OPPORTUNITY ROVER

'MER-B' ('Mars Exploration Rover - B'), known as '''Opportunity''', is the second of the two rovers of NASA's Mars Exploration Rover Mission. It landed successfully at Meridiani Planum on Mars on January 25, 2004 05:05 Ground UTC (''circa'' 13:15 local time), three weeks after its twin ''Spirit'' (MER-A) had landed on the other side of the planet.^[1] Its name was chosen through a NASA-sponsored student essay competition.
The rover has continued to function effectively over thirteen times longer than NASA planners expected, allowing it to perform extensive geological analysis of Martian rocks and planetary surface features; as of 2007 its mission is ongoing. An archive of approximately weekly updates on its status can be found at the NASA/JPL website.

Contents

Mission overview

2004: Landing and initial surveys

Landing site: "Eagle" crater

"Opportunity Ledge" outcroppings

''El Capitan'' outcropping

''Opportunity'' digs a trench

Endurance Crater

2005 explorations, difficulties

Heat Shield Rock

Southern transit

Opportunity gets stuck

Erebus crater, mild mechanical problems

2006/2007

Latest status

Rover activities

Rover status

Dust Storms

Future plans

Scientific findings

Honors

See also

References

External links

Mission overview

The primary surface mission for ''Opportunity'' was planned to last 90 sols. The mission has received several extensions and as of November 17, 2006 had passed 1,000 sols. From her initial landing, by chance, into an impact crater amidst an otherwise generally flat plain, ''Opportunity'' has successfully investigated soil and rock samples and taken panoramic photos of her landing site. Her sampling allowed NASA scientists to make hypotheses concerning the presence of hematite and past presence of water on the surface of Mars.

Following this, she was directed to travel across the surface of Mars to investigate another crater site, Endurance crater, which she investigated from June — December 2004. Subsequently, ''Opportunity'' examined the impact site of its own heat shield and discovered an intact meteorite, now known as Heat Shield Rock, on the surface of Mars.
From late April 2005 to early June of that year, ''Opportunity'' was perilously lodged in a sand dune, with several wheels buried in the sand. Over a six week period Earth-based physical simulations were performed to decide how best to extract the rover from its position without risking a permanent immobilization of the valuable vehicle. Successful maneuvering a few centimeters at a time eventually freed the rover, which resumed its travels.
''Opportunity'' was directed to proceed in a southerly direction to Erebus crater, a large, shallow, partially buried crater and a stopover on the way south towards "Victoria" crater, between October 2005 and March 2006. It experienced some mechanical problems with its robotic arm.
In late September 2006 Opportunity reached the rim of Victoria crater and is currently exploring along the rim in a clockwise direction. Feasible routes into the crater are being sought, and it is likely that Opportunity will be sent into Victoria crater in early 2007.
In over two earth years of functioning, the rover has traversed over 10,000 meters.^[2]
Both Spirit and Opportunity have pieces of the fallen World Trade Center's metal on them.^[3]

2004: Landing and initial surveys

Landing site: "Eagle" crater

Main articles: Eagle crater


''Opportunity'' landed in Meridiani Planum at 354.47°E 1.94°S (planetocentric coordinates), about 24 km downrange (east) of her intended target. Although Meridiani is a flat plain, without the rock fields seen at previous Mars landing sites, ''Opportunity'' rolled into an impact crater approximately 20 meters in diameter, with the rim of the crater approximately 10 meters (32 feet) from the rover. NASA Scientists were so excited about landing in a crater that they called the landing a "hole in one." Later, the crater was named ''Eagle crater''. This was the darkest landing site ever visited by a spacecraft on Mars. It would be two weeks before she was able to get a better look of her surroundings.
Scientists were intrigued by the abundance of rock outcrops dispersed throughout the crater, as well as the crater's soil, which appeared to be a mixture of coarse gray grains and fine reddish grains. This sweeping look at the unusual rock outcropping near ''Opportunity'' was captured by the rover's panoramic camera. Scientists believe the seemingly layered rocks are either volcanic ash deposits or sediments laid down by wind or water. It was given the name ''Opportunity Ledge''.
Geologists said that the layers—some no thicker than a finger—indicate the rocks likely originated either from sediments carried by water or wind, or from falling volcanic ash. "We should be able to distinguish between those two hypotheses", said Dr. Andrew Knoll of Harvard University, Cambridge, a member of the science team for ''Opportunity'' and her twin, ''Spirit''. If the rocks are sedimentary, water is a more likely source than wind, he said.^[4]




These layered rocks measure only 10 centimeters (4 inches) tall and are thought to be either volcanic ash deposits or sediments carried by water or wind. The layers are very thin measuring just a few millimeters thick in some cases.

