Curiosity Follows the Water on Mars to Ancient Lake in Gale Crater

Summary: NASA's Curiosity follows the water on Mars to an ancient lake in Gale Crater, according to Mars Science Laboratory team's Oct. 9 report in Science.

Higher regions of Mount Sharp showing changing mineralogy (long ridge of hematite, undulating clay-rich plain, sulfate-rich rounded buttes) ~ composite image taken Sept. 9, 2015, by Curiosity: NASA/JPL-Caltech/MSSS, Public Domain, via NASA JPL Photojournal

MSL (Mars Science Laboratory) rover Curiosity’s successful follow-the-water exploration in Gale Crater finds Mount Sharp’s lower layers formed by sediment from lakes filling the crater over 3 billion years ago, according to a report by the MSL team published in Science on Oct. 9, 2015.

Located in the Southern Hemisphere near the Martian equator, Gale Carter presents ideal terrain for an ancient scenario of life-supporting, wet Mars. Alluvial fans, deltas, clay and sulfate byproducts of water, and layers of sediment all suggest the presence of water. Finely laminated, or layered, mudstone indicate standing water. Deposits from fast-moving streams and standing lake water seem to have built up Mount Sharp’s lower layers by filling in the underlying basin. The process of mountain building is thought to have taken place over a period of less than 500 million years.

Ashwin Vasavada, co-author and MSL project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, sums up Curiosity’s successful diggings: “Observations from the rover suggest that a series of long-lived streams and lakes existed at some point between about 3.8 to 3.3 billion years ago, delivering sediment that slowly built up the lower layers of Mount Sharp.”

Curiosity has been drilling for samples and gathering information on Mount Sharp since the car-sized rover’s arrival on Sept. 11, 2014, at Pahrump Hills, an outcrop serving as one of the mountain’s entryways. The sophisticated, car-sized rover’s original two-year mission began with its landing on Aolis Palus, the plain on Mount Sharp’s northern foothills, at 10:32 p.m. Pacific Daylight Time on Aug. 5, 2012.

On Dec. 4, 2012, NASA announced an indefinite extension to Curiosity’s mission of searching for evidence of microbial life on Mars. A radioisotope thermoelectric generator (RTG) powers the $2.5 billion rover through heat conversion of plutonium-238’s radioactive decay into electricity.

John Grunsfled, NASA’s associate administer for science, gives an informed guess on Curiosity’s lifespan: “I never get a straight answer on this, but I think it has 55 years of positive power margin.”

Mount Sharp, known officially as Aeolis Mons, rises as Gale Crater’s central peak to a height of 3.4 miles (5.5 kilometers) above the crater’s northern floor and 2.8 miles (4.5 kilometers) above the southern floor. With a sprawling diameter of 55+ miles (88+ kilometers), Mount Sharp dominates the crater’s 96-mile-diameter (154-kilometer-diameter) and roughly covers an area equal to that of the combined states of Connecticut and Rhode Island.

Water deposits appear to have formed the mountain’s lower layers, from the base up to one-half mile (800 meters). Dry, wind-driven deposits seem to be responsible for the bulk of Mount Sharp.

As with the big questions of the source for the water that sculpted the crater’s terrain and the triggers for the planet’s apparent change from anciently wet Mars to today’s dry Mars, Curiosity’s diggings show Mars as a big question mark.

“We have tended to think of Mars as being simple. We once thought of the Earth as being simple too," John Grotzinger, former MSL project scientist and the report’s lead author, notes. "But the more you look into it, questions come up because you’re beginning to fathom the real complexity of what we see on Mars. This is a good time to go back to reevaluate all our assumptions. Something is missing somewhere.”

Curiosity's selfie of drilling in cross-bedded sandstone Oct. 6, 2015, at Big Sky site for mission's "fifth taste of Mount Sharp": NASA/JPL-Caltech/MSSS, Public Domain, via NASA Mars Exploration

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

Mount Sharp: NASA/JPL-Caltech/MSSS, Public Domain, via NASA Jet Propulsion Laboratory Photojournal @ http://photojournal.jpl.nasa.gov/catalog/PIA19912

Curiosity’s selfie: NASA/JPL-Caltech/MSSS, Public Domain, via NASA Jet Propulsion Laboratory Photojournal @  http://mars.jpl.nasa.gov/msl/multimedia/images/?ImageID=7507

For further information:

Clavin, Whitney. "NASA's Curiosity Rover Team Confirms Ancient Lakes on Mars." NASA > Mars. Oct. 8, 2015.
Available @ https://www.nasa.gov/feature/jpl/nasas-curiosity-rover-team-confirms-ancient-lakes-on-mars

Grotzinger, J.P., et al. "Deposition, exhumation, and paleoclimate of an ancient lake deposit, Gale Crater, Mars." Science, vol. 350, issue 6257 (Oct. 9, 2015). DOI: 10.1126/science.aac7575
Available @ http://www.sciencemag.org/content/350/6257/aac7575

Klotz, Irene/Reuters. "NASA Mars rover finds clear evidence for ancient lakes." Review Journal. Oct. 8, 2015.
Available @ http://www.reviewjournal.com/news/nation-and-world/nasa-mars-rover-finds-clear-evidence-ancient-lakes