20 Years After Landing: How NASA’s Twin Rovers Transformed Mars Science

Opportunity Views Its Own Shadow: NASA’s Spirit and Opportunity Mars rovers landed on the Red Planet on Jan. 3 and 24, 2004, respectively. This image shows a view Opportunity captured of its own shadow on July 26 of that year, the 180th Martian day, or sol, of its mission. Credit: NASA/JPL-Caltech

This month marks the 20th anniversary of Spirit and Opportunity’s landing on MarsMars is the second smallest planet in our solar system and the fourth planet from the sun. It is a dusty, cold, desert world with a very thin atmosphere. Iron oxide is prevalent in Mars' surface resulting in its reddish color and its nickname "The Red Planet." Mars' name comes from the Roman god of war.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>Mars, part of a mission whose legacy will extend far into the future.

In January 2004, twin NASAEstablished in 1958, the National Aeronautics and Space Administration (NASA) is an independent agency of the United States Federal Government that succeeded the National Advisory Committee for Aeronautics (NACA). It is responsible for the civilian space program, as well as aeronautics and aerospace research. Its vision is "To discover and expand knowledge for the benefit of humanity." Its core values are "safety, integrity, teamwork, excellence, and inclusion." NASA conducts research, develops technology and launches missions to explore and study Earth, the solar system, and the universe beyond. It also works to advance the state of knowledge in a wide range of scientific fields, including Earth and space science, planetary science, astrophysics, and heliophysics, and it collaborates with private companies and international partners to achieve its goals.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>NASA rovers named Spirit and Opportunity touched down on opposite sides of Mars, kicking off a new era of interplanetary robotic exploration. They arrived in dramatic fashion three weeks apart, each nestled in a cluster of airbags that bounced along the surface around 30 times before coming to a stop and deflating. The golf cart-size rovers’ mission: to look for evidence that water once flowed on the Red Planet’s surface.

Groundbreaking Discoveries: Rewriting Science

Their findings would rewrite science textbooks, including Opportunity’s discovery soon after landing of the famous “blueberries” – spherical pebbles of the mineral hematite that had formed in acidic water. Several years into the mission, Spirit, undaunted but now dragging a damaged wheel, uncovered signs of ancient hot springs that could have been ideal habitats for microbial life billions of years ago (if any ever existed on the Red Planet).

Scientists suspected Mars had long ago been radically different than the freezing desert it is today: Orbital images had shown what looked like networks of water-carved channels. But before Spirit and Opportunity, there was no proof that liquid water had formed those features.

“Our twin rovers were the first to prove a wet, early Mars once existed,” said former project scientist Matt Golombek of NASA’s Jet Propulsion Laboratory in Southern California, which managed the Mars Exploration Rover mission. “They paved the way for learning even more about the Red Planet’s past with larger rovers like Curiosity and Perseverance.”

Spirit and Opportunity 20th Anniversary Poster

Spirit & Opportunity 20th Anniversary Poster: On the 20th anniversary of the landing of Spirit and Opportunity, celebrate NASA’s Mars Exploration Rover project with this two-sided poster that lists some of the pioneering explorers’ accomplishments on the Red Planet. Credit: NASA/JPL-Caltech Download poster

An Enduring Legacy

Thanks in part to the science collected by Spirit and Opportunity, NASA approved development of the SUV-size Curiosity rover to investigate whether the chemical ingredients that support life were present billions of years ago on what was once a watery world. (The rover found soon after its 2012 landing that they were.)

Perseverance, which arrived at the Red Planet in 2021, is building on Curiosity’s success by collecting rock cores that could be brought to Earth to check for signs of ancient microbial life through the Mars Sample Return campaign, a joint effort by NASA and ESA (European Space AgencyThe European Space Agency (ESA) is an intergovernmental organization dedicated to the exploration and study of space. ESA was established in 1975 and has 22 member states, with its headquarters located in Paris, France. ESA is responsible for the development and coordination of Europe's space activities, including the design, construction, and launch of spacecraft and satellites for scientific research and Earth observation. Some of ESA's flagship missions have included the Rosetta mission to study a comet, the Gaia mission to create a 3D map of the Milky Way, and the ExoMars mission to search for evidence of past or present life on Mars.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>European Space Agency).

