Ten Years On: Opportunity’s unparalleled time and mission on Mars

by Chris Gebhardt

Ten years ago, 25 January 2004, the Mars Exploration Rover Opportunity slammed into the Martian atmosphere, beginning what was supposed to be a 90 Mars day (sol) mission on the surface of Mars. Ten years and 3,557 Mars days (3,653 Earth days) later, Opportunity is remarkably still functioning, unlocking the mysteries of Mars and serving as a symbol of endurance for inter-planetary exploration.

The original mission:

The Mars Exploration Rover –B’s (MER-B’s) mission was based around a 90-solar day (Mars daily timekeeping based on the planet’s orbital rotation rate) mission on surface of Mars.

A solar day on Mars is clocked at 24 hours 39 minutes 35.24409 seconds. Compared to Earth’s 24 hour 00 minute 00.002 second solar day length, the difference in the Earth-Mars solar day results in the Martian solar day lasting 2.7% longer than Earth’s.

Overall, MER-B’s mission was designed to determine the distribution and composition of minerals, rocks, and soils surrounding its target landing site; determine what geologic processes have shaped the local terrain and influenced the chemistry, including water or wind erosion, sedimentation, hydrothermal mechanisms, volcanism, and cratering; and perform calibrations and validations of surface observations made by the Mars Reconnaissance Orbiter to help determine the accuracy and effectiveness of various instruments that survey the Martian geology from orbit.

MER-B was also tasked with the search for iron-containing minerals, including the identification and quantification of the relative amounts of specific mineral types that contain water or were formed in water; the characterization of the mineralogy and textures of rocks and soils to determine the processes that created them; the search for geological clues to the environmental conditions of Mars’ past; and the assessment of whether the past Martian environment was conducive for life.

To accomplish these tasks, MER-B was truly built to last.

At a height of 4.9 ft, a width of 7.5 ft, and a length of 5.2 ft, the six-wheeled utility vehicle was constructed to power itself via solar panels installed on its “back.”

These solar panels, at peak operating performance (clear of Martian dust and dirt), produce 140 watts of power for four hours per day. The energy produced from the solar panels is then transferred to MER-B’s lithium ion batteries for storage and distribution – thus allowing the rover to conserve power when not needed and use energy during non-sunlit portions of the day.

Weighing in at 400 lbs, MER-B was built for mobility, containing the ability to drive itself, navigate around obstacles in its path, and negotiate grades in the terrain toward specific locations determined by its control team.

To accomplish this, each wheel on MER-B has its own motor and steering at the front and rear drive sections.

To accomplish the scientific objectives of the mission, MER-B was affixed with nine scientific experiments: a panoramic camera to examine the texture, color, mineralogy, and structure of the local Martian terrain; a navigation camera for driving purposes; the Miniature Thermal Emission Spectrometer to identify “promising rocks and soil” for examination; and two Hazcams with 120 degree views for “additional data about its surroundings.”

MER-B’s robotic arm was built with the Mossbauer spectrometer for close-up investigations of the mineralogy of iron-bearing rocks and soils, the Alpha particle X-ray spectrometer for close-up analysis of elements that make up rocks and soils, magnets for collection of magnetic dust particles, a Microscopic Imager for close-up, high-resolution images of rocks and soils, and the Rock Abrasion Tool (RAT) to expose fresh rock material for examination by instruments on-board the rover.

With it’s mission plan outlined, and launch approaching, it was time to name MER-B.

Like the Space Shuttle orbiter Endeavour and the Mars rover Sojourner before it, MER-B was named through a student essay competition.

The winning entry was written by a Russian-American student who spoke of the spirit and opportunity to achieve her dreams in the United States after living a portion of her life in an orphanage.

Thus, Opportunity was christened.

A Hole-in-One landing and the first 90 sols on Mars: 

On 7 July 2003, after nine-day launch delay, Opportunity lifted off aboard a Delta II Heavy rocket at 23:18:15 EDT from the Cape Canaveral Air Force Station, FL. Later that night, Opportunity was placed into a heliocentric Mars Transfer Orbit and began its 6.5-month cruise to Mars.

On 25 January 2004, Opportunity hit the Martian atmosphere just before 0500 UTC (just before midnight Eastern Standard Time on 24 January).

After descending through the Martian atmosphere, being slowed by atmospheric friction and a hypersonic parachute, Opportunity’s encasement was engulfed in airbags to cushion the rover for the drop down and bounce/roll onto the Martian surface.

Landing on the Meridiani Plamun 25km downrange of its targeted landing site, Opportunity rolled to a stop at 0505 UTC.

