Science Highlights

Finding Signs of Water and Conditions for Life

The Mars Exploration Rovers told us of an ancient time when Mars was awash in water, with good conditions for supporting microbial life. Here are some of the rovers' most significant discoveries about the Red Planet:

  • A collection of spherical pebbles on Mars.

    Soaked in Salty Waters Long Ago

    By landing in a crater, Opportunity scored a "hole in one" by finding small, spherical deposits of the mineral hematite, which typically forms in water. These iconic mineral features were nicknamed the "blueberries." Water is key to life as we know it. Yet, acidic water soaked this area in Mars' ancient past, making conditions harder for life to thrive.

    Caption: The small spherules on the Martian surface in this close-up image are near Fram Crater, visited by NASA's Mars Exploration Rover Opportunity during April 2004. These are examples of the mineral concretions nicknamed "blueberries." Opportunity's investigation of the hematite-rich concretions during the rover's three-month prime mission in early 2004 provided evidence of a watery ancient environment.
    Credit: NASA/JPL-Caltech/Cornell/USGS

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  • Slabs of rock dominate this rugged view of the surface of Mars.

    Bathing in Neutral Water in a Warmer Climate

    At a place called Comanche, Spirit found rocks 10 times richer in key chemicals (magnesium and iron carbonates) than any other Martian rocks studied before. These rocks formed when Mars was warm and wet (with a thicker carbon-dioxide atmosphere and near-neutral-pH water). This warmer, watery environment could have supported life much better than the harshly acidic conditions the rover found elsewhere.

    Caption: Lengthy detective work with data NASA's Mars Exploration Rover Spirit collected in late 2005 has confirmed that an outcrop called "Comanche" contains a mineral indicating that a past environment was wet and non-acidic, possibly favorable to life.
    Credit: NASA/JPL-Caltech/Cornell University

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  • Steamy Times in Ancient Hot Springs

    While dragging a wheel, Spirit churned up soil and found 90% pure silica at "Home Plate." On Earth, this kind of silica usually exists in hot springs or hot steam vents, where life as we know it often finds a hot, happy home – perhaps ancient microbes on Mars did as well.

    Caption: In March 2007, NASA's Spirit rover found a patch of bright-toned soil so rich in silica that scientists proposed water must have been involved in concentrating it.
    Credit: NASA/JPL/Cornell.

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  • Explosive Signs of a Once-Heated Habitat

    Spirit discovered that an ancient volcano erupted at "Home Plate," the rover's final resting place. Together, powerful steam eruptions from heated underground water produced some explosive volcanism. While violent, these extreme conditions can support microbial life on Earth. Once upon a time, maybe they did on Mars.

    Caption: The lower coarse-grained unit shows granular textures toward the bottom of the image and massive textures. Also shown in this false-color view is a feature interpreted to be a "bomb sag," which is 4 centimeters across.
    Credit: NASA/JPL-Caltech/USGS/Cornell.

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  • A light mineral vein is revealed in rectangular chunks in the Martian dirt.

    Slam-Dunk Signs of Flowing Water

    Score! Near the rim of Endeavour Crater, Opportunity found bright-colored veins of gypsum in the rocks. These rocks likely formed when water flowed through underground fractures in the rocks, leaving calcium behind – a slam-dunk sign that Mars was once more hospitable to life than it is today!

    Caption: This color view of a mineral vein called "Homestake" comes from the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity.
    Credits: NASA/JPL-Caltech/Cornell/ASU.

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  • The rim of a large Martian crater rises in the foreground of this Martian landscape.

    Compelling Clays: A Friendly Place for Life

    Opportunity found compelling signs of a watery past on Mars: clay minerals formed in neutral-pH water. Of all the places studied by Opportunity, this environment at Endeavour Crater once had the friendliest conditions for ancient microbial life.

    Caption: This scene from the panoramic camera (Pancam) of NASA's Mars Exploration Rover Opportunity catches "Pillinger Point," on the western rim of Endeavour Crater, in the foreground.
    Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ.

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  • An orbital view of Endurance crater is annotated with the rover's path along its rim.

    Craters and the Story They Tell

    Opportunity was a crater explorer. The rover visited and studied the geology of well over 100 impact craters of all sizes in its 14 years on Mars. It learned about the lives of craters, studying how they form and erode through time.

    Caption: NASA's Mars Exploration Rover Opportunity, working on Mars since January 2004, passed a marathon distance in total driving on March 24, 2015, during the mission's 3,968th Martian day, or sol. A drive of 153 feet (46.5 meters) on Sol 3968 brought Opportunity's total odometry to 26.221 miles (42.198 kilometers).
    Credit: NASA/JPL-Caltech/MSSS/NMMNHS

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  • This composite view shows the rover and its dusty solar panels from above.

    Long-term Study of the Martian Environment

    Opportunity continually monitored Mars for more than 14 years. It collected a wealth of scientific riches on the Martian environment by studying Mars' clouds and dust, the opacity (tau) of its atmosphere, and how those conditions affected its solar panels (and solar energy). This type of information continues to help inform subsequent Mars missions.

    Caption: A self-portrait of NASA's Mars Exploration Rover Opportunity taken in late March 2014 shows that much of the dust on the rover's solar arrays has been removed since a similar portrait from January 2014, seen below. Both were taken by Opportunity's panoramic camera (Pancam).
    Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ

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An overhead view of a Mars rover, of which you can only see its triangular top deck, at the center of the image pointing toward the top of the frame, and the deck is surrounded by five trapezoidal solar panels – two each extending from the top two sides of the triangle, and the fifth one extending from the triangle's base. But the entire thing is so covered in cinnamon-colored dust, it's almost impossible to distinguish from the surrounding terrain. A silvery mast, also dust-covered, extends upward from the deck toward the viewer.
NASA's Mars Exploration Rover Opportunity recorded the component images for this self-portrait about three weeks before completing a decade of work on Mars. The rover's panoramic camera (Pancam) took the images during the interval Jan. 3, 2014, to Jan. 6, 2014, a few days after winds removed some of the dust that had been accumulating on the rover's solar panels. Opportunity landed on Mars on Jan. 25, 2004, Universal Time (Jan. 24, 2004, PST) for a mission that was planned to last three months. It is still active 10 Earth years later. This image is presented as a vertical projection. The mast on which the Pancam is mounted does not appear in the image, though its shadow does.
NASA/JPL-Caltech/Cornell/Arizona State University
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