Spirit (rover)

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The launch patch for Spirit, featuring Marvin the Martian.

MER-A (Mars Exploration Rover - A), known as Spirit, is the first of the two rovers of NASA's Mars Exploration Rover Mission. It landed successfully on Mars on 04:35 Ground UTC on January 4, 2004, three weeks before its twin Opportunity (MER-B) landed on the other side of the planet. Its name was chosen through a NASA-sponsored student essay competition.

The rover has continued to function effectively over twenty times longer than NASA planners expected, allowing it to perform extensive geological analysis of Martian rocks and planetary surface features. By March 31, 2009, the rover had traveled over 4.75 miles. In November 2008 a dust storm cut the solar panel electrical output to a critical level, leaving the rover in a vulnerable state. However, dust clearing events occurred which restored the rover's power levels. An archive of approximately weekly updates on its status can be found at the NASA/JPL website. Initial scientific results from the first phase of the mission (roughly, the 90-sol prime mission) were published in a special issue of the journal Science

Objectives

Spirit rover images its lander on the surface of Mars on January 18/19th 2004 (MER-A Sol 16)

The scientific objectives of the Mars Exploration Rover mission are to:

• Search for and characterize a variety of rocks and soils that hold clues to past water activity. In particular, samples sought will include those that have minerals deposited by water-related processes such as precipitation, evaporation, sedimentary cementation or hydrothermal activity.
• Determine the distribution and composition of minerals, rocks, and soils surrounding the landing sites.
• Determine what geologic processes have shaped the local terrain and influenced the chemistry. Such processes could include water or wind erosion, sedimentation, hydrothermal mechanisms, volcanism, and cratering.
• Perform calibration and validation of surface observations made by Mars Reconnaissance Orbiter instruments. This will help determine the accuracy and effectiveness of various instruments that survey Martian geology from orbit.
• Search for iron-containing minerals, identify and quantify relative amounts of specific mineral types that contain water or were formed in water, such as iron-bearing carbonates.
• Characterize the mineralogy and textures of rocks and soils and determine the processes that created them.
• Search for geological clues to the environmental conditions that existed when liquid water was present.
• Assess whether those environments were conducive to life.

During the next two decades, NASA will conduct several missions to address whether life ever arose on Mars. The search begins with determining whether the Martian environment was ever suitable for life. Life, as we understand it, requires water, so the history of water on Mars is critical to finding out if the Martian environment was ever conducive to life. Although the Mars Exploration Rovers do not have the ability to detect life directly, they are offering very important information on the habitability of the environment in the planet's history.

Science instruments carried

Panoramic Camera (Pancam)

for determining the mineralogy, texture, and structure of the local terrain.

Miniature Thermal Emission Spectrometer (Mini-TES)

for identifying promising rocks and soils for closer examination and for determining the processes that formed Martian rocks. The instrument also scans skyward to provide temperature profiles of the Martian atmosphere.

Mössbauer Spectrometer (MB)

for close-up investigations of the mineralogy of iron-bearing rocks and soils.

Alpha Particle X-Ray Spectrometer (APXS)

for analysis of elements that make up rocks and soils.

Magnets

for collecting magnetic dust particles. The Mössbauer Spectrometer and the Alpha Particle X-ray Spectrometer will analyze the particles collected and help determine the ratio of magnetic particles to non-magnetic particles.

Microscopic Imager (MI)

for obtaining close-up, high-resolution images of rocks and soils.

Rock Abrasion Tool (RAT)

for removing dusty and weathered rock surfaces and exposing fresh material for examination by instruments onboard.

Landing site: Columbia Memorial Station

Spirit's landing site (denoted with a star)

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Rover tracks on sol 85 from Mars Global Surveyor

Spirit landing site, as imaged by MRO (2006-12-04)

Spirit was targeted to a site that appear to have been affected by liquid water in the past, the crater Gusev, a possible former lake in a giant impact crater about 10 km from the center of the target ellipse at latitude 14.5718° S, longitude 175.4785° E.

After the airbag-protected landing craft settled onto the surface, the rover rolled out to take panoramic images. These give scientists the information they need to select promising geological targets and drive to those locations to perform on-site scientific investigations.

The panoramic image below shows a slightly rolling surface, littered with small rocks, with hills on the horizon up to 27 km away. The MER team named the landing site "Columbia Memorial Station," in honor of the seven astronauts killed in the Space Shuttle Columbia disaster.

