Mars Rover Opportunity (MER-B), artist impression
|Mission goal||Mars , Meridiani Planum|
|Launcher||Delta II 7925 "Heavy"|
|Takeoff mass||1063 kg|
|Course of the mission|
|Start date||July 7, 2003|
|launch pad||Cape Canaveral , LC-17B|
|End date||June 10, 2018 (last contact), February 13, 2019 (attempts to establish contact terminated)|
Opportunity ( English for chance / opportunity is) an American reconnaissance robots for geological exploration of Mars , which was active from 2004 to 2018. The probe was launched by NASA on July 7, 2003 as part of the Mars Exploration Rover program . Its original name was therefore Mars Exploration Rover B ( MER-B ) and was later changed to Opportunity.
It landed successfully on January 25, 2004 in a small crater (in the Meridiani Planum Great Plain ), which NASA later named Eagle Crater . Although Opportunity was only designed for a mission duration of 90 sol , it remained active in 5111 sol until June 10, 2018. Its mission ended after 14 years and 219 days when the probe could not be woken up from hibernation after a dust storm . During this time, Opportunity covered a distance of 45.16 km. NASA stated on February 13, 2019 that the program ended successfully after all attempts to communicate with the probe failed.
The aim of the Opportunity probe (MER-B) and its sister probe Spirit (MER-A) was the landing and geological (actually: areological) exploration in areas that were used by NASA's earlier Mars orbiters according to the follow-the-water strategy (" follow the water ”) had been recognized as possibly formerly water-bearing. They had line structures or minerals that suggested the influence of liquid water or perhaps even of previously open water surfaces. A landing site near the planetary equator on the Meridiani Planum plain was selected for Opportunity because there were extensive deposits of hematite on the surface. Among other things, hematite can arise in open water or hydrothermally . Another interesting aspect for the selection of this area was that an orbiter discovered an almost flat, apparently very finely layered light rock formation there, although this was never officially confirmed in advance. Whether these rocks are aeolian (wind deposited ) or aquatic (water deposited) sediments or whether they are tuffites (volcanic ash), light volcanic blankets ( lava ) or special impactites (layered deposits of so-called "rock clouds" from meteorite impacts ), was on the Martian soil before the investigation still completely open.
The mission duration should initially be a guaranteed 90 Martian days (90 Sol corresponds to almost 92.5 Earth days), but Opportunity had exceeded this by far. The mission was extended regularly. The rover passed the 40 km mark on July 27, 2014. With it he drove the furthest distance ever covered on a strange celestial body. By June 2018, 45.16 km had been covered
Technology of the probe
In contrast to Mars Pathfinder , Opportunity was not a fixed ground station, but a mobile robot called a “rover”. It was 1.6 m long, up to 1.5 m high and weighed 185 kg. According to the specification, it should be able to cover around 100 m, a total of around 3 km, per day, depending on the surface properties, and remain operational on the planet's surface for up to six months. This exceeded the capabilities of its predecessor Sojourner from the Mars Pathfinder mission in 1997 by a factor of about 60. The rover was referred to by NASA as a "robotic geologist " and had six independently driven wheels on stilted telescopic legs . He wore in addition to various panoramic - (Pancam), navigation - (navcam) and hazard detection cameras (hazcams - hazard recognition cameras) a pivotable arm with a rock microscope (also with camera), a plurality of spectrometers ( Mößbauer , alpha particles , infrared ) and a mechanical Tool that was able to brush off rock surfaces and drill several millimeters deep on a few square centimeters in order to be able to examine the inside of accessible rock (RAT - rock-abrasion tool). The wheels were moved individually and are not only used for locomotion, but could also be used as scrapers to dig up the ground and thus examine a few centimeters of the soil profile mechanically and photographically. The rover had rechargeable batteries via solar panels and was put to sleep at night to save energy. With the help of its antennas, the device was able to send images and measurement results either to the orbiting orbiters of NASA and ESA used as intermediate stations to earth or directly to earth and to receive commands from there. Because of the relatively long transit time of the signals from the earth (depending on the constellation between 1.4 and 22.3 minutes in each direction), the rover had to be able to act autonomously to a certain extent with its on-board computers.
Course of the mission
Opportunity successfully launched on July 7, 2003 with a Delta II 7925H launcher and landed in the early morning of January 25, 2004 (6:05 a.m. CET ) in the Meridiani-Planum lowlands of Mars. In contrast to previous missions, the lander was not released from orbit, but brought down directly from its flight path with an error tolerance of a few kilometers, which required extreme accuracy on the approach. The probe, protected by a heat shield , was first decelerated in the atmosphere to the speed of sound. Then a parachute unfolded with a rocket system attached to its lines above the probe that was supposed to compensate for horizontal movements in the atmosphere. Shortly before touchdown , the airbag landing system around the probe, developed by ILC Dover , was suddenly inflated to protect it . After touching down, the lander hopped over the surface several times until it came to a standstill in a small crater. After deflating the airbags and opening the landing capsule, the first photos of the rover revealed structures on the edge of the small crater that had never been seen before and which were to become one of the most important objects of observation for Opportunity. They showed that the probe had landed in the most favorable position only a few meters from an exposed section of the targeted light-colored rock formation.
First half of 2004 (Sol 0 to 153) - primary mission
After several days, the rover was unfolded on its landing platform (now called Challenger Memorial station ) and could leave it via a folded down ramp. The floor of the crater, the Eagle Crater is named, was dotted with small beads Blueberries called. In the crater, the marks of the landing airbags were clearly visible. A picture of the infrared spectrometer MiniTES showed the hematite distribution within the crater. No hematite was found where the airbag hit. Apparently the blueberries were pressed into the ground by the airbags and could not be found by the MiniTES. A later examination of an accumulation of blueberries with the Mössbauer spectrometer also showed that these spheres consist of hematite .
Stratified rock was found on the crater rim just a few meters away, the individual layers of which were only a few millimeters thick. For geologists, this meant the advantage of examining rock where it was formed. The blueberries were partly embedded in these rock layers or were scattered in front of them. This indicates the formation of the blueberries within the rock. When examining the rock with the APXS and the Mössbauer spectrometer, indications were found that it contains jarosite . This potassium iron sulphate - hydroxide normally develops in an aquatic environment. In some of the layers, you could see corrugated and cross-bedding structures that usually form in running water. Narrow elongated cavities were found in an outcrop called El Capitain . These spaces arise when crystals form in the rock and are then eroded out. In order to examine the ground, a 50 cm long and 10 cm deep trench was dug with the right front wheel; the blueberries were also found here. It was also found that the soil has a very lumpy structure.
After a two month investigation, Opportunity exited the crater. In order to find out whether the evidence found for liquid water could only be found locally or in the entire region, a crater 750 m away was determined as the next target. This was named after the research ship Endurance , which was used on the Imperial Transantarctic Expedition under the direction of the British polar explorer Ernest Shackleton . Other craters examined were also given names of famous research vessels.
On the way there, a stone called Bounce Rock was examined. This was accidentally hit by the impact of the landing airbag and was broken open. The stone has a volcanic nature and is very similar to the Shergottites, a subgroup of the so-called Martian meteorites . It was believed to have been ejected by an impact from a relatively fresh impact crater 75 km southwest of Eagle Crater.
The rover could cover distances of up to 100 m per Martian day and made very good progress on the flat plain. On the way fissures or fissures were discovered at a place called Anatolia , which could either have been tectonically formed or were formed by a series of impact craters. In a smaller crater called Fram , rock rich in sulfur, chlorine and bromine was discovered. This gave an indication that there must once have been a great deal of surface water that covered the entire Meridiani level.
