Mars Exploration Rover team members with rover

This rock, dubbed "Gasconade," was investigated by NASA's Mars Exploration Rover Opportunity while the rover was perched on "Spirit Mound" at the western edge of Mars' Endeavour Crater. Four Oct. 2...

This full-circle, stereo panorama shows the terrain around the NASA Mars Exploration Rover Opportunity during the 3,071st Martian day, or sol, of the rover's work on Mars (Sept. 13, 2012).

Locations of landers and rovers on Mars.

This view taken by Spirit show's the "Columbia Hills" up ahead.

This image superimposes an artist's concept of the Mars Exploration Rover Opportunity on the rim of Victoria Crater. It is done to give a sense of scale.

Chile's Atacama Desert is the driest place on Earth -- and a ready analog for Mars' rugged, arid terrain.

This enhanced-color view of ground sloping downward to the right in "Perseverance Valley" shows textures that may be due to abrasion by wind-driven sand. The Pancam on NASA's Mars rover Opportunity...

This 360-degree panorama shows "Endurance Crater" and the surrounding plains of Meridiani Planum.

This stereo view shows the "Murray Ridge" portion of the western rim of Endeavour Crater on Mars. It appears three-dimensional when seen through blue-red glasses with the red lens on the left. NASA...

The "Lion King" panorama was the largest panorama obtained by either rover in 2004.

NASA's Mars Exploration Rover Opportunity used its navigation camera to record this view at the end of a 111-meter (364-foot) drive on the 2,353rd Martian day, or sol, of the rover's mission on Mar...

This scene from NASA's Mars rover Opportunity shows "Wharton Ridge," on the western rim of Endeavour Crater. The ridge's name honors the memory of astrobiologist Robert A. Wharton (1951-2012). The ...

Spirit drove through the basin south of "Husband Hill," mainly driving over sand and dune deposits until it came across this spectacular example of basaltic rocks called "Lorre Ridge."

Athena Science team members and other Mars Exploration Rover team members pose for a photo at JPL.

The enhanced-color image taken by the microscopic imager on the Mars Exploration Rover Spirit shows the rock dubbed "Mazatzal" after a portion of its surface was brushed clean by the rover's rock a...

This May 29, 2016, image of a target called "Private Joseph Field" combines images from the microscopic imager on NASA's Mars Exploration Rover Opportunity with enhanced color information from the ...

NASA's Opportunity Mars rover, working on Mars since January 2004, passed marathon distance in total driving on March 24, 2015. This map shows the rover's entire traverse from landing to that point.

In this selfie, Spirit shows her solar panels gleaming in the Martian sunlight and carrying only a thin veneer of dust two years after the rover landed and began exploring the red planet.

This mosaic image shows an extreme close-up of round, blueberry-shaped formations in the martian soil near a part of the rock outcrop at Meridiani Planum called Stone Mountain

Members of the Mars Exploration Rovers Assembly, Test and Launch Operations team gather around Rover 2 and its predecessor, a flight spare of the Pathfinder mission's Sojourner rover, named Marie C...

With a model of NASA's Opportunity rover behind him, John Callas, project manager of the Spirit and Opportunity Mars rovers, speaks about the rovers' achievements at the agency's Jet Propulsion Lab...

This self-portrait of NASA's Mars Exploration Rover Opportunity comes courtesy of the Sun and the rover's front hazard-avoidance camera.

This before-and-after pair of images of the same patch of ground in front of NASA's Mars Exploration Rover Opportunity 13 days apart documents the arrival of a bright rock onto the scene.

Spirit examined spectacular layered rocks exposed at "Home Plate."

Researchers used the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity to capture this view of comet C/2013 A1 Siding Spring as it passed near Mars on Oct. 19, 2014.