Upon opening of the descent and landing encasement, Opportunity took panoramic images of its landing site – images that gave mission controllers quite a surprise.

Mission controllers were amazed to find the rover sitting in the bottom of an impact crater and quickly described the landing as an inter-planetary “hole in one” – even though Opportunity did not target that specific area for landing.

With the rover safely on the ground, Opportunity’s landing team christened the crater “Eagle crater,” and officially named Opportunity’s landing site “Challenger Memorial Station” in honor of the Space Shuttle Challenger and her crew who were lost in the Challenger/STS-51L launch accident – the 18th anniversary of which was just 3 days after Opportunity’s landing.

While great excitement surrounded Opportunity’s plunk into the crater, the landing presented a challenge for the control team as the rover now had to climb a relatively steep embankment to get out of the crater.

From a stationary position on its landing bed, Opportunity spent its first two weeks on Mars observing the rock outcropping along the rim of Eagle crater and the compilation of course gray grains in the otherwise reddish sand within the crater.

By Sol 15 (15 Mars days after landing), Opportunity was mobile, examining the rock outcroppings at Eagle crater. Observations made by Opportunity at the time led to the hypothesis that the rocks were formed from “fine grain or dust” instead of compacted sand such as Earth sandstone.

This hypothesis led to the understanding that the rocks were formed from volcanic flow, wind, or water. With water as a potential forming agent for the Eagle crater rock outcroppings, Opportunity’s goal of determining the potential that water had once existed on the surface of Mars for a long enough period to effect local geology was underway.

Following this discovery, Opportunity used its robotic arm RAT for the first time on Sol 30 to cut into a rock. Examination of that rock, located at the El Capitan outcropping, showed signs of erosion (small, elongated voids both on the surface of the rock and in its interior) that suggested the presence of liquid water at one point in Mars’ past.

Specifically, scientists stated that the voids were similar and “consistent” with vugs on Earth rocks.

Opportunity’s control team also took this time to dig the first-ever trench by the Mars Rover pair by using Opportunity’s front wheels. The process, which took less than a half-hour, created a trench 20 inches long by 4 inches deep.

The resultant dig revealed a “clotty texture” to the soil in the upper part of the trench and bright soil in the trench’s bottom.

The dig also revealed rounded, shiny pebbles and fine-grained soil particles too small for the rover’s microscope to discern.

Beyond the 90-sol-day warranty: Opportunity at Endurance Crater

After leaving its landing site behind, Opportunity reached Endurance crater on Sol 95 – five days beyond its expected life time on Mars.

After completing a circumnavigation of the crater, Opportunity was directed toward the rock Lion Stone where it found that the rock had a similar composition as those at Eagle Crater.

By 4 June 2004, Opportunity’s team made the decision to send the rover itself into Endurance crater to examine an interesting area of rocks. This decision was made with the knowledge that the rover may not be able to climb back out of the crater.

Opportunity spent 180 sols inside the crater examining the various rock formations – and even observing Earth-like wispy clouds in Mars’ atmosphere.

During this time, Opportunity returned valuable scientific data on the soil composition and sedimentary geology of Endurance crater.

A Stellar Find for Opportunity and a drive south:

After completing operations at Endurance crater, Opportunity drove toward its own discarded heat shield that protected it during Martian atmospheric entry almost one year prior.

While conducting examination of its heat shield, Opportunity stumbled upon a rock that would prove to be one the rover’s most significant finds: a meteorite on the surface of another planet.

Discovered on Sol 345, the meteorite was the first one ever discovered on a planet other than Earth (though two meteorites had already been discovered on the Moon) and was first identified an “unusual” because it had an infrared spectrum similar in appearance to a reflection of the Martian sky.

Measurements and examinations by Opportunity showed the meteorite was composed of 93 percent iron and 7 percent nickel.

After the discovery, Opportunity began driving toward Vostok crater before being redirected toward an area of “etched terrain.”

During the drive to the etched terrain, Opportunity set a single-day distance driving record of 772 ft.

Shortly thereafter, Opportunity became the unwitting victim of a sand trap when it became stuck in the sand on 26 April 2005 while attempting to climb over a small dune only 12 inches in height.

The dune was quickly dubbed “purgatory dune” because of the predicament it posed.

Opportunity spent the next 38 Sols stuck in the sand as ground controllers simulated the conditions on Earth.

Guiding Opportunity through a precise series of maneuvers, which saw the rover move just centimeters at a time so mission controllers could monitor progress and assess a next best move, Opportunity was finally freed of its sand trap and spent 12 Sols studying the dune before continuing southward toward its new target: Erebus crater.