At the end of April 2004, Opportunity reached the endurance crater. In order to observe the inside of the crater and to discover a possible entry point, the rover first drove along the edge of the crater. Inside, the hoped-for deeper stratifications showed, the ground itself was covered by sand dunes. That is why NASA decided to send the rover into the crater, also at the risk of it not being able to come out. On June 10, NASA engineers began to make some attempts to descend into and out of the crater with the rover, as it was not yet clear whether and how well Opportunity would cope with the underground. After two successful driving attempts, the rover drove deeper into the crater at Sol 133 at a place called Karatepe .
Second half of 2004 (Sol 154 to 332) - Endurance crater
Now the investigation of the layers of the Endurance crater , which is approx. 12 m deep, began. Each layer was photographed and holes were drilled in the rock in several places with the stone grinding tool. This made it possible to create a stratigraphy of the floor of the Meridiani level. By mid-August (Sol 192), the rover analyzed the individual layers almost down to the dunes on the ground. However, examining the dunes themselves was considered too dangerous as the rover's wheels could get stuck in the dunes. While driving on the slopes of the crater, the wheels of the rover slide heavily, so that the exact positioning on interesting objects was very difficult.
A rock formation called Escher on the south-western slope of the crater was examined more closely. This stone contained fault lines that divided the surface into polygons. These fault lines could either have been caused by an impact or by the influence of water and subsequent drying out. In the middle of September 2004 the solar conjunction occurred, i. That is, the sun was between Mars and Earth, so that there was no communication with the probe for about two weeks. On the way to Burns Cliff , a steep slope on the edge of the crater, the large rock Wopmay measuring 1 m in diameter was examined. Like Escher , its unusual surface showed the possibility of strong water influence. The layers of Burns Cliff could not be reached due to the steep terrain. Instead, an extensive panorama was created from it. After this investigation, the rover drove again below Burns Cliff to the entry point Karatepe and from there on December 21, 2004 (Sol 318) again.
The investigations in the Endurance crater showed that the region was not only covered once by shallow, salty water, but was also covered by water several times and dried out again. To confirm these results, a new long-range target called Victoria was selected at a distance of 5.6 km.
First half of 2005 (Sol 333 to 508) - Incident at the dune
The first stop after Endurance was to examine your own heat shield, which had appeared on landing a little south of the crater. This was a unique opportunity to examine this component after its use, including how the heat-resistant material had changed when it entered the atmosphere. Among other things, it was found that the inside had turned inside out upon impact. A few meters from the heat shield, Opportunity discovered its first iron meteorite called Heat Shield Rock .
After examining the heat shield, the rover began its way to the Victoria Crater. Since the area was very flat and monotonous, the rover made rapid progress; so in some cases more than 400 m were driven a day. A first interim goal was reached on Sol 399 (March 8, 2005) at the Vostok crater. However, the crater was completely filled with sand and therefore unsuitable for a detailed investigation. Therefore, we drove further south, to an area called Etched Terrain , which consists of large-scale structures made of bedrock. During the next few trips, the dunes that Opportunity crossed became higher. After the engine of the right front wheel blocked on April 17, 2005, the rover was instructed to drive backwards from now on in order to relieve this wheel.
On April 26, 2005, after a distance of 5.346 km, the wheels of the rover buried themselves in the loose sand when crossing a dune. Since the software was not prepared for such a situation, the wheels continued to turn until the programmed end. All six wheels were now stuck in the sand up to the axles. After that, NASA technicians tried to find a way to free the rover with the help of simulations on earth. Pessimists feared that the mobile mission would end prematurely. On May 13th, the attempt began to carefully pull the rover back in small steps. By June 3, 2005, Opportunity had already been moved 93 cm out of the dune. The wheel revolutions required for this would have been sufficient for a distance of 177.2 m on the open road. Finally, on June 4th, the rover was maneuvered out of the dune. After this five-week breakdown, all wheels could now move freely again. Then the dune, named Purgatory ("purgatory"), was examined to determine what distinguishes it from the numerous dunes that have been crossed without any problems. Since July 5, 2005, Opportunity had been heading for the Erebus Crater again .
Second half of 2005 (Sol 509 to 687) - Erebus crater
After being freed from the sand dune, long distances were no longer driven, which is why the rover did not move as fast as before. Since the alignment of the dunes was mainly in a north-south direction, the space probe could mostly drive along between the dunes and only had to cross a dune every now and then. The terrain called Etched Terrain was reached and it turned out that there was more bedrock between the dunes. This was positive for the ride as the rover had fewer problems on solid rock than when driving on sandy ground. A computer crash occurred on August 21st. This problem was investigated during the next sols, so the drive to the Erebus crater could not resume until September.
On October 5th, a picture of the rover in the Martian dunes was taken by the Mars Global Surveyor . These recordings were important aids for navigation. On November 2nd, the Erebus crater was reached. It was circled on the eastern edge because the ground there was rockier. The crater itself is filled with sand, but smaller cliffs are open at the edges; these were examined later.
On November 20, 2005, the instrument arm was scheduled to extend, but a problem with the shoulder joint motor blocked the command. One reason for this could be that the rover has now been in service for a long time. Engineers investigated the problem over the next few weeks. Meanwhile, the rover stayed in this position and took the panorama called Erebus Rim , which consists of over 1300 individual images.
First half of 2006 (Sol 588 to 863) - Departure for the Victoria Crater
The instrument arm had to be retracted again, as it was hardly possible to drive with the arm extended. On January 20 (Sol 695), the rover continued again after the instrument arm could be stowed elsewhere on the device. Opportunity also carried out coordinated investigations of the atmosphere with its MiniTES spectrometer in combination with the Mars Express probe of the European Space Agency and photographed the passage of the Martian moon Phobos through the solar disk. This allows z. B. the orbit of the moon can be determined more precisely.
From Erebus Crater, a cliff called Payson and the Mogollon Rim, which were still visible from the crater rim, were then examined more closely. Here, too, there were stratified rock layers that were interpreted as sedimentary rock.
On March 17, Opportunity completed its investigation of Erebus and began its journey to Victoria Crater, which is located 2 km southeast. The rover made faster progress over the next few weeks, partly because the dunes were getting lower again, and by June 27, 2006 had covered a total of 8.392 km on Mars. Despite all caution, the rover got stuck in a small dune on May 29th (Sol 833), but was freed from it after a week.
Second half of 2006 (Sol 684 to 1042) - arrival at Victoria Crater
The rover's software was updated in the first half of July. This gave him greater driving autonomy and improved energy management. At the beginning of August, the vehicle reached the Beagle crater , which is about 35 m in diameter and only 500 m from the edge of Victoria ; a month later the vehicle was only 200 m away from the crater rim. During the trip, a cleaning event also occurred again, with dust being blown off the solar panels, greatly improving the power supply. It is precisely because of these events that the service life of the robot has been extended again and again.
The rover reached on 28/29. September 2006 after several short journeys on the three previous sols (30.2 m, 26.4 m and 3.5 m) the edge of the approx. 60 m deep and 800 m wide crater at an indentation that was called Duck Bay . The investigation of the rock layers of the crater should enable even more detailed knowledge about the existence of water on the red planet. During the first recordings of the inside of the crater, the hoped-for rock layers were discovered, which piled up in cliffs up to 6 m high. The task now was to find the best way to get into the crater. So the rover headed north first, partially circling the crater clockwise over the next few months. In each case, images from locations approx. 10 m away were combined into stereo images in order to create a three-dimensional map of the crater.
The Mars Reconnaissance Orbiter (MRO) arrived on Mars in March 2006 and then went into scientific operation in late November. Since the camera resolution of this orbiter far exceeded the previous quality of the previous missions, the surroundings of Opportunity could be recorded in great detail. In early October 2006, NASA released images of the Mars Reconnaissance Orbiter showing the crater and the rover itself.