Apollo Hills panorama from the Spirit landing site

Timeline

Current Spirit traverse map, to sol 1506 (April 02,2008), click image to enlarge.

The primary surface mission for Spirit was planned to last 90 Sols. The mission received several extensions and as of April 2008 had passed 1500 Sols, more than 17 times the primary mission length. On August 11, 2007, Spirit became the Mars lander with the second longest operational duration on the surface of Mars at 1282 Sols, one Sol longer than the Viking 2 lander. Viking 2 was powered by a nuclear cell whereas Spirit is powered by solar arrays. Currently the Mars lander with longest operational period is Viking 1 which lasted for 2245 Sols on the surface of Mars.

As of sol 1736 (November 20, 2008), Spirit's total odometry was 7,529 metres (4.68 mi).

An archive of approximately weekly updates on the rover's status can be found at Spirit Update Archive. The following paragraphs discuss the more notable findings.

Events and discoveries 2004-2005

MER-A Spirit mars rover and lander arrived successfully on the surface of Mars on 04:35 Ground UTC on January 4, 2004.

Sleepy Hollow

"Sleepy Hollow," a shallow depression in the Mars ground near NASA's Spirit rover, was targeted as an early destination when the rover drove off its lander platform. NASA scientists were very interested in this crater. It is 9 meters (30 feet) across and about 12 meters (40 feet) north of the lander.

"Just as the ancient mariners used sextants for 'shooting the Sun,' as they called it, we were successfully able to shoot the Sun with our panorama camera, then use that information to point the antenna," said JPL's Matt Wallace, mission manager.

First color photograph

The first color photograph sent by Spirit; it was the highest resolution color photograph taken on another planet.

To the right is the first color image taken by the panoramic camera on the Mars Exploration Rover Spirit. It was the highest resolution image taken on the surface of another planet. "We're seeing a panoramic mosaic of four pancam images high by three wide," said camera designer Jim Bell of Cornell University. The picture shown originally had a full size of 4,000 by 3,000 pixels. However, a complete pancam panorama is even 8 times larger than that, and could be taken in stereo (I.e., two complete pictures, making the resolution twice as large again.) The colors are fairly accurate. (For a technical explanation, see colors outside the range of the human eye.)

January 21 flash memory management anomaly

On 2004 January 21 (Sol 18), Spirit abruptly ceased communicating with mission control. The next day the rover radioed a 7.8 bit/s beep, confirming that it had received a transmission from Earth but indicating that the craft believed it was in a fault mode. Commands would only be responded to intermittently. This was described as a very serious anomaly, but potentially recoverable if it were a software or memory corruption issue rather than a serious hardware failure. Spirit was commanded to transmit engineering data, and on January 23 sent several short low-bitrate messages before finally transmitting 73 megabits via X band to Mars Odyssey. The readings from the engineering data suggested that the rover was not staying in sleep mode. As such, it was wasting its battery power and overheating — risk factors that could potentially destroy the rover if not fixed soon. On Sol 20, the command team sent it the command SHUTDWN_DMT_TIL ("Shutdown Dammit Until ") to try to cause it to suspend itself until a given time. It seemingly ignored the command.

The leading theory at the time was that the rover was stuck in a "reboot loop". The rover is programmed to reboot if there's a fault aboard itself. However, if there is a fault that occurs during reboot, it could continue to reboot forever. The fact that the problem persisted through reboot suggested that the error was not in RAM, but in either the flash memory, the EEPROM, or a hardware fault. The last case would likely mean the doom of the rover. Anticipating the potential for errors in the flash memory and EEPROM, the designers had made it so that the rover could be booted without ever touching the flash memory. The radio itself could decode a limited commandset — enough to tell the rover to reboot without using flash. Without access to flash memory, Spirit booted fine, and the reboot cycle was broken.

On January 24 the rover repair team announced that the problem was with Spirit's flash memory and the software that wrote to it. The flash hardware was believed to be working correctly but the file management module in the software was "not robust enough" for the operations the Spirit was engaged in when the problem occurred, indicating that the problem was caused by a software bug as opposed to faulty hardware. NASA engineers finally came to the conclusion that there were too many files on the file system, which was a relatively minor problem. Most of these files contained unneeded in-flight data. After realizing what the problem was, the engineers deleted some files, and eventually reformatted the entire flash memory system. On February 6 (Sol 33), the rover was restored to its original working condition, and science activities resumed.