Erebus crater:

During Opportunity’s time at Erebus crater, a new program was uploaded to the rover to help prevent it from becoming stuck in another sand dune.

Z3This program proved invaluable on Sol 603 when the program triggered an “all stop” command to Opportunity when the rover’s wheel-slip percentage reached 44.5 percent.

The “all stop” command prevented Opportunity’s wheels from becoming mired in the loose sand.

By Sol 628, Opportunity was engulfed in a three-day-long dust storm – the first dust storm encountered by the rover. The storm deposited significant quantities of dust onto the rover’s solar panels and reduced the total power generation capabilities of the panels.

However, a sudden cleaning event of the solar panels took place less than three weeks after the dust storm, restoring Opportunity’s power generating capabilities to 80 percent of maximum.

By late March 2006, after 760 sols on Mars, Opportunity departed Erebus crater for the 191-sol drive to Victoria crater.

Time at Victoria crater – A struggle for survival:

Upon arriving at Victoria carter on 16 September 2006, Opportunity photographed the terrain and returned the first substantial views of Victoria’s 7-kilometer wide impact crater.

During initial observations, Opportunity revealed a dune field at the bottom of the crater as well as a slope leading into the crater itself.

While Opportunity investigated the rim of Victoria crater, mission controllers sent a software upgrade package to the rover that allowed it to make internal decisions on whether or not to transmit images back to Earth and whether or not to extend its robotic arm for scientific investigation.

The move gave Opportunity’s computers more autonomy than had previously been granted to NASA spacecraft.

By mid-May 2007, a series of significant cleaning events allowed for unprecedented power increases to the rover, restoring this power-generating capability to levels not seen since Sol 18 of the mission.

This dramatic increase in power-generating capability came at the best possible time as residual daily power was stored in Opportunity’s batteries just a month before devastating dust storms nearly claimed the rover.

Beginning in June 2007, Mars’ six Earth-year dust storm cycle began, clouding the Martian atmosphere in dust and blocking 99 percent of sunlight from reaching Opportunity’s solar panels – while at the same covering the solar panels and significantly reducing the rover’s ability to gather the small amount of sunlight actually reaching it.

As power levels dropped to dangerously low levels, NASA released a statement saying, “We’re rooting for our rovers to survive these storms, but they were never designed for conditions this intense.”

Normal solar panel generation of 700 watt-hours energy per day dropped to only 128 watt-hours on 18 July 2007 on Opportunity. As a result, Opportunity began draining its batteries to preserve system power and heating requirements.

The rover’s control team, in response, commanded the rover to only communicate with Earth every three days in an effort to conserve power for its heaters.

By late-July 2007, Opportunity was barely getting enough solar energy each day to survive, and the temperature in the rover’s electronics module was dropping.

If temperatures continued to drop, Opportunity’s low-power fault program could trip, disabling the rover’s batteries and putting Opportunity into sleep mode until sufficient available energy returned to wake the rover up.

Z4The real possibility arose that if Opportunity went to sleep, it might never wake up.

Somehow, despite these abysmal odds, Opportunity never tripped its low-power fault, and by 7 August 2007, with the dust storms beginning to subside, power levels were sufficient for Opportunity to start taking pictures of the Martian dust storm.

By 21 August, Opportunity’s batteries were fully charged, and the rover began driving again for the first time since the dust storm began – an amazing endurance story for the rover that had, by this point, survived the “un-survivable” scenario on Mars’ surface during full-fledged operations three years beyond its expected 90 sol death date from low power levels because of predicted dust accumulation on its solar panels.

Recovering from the dust storm, Opportunity began its descent into Victoria crater on 11 September 2007 at ramp named Duck Bay.

Opportunity spent the next Earth year (half a Martian year) examining the rock composition of Duck Bay and the face of Cape Verde in great scientific detail.

A new mission target – Endeavour crater:

With the rover in good health, Opportunity’s control team elected to send the rover on a 14 mile (22 kilometer) trek (from Victoria crater) to Endeavour crater.

Emerging from Victoria crater on Sols 1630-1634, Opportunity began the impressive trek for Endeavour crater, stopping along the way to investigate various “dark cobbles” on the Meridiani Planum.

Endeavour crater was chosen in large part due to expectations that deeper stacks of rocks would be seen at Endeavour crater than had been at Victoria crater and because of the discovery of phyllosilicate, clay-bearing rock, at Endeavour.

During the predicted two-year drive to Endeavour crater, Opportunity was temporarily out of contact with Earth during the solar conjunction of November/December 2008 – at which time Earth and Mars were on opposite sides of the sun from one another.

