Wednesday , 12 December 2018
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Liquid water on Mars and what this means

Dr. Nandkumar M. Kamat

An Italian team led by R. Orosei and 21 scientists as co-authors claimed to have detected liquid water 1500 meters below the south pole of Mars. Their paper published in SCIENCE claims that “the presence of liquid water at the base of the martian polar caps has long been suspected but not observed”.

They surveyed the Planum Australe region using the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) instrument, a low -frequency radar on the Mars Express spacecraft. They collected Radar profiles between May 2012 and December 2015 and found evidence of liquid water trapped below the ice of the South Polar Layered Deposits.

The area where they claim to have discovered deep subsurface Martian aquifer has anomalously bright subsurface reflections which they claim are “evident within a well-defined, 20 -kilometer -wide zone centered at 193 degrees to East and 81 degree to South, which is surrounded by much less reflective areas. They made quantitative analysis of the radar signals. It showed that this bright feature has high relative dielectric permittivity (>15), matching that of water -bearing materials. They interpreted this feature as “a stable body of liquid water on Mars”.

Their finding is based on data from the European Mars Express spacecraft, obtained by a radar instrument called MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding). The Italian Space Agency (ASI) led the development of the MARSIS radar. NASA provided half of the instrument, with management of the U.S. portion led by the agency’s Jet Propulsion Laboratory in Pasadena, California. The Science paper reports- “the presence of liquid water at the base of the martian polar caps was first hypothesized more than 30 years ago and has been inconclusively debated ever since. Radio echo sounding (RES) is a suitable technique to resolve this dispute, because low -frequency radars have been used extensively and successfully to detect liquid water at the bottom of terrestrial polar ice sheets. An interface between ice and water, or alternatively between ice and water -saturated sediments, produces bright radar reflections.

The Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument on the Mars Express spacecraft is used to perform RES experiments. MARSIS has surveyed the martian subsurface for more than 12 years in search of evidence of liquid water. Strong basal echoes have been reported in an area close to the thickest part of the South Polar Layered Deposits (SPLD), Mars’ southern ice cap. These features were interpreted as due to the propagation of the radar signals through a very cold layer of pure water ice having negligible attenuation. These findings are very encouraging for all future missions towards Mars.

NASA scientists were not part of this paper but when media interviewed Jim Green, Chief Scientist , NASA, he remarked-”The bright spot seen in the MARSIS data is an unusual feature and extremely intriguing. It warrants further study. Additional lines of evidence should be pursued to test the interpretation. We hope to use other instruments to study it further in the future.”

NASA’s future suite of instruments would include a heat probe that will burrow down as far as 5 meters below the Martian surface. The probe, built by the German Aerospace Center (DLR), will provide crucial data on how much heat escapes the planet and where liquid water could exist near its surface. ‘Follow the Water’ has been one of the major goals of NASA’s Mars program. India’s ambitious Mangalyan (Mars Orbital Mission) was a success and the latest claims by Italian scientists would encourage ISRO to properly plan the next mission to Mars.

They may get some guidance from NRI scientist in USA, Lujendra Ojha of the Georgia Institute of Technology (Georgia Tech) in Atlanta. Earlier he had found dark narrow streaks called recurring slope lineae emanating out of the walls of Garni crater on Mars. The dark streaks here were up to few hundred meters in length. These were hypothesized to be formed by flow of briny liquid water on Mars. Ojha found the hydrated salts only when the seasonal features were widest. According to him this suggests that either the dark streaks themselves or a process that forms them is the source of the hydration. In either case, the detection of hydrated salts on these slopes means that water plays a vital role in the formation of these streaks. So what a combination of previous claims by Ojha and new claims by the Italian scientists means is -that there could be sufficient water on Mars which could have gone undetected in previous surveys.

Water is very essential ingredient for life and even to generate power from Hydrogen. The new aquifer under South Pole points to similar subsurface lakes on Mars and now the competition to detect the same would grow. With Elon Musk’s ambitious plans to send manned Missions to Mars and colonize it in coming decades, the new discovery is very important for exploring life on Mars and plan future human colonies and more ambitious expeditions for terraforming the red planet.

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