646–649 | pmid=17410170 | issue=7136 |bibcode = 2007Natur.446..646F }}</ref><ref>[http://www.nature.com/news/2007/070402/full/070402-7.html Access : Hot times in the Solar System : Nature News<!-- Bot generated title -->]</ref> |
|||
==== Solar irradiance ==== |
|||
[[Khabibullo Abdusamatov|K. I. Abdusamatov]] has proposed that "parallel global warmings" observed simultaneously on Mars and on Earth can only be a consequence of the same factor: a long-time [[solar variation|change in solar irradiance]]."<ref>{{cite web | title = Look to Mars for the truth on global warming |
|||
| author = |
|||
| publisher = National Post |
|||
| url = http://www.canada.com/nationalpost/story.html?id=edae9952-3c3e-47ba-913f-7359a5c7f723&k=0 |
|||
| accessdate = March 2, 2007}}</ref> |
|||
While some individuals who reject the science of [[global warming]] take this as proof that humans are not causing climate change,<ref>{{cite web|title=Global warming on Mars, ice caps melting|url=http://www.skepticalscience.com/global-warming-on-mars-intermediate.htm|publisher=Skeptical Science|accessdate=September 17, 2013}}</ref> Abdusamatov's hypothesis has not been accepted by the scientific community. His assertions have not been published in the peer-reviewed literature, and have been dismissed by other scientists, who have stated that "the idea just isn't supported by the theory or by the observations" and that it "doesn't make physical sense."<ref>{{cite web | url=http://www.livescience.com/environment/070312_solarsys_warming.html | title=Sun Blamed for Warming of Earth and Other Worlds | author=Ker Than | publisher=Live Science | date=March 12, 2007 | accessdate=September 6, 2007}}</ref> <!--this should be expanded on and broken out into its own theory but we need more than one sentence -->Other scientists have proposed that the observed variations are caused by irregularities in the orbit of Mars or a possible combination of solar and orbital effects.<ref>{{cite web | title = Mars Melt Hints at Solar, Not Human, Cause for Warming, Scientist Says |
|||
| author = Kate Ravilious |
|||
| publisher = National Geographic Society |
|||
| url = http://news.nationalgeographic.com/news/2007/02/070228-mars-warming.html |
|||
| accessdate = March 2, 2007}}</ref> |
|||
[[File:Mars climate zones.jpg|thumb|Mars Global Climate Zones, based on temperature, modified |
|||
by topography, albedo, actual solar radiation.]] |
|||
== Climate zones == |
|||
Terrestrial Climate zones first have been defined by [[Wladimir Köppen]] based on the distribution of vegetation groups. Climate classification is furthermore based on temperature, rainfall, and subdivided based upon differences in the seasonal distribution of temperature and precipitation; and a separate group exists for extrazonal climates like in high altitudes. Mars has neither vegetation nor rainfall, so any climate classification could be only based upon temperature; a further refinement of the system may be based on dust distribution, water vapor content, occurrence of snow. [[Solar Climate Zones]] can also be easily defined for Mars.<ref>{{cite web | url=http://www.lpi.usra.edu/meetings/lpsc2010/pdf/1199.pdf | title=Climate Zones of Mars | author=Hargitai Henrik | publisher=Lunar and Planetary Institute | date=2009 | accessdate=May 18, 2010}}</ref> |
|||
== Current missions == |
|||
