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12.08.2014

NASA's Curiosity Rover Finds Clues to How Water Helped Shape Martian Landscape

Simulated View of Gale Crater Lake on Mars
This illustration depicts a lake of water partially filling Mars' Gale Crater, receiving runoff from snow melting on the crater's northern rim.
Observations by NASA's Curiosity Rover indicate Mars' Mount Sharp was built by sediments deposited in a large lake bed over tens of millions of years.

This interpretation of Curiosity's finds in Gale Crater suggests ancient Mars maintained a climate that could have produced long-lasting lakes at many locations on the Red Planet.

Inclined Martian Sandstone Beds Near 'Kimberley'
"If our hypothesis for Mount Sharp holds up, it challenges the notion that warm and wet conditions were transient, local, or only underground on Mars," said Ashwin Vasavada, Curiosity deputy project scientist at NASA's Jet Propulsion Laboratory in Pasadena, California. "A more radical explanation is that Mars' ancient, thicker atmosphere raised temperatures above freezing globally, but so far we don't know how the atmosphere did that."

Why this layered mountain sits in a crater has been a challenging question for researchers. Mount Sharp stands about 3 miles (5 kilometers) tall, its lower flanks exposing hundreds of rock layers. The rock layers - alternating between lake, river and wind deposits -- bear witness to the repeated filling and evaporation of a Martian lake much larger and longer-lasting than any previously examined close-up.

"We are making headway in solving the mystery of Mount Sharp," said Curiosity Project Scientist John Grotzinger of the California Institute of Technology in Pasadena. "Where there's now a mountain, there may have once been a series of lakes."

Curiosity currently is investigating the lowest sedimentary layers of Mount Sharp, a section of rock 500 feet (150 meters) high, dubbed the Murray formation. Rivers carried sand and silt to the lake, depositing the sediments at the mouth of the river to form deltas similar to those found at river mouths on Earth. This cycle occurred over and over again.

"The great thing about a lake that occurs repeatedly, over and over, is that each time it comes back it is another experiment to tell you how the environment works," Grotzinger said. "As Curiosity climbs higher on Mount Sharp, we will have a series of experiments to show patterns in how the atmosphere and the water and the sediments interact. We may see how the chemistry changed in the lakes over time. This is a hypothesis supported by what we have observed so far, providing a framework for testing in the coming year."

Multiple Deltas Built Out Over Time
After the crater filled to a height of at least a few hundred yards, or meters, and the sediments hardened into rock, the accumulated layers of sediment were sculpted over time into a mountainous shape by wind erosion that carved away the material between the crater perimeter and what is now the edge of the mountain.

On the 5-mile (8-kilometer) journey from Curiosity's 2012 landing site to its current work site at the base of Mount Sharp, the rover uncovered clues about the changing shape of the crater floor during the era of lakes.

"We found sedimentary rocks suggestive of small, ancient deltas stacked on top of one another," said Curiosity science team member Sanjeev Gupta of Imperial College in London. "Curiosity crossed a boundary from an environment dominated by rivers to an environment dominated by lakes."

Despite earlier evidence from several Mars missions that pointed to wet environments on ancient Mars, modeling of the ancient climate has yet to identify the conditions that could have produced long periods warm enough for stable water on the surface.

NASA's Mars Science Laboratory Project uses Curiosity to assess ancient, potentially habitable environments and the significant changes the Martian environment has experienced over millions of years. This project is one element of NASA's ongoing Mars research and preparation for a human mission to the planet in the 2030s.

"Knowledge we're gaining about Mars' environmental evolution by deciphering how Mount Sharp formed will also help guide plans for future missions to seek signs of Martian life," said Michael Meyer, lead scientist for NASA's Mars Exploration Program at the agency's headquarters in Washington.

Cross-Bedding at 'Whale Rock'
JPL, managed by Caltech, built the rover and manages the project for NASA's Science Mission Directorate in Washington.

For more information about Curiosity, visit:
http://www.nasa.gov/msl and http://mars.nasa.gov/msl/

Follow the mission on Facebook and Twitter at:
http://www.facebook.com/marscuriosity and http://www.twitter.com/marscuriosity

Guy Webster
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6278
guy.webster@jpl.nasa.gov