By March 2009, Opportunity’s cameras could see the rim of Endeavour crater, as well as Iazu crater – which was 38 kilometers (24 miles) away from the rover at the time.

By 18 July 2009 (Sol 1850), Opportunity was directed to reverse course away from Endeavour crater and toward a large, black rock.

The rover reached the rock ten Earth-days later, at which point it was discovered that the rock was yet another meteorite.

After examination of the meteorite, Opportunity was again commanded to drive toward Endeavour crater but was stopped again on Sol 2022 when it found yet another meteorite. After examining this meteorite for 12 Sols, Opportunity found yet another meteorite on Sol 2038.

This time, the rover did a “drive by” investigation, taking photographs of the meteorite while continuing on toward Endeavour crater.

Opportunity arrived at Concepcion crater on 28 January 2010 and circumnavigating the crater as it continued toward Endeavour crater.

By 5 May 2010, a new route to Endeavour crater was plotted to avoid potentially hazardous sand dunes that lay between it and its long-sought destination.

On Sol 2246 (19 May 2010), Opportunity reached a significant milestone and record – one it still holds today.

Despite arriving on Mars three weeks after its twin rover Spirit (which ceased all communications on 22 March 2010), on 19 May 2010, Opportunity became the longest-surviving surface mission on Mars, surpassing the previous 2245 Sol duration set by the Viking 1 mission from the late 1970s to early 1980s.

By mid-December 2010, Opportunity began several weeks of observations at Santa Maria crater (while en route to Endeavour crater) – observations that were compared to orbital data from the Mars Reconnaissance Orbiter (MRO).

At the conclusion of the 2010 Earth-year, Opportunity had driven more miles since leaving Victoria crater in August 2008 (the equivalent of 1 Martian year) than it had in any previous year – all while being 4-6 years beyond its originally estimated life span.

Opportunity spent the two-week solar conjunction of early 2011 at Santa Maria crater before beginning the final 6.5 kilometer journey to Endeavour crater in late March 2011.

By 1 June 2011, Opportunity passed the 30km lifetime traverse mark – a distance 50 times greater than its operational-design traverse distance.

After 3 years of travels, Opportunity safely and successfully arrived at Endeavour crater on 9 August 2011 after traveling 13 miles from Victoria crater – a distance more than half of its total traversed distance at the time.

Opportunity’s arrival point at Endeavour crater was quickly named “Spirit Point” by Opportunity’s control team in honor of Opportunity’s twin, Spirit, which did not survive the 2010 Martian winter.

Upon arriving at the crater, Opportunity quickly confirmed that the rocks on the crater rim were older than any other rock previously studied by the rover.

By early December 2011, Opportunity made what is, at this time, its most important discovery while analyzing the “Homestake” formation.

Instruments on the rover were able to confirm that the “Homestake” formation is composed of gypsum – a mineral that does not occur except in the presence of water.

The rock was quickly nick-named “slam dunk” as it finally provided hard evidence that liquid water once flowed on Mars – thus providing substantial support for one of Opportunity’s primary mission scientific objectives.

By January 2012, Opportunity celebrated its 8th full year of operation on Mars.

Z6As 2012 began, and Opportunity prepared for its 5th Martian winter, the rover arrived at Greeley Haven, a place that provided a sun-facing slope to aid in maintaining adequate solar power during winter while at the same time still providing adequate targets of scientific interest.

This marked the first time that Opportunity needed to find a sun-facing slope for winter operations. During all four previous winters, Opportunity’s power-generating abilities and proximity to Mars’ equator were sufficient to allow the rover to continue normal operations.

However, Opportunity’s solar panels now carried a thicker coating of dust than in previous winters, thus necessitating the need for Opportunity to find the sun-facing slope.

Z7Throughout its winter hiatus, Opportunity maintained an approximate 15 degree tilt to keep its solar panels favorably aligned toward the winter sun that was low in the northern sky.

For its winter worksite, Opportunity was tasked with radio science investigation of the interior of Mars, inspections of mineral compositions and textures on the outcropping of Endeavour Crater, and recording a full-circle, color panorama of Greeley Haven.

In all, Opportunity spent 19 weeks at Greeley Haven investigating dozens of targets within reach of its robot arm.

Opportunity came through its fifth Martian winter in as near to perfect condition as possible for an eight-and-a-half-year-old rover.

Z9Taking its first drive in nearly six months, Opportunity moved further north on the Cape York area of Endeavour Crater on 8 May 2012, bringing itself closer to a bright-looking patch of what rover scientists hoped was dust.