"Opportunity Ledge" outcroppings

On Sol 15, ''Opportunity'' took a close up of the rock "Stone Mountain" in the outcrop area of the crater, raising speculation that the rock consisted of very fine grain or dust, in contrast to Earth sandstone, which is compacted sand with rather large grains. The weathering agent eroding away layers of this rock seemed to be visible as dark spots.^[5]
A picture received on February 10 (taken on Sol 16) showed that the thin layers in the bedrock converge and diverge at low angles, suggesting that some "moving current" such as volcanic flow, wind, or water formed these rocks. The discovery of these layers was significant for scientists who had planned this mission to test the "water hypothesis" rigorously.

''El Capitan'' outcropping

On February 19 the survey of "Opportunity Ledge" was declared successful. A specific target in the outcrop (dubbed "''El Capitan''"), whose upper and lower portions appeared to differ in layering and weathering characteristics, was selected for further investigation. ''El Capitan'', about 10 centimeters (4 inches) high, was named after a mountain in Texas. ''Opportunity'' reached "''El Capitan''" on Sol 27, and took a first picture of the rocks with her panoramic camera.
On Sol 30, ''Opportunity'' used her Rock Abrasion Tool (RAT) for the first time to investigate the rocks around ''El Capitan''. The image on the right-hand side shows a close up view taken after the drilling and cleaning process was complete. Due to chance, two spherules were also cut partially, and seem to show scratches and other marks made by the diamond-crusted grind tool. The black areas are artifacts of the imaging process, when parts of the picture are missing.
During a press conference on March 2 mission scientists discussed their conclusions about the bedrock, and the evidence for the presence of liquid water during their formation. They presented the following reasoning to explain the small, elongated voids in the rock visible on the surface and after grinding into it (see last two images below).^[6]
These voids are consistent with features known to geologists as "vugs". These are formed when crystals form inside a rock matrix and are later removed through erosive processes, leaving behind voids. Some of the features in this picture are "disk-like", which is consistent with certain types of crystals, notably sulfate minerals.
Additionally, mission members presented first data from the Mossbauer spectrometer taken at the bedrock site. The iron spectrum obtained from the rock ''El Capitan'' shows strong evidence for the mineral jarosite. This mineral contains hydroxyl radicals, which indicates the presence of water when the minerals were formed. Mini-TES data from the same rock showed that it consists of a considerable amount of sulfates.

''Opportunity'' digs a trench

The rover alternately pushed soil forward and backward out of the trench with its right front wheel while other wheels held the rover in place. The rover turned slightly between bouts of digging to widen the hole. "We took a patient, gentle approach to digging", Biesiadecki said. The process lasted 22 minutes.
The resulting trench—the first dug by either Mars Exploration Rover—is about 50 centimeters (20 inches) long and 10 centimeters (4 inches) deep. "It came out deeper than I expected", said Dr. Rob Sullivan of Cornell University, Ithaca, N.Y., a science-team member who worked closely with engineers to plan the digging.^[7]
Two features that caught scientists' attention were the clotty texture of soil in the upper wall of the trench and the brightness of soil on the trench floor, Sullivan said.
By inspecting the sides and floor of a hole it dug, ''Opportunity'' is finding some things it did not see beforehand, including round pebbles that are shiny and soil so fine-grained that the rover's microscope cannot make out individual particles.
"What's underneath is different than what's at the immediate surface", said Dr. Albert Yen, rover science team member at NASA's Jet Propulsion Laboratory, Pasadena, Calif.^[8]
Initial scientific results from the Opportunity rover were published in the journal ''Science'' ^[9]

Endurance Crater

Main articles: Endurance crater

On April 30, 2004 ''Opportunity'' reached Endurance crater, which was known to have many layers of rocks. In May the rover circumnavigated the crater, and made observations with Mini-TES and the panoramic camera. The rock "Lion Stone" was investigated and found to be similar in composition to the layers found in Eagle crater.