History's first grinding of a rock on Mars

Digital camera (the Pancam) image of a Mars rock (called Adirondack) taken after a RAT grind (the rock grinding tool)

The round, shallow depression in this image resulted from history's first grinding of a rock on Mars. The Rock Abrasion Tool on NASA's Spirit rover ground off the surface of a patch 45.5 millimeters (1.8 inches) in diameter on a rock called Adirondack during Spirit's 34th sol on Mars, February 6, 2004. The hole is 2.65 millimeters (0.1 inch) deep, exposing fresh interior material of the rock for close inspection with the rover's microscopic imager and two spectrometers on the robotic arm. This image was taken by Spirit's panoramic camera, providing a quick visual check of the success of the grinding.

"The RAT performed beyond our expectations," beamed Steve Gorevan, of Honeybee Robotics, New York, lead scientist for the rock abrasion tools on both rovers. "With the docile cutting parameters we set, I didn't think that it would cut this deep. In fact, when we saw virtually a complete circle, I was thrilled beyond anything I could have ever dreamed. Following up that glorious circular brushing — it's like back-to-back homers."

Mimi

False color image of "Mimi".

This color image taken by the Mars Exploration Rover Spirit's panoramic camera on Sol 40 (13-Feb-2004) is centered on an unusually flaky rock called Mimi. Mimi is only one of many features in the area known as "Stone Council", but looks very different from any rock that scientists have seen at the Gusev crater site so far. Mimi's flaky appearance leads scientists to a number of hypotheses. Mimi could have been subjected to pressure either through burial or impact, or may have once been a dune that was cemented into flaky layers, a process that sometimes involves the action of water.

Humphrey and clues for water

On March 5, 2004, NASA announced that Spirit had found hints of water history on Mars in a rock dubbed "Humphrey". Dr. Raymond Arvidson, Ph.D., the McDonnell University Professor and chair of Earth and planetary sciences at Washington University in St. Louis, reported during a NASA press conference: "If we found this rock on Earth, we would say it is a volcanic rock that had a little fluid moving through it." In contrast to the rocks found by the twin rover Opportunity, this one was formed from magma and then acquired bright material in small crevices, which look like crystallized minerals. If this interpretation holds true, the minerals were most likely dissolved in water, which was either carried inside the rock or interacted with it at a later stage, after it formed.

Bonneville Crater

On 11 March 2004, the Spirit rover reached Bonneville crater after a 400-yard (370 m) journey. This crater is about 200 metres (220 yd) across with a floor about 10 metres (11 yd) below the surface. JPL decided that it would be a bad idea to send the rover down into the crater, as they saw no targets of interest inside. Spirit drove along the southern rim and continued to the southwest towards the Columbia Hills.

Looking back at the lander.

Bonneville Crater.

Missoula and Lahontan Craters, en route to Columbia Hills

Missoula Crater

Spirit reached Missoula crater on Sol 105. The crater is roughly 100 yards (91 m) across and 20 yards (18 m) deep. Missoula crater was not considered a high priority target due to the older rocks it contained. The rover skirted the northern rim, and continued to the southeast.

Lahontan crater on Sol 120

It then reached Lahontan crater on Sol 118, and drove along the rim until Sol 120. Lahontan is about 60 yards (55 m) across and about 10 yards (9.1 m) deep. A long, snaking sand dune stretches away from its southwestern side, and Spirit went around it, because loose sand dunes present an unknown risk to the ability of the rover wheels to get traction.

Columbia Hills

On Sol 159, Spirit reached the first of many targets at the base of the Columbia Hills called West Spur. Hank's Hollow was studied for 23 sols. Within Hank's Hollow was the strange looking rock dubbed "Pot of Gold".

From here, Spirit took a northerly path along the base of the hill towards the target Wooly Patch, which was studied from Sol 192 to Sol 199. By Sol 203, Spirit had driven southward up the hill and arrived at the rock dubbed "Clovis". Clovis was ground and analyzed from Sol 210 to Sol 225. Following Clovis came the targets of Ebenezer (Sols 226-235), Tetl (Sol 270), Uchben and Palinque (Sols 281-295), and Lutefisk (Sols 296-303). From Sols 239 to 262, Spirit powered down for solar conjunction, when communications with the Earth are blocked.

Slowly, Spirit has made its way around the summit of Husband Hill, and at Sol 344 was ready to climb over the newly designated "Cumberland Ridge" and into "Larry's Lookout" and "Tennessee Valley".

On Sol 371, Spirit arrived at a rock named "Peace" near the top of Cumberland Ridge. Spirit ground it with the RAT tool on Sol 373.

