In the News

This summer, a global dust storm encircled Mars, blocking much of the vital solar energy that NASA’s Opportunity rover needs to survive. After months of listening for a signal, the agency has declared that the longest-lived rover to explore Mars has come to the end of its mission. Originally slated for a three-month mission, the Opportunity rover lived a whopping 14.5 years on Mars. Opportunity beat the odds many times while exploring the Red Planet, returning an abundance of scientific data that paved the way for future exploration.

Scientists and engineers are celebrating this unprecedented mission success, still analyzing data collected during the past decade and a half and applying lessons learned to the design of future spacecraft. For teachers, this historic mission provides lessons in engineering design, troubleshooting and scientific discovery.

How They Did It

Launched in 2003 and landed in early 2004, the twin Mars Exploration Rovers, Spirit and Opportunity, were the second spacecraft of their kind to land on our neighboring planet.

Preceded by the small Sojourner rover in 1997, Spirit and Opportunity were substantially larger, weighing about 400 pounds, or 185 kilograms, on Earth (150 pounds, or 70 kilograms, on Mars) and standing about 5 feet tall. The solar-powered rovers were designed for a mission lasting 90 sols, or Mars days, during which they would look for evidence of water on the seemingly barren planet.

Dust in the Wind

Scientists and engineers always hope a spacecraft will outlive its designed lifetime, and the Mars Exploration Rovers did not disappoint. Engineers at NASA’s Jet Propulsion Laboratory in Pasadena, California, expected the lifetime of these sun-powered robots to be limited by dust accumulating on the rovers’ solar panels. As expected, power input to the rovers slowly decreased as dust settled on the panels and blocked some of the incoming sunlight. However, the panels were “cleaned” accidentally when seasonal winds blew off the dust. Several times during the mission, power levels were restored to pre-dusty conditions. Because of these events, the rovers were able to continue their exploration much longer than expected with enough power to continue running all of their instruments.

Side-by-side images of Opportunity on Mars, showing dust on its solar panels and then relatively clean solar panels

A self-portrait of NASA's Mars Exploration Rover Opportunity taken in late March 2014 (right) shows that much of the dust on the rover's solar arrays was removed since a similar portrait from January 2014 (left). Image Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ. | › Full image and caption

Terrestrial Twin

To troubleshoot and overcome challenges during the rovers’ long mission, engineers would perform tests on a duplicate model of the spacecraft, which remained on Earth for just this purpose. One such instance was in 2005, when Opportunity got stuck in the sand. Its right front wheel dug into loose sand, reaching to just below its axle. Engineers and scientists worked for five weeks to free Opportunity, first using images and spectroscopy obtained by the rover’s instruments to recreate the sand trap on Earth and then placing the test rover in the exact same position as Opportunity. The team eventually found a way to get the test rover out of the sand trap. Engineers tested their commands repeatedly with consistent results, giving them confidence in their solution. The same commands were relayed to Opportunity through NASA’s Deep Space Network, and the patient rover turned its stuck wheel just the right amount and backed out of the trap that had ensnared it for over a month, enabling the mission to continue.

Engineers test moves on a model of the Opportunity rover in the In-Situ Instrument Laboratory at JPL

Inside the In-Situ Instrument Laboratory at JPL, rover engineers check how a test rover moves in material chosen to simulate some difficult Mars driving conditions. | › Full image and caption

A few years later, in 2009, Spirit wasn’t as lucky. Having already sustained some wheel problems, Spirit got stuck on a slope in a position that would not be favorable for the Martian winter. Engineers were not able to free Spirit before winter took hold, denying the rover adequate sunlight for power. Its mission officially ended in 2011. Meanwhile, despite a troubled shoulder joint on its robotic arm that first started showing wear in 2006, Opportunity continued exploring the Red Planet. It wasn’t until a dust storm completely enveloped Mars in the summer of 2018 that Opportunity finally succumbed to the elements.

The Final Act

animation showing a dust storm moving across Mars

This set of images from NASA’s Mars Reconnaissance Orbiter (MRO) shows a giant dust storm building up on Mars in 2018, with rovers on the surface indicated as icons. Image credit: NASA/JPL-Caltech/MSSS | › Full image and caption

simulated views of the sun as the 2018 dust storm darkened from Opportunity's perspective on Mars

This series of images shows simulated views of a darkening Martian sky blotting out the Sun from NASA’s Opportunity rover’s point of view in the 2018 global dust storm. Each frame corresponds to a tau value, or measure of opacity: 1, 3, 5, 7, 9, 11. Image credit: NASA/JPL-Caltech/TAMU | › Full image and caption

Dust storm season on Mars can be treacherous for solar-powered rovers because if they are in the path of the dust storm, their access to sunlight can be obstructed for months on end, longer than their batteries can sustain them. Though several dust storms occurred on Mars during the reign of the Mars Exploration Rovers, 2018 brought a large, thick dust storm that covered the entire globe and shrouded Opportunity’s access to sunlight for four months. Only the caldera of Olympus Mons, the largest known volcano in the solar system, peeked out above the dust.

