The waters of Mars


  • Living
  • Tuesday, 16 Dec 2014

Traces in the rock: Beds of sandstone inclined to the south-west toward Mount Sharp and away from the Gale Crater rim on Mars. The beds are interpreted as the deposits of small deltas fed by rivers flowing down from the crater rim to the north and building out into a lake to the south, where Mount Sharp is now. Scientists say the mountain may have built up over time from lake sediments. — AFP photos

Gale Crater once held a vast long-lived lake, Curiosity rover finds.

Water is going “mainstream” on Mars. Nasa’s Curiosity rover has discovered evidence of a vast lake in Gale Crater that potentially lasted millions of years – findings that may contradict the idea that much of the planet’s water reserves were held only in ice or underground, and made only transient appearances on the surface.

The new results from studying rocks at the base of Mount Sharp (the 4.8km-high mound in the middle of Gale Crater) points to a lake that filled and drained over tens of millions of years and that could have spanned the 155km-wide crater, scientists at Jet Propulsion Laboratory in La Canada Flintridge, California, said.

The sediments deposited in this lake could be what helped form Mount Sharp in the first place.

“The puzzle pieces are coming together,” Michael Meyer, lead scientist for Nasa’s Mars Exploration Program, said in a press briefing.

The findings from Curiosity, known formally as the Mars Science Laboratory, show that water could have lasted long enough for microbial life potentially to emerge, the scientists said.

The results also have implications for other theories of Martian planetary evolution. After all, if such lakes were able to survive for so long, then Mars must have had a much thicker atmosphere in order to protect that water from escaping into space.

“The climate system must have been loaded with water ... To sustain a lake at Gale Crater for millions of years, Mars would need a vigorous hydrological cycle to keep the atmosphere humid,” Curiosity’s deputy project scientist Ashwin Vasavada of Jet Propulsion Laboratory said in the briefing.

Artist’s concept of a lake of water partially filling Mars’ Gale Crater, receiving runoff from snow melting on the northern rim. Patterns of sedimentary deposits in Gale Crater suggest it held a lake such as this more than three billion years ago.

The problem is, it’s very difficult to generate a realistic model of Martian atmospheric evolution that explains how it could have been warm enough, not just thick enough, Vasavada said.

The researchers had examined rocks that seemed to be forming at strange slanting angles – the kind of buildup you get when fast-moving river water suddenly hits a lake and has to decelerate.

Curiosity spotted these deposits at many different elevations, which means this cycle probably happened many times through the crater’s history, said Curiosity participating scientist Sanjeev Gupta of Imperial College in London.

“We believe what we’re seeing is multiple cycles of delta migration interspersed between river deposits and probably desert dune deposits, creating quite a complex collage of ancient environments,” Gupta said.

Curiosity is in its third year of exploration on the Red Planet. Originally sent to study Mount Sharp, the US$2.5bil (RM8.7bil) laboratory on wheels landed in August 2012 and took a detour from its looming target to study a spot called Yellowknife Bay.

There, the rover drilled up rocks that revealed signs of a past, water-rich, life-friendly environment on Mars.

Now, the rover is finally studying the base of Mount Sharp, whose sedimentary layers could hold the key to whether Mars was a much more habitable planet than it appears today. – Los Angeles Times/Tribune News Service

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The waters of Mars

   

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