[meteorite-list] NASA's Curiosity Rover Finds Clues to How Water Helped Shape Martian Landscape

[Ron Baalke]

December 8, 2014
     
NASA's Curiosity Rover Finds Clues to How Water Helped Shape Martian Landscape

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.

"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. "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, California. "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."

After the crater filled to a height of at least a few hundred yards 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.

JPL, managed by the California Institute of Technology, 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.jpl.nasa.gov/msl/

Follow the mission on Facebook and Twitter at:

http://www.facebook.com/marscuriosity

and

http://www.twitter.com/marscuriosity

-end-

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

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