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The launch patch for Spirit, featuring Marvin the Martian.
Artist's Concept of Rover on Mars (credit: Maas Digital LLC)
Spirit (official designation: MER-A) is the first of the two rovers in the Mars Exploration Rover mission. She successfully landed on Mars at 04:35 Ground UTC on January 4, 2004 and has been functioning successfully for over one full Martian year or three Earth years. As of 2007 her mission is ongoing. Her twin Opportunity landed successfully on Mars on January 25, 2004 UTC. (Mission members decided to reference both rovers using the feminine gender.) Spirit was named by a winning entry in a student essay competition—see Naming of Spirit and Opportunity. Both Opportunity and Spirit have pieces of the fallen World Trade Center's metal on them.
 Landing site: Columbia Memorial Station
Rover tracks on sol 85 from Mars Global Surveyor
Spirit landing site, as imaged by MRO (2006-12-04)
A panorama 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.
On January 27 NASA memorialized the crew of Apollo 1 by naming three hills to the north of "Columbia Memorial Station" as the Apollo 1 Hills. On February 2, the astronauts on Columbia's final mission were further memorialized when NASA named a set of hills to the east of the landing site the Columbia Hills Complex, denoting seven peaks in that area Anderson, Brown, Chawla, Clark, Husband, McCool and Ramon. (NASA has submitted these geographical feature names to the IAU for approval.)
Apollo Hills panorama from the Spirit landing site
 Events and discoveries
Current Spirit traverse map, to sol 1055 (December 21, 2006)
A detailed chronology of events and discoveries may be found in the Spirit rover timeline entry. The following paragraphs discuss the more notable findings.
An archive of approximately weekly updates on the rover's status can be found at Spirit Update Archive.
 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.
First 3-D panorama of landing site: the crater under the sun is "Sleepy Hollow" received on 5 January.
"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.
The press release cut of the first color photograph. "Sleepy Hollow" is visible at the right of this photograph.
To the right is the first color image of Mars taken by the panoramic camera on the Mars Exploration Rover Spirit. It is the highest resolution image ever 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. There are actually 12 million pixels in this image, it's 4,000 high by 3,000 wide. This, however, is only the tip of the iceberg, as this image, received on 6 January 2004, is about one eighth of a single pancam panorama and isn't stereo.
 January 21 flash memory management anomaly
On 21 January (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 spacecraft 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 was a software or memory corruption issue rather than a serious hardware failure. Spirit was commanded to transmit engineering data, and on 23 January 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 <time>") 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 potentially 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 24 January 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 6 February (Sol 33), the rover was restored to its original working condition, and science activities resumed.
 History's first grinding of a rock on Mars
Pancam image of Adirondack taken after RAT grind.
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, Feb. 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."
False color image of "Mimi".
This color image taken by the Mars Exploration Rover Spirit's panoramic camera on Sol 40 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. Ray Arvidson of Washington University, 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 journey. This crater is 150 yards across and about 30 yards deep. 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, tore up some sand dunes, and continued to the southwest towards the Columbia Hills.
 Missoula and Lahonten Craters, en route to Columbia Hills
Spirit reached Missoula crater on Sol 105. The crater is roughly 100 yards across and 20 yards 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.
Lahonten crater on Sol 120
It then reached Lahonten crater on Sol 118, and drove along the rim until Sol 120. Lahonten is about 60 yards across and about 10 yards deep. A long, snaking sand dune stretches away from its southwestern side, and Spirit went around it.
 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.
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 backwards 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".
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.
 Husband Hill summit
 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.
 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
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. As of sol 1102 (February 7, 2007), Spirit's total odometry was 6,926.42 meters (4.3 miles).
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.
Earth from Mars
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 fall of 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 but no images of meteors have been formally released.
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.
 Technical data
Height: 1.5m / 4.9 ft (inc. deployed PMA) Width: 2.3m / 7.5 ft Length: 1.6m / 5,2 ft Mass: 174 kg / 384 lb : However, this may not be quite correct. According to Design and Verification of the MER Primary Payload, the total mass of the Mars Exploration Rover is 180.1 kg. Of this, the mass of the Rover WEB is 145.6 kg, and the mass of Rover mobility components (e.g. wheels, rocker-bogie suspension) is 34.5 kg.
 Software Upgrades
On Jan. 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 to transmit an image, and whether 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
Both rovers have passed their original mission time of 90 sols many times over. However, some problems have developed. By sol 415, Spirit's solar power generation was down 40 percent; however, a high wind later cleared dust off the panels, bringing them back to 93 percent. On sol 779, the right front wheel ceased working after having covered 4.2 miles on Mars. Engineers began driving the rover backwards, dragging the dead wheel. They struggled to find a suitable place for the rover to rest, as the Martian winter was coming and the sun was sinking lower and lower. They finally picked Low Ridge Haven.
Honoring Spirit's great contribution to the exploration of Mars, the 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 also has a IMAX show called Roving Mars that documents the journey of both Spirit and Opportunity on their travel to Mars with both CG concepts of their travel and original pictures and videos of their arrival on Mars.
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