By Sol 390 (Mid-February 2005), Spirit was advancing towards "Larry's Lookout", by driving up the hill in reverse. The scientists at this time were trying to conserve as much energy as possible for the climb.

Spirit also investigated some targets along the way, including the soil target, "Paso Robles", which contained the highest amount of salt found on the red planet. The soil also contained a high amount of phosphorus in its composition, however not nearly as high as another rock sampled by Spirit, "Wishstone". Squyres said of the discovery, "We're still trying to work out what this means, but clearly, with this much salt around, water had a hand here".

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  Pot of Gold rock
• 
  Spirit's traverse up Husband Hill
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  Spirit artificially added to image (taken by itself) of Larry's Lookout
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  Photograph of a Martian sunset taken by Spirit at Gusev crater, May 19th 2005.

Dust devils

On 9 March 2005 (probably during the Martian night), the rover's solar panel efficiency jumped from around 60% of what it had originally been to 93%, followed on 10 March by the sighting of dust devils. NASA scientists speculate a dust devil must have swept the solar panels clean, possibly significantly extending the duration of the mission. This also marks the first time dust devils had been spotted by either Spirit or Opportunity, easily one of the top highlights of the mission to date. Dust devils had previously been photographed by only the Pathfinder probe.

Mission members monitoring the Spirit rover on Mars reported on March 12, 2005, that a lucky encounter with a dust devil had cleaned the solar panels of that robot. Power levels dramatically increased and daily science work was anticipated to be expanded.

Dust devil on Mars, photographed by the Mars rover Spirit. The counter in the bottom-left corner indicates time in seconds after the first photo was taken in the sequence. At the final frames, one can see that the dust devil has left a trail on the Martian surface. Three other dust devils also appear in the background. For full animation click File:Marsdustdevil2.gif (over 4 megabytes download)

Husband Hill summit

On Sol 582, August 21, 2005, Spirit reached the summit of Husband Hill and acquired a 360 degree panorama picture.

View from the Summit taken by Spirit on August 23, 2005 as the rover completed climb up "Husband Hill."

Vista while descending Husband Hill

Events and discoveries 2006-2009

Home Plate

Spirit arrived at the north west corner of Home Plate, a raised and layered outcrop on sol 744 after an effort to maximize driving. Scientific observations have been conducted with Spirit's robotic arm.

Curious rock near edge of "Home Plate" with a jutting portion. (Animated GIF image for stereoscopic perception).

Picture of Spirit, including tracks, taken from the Mars Reconnaissance Orbiter

During 2007 Spirit spent several months near the base of the Home Plate plateau. On sol 1306 Spirit climbed onto the eastern edge of the plateau. In September and October it examined rocks and soils at several locations on the southern half of the plateau. On November 6 Spirit had reached the western edge of Home Plate and starting taking pictures for a panoramic overview of the western valley with Grissom Hill and Husband Hill visible. The panorama image was published on NASA's website on January 3, 2008 to little attention, until January 23, when an independent website (Image w/ closeup) published a magnified detail of the left side of the original image in which is visible what looks much like a dark green humanoid sitting on a rock or walking down a hill with the right arm raised. This strange formation is also visible when viewing the image in full resolution on the NASA website. The presence of the feature in all separate images which were combined to make the color image as well as NavCam images from several days earlier, conclusively show that it is a permanent feature.

McCool Hill

Spirit's next stop was originally planned to be the north face of McCool Hill, where Spirit would receive adequate sunlight during the Martian winter. On March 16, 2006 JPL announced that Spirit's troublesome front wheel had stopped working altogether. Despite this, Spirit was still making progress toward McCool Hill because the control team programmed the rover to drive toward McCool Hill backwards, dragging its broken wheel. In late March, Spirit encountered loose soil which was impeding its progress toward McCool Hill. A decision was made to terminate attempts to reach McCool Hill and instead park on a nearby ridge named Low Ridge Haven.

Low Ridge Haven

Possible meteorites found at Low Ridge

Reaching the ridge on April 9, 2006 and parking on the ridge with an 11° incline to the north, Spirit spent the next eight months on the ridge during which time undertaking observations of changes in the surrounding area. No drives were attempted because of the low power levels the rover was experiencing during the Martian winter. The rover made its first drive, a short turn to position targets of interest within reach of the robotic arm, in early November 2006, following the shortest days of winter and solar conjunction when communications with Earth were severely limited.