Dwayne Brown
NASA Headquarters, Washington
202-358-1726
dwayne.c.brown@nasa.gov


All Related Images
  • This map shows the route driven by NASA's Curiosity Mars rover from the location where it landed in August 2012 to the "Pahrump Hills" outcrop at the base of Mount Sharp.
    Curiosity Mars Rover's Route from Landing to Base of Mount Sharp
  • This image from Curiosity's Mastcam shows inclined beds of sandstone interpreted as the deposits of small deltas fed by rivers flowing down from the Gale Crater rim and building out into a lake where Mount Sharp is now. It was taken March 13, 2014, just north of the "Kimberley" waypoint.
    Inclined Martian Sandstone Beds Near 'Kimberley'
  • This image from Curiosity's Mastcam shows inclined beds of sandstone interpreted as the deposits of small deltas fed by rivers flowing down from the Gale Crater rim and building out into a lake where Mount Sharp is now. It was taken March 13, 2014, just north of the "Kimberley" waypoint.
    Inclined Martian Sandstone Beds Near 'Kimberley'
  • This March 25, 2014, view from the Mastcam on NASA's Curiosity Mars rover looks southward at the Kimberley waypoint. In the foreground, multiple sandstone beds show systematic inclination to the south suggesting progressive build-out of delta sediments in that direction (toward Mount Sharp).
    Bedding Pattern Interpreted as Martian Delta Deposition
  • This March 25, 2014, view from the Mastcam on NASA's Curiosity Mars rover looks southward at the Kimberley waypoint. In the foreground, multiple sandstone beds show systematic inclination to the south suggesting progressive build-out of delta sediments in that direction (toward Mount Sharp).
    Bedding Pattern Interpreted as Martian Delta Deposition
  • This April 4, 2014, image from Curiosity's Mastcam looks to the west of a waypoint on the rover's route to Mount Sharp. The mountain lies to the left of the scene. The image shows sets of sandstone beds inclined to the south (left), indicating progressive build-out of sediment toward Mount Sharp.
    Sets of Beds Inclined Toward Mount Sharp
  • This April 4, 2014, image from Curiosity's Mastcam looks to the west of a waypoint on the rover's route to Mount Sharp. The mountain lies to the left of the scene. The image shows sets of sandstone beds inclined to the south (left), indicating progressive build-out of sediment toward Mount Sharp.
    Sets of Beds Inclined Toward Mount Sharp
  • This diagram depicts rivers entering a lake. Where the water's flow decelerates, sediments drop out, and a delta forms, depositing a prism of sediment that tapers out toward the lake's interior. Progressive build-out of the delta through time produces sediments inclined toward the lake body.
    How a Delta Forms Where River Meets Lake
  • This image shows inclined beds characteristic of delta deposits where a stream entered a lake, but at a higher elevation and farther south than other delta deposits north of Mount Sharp. This suggests multiple episodes of delta growth building southward. It is from Curiosity's Mastcam.
    Multiple Episodes of Delta Growth in Gale Crater
  • This image shows inclined beds characteristic of delta deposits where a stream entered a lake, but at a higher elevation and farther south than other delta deposits north of Mount Sharp. This suggests multiple episodes of delta growth building southward. It is from Curiosity's Mastcam.
    Multiple Episodes of Delta Growth in Gale Crater
  • This diagram depicts a vertical cross section through geological layers deposited by rivers, deltas and lakes. Deposits from a series of successive deltas build out increasingly high in elevation as they migrate toward the center of the basin, over lake deposits.
    Multiple Deltas Built Out Over Time
  • This evenly layered rock photographed by the Mast Camera (Mastcam) on NASA's Curiosity Mars Rover on Aug. 7, 2014, shows a pattern typical of a lake-floor sedimentary deposit not far from where flowing water entered a lake.
    Sedimentary Signs of a Martian Lakebed
  • This diagram depicts a vertical cross section through geological layers deposited by rivers, deltas and lakes. Deposits from a series of successive deltas build out increasingly high in elevation as they migrate toward the center of the basin, over lake deposits.
    Multiple Deltas Built Out Over Time
  • This image shows an example of a thin-laminated, evenly stratified rock type that occurs in the "Pahrump Hills" outcrop at the base of Mount Sharp on Mars. The Mastcam on NASA's Curiosity Mars rover acquired this view on Oct. 28, 2014. This type of rock can form under a lake.
    Thin-Laminated Rock in 'Pahrump Hills' Outcrop
  • This image shows an example of a thin-laminated, evenly stratified rock type that occurs in the "Pahrump Hills" outcrop at the base of Mount Sharp on Mars. The Mastcam on NASA's Curiosity Mars rover acquired this view on Oct. 28, 2014. This type of rock can form under a lake.
    Thin-Laminated Rock in 'Pahrump Hills' Outcrop
  • This view from the Mastcam on NASA's Curiosity Mars rover shows an example of cross-bedding that results from water passing over a loose bed of sediment. It was taken Nov. 2, 2014, at a target called "Whale Rock" within the "Pahrump Hills" outcrop at the base of Mount Sharp.
    Cross-Bedding at 'Whale Rock'
  • This view from the Mastcam on NASA's Curiosity Mars rover shows an example of cross-bedding that results from water passing over a loose bed of sediment. It was taken Nov. 2, 2014, at a target called "Whale Rock" within the "Pahrump Hills" outcrop at the base of Mount Sharp.
    Cross-Bedding at 'Whale Rock'
  • Lozenge-shaped crystals are evident in this magnified view of a Martian rock target called "Mojave," taken on Nov. 15, 2014, by the Mars Hand Lens Imager on the arm of NASA's Curiosity Mars rover. These features record concentration of dissolved salts, possibly in a drying lake.
    Crystals May Have Formed in Drying Martian Lake
  • This series of images reconstructs the geology of the region around Mars' Mount Sharp, where NASA's Curiosity Mars rover landed and is now driving. The images, taken on Earth, have been altered for the illustration of how sediments can accumulate in alternating dry periods and wet periods.
    Sediment Accumulation in Dry and Wet Periods
  • This diagram illustrates how Mount Sharp in Gale Crater, Mars, where NASA's Curiosity rover is now driving, might have formed billions of years ago.
    Sedimentation and Erosion in Gale Crater, Mars
  • This simulation depicts a lake partially filling Mars' Gale Crater, receiving runoff from snow melting on the crater's rim. Evidence that NASA's Curiosity rover has found of ancient streams, deltas and lakes suggests the crater held a lake such as this more than three billion years ago.
    Simulated View of Gale Crater Lake on Mars
  • Cross-bedding seen in the layers of this Martian rock is evidence of movement of water recorded by the waves or ripples of loose sediment the water passed over, such as a current in a lake. This image was acquired by the Mastcam on NASA's Curiosity Mars rover on Nov. 2, 2014.
    Martian Rock's Evidence of Lake Currents
  • Cross-bedding seen in the layers of this Martian rock is evidence of movement of water recorded by waves or ripples of loose sediment the water passed over.
    Martian Rock's Evidence of Lake Currents

Credit: NASA/JPL-Caltech

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