By 4 December, Opportunity had completed one full walkabout circuit of Endeavour Crater – a process that began with the rover’s arrival at the crater.

On 25 January 2013, the rover marked its ninth year on Mars. By this point, mission planners where well into executing their winter 2014 ride-out plan for Opportunity.

Solander Point, a northward facing slope with geologic formations that Opportunity could explore during winter, was chosen for the rover’s sixth Martian winter ride-out location.

Z10By the end of January, Opportunity was on its way to Solander Point.

By mid-May, the rover passed through the three-week communications black out caused by the solar conjunction as Earth and Mars reached opposite sides of the sun from one another in their respective orbits.

During the communications blackout, Opportunity’s arm was extended into position on a nearby rock so that it could continue to collect scientific data on the geologic formation during the solar conjunction.

By 16 May 2013, Opportunity reached a major milestone in its exploration of Mars when it surpassed the total driving distance of the Apollo 17 lunar roving vehicle to become the farthest-traveling NASA/U.S. vehicle on a celestial body other than Earth.

Opportunity reached this milestone when its total odometry surpassed 35.744 km (22.210 miles) – the distance traveled by the Apollo 17 lunar roving vehicle.

With its place in NASA history secure, Opportunity now stands as the second farthest-traveling vehicle on another world, with only the Soviet Union’s Lunokhod 2 lunar rover having driven a greater distance (42km).

Opportunity could, assuming it drives the same distance in 2014 as it did in 2013 (and survives the depth of the coming Martian winter), break Lunokhod 2’s record before the end of 2014 to become humanity’s farthest-travelling vehicle on another world.

Z35Nevertheless, the following day, 17 May, NASA released preliminary scientific information regarding rock outcroppings that Opportunity surveyed during its stay at Endeavour Crater.

The results indicated a neutral pH water on the surface of Mars in the past, a result that further advanced the idea that ancient Mars was a water-rich world with conditions amenable for life.

On 21 June, Opportunity marked the beginning of its fifth Martian year on the red planet – a date which roughly coincided with the 9.5 Earth-year mark in its operational history on Mars.

After nearly eight Earth-months of travel, Opportunity arrived at its winter home on Solander Point in early August.

In August and September, Opportunity continued to rover around Solander Point to explore numerous surface targets and rock formations while the rover’s controllers continued to monitor the power level drop as the Martian winter began to set it.

On 20 November, Opportunity transferred its 186,246th photograph to Earth.

Z12As the depth of the Martian winter at Opportunity’s location approached, the rover entered Earth year 2014 with quite a stir for the general public when a rock seemingly appeared out of the nowhere near the rover.

The rock, which appeared suddenly in a 12 Sol period, is currently believed to have been moved to its current position by Opportunity itself.

According to NASA, the most-likely explanation for the rock’s sudden appearance is that one of Opportunity’s wheels clipped the rock and flung it to its current position.

Nevertheless, the event garnered much media and public attention for the rover ahead of its unparalleled, unpredictable, and all-around good-feeling anniversary.

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Now, a full decade after its landing, Opportunity’s story of longevity and endurance on the surface of another world is one of true engineering marvel and a testament to all those who built and have operated the Opportunity.

As the heart of the Martian winter for Opportunity arrives in February 2014, all evidence suggests that Opportunity will survive the Martian winter with more than enough power to continue life critical system operations – thus allowing Opportunity to continue operations.

An enduring legacy:

Throughout its 10 year tenure on Mars, Opportunity has greatly and in many ways drastically increased our knowledge of Mars and how our technology survives on the Martian surface.

In all, Opportunity has survived 40 times longer than its original mission duration called for, a whopping 3,852 percentage increase over its original 90 day mission.

Based on its tremendous scientific finds, life-span, and endurance beyond all odds, several honors have been conferred upon the Opportunity rover.

Asteroid 39382 was officially named Opportunity, and Opportunity is one of only 16 real-world (not characters from TV shows or movies) robots to be inducted into the robot hall of fame alongside the da Vinci Surgical System, fellow Mars rover Sojourner, Unimate (the first industrial robot which worked on the General Motors assembly line in 1961), and twin rover Spirit.

Moreover, Opportunity itself stands as a tribute and memorial to the men and women lost in the September 11th terrorist attacks on the World Trade Center and Pentagon as metal from the twin towers was repurposed and used as cable protection shields on Opportunity.

A decade ago, few could have imagined that Opportunity would reach this historic anniversary. And yet, here it is – a robust craft built by the best engineers on Earth, still going strong.

Ten years… for a rover that was only supposed to last for 90 days.

(All Images via NASA, NASA JPL, NASA APOD).

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