First half of 2007 (Sol 1043 to 1219) - circumnavigation of the crater
In January 2007 Opportunity drove on to the northern edge of the crater and photographed the cliffs from different perspectives. These were found to be formed from sand dunes that were piled up by north-south winds and then petrified. Another meteorite called Santa Catarina was found and examined here on the northern rim of the crater. On February 9, the 10 km mark was exceeded.
The APXS was used for the first time to determine the content of the noble gas argon in the Martian atmosphere. To do this, the instrument was pointed towards the sky and measurements were then taken for about three hours. These investigations were also carried out by the twin rover Spirit on the other side of Mars. This was hoped to provide a better understanding of how the mixing ratio of argon to carbon dioxide changes over the course of the seasons when the carbon dioxide precipitates at the poles.
In March the valley without peril was reached, which was seen as a possible entry point into the crater. Here it turned out that the slope was too steep to drive into this point safely. After examining two more cliff ledges, it was decided to drive all the way 600 m back to the original destination in order to descend into the crater. On the way back, the solar cells were cleaned by a few gusts of wind. The available energy rose to almost 800 Wh (watt hours) per sol. This was almost as much as it was after the landing three and a half years earlier. On June 15, Opportunity reached Duck Bay again , preparing to enter the crater.
On January 4th, 2007, both rovers got new control software for their computers. The new system gave the rover more freedom of choice as to whether an image should be transmitted or whether the instrument arm should be extended. This saved the scientists time, as they no longer had to evaluate hundreds of images.
Second half of 2007 (Sol 1219 to 1398) - The dust storm
The planned entry had to be postponed because from the end of July 2007 a dust storm obstructed the probe, which soon encompassed large parts of Mars. The dust that was blown up almost completely darkened the sky so that the solar panels could no longer recharge the batteries. To save electricity, all activities have been stopped. The probe should wait for the storm to end with the lowest possible power consumption. This waiting turned out to be very difficult because the probe (also due to its short life expectancy) was not designed for such situations. In power-saving mode, the probe generates too little heat to keep the electronics at operating temperature. If the temperature of the electronics falls below a certain value, the automatic heaters start to prevent cold damage to the electronic components (below -37 ° C). However, these consumed more electricity than the probe could still produce during the storm (at temperatures as low as −80 ° C). The heaters would therefore empty the batteries very quickly, which would lead to a permanent shutdown of the probe. Since the end of July, the rover has been kept active a little longer to prevent the heaters from starting.
The probe switches itself off when the batteries are at a critical charge level and only checked each sol once to see whether enough energy would be available to switch it on again. Excessive dust deposits on the panels were also feared, so that the probe would not have been able to gain enough energy to switch itself on again completely.
In mid-August the storm weakened and the transparency of the atmosphere increased again. Opportunity had weathered the six-week dust storm. The next problem was that the dust raised by the storm was deposited on the solar cells.
On September 11th, Opportunity was able to drive into the crater. Here, a lighter layer of rock (bright band) was first examined , which was discovered while driving around the crater. This layer is visible everywhere on the crater rim. The investigations showed that this lighter rock layer was formed by diagenesis . This rock layer separates the bedrock from the material that was ejected by the impact.
First half of 2008 (Sol 1399 to 1575) - Victoria Crater
Over the next few weeks, Opportunity investigated this geologically interesting rock layer and worked its way deeper into the interior of the crater. Among other things, a narrow, protruding rock ridge was discovered at a location called Gilbert . This ridge is made up of minerals that were originally deposited in crevices and then left over after the surrounding rock was eroded away. Analyzes with the APXS and the Mössbauer spectrometer showed that the ridge, like the blueberries, consists of hematite.
At the end of April, the measurements were completed and the Cape Verde cliff should now be explored more closely. The drive there turned out to be problematic: the rover slipped very badly on the sandy and 25 ° steep rock bottom and in mid-May the middle right wheel also buried itself in the sandy soil. In addition, problems with the instrument arm reappeared in April. This could not be unfolded because of the shoulder joint motor. Only after several attempts could it be moved again. The further routes had to be planned carefully, however, as the journey with an extended instrument arm was difficult.
On June 19, 2008, Sol 1565, Opportunity was within 10 meters of the lower area of Cape Verde . From this position, called Cape St. Mary , a detailed panoramic view of the cliffs was then taken. In the vicinity of the cliff, attention had to be paid to the shadow cast by the cliffs so as not to endanger the power supply. The cliffs themselves could not be reached because the ground in front of them was too steep and sandy.
Second half of 2008 (Sol 1576 to 1754) - Farewell to Victoria Crater
In July an attempt was made to reach some geologically interesting rocks near Cape Verde . However, the terrain turned out to be too difficult to navigate. On July 24th (Sol 1600) an unusually high current was measured on the motor of the right front wheel. On the Rover Spirit, a wheel failed after a similar power surge and could not be reactivated. Since Opportunity could never leave the crater with a defective wheel, the decision was made to abort the investigation of the crater and to drive out of the crater as quickly as possible. On August 24, 2008, the rover drove out of the crater at Duck Bay .
After Opportunity had reached level ground again, it was tested at the beginning of September how to drive and work with the defective instrument arm. Following the tests, the rover drove on to the southern edge of Victoria Crater to take pictures of the cliffs located here. In the flat environment, distances of more than 200 m could be driven per day.
At the end of October the journey to the Endeavor Crater began . This crater is about 12 km away and has a diameter of 22 km and a depth of 300 m. Here, too, they promised access to deeper rock layers and thus insight into the earlier history of Mars. However, since the dune fields were too high on the direct route, the rover had to make a detour of about 19 km. So the rover headed southwest first. Thanks to the high-resolution images of the Mars Reconnaissance Orbiters, on which even individual rocks and the dune ridges can be seen, the route could be planned very well in advance.
On November 29th the solar conjunction began and with it another phase in which no probe on Mars could communicate. During this time Opportunity took a panorama and analyzed the Santorini stone with the Mössbauer spectrometer. Santorini turned out to be a mesosiderite meteorite.
First half of 2009 (Sol 1755 to 1930) - trip in the Meridiani plain
After the solar conjunction, the rover continued in a southwesterly direction. Thanks to the autonomous control system, distances of up to 150 m per day could be covered again and again. But the age of the rover and its components became noticeable: after some stretches of sandy soil had been covered, the currents in the front-wheel motor increased again. Therefore, some stretches were covered by reversing. This improved the behavior of the engine, but the rover made slower progress in this mode. In addition, rest breaks were repeatedly taken so that the bike could recover. During the breaks, the lubricant is distributed in the wheel bearing. This results in less resistance and also less power consumption on the next trips. Opportunity passed a few smaller craters that are estimated to be only 10,000 to 100,000 years old. On Sol 1884 (May 12, 2009) the probe discovered its fifth meteorite: Kasos.
Opportunity gave its sibling rover an unusual help on May 19, 2009. Spirit had buried itself in sandy soil on the other side of Mars. In order to better assess the situation, it was necessary to get a picture of the situation that was as precise as possible. The only camera that could look under the rover was the microscope camera on the instrument arm. However, this was only intended for close-ups, but the recorded image could be rendered sharp afterwards due to the known optics . To do this, Opportunity took some pictures of its sub-floor to see if this technique was delivering the desired results.
By June 29, the distance covered had grown to 16.712 km. While previously driving in a southerly direction, Opportunity now moved a few hundred meters in an easterly direction to avoid a field with high dunes.