While working on Spirit and Opportunity, engineers developed practices for exploring the surface that continue today, including the use of specialized software and 3D goggles to better navigate the Martian environment. And after honing years of expertise during the twin rovers’ travels over Mars’ rocky, sandy surface, engineers are able to plan safer, longer drives, and to quickly put together the far more complex daily plans required to operate Curiosity and Perseverance.

Science team members have also become more adept in their role as virtual field geologists, drawing on years of knowledge to select the best ways to investigate Martian terrain using the robotic “eyes” and tools carried by their roving partners.

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Using footage filmed at JPLThe Jet Propulsion Laboratory (JPL) is a federally funded research and development center that was established in 1936. It is owned by NASA and managed by the California Institute of Technology (Caltech). The laboratory's primary function is the construction and operation of planetary robotic spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA's Deep Space Network. JPL implements programs in planetary exploration, Earth science, space-based astronomy and technology development, while applying its capabilities to technical and scientific problems of national significance.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>JPL when Spirit touched down on Jan. 3, 2004, as well an animation depicting the rover’s arrival at the Red Planet, this video celebrates the 20th anniversary of Mars Exploration Rover Project landings. Spirit’s twin Opportunity arrived at Mars three weeks later. Credits: NASA/JPL-Caltech

Martian Marathon

Designed to last just 90 days, Spirit landed on Jan. 3; Opportunity on Jan. 24. The Mars Exploration Rovers soldiered on for years – in the case of Opportunity, nearly 15 years, finally succumbing to a planet-enveloping dust storm in 2018. That durability surpassed the wildest dreams of scientists and engineers, who had only expected localized exploration over a distance of no more than one-third of a mile (600 meters).

Instead, through their long-lived robotic surrogates, the team got the chance to roam a wide variety of Martian terrains. Opportunity, the first rover to go a marathon-length distance on another planet, would ultimately cover nearly 30 miles (45 kilometers) in total – the farthest distance driven on another planet.

This illustration depicts some highlights along the route as NASA’s Mars Exploration Rover Opportunity drove as far as a marathon race during the first 11 years and two months after its January 2004 landing in Eagle Crater.
The vehicle surpassed marathon distance of 26.219 miles (42.195 kilometers) with a drive completed on March 24, 2015, during the 3,968th Martian day, or sol, of Opportunity’s work on Mars. For this map, north is on the left.
Credit: NASA/JPL-Caltech/CornellUniv./USGS/Arizona State Univ.

“This was a paradigm shift no one was expecting,” said former project manager John Callas of JPL. “The distance and time scale we covered were a leap in scope that is truly historic.”

The chance to see so much was critical for revealing that not only was Mars once a wetter world, but also that it supported many different kinds of watery environments – fresh water, hot springs, acidic and salty pools – at distinct points in its history.

Continuing Inspiration

The roving twins would also inspire a new generation of scientists. One of those was Abigail Fraeman, who was a high school student invited to JPL on the night of Opportunity’s landing. She got to watch the excitement as the first signal returned, confirming Opportunity had safely landed.

She would go on to pursue a career as a Mars geologist, returning to JPL years later to help lead Opportunity’s science team. Now deputy project scientist for Curiosity, Fraeman calls many of the people she met on Opportunity’s landing night her close colleagues.

Artist’s Concept of One of the Mars Exploration Rovers: This artist’s concept depicts one of NASA’s Mars Exploration Rovers on the Red Planet. The twin rovers, Spirit and Opportunity, landed in 2004 and lasted years beyond their expected 90-day mission. Credit: NASA/JPL-Caltech

“The people who kept our twin rovers running for all those years are an extraordinary group, and it’s remarkable how many have made exploring Mars their career,” Fraeman said. “I feel so lucky I get to work with them every day while we continue to venture into places no human has ever seen in our attempt to answer some of the biggest questions.”