On June 4, 2004 mission members announced their intention to drive ''Opportunity'' into Endurance, even if it should turn out to be impossible to get back out, targeting the various rock layers that were identified in the pictures from the crater rim. "This is a crucial and careful decision for the Mars Exploration Rovers' extended mission", said Dr. Edward Weiler, NASA's associate administrator for space science. Dr Squyres, principal investigator from Cornell University said: "Answering the question of what came before the evaporites is the most significant scientific issue we can address with ''Opportunity'' at this time." Mars Rover Opportunity Gets Green Light To Enter Crater
A first drive into the crater was executed June 8 and ''Opportunity'' backed out again the same day. It was found that the angle of the surface was well inside the safety margin (about 18 degrees), and the full excursion towards the rock layer of interest was started. During Sols 134 (June 12), 135, and 137 the rover drove deeper and deeper into the crater. Although some wheel slip was observed, driving was discovered to be possible even at slope angles up to 30 degrees.
Wispy clouds, similar to Earth's cirrus clouds, were spotted.
''Opportunity'' spent roughly 180 sols inside the crater, before backing out of it again in late December 2004. Scientific results of the sedimentary geology of the crater were published in the journal ''Earth and Planetary Science Letters'' ^[10]

2005 explorations, difficulties

Heat Shield Rock

Main articles: Heat Shield Rock

After exiting Endurance crater, in January 2005 ''Opportunity'' went to examine its own discarded heat shield. While in the vicinity of the heat shield, it happened to come upon an object which was immediately suspected and soon confirmed to be a meteorite. The meteorite was promptly named Heat Shield Rock, and is the first meteorite identified on another planet or moon.
After about 25 Sols of observations ''Opportunity'' headed south for a crater named Argo, nearly 300 m from the heat shield.

Southern transit

The rover was commanded to dig another trench on the vast plains of Meridiani Planum, on Sol 366, and observations continued until Sol 373 (February 10, 2005). The rover then passed the craters "Alvin" and "Jason", and by Sol 387, approached a "crater triplet" on its way to Vostok Crater. Along the way, ''Opportunity'' set a distance record for one-day travel by either rover: 177.5 meters (582 feet), on February 19, 2005. On Sol 389 (February 26, 2005), the rover approached one of the three craters, dubbed Naturaliste. A rock target named "Normandy" was chosen for investigation on Sol 392, and ''Opportunity'' remained there until Sol 395.

''Opportunity'' reached Vostok Crater on Sol 399, finding it mostly filled with sand and lined by outcrops. It was then ordered south into what has been called "etched terrain", to search for more bedrock.



By Sol 415, ''Opportunity'' stopped by some soil ripples to investigate the differences between soil in the trough of a ripple and its crest. Various soil targets included "Mobarak" in the trough, named in honor of Persian New Year, and "Norooz" and "Mayberooz" on the crest. By Sol 421, the rover left the ripple for "Viking" crater.

Opportunity gets stuck

On April 26, 2005 (Sol 446) ''Opportunity'' inadvertently dug itself into a sand dune: Mission scientists reported that images indicated all four corner wheels were dug in by more than a wheel radius, just as the rover attempted to climb over a dune about 30 centimeters (12 inches) tall. The sand dune was designated "Purgatory Dune" by mission planners.
The rover's condition was simulated on Earth prior to any attempt to move, out of concern that the rover might become permanently immobilized. After various simulations intended to mimic the properties and behavior of Martian sand were completed, the rover executed its first wheel movements on May 13, 2005 (Sol 463), intentionally advancing only a few centimeters, after which mission members evaluated the results.

During Sol 465 and 466 more drive commands were executed, and with each trial the rover moved another couple of centimeters. At the end of each movement, panoramic images were acquired to investigate the atmosphere and the surrounding dune field. The sand dune escape maneuver was successfully completed on June 4, 2005 (Sol 484), and all six wheels of ''Opportunity'' were on firmer ground. After studying "Purgatory" from sol 498 to sol 510, ''Opportunity'' proceeded southwards towards "Erebus crater".