Second half of 2009 (Sol 1931 to 2109) - meteorite finds
On July 19, a larger stone was discovered in older photos, which Opportunity had previously driven past at some distance. Since the stone appeared unusually large, it was decided to let the rover drive back the distance of approx. 200 m that had just been driven in order to examine this stone. Within a few days, the 70 cm boulder called Block Island was reached. Like Heat Shield Rock, it turned out to be another iron meteorite. What was particularly striking about this meteorite were the unusual depressions that must have been created by weathering processes. In order to determine the most precise three-dimensional model of the object possible, the rover circled the meteorite and took pictures from a total of six different positions. Shortly after Block Island was left, the next meteorite, Shelter Island , came into view on the plain at the end of September . This was also examined more closely. On October 15, the third meteorite, Mackinac , was discovered. Apparently these meteorites are fragments of a larger meteorite that came down in this area.
Opportunity now drove south in larger stages on solid rock to aim for a newer crater that could already be seen from Mars orbit. On the way there, the rover came across the next larger boulder, Marquette Island , in early November , where the origin was initially unclear. With the stone grinding tool, which had become almost blunt due to years of use, at least the top layer could be ground off and the stone at this point examined with the remaining instruments. In addition, the stone itself had already broken apart on one edge, which made it easier to access its interior. It turned out that Marquette Island must be a basaltic rock from the interior of Mars that one day was hurled out of the depths by a crater impact.
First half of 2010 (Sol 2110 to 2285) - Concepción impact crater
On Sol 2122, January 12, 2010, Opportunity completed its analysis at Marquette Island and continued its journey. The next target was already visible on images from MRO: An apparently fresh impact crater called Concepción, surrounded by dark ejector rays. The researchers estimated its age to be on the order of 1,000 years. This made Concepción the youngest crater ever examined. The rover circled the crater and took it from different perspectives. A stone called Chocolate Hills was examined more closely because a dark crust was discovered on its surface. This could have been caused by melting processes during impact. On March 9th (Sol 2177) the investigation of Concepción was completed and the journey continued in a southerly direction. In March 2010, another software update was put into operation, which gave the rover even more autonomy: after a completed journey, the system called “AEGIS” (Autonomous Exploration for Gathering Increased Science) searched for conspicuous objects and automatically photographed them.
The journey continued south past a double crater. The Martian winter made itself felt. Due to the energy-intensive journeys, the batteries have to be charged, so the rover paused one or two sols between individual journeys. In order to get as much solar energy as possible, the rover was parked at an angle on the dune slopes. In order to prevent the energy-consuming heating elements from starting in the cold weather, the rover was kept awake longer.
In May, an attempt was made to use the inertial measuring device to detect a mars quake, but it did not succeed.
On May 19, Opportunity broke the record for the longest-running spacecraft on a planet, set by Viking 1 with a duration of 6 years and 116 days.
Second half of 2010 (Sol 2286 to 2464) - stopover at Santa Maria crater
Due to the increasingly long sunshine and wind cleaning events of the solar panels, more energy was available again for Opportunity's trips. On July 28, the rover was able to take a photo for the first time of a dust devil occasionally cleaning the solar cells. So far this has only been achieved by Spirit in Gusev Crater on the other side of Mars.
On the way to the Endeavor Crater, the rover's automatic navigation, supported by the hazard avoidance cameras (Hazcam), was tested, which allows the rover to drive autonomously. The rover drives backwards because the field of view of the forward-looking Hazcam is partially blocked by an unfavorably mounted antenna. On December 16 (Sol 2450) the rover reached the 80 m large crater Santa Maria and examined it more closely over the next few weeks.
First half of 2011 (Sol 2465 to 2640) - Course on Cape York
At the beginning of the year, the rover circumnavigated the crater halfway and positioned itself at one point on the crater rim. At this location hydrated sulfate minerals were discovered on images taken by the MRO probe. This only forms in connection with water. At that time the solar conjunction began again. This time was used to examine this rock with the Mössbauer spectrometer.
By March 24, research on Santa Maria Crater was completed and the rover resumed its journey to Endeavor Crater. The distance between Cape York and Santa Maria is approximately 6.5 km.
Second half of 2011 (Sol 2641 to 2819) - Endeavor Crater and Cape York
By July 5, the rover had made 18.0 km or 90% of the way to the Endeavor crater. At this point in time the total distance traveled in the Meridiani Plain was 31 km. Further (possible) meteorites were photographed on the way, but they were not analyzed further. Although Opportunity was only 1.1 miles from Cape York, this property was not yet in sight. The reason was that Cape York was on a slope on the edge of the crater of the Endeavor crater and thus remained hidden from the rover. The small crater Spirit Point (named after the twin rover Spirit ) to the south of this structure was announced as the arrival point at Cape York .
After Opportunity left the Victoria Crater on August 28, 2008 (Sol 1634), the rover was able to cover more than 21 km in over 1000 Sols and, on August 9, 2011 (Sol 2681), almost three Earth years later, the Endeavor Crater to reach. Together with the distance covered before August 28, 2008, on August 9, 2011 it was 33.49 km. In the next earth year it moved a little more than 1 km along the crater rim. The low mileage is mainly due to the Martian winter, which lasted about half of the 12 earth months (December 2011 to June 2012).
The Endeavor crater has a diameter of 22 km - about the size of the Nördlinger Ries - and offered researchers new opportunities to examine older rock layers. In particular, they were on the lookout for layered silicates, which can only form in connection with water. The interior of the crater should not be driven into, as the same rock layers were expected there that had previously been examined in the Meridiani plain.
A rock called Tisdale was hurled out of the rim of the Endeavor crater by a later impact. It was on the southern edge of the Odyssey crater. He was found to have a high concentration of the element zinc . This indicated that it was altered by hydrothermal processes. After the impact that caused the Endeavor Crater to form, heat was released, which melted the water ice in the underground. This water distributed the dissolved minerals into the surrounding rock.
During the investigation of the Cape York area, noticeably lighter colored veins were discovered. On closer examination of such a vein called Homestake with the X-ray spectrometer, it turned out that it consists of pure calcium sulfate (gypsum). One explanation for this is that water used to flow through the subsoil. The dissolved calcium sulfate then settled in the cavities. These two discoveries are further indications that liquid water was at least temporarily available on Mars to provide a livable environment.
Since the energy supply of the rovers had become more critical than in previous years due to the accumulated dust, they looked for a wintering place where the rover could better survive the winter inclined to the sun. This location was found in the north of Cape York and was approached by December 2011.
First half of 2012 (Sol 2829 to 2997) - Greeley Haven
The place where Opportunity was supposed to hibernate was named Greeley Haven after a late NASA scientist . At this point there is a rock outcrop that was examined more closely with the instrument arm. Since the rover was not moved during the winter months, an experiment with radio waves was carried out during this time: An attempt was made to detect the smallest tilting movements of the axis of rotation of Mars using radio signals from the rover. This enables knowledge to be gained about the internal structure of the planetary core. After a long winter break, Opportunity moved the first 3.7 m away from its winter quarters on May 9, 2012 in order to continue the investigation of Cape York. First, recordings of the wintering position were made in order to be able to assess the measurements carried out during the winter time in context. The journey was continued from Cape York in a northerly direction in order to carry out further investigations of the soil and further gypsum veins.
Second half of 2012 (Sol 2998 to 3176) - Further investigation of Cape York
On July 2nd, 2012 Opportunity was able to celebrate its 3000th Martian day (corresponding to 3078 days on Earth). On July 5, NASA published a new panorama of Cape York and the Endeavor Crater, which the rover had taken in high resolution during its winter break. The panorama image consists of over 800 individual images that were taken between December 21, 2011 and May 8, 2012.