While at Low Ridge, Spirit imaged two rocks of similar chemical nature to that of Opportunity's Heat Shield Rock, a meteorite on the surface of Mars. Named "Zhong Shan" for Sun Yat-sen and "Allan Hills" for the location in Antarctica where several Martian meteorites have been found, they stood out against the background rocks which were darker. Further spectrographic testing is being done to determine the exact composition of these rocks, which may turn out to also be meteorites.

Dust storms

Circular projection showing Spirit's solar panels covered in dust - October 2007.

Towards the end of June, 2007, a series of dust storms began clouding the Martian atmosphere with dust. The storms intensified and by July 20, both Spirit and Opportunity were facing the real possibility of system failure due to lack of power. NASA released a statement to the press which said (in part) "We're rooting for our rovers to survive these storms, but they were never designed for conditions this intense" . The key problem caused by the dust storms is a dramatic reduction in solar power. There was so much dust in the atmosphere that it was blocking 99 percent of direct sunlight to the rover Opportunity, whereas Spirit was getting slightly more sunlight.

Normally the solar arrays are able to generate up to 700 watt hours of power a day. After the storms, the amount of power generated was greatly reduced to 128 watts. If the rovers generate less than 150 watt hours per day they have to start draining their batteries to run survival heaters. If the batteries run dry, key electrical elements are likely to fail due to the intense cold. Both landers were put into the lowest-power setting to wait out the storms. In early August the storms began to clear slightly and the rovers successfully charged their batteries. They were kept in hibernation to wait out the rest of the storm.

On November 10, 2008, a large dust storm further reduced the output of the solar panels to 89 watt hours per day -- a critically low level not seen heretofore. NASA officials were hopeful that Spirit would survive the storm and the power level would rise once the storm had passed and the skies started clearing. They have attempted to conserve power and keep manual control of the rover. On Thursday November 13, 2008 the rover awoke and communicated back again.

From November 14, 2008 to November 20, 2008 Spirit averaged 169 watt hours per day and the heaters for the thermal emission spectrometer, which uses about 27 watt hours per day, have been disabled since November 11, 2008. Tests on the thermal emission spectrometer indicate that it is undamaged and the heaters for it will be enabled when there is sufficient power. The skies over Spirit are expected to clear over the next few weeks. The solar conjunction, where the Sun is between Earth and Mars, started on November 29, 2008 and communication with the rovers was not possible until December 13, 2008.

On February 6, 2009, a beneficial wind blew off the some of the dust accumulated on the panels. This has led to an increase in power output to 240 watt hours per day. NASA officials have said that this increase in energy will be used predominantly for driving.

Microbe clue

Spirit's dead wheel turned out to be a mixed blessing. As it was traveling, pulling the dead wheel behind, the wheel scraped off the upper layer of the martian soil, uncovering a patch of ground that scientists say shows evidence of a past environment that would have been perfect for microbial life. It is similar to areas on Earth where water or steam from hot springs came into contact with volcanic rocks. On Earth, these are locations that tend to teem with bacteria, said rover chief scientist Steve Squyres. "We're really excited about this," he told a meeting of the American Geophysical Union (AGU). The area is extremely rich in silica - the main ingredient of window glass. The researchers have now concluded that the bright material must have been produced in one of two ways. One: hot-spring deposits produced when water dissolved silica at one location and then carried it to another (i.e. a geyser). Two: acidic steam rising through cracks in rocks stripped them of their mineral components, leaving silica behind. "The important thing is that whether it is one hypothesis or the other, the implications for the former habitability of Mars are pretty much the same," Squyres explained to BBC News. Hot water provides an environment in which microbes can thrive and the precipitation of that silica entombs and preserves them. Squyres added, "You can go to hot springs and you can go to fumaroles and at either place on Earth it is teeming with life - microbial life.

Astronomy

Earth from Mars

Night sky of Mars showing Deimos (left) and Phobos (right) in front of Sagittarius, as seen by Mars Exploration Rover Spirit on August 26, 2005. For full animation click on Image:Phobos & Deimos full.gif

Spirit pointed its cameras towards the sky and observed a transit of the Sun by Mars' moon Deimos (see Transit of Deimos from Mars). It also took the only photo of Earth from the surface of another planet in early March 2004.

In late 2005, Spirit took advantage of a favorable energy situation to make multiple nighttime observations of both of Mars' moons Phobos and Deimos. These observations included a "lunar" (or rather phobal) eclipse as Spirit watched Phobos disappear into Mars's shadow. Some of Spirit's star gazing was designed to look for a predicted meteor shower caused by Halley's Comet, and although at least four imaged streaks were suspect meteors, they could not be unambiguously differentiated from those caused by cosmic rays.

