CURIOSITY ROVER FINDS EVIDENCE OF ANCIENT LAKE INSIDE GALE CRATER
This illustration depicts a lake of water partially filling Mars' Gale Crater, receiving runoff from snow melting on the crater's northern rim. Image Credit: NASA /JPL-Caltech / ESA / DLR / FU Berlin / MSSS
Recent observations by NASA’s Curiosity Mars Science Laboratory rover indicate that Mount Sharp, a layered mountain that sits inside Gale Crater, may have been formed by sediments deposited in a large lake bed over millions of years. These findings are evidence that ancient Mars may have had a climate the could have produced long-lasting lakes at many locations on the Martian surface. The findings were discussed by Curiosity team scientists during a media teleconference held on Monday, December 8.
“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.”
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. Image Credit: NASA/JPL-Caltech/MSSS
Why the 3 mile-high Mount Sharp sits in the middle of Gale Crater has been a puzzle for researchers. The rock layers, which alternate between river, lake and wind deposits, indicate the repeated filling and evaporation of a Martian lake that was much larger and longer lasting than any previously examined.
“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 is currently studying a section of rock 500 feet high called the Murray formation which contains the lowest sedimentary layers of Mount Sharp. Rivers carried sand and silt to the lake, depositing 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.
This diagram shows how a mountain inside a Mars’ Gale Crater might have formed. Image Credit: NASA/JPL-Caltech
“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 Curiosityclimbs 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.”
The accumulated layers of sediment filled the crater to a height of a few hundred yards and hardened into rock. The layers of sediment were sculpted into a mountainous shape over time by wind erosion that carved away the rock between the rim of the crater and what is now the edge of the mountain.
During Curiosity’s 5-mile drive from the site of its landing in 2012 to its current study area the rover has discovered clues about the changing sharp of the Gale 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.”
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.
Image Credit: NASA / JPL-Caltech / MSSS
While there is evidence from Curiosity and previous Mars missions that indicate wet environments on ancient Mars, current models of the ancient Martian climate can’t identify the conditions that could have produced long enough periods of temperatures warm enough for stable water on the surface. It is possible that the Martian atmosphere may have been much thicker and humid than previously thought.
Curiosity’s mission is to assess ancient, potentially habitable environments and the changes in the Martian environment over millions of years. The rover is just one element of NASA’s ongoing Mars research and preparation for a planned human mission to Mars 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.
JIM SHARKEY
Jim Sharkey is a lab assistant, writer and general science enthusiast who grew up in Enid, Oklahoma, the hometown of Skylab and Shuttle astronaut Owen K. Garriott. As a young Star Trek fan he participated in the letter-writing campaign which resulted in the space shuttle prototype being named Enterprise. While his academic studies have ranged from psychology and archaeology to biology, he has never lost his passion for space exploration. Jim began blogging about science, science fiction and futurism in 2004 and has been writing about NASA and space issues for Examiner.com since 2011. Jim resides in the San Francisco Bay area and has attended NASA Socials for the Mars Science Laboratory Curiosity rover landing and the NASA LADEE lunar orbiter launch.
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