The energy production of the rover increased from Sol 2989 (June 20, 2012), due to better solar radiation, clear skies and solar cells cleaned by wind, from below 400 to over 500 Wh per sol.
A few days before Curiosity's arrival , Opportunity was programmed for 9 days and then “parked” to keep the orbiter and radio network free while Curiosity arrived. The odometer count was on August 7, 2012 (Sol 3035): 34.64 km.
On August 12th (Sol 3040) the journey was continued and the small crater Sao Rafael was recorded with the panorama camera while driving past.
Opportunity hadn't moved very far since late August. The 35-kilometer mark was already exceeded on August 28, the 22-mile mark only at the beginning of November. After one of the shortest movements of 23 cm (9 inches), the odometer reading on December 4, 2012 is given as 35.43 km (22.02 mi).
First half of 2013 (Sol 3177 to 3352) - end of the investigation of Cape York
Even if the exact location had changed (Opportunity was at Copper Cliff in early January and at Fullerton 1 in late January ), the rover moved very little (50 m in 2 months). For the holidays at the turn of the year, research work had been programmed on site. In addition to the continuation of the soil investigations in the run-up to Christmas, the atmosphere (density and argon) was investigated. The day before the perihelion of Mars was Sol 3200. Opportunity had reached 35.5 times its primary mission time and traveled about one kilometer per 90 sols. From January 7th to February 27th there were no "dementia" problems with the flash file system.
On February 28th an unexpected reset was triggered due to an error in the flash file system. Afterwards, Opportunity was in the so-called “auto mode” for 2 days, that was a safe state with daily waking up, in which the rover only monitored its own state (especially its own temperature). On March 2, the command memory was deleted by a targeted immediate command and new commands were uploaded. After that, the rover worked fine again for a week. If the problems worsened, the flash file system should be reformatted in order to achieve a complete recovery. On March 9th there were again minor problems with the flash file system, but not the same as before. Therefore, the system should first be observed further.
On March 11th, the rover finished its local "walk" and looked again at the Newberries at Kirkwood . After 10 days on site, the rover started moving again on March 21 and positioned itself at Big Nickel . He observed this place for about 3 weeks because due to the conjunction on April 18th, communication with the Mars rovers and orbiters was not possible between April 9th and 26th. For this reason, no trips were planned from April 9th to 26th, only movements of the arm and analyzes of the immediate surroundings. When contact was made again on April 27, it was found that Opportunity had gone into standby mode on April 21 due to a memory error. On May 1st, the rover could be returned to normal operating condition. On May 16, 2013 Opportunity had covered a total of 35.76 km, more than the Apollo 17 moon car . The rover with the longest covered distance was at this point still Lunochod 2 with 39 km.
In June, the exploration of the Cape York rocks was completed and the course set for a new target: Solander Point . These are hills south of the Cape, which should be reached after a drive of 2.2 km. There are north-facing slopes on which Opportunity would survive the approaching Martian winter.
Second half of 2013 (Sol 3353 to 3531) - Solander Point
On July 10th, the energy production was at least 435 Wh. Dust had still deposited on the panels, so that only 60% of the incident light could be used to generate electricity.
During the journey the rover made so good progress that it was decided to take a detour into the crater. After this detour, the foot of the hill called Solander Point was reached around August 8th. For the ascent to the hill, a route was chosen so that the angle of inclination of the solar panels was optimal. The slopes of Solander Point give an insight into the Noachian period . Rocks from this early Martian historical period are usually buried beneath the surface of the Meridiani Planum. It was only through the impact that created the crater that these layers were lifted upwards. Solander Point rises approx. 55 m above the Meridiani Planum. On October 1st, attempts were also made to photograph comet ISON . This failed because it was not bright enough for the rover's panorama camera.
On December 6th, the probe switched to safety mode after transmission problems. At this point in time, solar energy production was only 268 Wh per day. Further transmission problems occurred in the following 3 days. A functional check showed no technical problems with the system. On December 10th, Opportunity exited safe mode. The mileage was now 38.7 km.
First half of 2014 (Sol 3532 to 3707) - Murray Ridge
At the beginning of 2014, the rover had kept an incline that best captured the sun shining from the north. Mars reached its aphelion on January 3, 2014, the most distant point in its orbit. On January 1st another cleaning event of the solar panels happened, which increased the energy production by 35 Wh to 371 Wh per sol. The rover was positioned at a rock outcrop where observations from Mars probes suggested small amounts of clay minerals. A rock fragment, called Pinnacle Island , which was not present on previous images, first appeared in the January 7th images. It turned out that the rock was run over by the rover, whereupon it jumped to the position where it was found. January 25th was the 10th anniversary of the landing, which NASA celebrated accordingly. The mission was originally only intended for 3 months, but could be extended again and again.
With the goal of Solander Point and Cape Tribulation , Opportunity continued on February 14th: At these locations, too, clay-containing rock was discovered from orbit, which indicates former pH-neutral water resources. Opportunity should go up there and categorize the rocks.
During the ascent along the Murray Ridge , an area called Cook Haven was examined in more detail. In the middle of April, panoramic photos were taken as the view into the Endeavor crater was excellent. On Sol 3655 (May 6, 2014), Opportunity began the first of a series of steps to correct the internal clock drift. This clock, on which some important timed actions of the rover depend, is easily wrong. Due to the long duration of the mission, the clock has accumulated such a difference to real time that some subsystems are affected. In order to correct this, a few corrections in the range of seconds were carried out over the course of a year in order to finally correct the deviation. Towards the end of the Martian winter, energy production improved noticeably and rose to 661 Wh on April 1, also thanks to the support of several cleanup events.
Opportunity reached Pillinger Point in May and investigated this area of clayey rocks on the edge of the crater. At the beginning of June 2014, write errors occurred in the rover's flash memory, with the result that the on-board computer restarted.
Second half of 2014 (Sol 3708 to 3886) - Ascent to Cape Tribulation and other memory errors
In July 2014 Opportunity exceeded the record set by Lunochod 2 of 39 km traveled on a foreign celestial body. Opportunity drove south along the ridge of the Solander Point. At the beginning of July 2014, electricity generation rose to 745 Wh per sol. Due to the good energy situation, the Martian moon Phobos could again be observed at night. In addition, measurements of the argon content of the Martian atmosphere were made with the APXS.
On August 7th, Wdowiak Ridge , a protruding rock formation with an adjacent crater (Ulysses), was reached. There was a very good view of the Endeavor crater and the surrounding Meridiani plain. However, further memory errors occurred which caused the probe computer to restart. These errors delayed the work, as several days pass before the error was identified and corrected. To eliminate these problems, the flash memory was reformatted and the defective memory areas were mapped out. 5 years earlier, problems with the Spirit rover could be resolved with it; this was done for the first time with Opportunity. Its storage units have been in continuous use for 10 years and exposed to cosmic rays. In September, however, further errors occurred with the flash memory: The memory could not be accessed after the morning start.
On October 19, Comet Siding Spring C / 2013 A1 flew very close (139,000 km) past Mars. Opportunity was part of a campaign by the entire Mars space probe armada to take pictures and take measurements of the comet. Here the rover actually got some (blurred) images of the comet.
On November 4th, measurements at Wdowiak Ridge were completed. By December 17, the rover drove a total of 41.42 km. The next goal was a deepening called Marathon Valley (after the distance in the marathon run ), also a possible location of clay-containing minerals.
Due to the existing problems, the flash memory was reformatted again in December 2014, but without success. So the decision was made to run the rover without Flash. This was possible, but all results had to be sent back one day before the computer was “put to sleep”, otherwise they would be lost when the computer was asleep.