Erebus crater, mild mechanical problems

''Opportunity '' studied Erebus crater, a large, shallow, partially buried crater and a stopover on the way south towards Victoria crater, between October 2005 and March 2006.
New programming to measure the percentage of slip in the wheels was successful in preventing the rover from getting stuck. Another "Purgatory"-like incident was averted on sol 603, when onboard slip check software stopped a drive after slip reached 44.5%.^[11] It proceeded over many ripples and 'half-pipes' taking photographs after each sol's journey.
On sol 628 (November 3, 2005) ''Opportunity'' woke up in the midst of a mild dust storm that lasted three days. The rover was able to drive in self protective auto-mode during the storm but could not take any post drive images. Less than three weeks later, another cleaning event cleared the dust off of the solar array so as to produce around 720 watt-hours (80% of max). On sol 649 (December 1, 2005), it was discovered the motor used to stow the robotic arm for travel was stalling. This problem took nearly two weeks to fix. Since then, the arm is only stowed for travel and is extended at night to save the arm from getting stuck.

2006/2007

Panorama taken on the rim of Erebus crater

Payson outcrop on the western edge of Erebus crater

''Opportunity'' observed numerous outcroppings around Erebus crater. It also collaborated with ESA's Mars Express by using the miniature thermal emission spectrometer and panoramic camera, and took images of a transit across the sun by Phobos. On sol 760 (March 22, 2006), ''Opportunity'' began the journey to its next destination, "Victoria" crater.

Latest status

Main articles: Victoria (crater)

Opportunity at the rim of Victoria Crater, as imaged by MRO (03 October 2006)

Opportunity at the rim of Victoria Crater, as imaged by MRO (2006-11-29)

Opportunity landing site, 'lander' , as imaged by MRO (2006-11-29)

Opportunity landing site, 'parachute' and 'backshell', as imaged by MRO (2006-11-29)

Opportunity landing site, 'heat shield', as imaged by MRO (2006-11-29)

Opportunity landing site, sand dunes around of Victoria Crater. MRO (2006-11-29)

Rover activities

Victoria crater is a massive impact crater approximately 7 kilometers from the original landing site. Victoria's diameter is six times larger than Endurance crater. Scientists believe that rock outcrops along the walls of Victoria will yield more information about the geologic history of Mars, if the rover survives long enough to investigate them.
On Sol 951 (September 26, 2006) Opportunity reached the rim of Victoria Crater^[12] and transmitted the first substantial views of Victoria, including the dune field at the bottom of the crater. The Mars Reconnaissance Orbiter recently photographed Opportunity at the rim of the crater. [2]

Rover status

A series of cleaning events beginning on Sol 1151 (2007-04-20) have allowed Opportunity's solar energy production to rise to above 800 watt-hours per Sol. By Sol 1164 (2007-05-04) the solar array current was peaking above 4.0 amps, values not seen since Sol 18 (2004-02-10).^[13] However, with the recent advent of extensive dust storms on Mars (in-line with Mars' six Earth-year global dust storm cycle), power levels have dropped to 280 watt-hours.^[14]
''Opportunity's total odometry as of sol 1225 (July 6, 2007) was 11,424.67 meters (7.1 miles).[3]

Dust Storms

Towards the end of June, 2007, a series of dust storms began clouding the Martian atmosphere with dust. The storms have intensified and by July 20, both Opportunity and Spirit were facing the real possibility of system failure due to lack of power. NASA released a statement to the press which said (in part) "We're rooting for our rovers to survive these storms, but they were never designed for conditions this intense" ^[15]. The key problem caused by the dust storm was a dramatic reduction in solar power. There is now so much dust in the atmosphere that it is blocking 99 percent of direct sunlight to the rover. The Spirit rover, on the other side of the planet is getting slightly more sunlight than Opportunity.
Normally the solar arrays are able to generate about 700 watt-hours of energy per day. Since the storms, the power generated has been greatly reduced. If the rovers get less than 150 watt-hours per day they have to start draining their batteries. If the batteries run dry, key electrical elements are likely to fail due to the intense cold. On July 18, 2007, the rover's solar-panel only generated 128 watt-hours, the lowest level ever. NASA responded by commanding Opportunity to only communicate with Earth once every three days, the first time this has happened since the start of the mission.
The dust storms continued through July and at the end of the month, NASA announced that the rovers, even under their very-low-power mode were barely getting enough energy to survive. If the temperature of the Opportunity's electronics module continues to drop "there is a real risk that Opportunity will trip a low-power fault. When a low-power fault is tripped, the rover's systems take the batteries off-line, putting the rover to sleep and then checking each sol to see if there is sufficient available energy to wake up and perform daily fault communications. If there is not sufficient energy, Opportunity will stay asleep. Depending on the weather conditions, Opportunity could stay asleep for days, weeks or even months, all the while trying to charge her batteries with whatever available sunlight there might be."^[16] It is quite possible that the rover would never wake up from a low-power fault.
By 7th August 2007 the storm appeared to be weakening, and although power levels were still low they were sufficient for Opportunity to begin taking and returning images.^[17]