The transparency or “thickness” of the dust in Mars’ atmosphere is denoted by the Greek letter tau. The higher the tau, the less sunlight is available to charge a surface spacecraft’s batteries. An average tau for Opportunity’s location is 0.5. The tau at the peak of the 2018 dust storm was 10.8. This thick dust was imaged and measured by the Curiosity Mars rover on the opposite side of the planet. (Curiosity is powered by a radioisotope thermoelectric generator.)

Since the last communication with Opportunity on June 10, 2018, NASA has sent more than 1,000 commands to the rover that have gone unanswered. Each of these commands was an attempt to get Opportunity to send back a signal saying it was alive. A last-ditch effort to reset the rover’s mission clock was met with silence.

Why It’s Important

The Mars Exploration Rovers were designed to give a human-height perspective of Mars, using panoramic cameras approximately 5 feet off the surface, while their science instruments investigated Mars’ surface geology for signs of water. Spirit and Opportunity returned more than 340,000 raw images conveying the beauty of Mars and leading to scientific discoveries. The rovers brought Mars into classrooms and living rooms around the world. From curious geologic formations to dune fields, dust devils and even their own tracks on the surface of the Red Planet, the rovers showed us Mars in a way we had never seen it before.

tracks on Mars with a patch of white soil showing

This mosaic shows an area of disturbed soil made by the Spirit rover's stuck right front wheel. The trench exposed a patch of nearly pure silica, with the composition of opal. Image credit: NASA/JPL-Caltech/Cornell | › Full image and caption

Mineral vein on the surface of Mars

This color view of a mineral vein was taken by the Mars rover Opportunity on Nov. 7, 2011. Image credit: NASA/JPL-Caltech/Cornell/ASU | › Full image and caption

The rovers discovered that Mars was once a warmer, wetter world than it is today and was potentially able to support microbial life. Opportunity landed in a crater and almost immediately discovered deposits of hematite, which is a mineral known to typically form in the presence of water. During its travels across the Mars surface, Spirit found rocks rich in magnesium and iron carbonates that likely formed when Mars was warm and wet, and sustained a near-neutral pH environment hospitable to life. At one point, while dragging its malfunctioning wheel, Spirit excavated 90 percent pure silica lurking just below the sandy surface. On Earth, this sort of silica usually exists in hot springs or hot steam vents, where life as we know it often finds a happy home. Later in its mission, near the rim of Endeavor crater, Opportunity found bright-colored veins of gypsum in the rocks. These veins likely formed when water flowed through underground fractures in the rocks, leaving calcium behind. All of these discoveries lead scientists to believe that Mars was once more hospitable to life than it is today, and they laid the groundwork for future exploration.

Imagery from the Mars Reconnaissance Orbiter and Mars Odyssey, both orbiting the Red Planet, has been combined with surface views and data from the Mars Exploration Rovers for an unprecedented understanding of the planet’s geology and environment.

Not only did Spirit and Opportunity add to our understanding of Mars, but also the rovers set the stage for future exploration. Following in their tracks, the Curiosity rover landed in 2012 and is still active, investigating the planet’s surface chemistry and geology, and confirming the presence of past water. Launching in 2020 is the next Mars rover, currently named Mars 2020. Mars 2020 will be able to analyze soil samples for signs of past microbial life. It will carry a drill that can collect samples of interesting rocks and soils, and set them aside in a cache on the surface of Mars. In the future, those samples could be retrieved and returned to Earth by another mission. Mars 2020 will also do preliminary research for future human missions to the Red Planet, including testing a method of producing oxygen from Mars’ atmosphere.

It’s thanks to three generations of surface-exploring rovers coupled with the knowledge obtained by orbiters and stationary landers that we have a deeper understanding of the Red Planet’s geologic history and can continue to explore Mars in new and exciting ways.

Teach It

Use these standards-aligned lessons and related activities to get students doing engineering, troubleshooting and scientific discovery just like NASA scientists and engineers!

Explore More

Try these related resources for students from NASA’s Space Place

TAGS: K-12 Education, Teachers, Educators, Students, Opportunity, Mars rover, Rovers, Mars, Lessons, Activities, Missions

  • Ota Lutz
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I was inspired by the Hubble Space Telescope. I was required to do a mini research project on the telescope. I was so inspired by NASA and space, that I knew that I wanted to make a positive impact.

When I learned about the Mars Exploration Rover mission, I was hooked. I had always had a passion for robots, and now my two inspirations were combined.

Now I am working on Mars 2020 and living my dream.

TAGS: #InspiredBy, Student Stories, Spirit, Opportunity, Internships & Fellowships

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