First half of 2015 (Sol 3887 to 4062) - Spirit of St. Louis crater
On January 5th, Opportunity reached the summit of Cape Tribulation , the highest point of its 11-year journey to date. This point is 135 m higher than the Botany Bay plain from which the rover began the ascent of the rim hill.
The technicians tried to find out which part of the flash memory was no longer working so that it could be deactivated and the remaining memory could be used again.
After the rover's flash memory had not been used for three months to avoid errors, the memory was reformatted on March 20th. In addition, the software was updated so that the rover no longer used the probably defective memory bank no. 7. (The rover's memory contains, among other things, a 256 Mbyte flash memory, divided into 7 address areas (banks).) On March 27th, however, another "amnesia" event occurred. The actual reason for these malfunctions could not be found (as of early April 2015). These could not always be assigned to a specific memory bank.
On March 24, 2015, the rover had covered a distance of 42.195 km from the landing site, the length of a marathon.
The Marathon Valley was chosen as a scientific destination because spectroscopic images from orbit suggested exposed clay rocks here. Before the rover entered the valley, the Spirit of St. Louis crater was examined. Inside this crater there was a rock structure that rises higher than the crater rim.
On April 25, 2015, the rover reached the 4,000th Martian day (Sol) since landing in January 2004.
In June there was another solar conjunction, in which Mars passed behind the sun from the Earth's perspective. Meanwhile, Opportunity carried out some basic activities such as B. perform an APXS scan of a selected object. After the solar conjunction, the rover was still operated in "RAM-Only" mode. H. the determined data was not copied to the flash memory. The study area from April to June was the Spirit of St. Louis Crater on the western edge of the Endeavor Crater. This has a weathered crater rim and a crumbled central mountain, informally called "Lindbergh".
The energy production of the solar cells reached between 395 and 620 Wh per sol in the first half of 2015.
Second half of 2015 (Sol 4063 to 4241) - Entrance to the Marathon Valley
At the beginning of the 2nd half of 2015, the rover began entering the Marathon Valley. This extends over 330 m from west to east into the Endeavor crater.
Based on the orbit data, the highest concentration of phyllosilicates should be found here. In order to get a more precise map of the distribution of these silicates, the CRISM instrument on the MRO was operated in ATO mode (along-track oversample). This technique increases the resolution of the data from 18 m to around 5 m per pixel. This enables the scientists to determine the location of the silicates more precisely.
The route through the Marathon Valley was planned in such a way that Opportunity would drive along the southern slope in the Martian winter so that the maximum energy yield can be achieved here.
In June the rover continued to operate in RAM-only mode while the flash file system was examined. It was reactivated on July 18 and initially worked quite well; on the next sol, however, it was not possible for the rover to restart from the flash system. Therefore, the system switched back to RAM-only mode. However, this required the rover to remain active until the UHF link could be established for each sol. If the Mars Odyssey Orbiter is used for this, the connection came about later every sol.
During the Martian winter, Opportunity was able to rely more on the MRO as the connection could take place earlier in the day.
An additional challenge in establishing the radio link with the orbiters was the position in the Marathon Valley with its high walls to the north and west.
On September 25th, the rover was reset which interrupted all planned actions. The reason for the reset was suspected in the flash system.
In December the rover was positioned on a steep slope to improve the energy production from the solar panels. The immediate objective was to position the rover in such a way that an important object to be examined could be sharpened with the stone grinding tool. This object was intended to provide clues as to the origin of the spectral signature of clay minerals discovered in the Marathon Valley.
A distance of 42.65 km had been covered by December 15, 2015.
First half of 2016 (Sol 4242 to 4419) - Marathon Valley
In the first half of 2016, the rover drove a total of only 260 m in the Marathon Valley and covered a total distance of 42.91 km. One reason for this was the winter time, with the winter solstice on January 3rd. During this time, objects on the northern slope were examined in order to collect as much energy as possible through the solar cells. Stones were scraped off with the Rock Abrasion Tool (RAT) in order to obtain further information on the spectral signatures of clay soils.
In early February, the rover climbed a steep slope called Knudsen Ridge to reach objects with high scientific potential. A panorama of this hill was also taken for this purpose. Some objects were examined more closely with the microscope camera. Due to the steep slope (sometimes up to 32 °, the steepest slope that the rover had to drive in its previous mission) and loose ground, some journeys led to increased slip, so that these journeys were canceled by the rover.
In March he reached an area that the Mars satellites recognized as rich in clay. The rover took pictures of this with the panorama camera using different filters. This enabled the mineralogical composition of the stones to be estimated. At the end of May a small trench was dug with a rover wheel, which was then examined more closely with the microscope camera and the AXPS device. The measurements of the argon concentration continued.
The navigation camera was also used to take pictures for a cloud film. On March 31, the rover was able to take a photo of a dust tornado (dust devil). These are much rarer in Endeavor Crater than in Gusev Crater, where Spirit was stationed.
At the end of June, the investigation of the Marathon Valley was nearing completion. In June the MER mission was extended for the 10th time. The central object of investigation of this extended mission should now be the investigation of a small erosion channel (“gully”) in the Endeavor crater.
Second half of 2016 (Sol 4420 to 4598) - Marathon Valley surveys completed
During the journeys on the steep slopes of the Endeavor Crater, autonomous journeys were repeatedly canceled. In such a case, the team ran tests the next day to find the cause. Most of the time, the demolition was attributable to the difficult terrain. The rover interpreted increasing resistance on at least 3 wheels as an indication that the wheels were sinking into the ground. The immediate stop was to prevent the rover from digging in , as in April 2005 . However, high inclines also put more stress on the bikes' motors, which is why the software incorrectly intervened during these journeys.
If the data transfer rate allowed, the flash memory was also read out in order to obtain data for troubleshooting.
In August the rover drove to an area where interesting gullies were found. It has been speculated that these could have been caused by river-like events. Stereo images were also recorded. To do this, the rover drove to two points 5 m apart and created images in several wavelengths with its panorama camera. With the help of these recordings, the scientific team was able to create a detailed digital elevation map of the terrain containing the channels.
On September 1st (Sol 4482) Opportunity drove through a gap in the rock (called the Lewis and Clark Gap ) out of Marathon Valley to conduct further investigations on the slope of the crater rim.
As usual on Mars at this time of year, dust storms occurred. None of them threatened the rover directly, but they reduce the transparency of the atmosphere, which negatively impacted the rover's energy production (from 588 Wh on August 15 to 515 Wh on September 13).
By mid-November, the rover had a total distance of 43.51 km.
First half of 2017 (Sol 4599 to 4774) - drive to the Perseverance Valley
Earlier this year a small valley called Willamette was examined. Grooves had been discovered here in images taken from orbit. The rover had churned up the surface layer while driving and found interesting light-colored material there. This was examined with the AXPS and the microscope.
In January, the rover set out to investigate a ditch or channel one kilometer south of the current location. In this environment, however, it was difficult to move the rover as the slopes were up to 20 °. In addition, the ground broke into loose material under the weight of the rover. The programmed trips were aborted because one bike was drawing too much power. Analysis of the images recorded afterwards showed that the surface material crumbled and the wheel was therefore spinning.
The channel is located on the western edge of the Endeavor Crater at Cape Byron and is approx. 200 m long, but only a few dozen meters wide. On orbital images it appears as if it could have been cut by water. This is indicated by branching channels. A small, nearby crater superimposed on the crater rim shows that the channel is a very ancient geological formation, 3 to 4 billion years old.
Communication also took place via the MAVEN orbiter.
In February Opportunity left the crater rim in order to reach its scientific goal more quickly in the flatter Meridiani Plain. In addition, the rover created a new color panorama called Rocheport .