A transit of Mercury from Mars took place on January 12, 2005 from about 14:45 UTC to 23:05 UTC. Theoretically, this could have been observed by both Spirit and Opportunity; however, camera resolution did not permit seeing Mercury's 6.1" angular diameter. They were able to observe transits of Deimos across the Sun, but at 2' angular diameter, Deimos is about 20 times larger than Mercury's 6.1" angular diameter. Ephemeris data generated by JPL Horizons indicates that Opportunity would have been able to observe the transit from the start until local sunset at about 19:23 UTC Earth time, while Spirit would have been able to observe it from local sunrise at about 19:38 UTC until the end of the transit.

Software upgrades

On January 4, 2007, both rovers received new flight software to the onboard computers. The update was received just in time for the third anniversary of their landing. The new systems let the rovers decide whether or not to transmit an image, and whether or not to extend their arms to examine rocks, which would save much time for scientists as they would not have to sift through hundreds of images to find the one they want, or examine the surroundings to decide to extend the arms and examine the rocks.

Equipment failures

Although both rovers have passed their original mission time of 90 sols many times over, the extended time on the surface and therefore additional stress on components has resulted in some issues developing.

On sol 779, the right front wheel ceased working after having covered 4.2 mi (7 km) on Mars. Engineers began driving the rover backwards, dragging the dead wheel. Ironically, although this has resulted in changes to driving techniques the dragging effect has also had a positive effect in the fact that the wheel dragging has partially cleared soil away on the surface as the rover travels and allows for imaging areas that would normally be covered in soil.

The grinding surface of the Rock Abrasion Tool has also worn down, and the device can only be used to brush targets.

All of the other science instruments and engineering cameras continue to function. The Mössbauer spectrometer takes much longer to produce results than it did earlier in the mission because of the decay of its radioactive source.

Honors

To commemorate Spirit's great contribution to the exploration of Mars, a asteroid, 37452 Spirit has been named after it. The name was proposed by Ingrid van Houten-Groeneveld who along with Cornelis Johannes van Houten and Tom Gehrels discovered the asteroid on September 24, 1960.

Ruben H. Fleet Museum and the Liberty Science Center also has an IMAX show called Roving Mars that documents the journey of both Spirit and Opportunity, using both CG and actual imagery.

See also

• Exploration of Mars
• Space exploration
• Unmanned space missions
• Autonomous robot
• Opportunity rover
• Comparison of embedded computer systems on board the Mars rovers

External links

JPL, MSSS, and NASA links

• JPL's Mars Exploration Rover Mission home page
• (obsolete JPL Mars Exploration Rover home page)
• Spirit Mission Profile by NASA's Solar System Exploration
• Planetary Photojournal, NASA JPL's Planetary Photojournal for Spirit
• NASA TV Special Events Schedule for MER News Briefings at JPL
• Mission Status updates from NASA JPL
• Wikisource:NASA MER press briefings
• Finding Spirit: high resolution images of landing site (Mars Global Surveyor - Mars Orbiter Camera)

Other links

• SpaceFlightNow Status Page last updated May 2004
• Marsbase.net, a site that tracks time on Mars.
• MAESTRO - public version of rover simulation software (requires download, last update October 25, 2004)
• Cornell's rover site: Athena last update 2006
• Finding Spirit: interactive Mars atlas based on Viking images: you can zoom in/out and pan images, to find your preferred site. "Spirit" approximate position is 14.82°S (= -14.82°N) , 184.85°W (= 5.15°E) (not working as of 2008-06-04)
• Google map with Spirit landing site marked
• (AXCH) 2004 Mars Exploration Rovers Highlights - News, status, technical info, history, and more.
• New Scientist on Spirit Dust Devils, 15 March 2005
• New Scientist on Spirit Wheel Status, 03 April 2006
• Unmanned Spaceflight.com discussion on Spirit as of 2008-06-04 last updated 2008-06-04
• "Mars Rover Beginning To Hate Mars", satire from The Onion, October 24, 2006
• Full-page, High-res spherical panorama of Spirit in the Columbia Hills, nasatech.net, Nov 23 to Dec. 5, 2005 (long download, uses Java)
• Full-page, High-res spherical panorama of Spirit at the summit of Husband Hill, nasatech.net, Nov 23 to Dec. 5, 2005 (long download, uses Java)