Future plans

After undertaking a partial reconnaissance of the perimeter of Victoria crater Opportunity was steered back to its original encounter point at ''Duck Bay'' in June 2007. This is seen as the most likely place to attempt an entry to the crater floor. The plan is to undertake a study of the crater from within and eventually exit again to continue to work on the plain above. A risk assessment of the descent to the floor and chance of return is currently (June 2007) being undertaken. ^[18]

Scientific findings

Main articles: Scientific information from the Mars Exploration Rover mission

''Opportunity'' has provided substantial evidence in support of the mission's primary scientific goals: to search for and characterize a wide range of rocks and soils that hold clues to past water activity on Mars. In addition to investigating the "water hypothesis", ''Opportunity'' has also obtained astronomical observations and atmospheric data.

Honors

Honoring ''Opportunity's great contribution to the exploration of Mars, the asteroid 39382 has been named Opportunity. 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.

See also

★ Exploration of Mars

★ Space exploration

★ Unmanned space missions

★ Spirit rover

References

1. "Spirit" landed on January 4, 2004.
2. Total odometry as of August 2006, according to "Mars rover status at NASA."
3. Steve Squyres, Roving Mars pp 113
4. Scientists Thrilled To See Layers in Mars Rocks Near Opportunity
5. "Embedded in it like blueberries in a muffin are these little spherical grains", said Dr. Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the rovers' scientific instruments. He also said: "One other treasure, a clue that just popped up, not gonna quote any numbers yet, but we have now completed an APXS measurement on the outcrop and it has got a lot of sulfur in it. Maybe a few times more sulfur than we've seen on any other location on
Mars." [1]
6. Opportunity Rover Finds Strong Evidence Meridiani Planum Was Wet
7. Opportunity Digs; Spirit Advances
8. Opportunity Examines Trench As Spirit Prepares To Dig One
9. S. Squyres, ''et al.'', "The Opportunity Rover's Athena Science Investigation At Meridiani Planum, Mars," ''Science, Vol. 306'', Issue 5702, 1698-1703 (Dec. 3 2004).
10. S. W. Squyres and A. H. Knoll, ''Sedimentary Geology at Meridiani Planum, Mars,'' Elsevier, Amsterdam, ISBN-13: 978-0-444-52250-4 (2005); reprinted from ''Earth and Planetary Science Letters, Vol. 240'', No. 1 (2005).
11. Opportunity Update: Opportunity Backs Out of Potentially Sticky Situation (Oct 11, 2005)
12. NASA Mars Rover Arrives at Dramatic Vista on Red Planet
13. Opportunity Status Updates: Sols 1152-1156, 1157-1163, and 1164-1170
14. 'Scary Storm' on Mars Could Doom Rovers
15. http://www.jpl.nasa.gov/news/news.cfm?release=2007-080
16. http://marsrovers.jpl.nasa.gov/newsroom/pressreleases/20070731a.html
17. http://marsrovers.jpl.nasa.gov/newsroom/pressreleases/20070807a.html
18. Mars Rover: Risky Business

External links

★ SpaceFlightNow Status Page

★ JPL's Mars Exploration Rover home page

★ Opportunity Mission Profile by NASA's Solar System Exploration

★ MER Analyst's Notebook, Interactive access to mission data and documentation

★ Mission Status updates from NASA JPL

★ Finding Opportunity: high resolution images of landing site (Mars Global Surveyor - Mars Orbiter Camera)

★ Finding Opportunity: interactive Mars atlas based on Viking images: you can zoom in/out and pan images, to find your preferred site

★ MER Imagery: automatically generated 3D stereo anaglyphs and pseudo-color images based on JPL raw images

★ (AXCH) 2004 Mars Exploration Rovers Highlights - News, status, technical info, history, and more.

★

★ Unmanned Spaceflight.com discussion on Opportunity

★ Dossier en français