At the end of February, a dust storm hit a few hundred kilometers west of the rover, so that the atmospheric permeability at its location fell. However, the rover was able to continue on its way south to the Perseverance Valley ("Valley of Endurance") in March.
In early May, the rover arrived at Perseverance Valley and began making stereo recordings for a detailed digital elevation model of the valley for route planning. Images from orbit also show a canal or ditch in Perseverance Valley. Opportunity took panoramic photos of the area around the rover to document the morphology of the canal and its surrounding structures.
On June 4th it was planned to move the rover backwards in a short arc. Here, however, the engine of the left front wheel blocked. The wheel remained aligned at a 33 ° angle. On June 8th, the bike should be aligned in the direction of travel again. Despite different tested currents, the wheel could not be moved. However, the same tests with the right rear wheel were successful. While the team checked the status of the rover and worked out possible solutions, recordings were made with the PanCam. After a few days the problem was resolved and the rover was able to continue driving. The cause of the problem could not be determined. The wheel could now be aligned so that it is pointing straight ahead in the direction of travel. This alignment of the wheel simplified the control of the rover considerably. Since the right front wheel has not been able to steer since April 2005, only the rear wheels were used to steer.
Second half of 2017 (Sol 4775 to 4953) - Perseverance Valley
From July 22nd to August 1st, NASA was unable to send signals to the Mars probes and rovers, as Mars, as always, passes the position of its conjunction beyond the Sun every 26 months at this time . Opportunity was parked at the top of Perseverance Valley. The rover was able to stay there for the next three weeks until the influence of the solar radiation , which was disrupting radio contact, had sufficiently subsided. Before that, tests were carried out to control the wheels.
Although no commands were sent, some data could be received from Opportunity to Sol 4797 . This limited amount of data indicated that Opportunity had entered a safe mode. The rover did not execute any of the programmed sequences until it received new instructions from ground control. It was suspected that a reset of the on-board computer had occurred during the morning communication session on the X-band. The rover was stable and was able to carry out the planned X-band and UHF relay communications during the remainder of the solar conjunction. A closer examination of the problem had to wait until communication was resumed after the conjunction.
After the solar conjunction, recordings were made again that had been lost due to the reset during the conjunction.
With the approaching winter, the energy levels dropped and the rover was forced to only charge its batteries on a few days. On August 8th, the energy production was 319 Wh with an atmospheric optical thickness of ≈ 0.723 and a dust coverage (dust factor) of the solar panels of 0.531. The strategy for the drives was to go down the valley and stop in places that sloped north or were sunlit. This strategy was called "Lily Pad" and should ensure the best possible energy yield. However, the energy production was sufficient to conduct research during the winter months. So far it has not been possible to determine whether and how much water had contributed to the formation of the Perseverance Valley. The researchers expected further evidence from the deposits at the bottom of the valley.
On December 18, the distance covered was 45.08 km. The energy production was 390 Wh, at = 0.459 and a dust factor of 62.2%. Between November 8th and 14th, the solar panels were partially freed of dust by wind, which improved the energy situation somewhat.
First half of 2018 (Sol 4954 to 5129) - Dust storm over the Perseverance Valley
Earlier this year, the rover was moving along the northern section of a local flow channel. With further cleaning events, the solar panels supplied more energy and the rover could work longer during the day, sometimes also at night. In addition, the AXPS could be operated overnight.
On February 16, 2018, the 5,000th Martian day since landing on Mars was reached. To celebrate this, recordings were made with the microscope camera at the end of the robot arm in order to create a “selfie”.
A scientifically interesting rock outcrop called "Aguas Calientes" was also examined. For this purpose, the Rock Abrasion Tool (RAT) was used, which was able to grind a 2 mm deep hole in the stone. A microscope camera was used to make a mosaic of this hole. With the APXS, measurements were then carried out over several Sols. In addition, multispectral images of the rock were made with the PanCam.
The dust storm
A local dust storm hit near Opportunity in June 2018 . The first signs of the storm, which is still 1000 km away, were discovered by the MRO on June 1, 2018. Further weather reports from the MRO and the Mars Color Imager team indicated a prolonged storm. At the time, this was still a long way from the rover, but it influenced the atmospheric permeability (opacity) at the location there.
Within a few days the storm had spread. As a result, plans were developed on June 4th and 5th to be prepared for the expected lower power supply. Since then the atmosphere over the rover had continued to cloud. On June 3rd, the 5105th Sol, Opportunity's solar panels were still generating 468 Wh. The optical thickness of the atmosphere was about 1.0, which means that only about 37% of the incoming sunlight penetrates the atmosphere.
On June 4th, the energy supply decreased to 345 Wh at = 2.1; on June 6th, only 133 Wh were generated ( ≈ 3.0). Opportunity has not seen such high values since the last dust storm in 2007 . At that time it was ≈ 5.5. The current storm caused ≈ 10.8 on June 10, 2018 and already covered an area of 41 million square kilometers, about as much as North America and Russia combined and thus a quarter of the surface of Mars.
The rover team created another plan in which the rover only receives the latest commands on the first sol in the morning and sleeps until the next morning. He then woke up in the afternoon to take atmospheric measurements with the pancam and have a short communication session with the MRO orbiter. However, scientific research has been discontinued.
The rover needed the electricity generated by solar panels to keep the central electrical components warm. The cold was believed to be the reason that Opportunity's twin rover Spirit stopped working in 2010.
Such dust storms are not surprising, but rare. They can arise within a short time and then last for weeks to months. During the southern Martian summer, sunlight heats dust particles and brings them higher into the atmosphere. This creates wind, which in turn raises more dust. The scientists are still trying to understand this positive feedback loop.
Opportunity's team had requested additional communication time from NASA's Deep Space Network in order to receive updated data from the Mars probe. From the data obtained, it was determined that the rover's temperature had dropped to -29 ° C. One advantage of a dust storm could be that the temperature differences are no longer as strong as they are on the surface of Mars. The dust that was blown up also absorbed solar radiation, so that the ambient temperature at the Opportunitys site was increased.
The storm was classified by NASA as a global dust storm (“Planet-encircling Dust Event” (PEDE)) at the end of June. If the dew value had risen even more or the dust coverage of the solar panels had increased even more, then it was possible that the rover's clock had also stopped working. Failure of the clock would have made it more difficult to restore functionality, but it would not have prevented it. It was also possible that the batteries had lost some of their total capacity from being completely discharged if the cell voltage had dropped to almost zero.
It was heard every day after signals from the rover. Since the mission clock could have failed, signals were also listened to during a larger time window. In addition, commands were sent with which the rover should send back a short beep when awake. The rover was not expected to answer until the dust storm had significantly calmed down and the atmosphere had cleared up significantly.
Second half of 2018 (Sol 5130 to 5308) - End of the dust storm and attempts to contact the rover
The rover, which is almost 15 years old, had not contacted us since June 10th. In the meantime the storm was in its final phase, i. H. more dust fell from the atmosphere than new dust rose. When the sky cleared up, the rover should recharge and try to re-establish communications.
From mid-July, signs were discovered that the dust storm was weakening. The areas where the dust rose became smaller and some surface structures became visible again. No new storm activity has been detected since mid-August, 3,000 km around Opportunity's location. Since then the value has fallen. Scientists had carried out several studies on the status of the batteries before the storm and the temperatures on site. Because the batteries were in relatively good condition, they shouldn't have been damaged too much. In addition, the ambient temperature is rather warm during a dust storm, so the rover should be warm enough to survive the storm.
During the storm, the dust content of the atmosphere had risen to ≈ 10.8; the usual value at this location on Mars is 0.5. As the storm calmed down, it dropped to just over 2. To recharge the rover batteries, a <2 was required.