The [[2001 Mars Odyssey]] is currently orbiting Mars and taking global atmospheric temperature measurements with the TES instrument. The Mars Reconnaissance Orbiter is currently taking daily weather and climate related observations from orbit. One of its instruments, the [[Mars climate sounder]] is specialized for climate observation work. The [[Mars Science Laboratory|MSL]] was launched in November 2011 and landed on Mars on August 6, 2012.<ref>{{cite news| url=http://www.cbsnews.com/8301-205_162-57487070/curiosity-rover-touches-down-on-mars/ | publisher=CBS News |title=Curiosity rover touches down on Mars}}</ref> |
|||
{{Auto images |
|||
|title=<center>[[Curiosity rover]] – [[Temperature]], [[Pressure]], [[Humidity]] at [[Gale Crater]] on [[Mars]] (August 2012 – February 2013).</center> |total_width=800 |width1=700 |height1=534 |image1=PIA16913-MarsCuriosityRover-SteadyTemperature-GaleCrater.jpg |caption1=[[Temperature]] |width2=664 |height2=531 |image2=PIA16912-MarsCuriosityRover-SeasonalPressure-GaleCrater.jpg |caption2=[[Pressure]] |width3=831 |height3=637 |image3=PIA16915-MarsCuriosityRover-Humidity-GaleCrater.jpg |caption3=[[Humidity]] }} |
|||
== Future missions == |
|||
*[[Mars Orbiter Mission]] - ''en route'', launched on November 5, 2013 |
|||
*[[MAVEN]] - ''en route'', launched on November 18, 2013 |
|||
*[[ExoMars Trace Gas Orbiter]] to launch in 2016 |
|||
== See also == |
|||
* [[Atmosphere of Mars]] |
|||
* [[Exploration of Mars]] |
|||
* [[Geology of Mars]] |
|||
* [[Mars analog habitat]] |
|||
* [[Mars Climate Orbiter]] |
|||
* [[MetNet]], a proposed meteorological network on Mars |
|||
* [[Planum Australe]], the southern polar plain |
|||
* [[Planum Boreum]], the northern polar plain |
|||
* [[Water on Mars]] |
|||
== References == |
|||
{{Reflist|2}} |
|||
== Further reading == |
|||
* {{cite journal|last=Jakosky|first=Bruce M.|author2=Phillips, Roger J.|title=Mars' volatile and climate history|journal=Nature|date=2001|volume=412|issue=6843|pages=237–244|doi=10.1038/35084184}} review article |
|||
== External links == |
|||
* [http://mars.jpl.nasa.gov/science/climate/ NASA Martian Climate page] |
|||
* [http://humbabe.arc.nasa.gov/MarsToday.html Mars Today], current conditions on Mars. |
|||
* [http://www.physorg.com/news4106.html Nature study explains mystery of Mars icecaps.] |
|||
* [http://www.newscientist.com/article.ns?id=dn1660 Mars could be undergoing major global warming] |
|||
* [http://www.msss.com/mars_images/moc/2005/07/13/index.html Mars Global Surveyor MOC2-1151 Release] |
|||
* [http://www.realclimate.org/index.php?p=192 Global warming on Mars?] |
|||
* [http://mars.jpl.nasa.gov/mgs/msss/camera/images/CO2_Science_rel/index.html Images of melting ice cap: Evidence for Recent Climate Change on Mars] |
|||
* [http://news.nationalgeographic.com/news/2007/02/070228-mars-warming.html Article from National Geographic on the issue of Martian Global Warming] |
|||
* [http://cab.inta-csic.es/rems/marsweather.html Weather Reports] from the [http://cab.inta-csic.es/rems Curiosity Rover (REMS)] |
|||
* [http://hrscview.fu-berlin.de/cgi-bin/ion-p?ION__E1=UPDATE%3Aion%3A%2F%2Fhrscview2.ion&ION__E2=control%3Aion%3A%2F%2Fhrscview2.ion&image=9520_0000&image1=3+images&pos=32.704N%2C+297.883E&scale=80&viewport=900x900&basemap_on=on&basemap=MOLAelevation&labels_on=on&hrsc_on=on&mode=nd&pansharpen=on&ir2re=on&persp=on&pview=South&exag=1&UPDATE=Update+view&image0=9520_0000&code=91663528 HRSC – Clouds] |
|||
<!--spacing, please do not remove--> |
|||
{{Mars}} |
|||
{{portal bar|Mars}} |
|||
[[Category:Mars]] |
|||
[[Category:Climate history]] |
|||
Revision as of 17:33, 12 February 2015
haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris haris