Attempts to contact Opportunity using the Deep Space Network were made several times a week. The antennas sent a ping signal during the times the rover was supposed to wake up. Then an attempt was made to detect signals from Opportunity. In addition, a wider range of frequencies was monitored with the DSN antennas.
First half of 2019 (Sol 5309 to 5351) - Mission end
The rover's software probably had to cope with several failures: too little energy (low-power fault), a wrong mission clock (mission clock fault) and a wrong timer in the event of a communication failure (up-loss timer). Since the loss of the signal, the team had repeatedly tracked the rover at different times, frequencies and polarizations with the Deep Space Network (DSN). A “sweep and beep” procedure was used for this. This was hoped to take into account the complexity of a bug in the rover's mission clock. Over 1000 recovery commands have been sent to the rover since the signal was lost.
At the beginning of 2019, the season began at the location of the rover in which cleaning events occurred repeatedly. It was hoped that such an event would clean the solar panels and allow the rover to recharge its batteries. However, no contact could be established. Therefore, NASA gave up attempts to contact Opportunity on February 13, 2019 and decided to end the mission.
Since the Meridiani Planum, in which Opportunity landed, is very flat and level, boulders can be seen from afar. The rock Bounce rock was hit at Opportunity's landing of the airbag, hence its name. He was examined on Sol 65. The investigation of the chemical composition showed a strong similarity to the Shergottites, a subgroup of the so-called Martian meteorites. This is another strong indication that the Martian meteorites really came from Mars. The Heat Shield Rock meteorite was encountered near Opportunity's heat shield (Sol 324) and is the first iron-nickel meteorite (93% iron, 7% nickel) to be discovered on an alien planet.
The stone Santorini (investigated Sol from 1713 to 1749) turned out to be an iron-rock meteorite ( mesosiderite ). It is 6 cm × 8 cm in size and has a similar composition to the objects Barberton (Sol 122) (3 cm diameter) and Santa Catarina (Sol 1045, 14 cm diameter). It is possible that these three rocks were part of the object that created the Victoria Crater. The Kasos meteorite was examined on Sol 1884 (May 12, 2009). Block Island was surveyed on Sol in 1957. It is a 900 kg iron meteorite. Such a body is too heavy to land unscathed after crossing today's Martian atmosphere. It is therefore assumed that Mars used to have a denser atmosphere so that the meteorite could land more gently. With the microscope camera, triangular structures were discovered that are similar to the structures of iron-nickel meteorites on Earth ( Widmanstätten structures ). These structures arise inside through extremely slow cooling over millions of years and become visible on the surface when they are suitably eroded by wind and sand. In addition, hole-like caves were found whose structure can be used to determine the weathering history of the meteorite.
Another iron meteorite called Shelter Island was examined on Sol 2020 (October 2, 2009) . It is 47 cm in diameter and just 700 m from Block Island. This meteorite is also badly weathered, has a porous surface and, like Block Island, shows the Widmannstatt figures on its surface . The Mackinac meteorite was reached on Sol 2035 (October 16, 2009). It was not investigated in further detail because this meteorite is also an iron meteorite with similarities to the previously examined objects.
The Marquette Island stone was surveyed from November 2009 to January 2010. Due to the lower nickel content than the other meteorites found, Marquette Island is believed to be of Martian origin. The stone contains more magnesium than the basalt rocks Spirit examined. Marquette Island is made up of coarse-grained rock and basalt. This composition suggests that the stone cooled slowly because it gave the crystals time to grow. Geologists therefore assume that the stone was formed deep in the Martian crust.
Pinnacle Island is the name of a stone that was surprisingly found in 2014, which resembles a Berlin pancake in size and shape and which had not been there twelve days before. He was probably catapulted there by a wheel of the rover during a driving maneuver. The stone is whitish on the outside, reddish in the center. NASA scientist Steve Squyers said it wasn't like anything you've seen before. The inside is very rich in sulfur and magnesium. The stone also contains twice as much manganese as the researchers usually measured in the Martian samples. The further investigation will take weeks.
Evidence of formerly liquid water on Mars
NASA was able to report indications from the ground to formerly liquid water on Mars for the first time on March 2, 2004: Opportunity's instruments discovered high sulfur concentrations in the rock, which under terrestrial conditions are usually only found in gypsum or anhydrite (both calcium sulfate with different amounts of crystal water) can be found. Gypsum or anhydrite-containing rock is formed on earth almost exclusively by the evaporation of mineral-containing water and is therefore one of the evaporites . The rover's instruments also found jarosite , an iron-sulfur mineral that is also only produced on earth with the help of water. The occurrence of these salts on earth in the present concentrations is a clear indication that the rock was either precipitated in open water or was exposed to groundwater over a longer period of time . These discoveries were developed in Germany with the two, only fist-sized and therefore extremely miniaturized instruments APXS ( Alpha Particle X-Ray Spectrometer ) and MIMOS II (Miniaturized Mössbauer - spectrometer ) become possible. The APXS from the Max Planck Institute for Chemistry in Mainz is a radiation detector , the heart of which, the alpha and X-ray semiconductor detectors, was developed and manufactured by the Munich company KETEK. The MIMOS II was developed at Johannes Gutenberg University Mainz . High-resolution close-ups of the finely layered sediments also showed centimeter-sized tabular cavities, such as those formed when water-soluble crystals such as gypsum, other sulphates or dolomite are detached from the rock. In addition, regularly distributed, millimeter-sized and spherical mineral aggregates of initially indeterminate composition were discovered in large numbers in the rock, which could soon be interpreted as concretions as they arise in an aqueous environment. The fact that the spheres were formed in the rock itself could be recognized by the storage conditions: they lie in the rock without any recognizable disturbance of the millimeter-fine stratification, which would have to be the case if they had been entered from outside as pebbles or volcanic or meteoritic precipitation . A little later, spectroscopic high hematite concentrations could be detected in these concretions, which further corroborated the above interpretation. In view of these discoveries, NASA was able to speak of the formation as formerly soaking wet . At first it was unclear whether the water itself was involved in the original formation of the strata, i.e. had been present at the site openly on the surface, or whether the observed rock properties were due to the subsequent effects of underground water (groundwater or hydrothermal solutions).
Evidence for previously open moving water
According to a NASA announcement of March 23, 2004, it can be considered certain that an open, shallow salt lake or ocean used to exist at the landing site . The rover was able to spatially record sedimentary structures in a series of more than 200 microphotos of a partial exposure of the rock layers , whose earthly equivalents are only created by moving water ( cross-bedding oblique stratification ). The scientists interpret these rocks as remnants of a former coastline and point out that precisely such deposits as found here would excellently conserve any (micro) fossils or other traces of biological activity. A return to the area for the purpose of automated or conventional sampling would therefore be very desirable and also likely. Satellite images show that the strata in question, a light-colored, finely stratified rock package, are evidently spread over at least several thousand square kilometers.
Discussion of previous discoveries
The double mission of the Mars Exploration Rovers can be regarded as extremely successful in technical and scientific terms. It ties in with the greatest historical successes of NASA and stands in a row with the manned moon landings , the Pioneer , Voyager and Viking probes and thus represents a technical peak performance. For the first time, it has been verified on site that liquid water resources exist or have existed on other planets and thus the prerequisites for the possible development of life on Mars . For the first time sedimentary rocks from a foreign planet were examined. Another novelty was that data material from the exploration of a strange celestial body was made publicly accessible via the Internet in almost real time, even before the project participants could evaluate it themselves. The investigation of the chemical composition of Bounce Rock , a stone that was almost hit by Opportunity when it landed, shows a strong similarity to the shergottites, a subgroup of the so-called Martian meteorites . This is another strong indication that the Martian meteorites actually came from Mars.
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