Mars once had water to support life. Curiosity rover now finds what made it uninhabitable

The Curiosity rover of NASA is exploring the Gale crater on Mars currently and is providing more details about how the Red Planet's climate turned from potentially suitable for life to inhospitable to terrestrial life. 

It has been known that Mars was holding widespread liquid water in ancient times, as per the evidence. 

Even though the surface of Mars is hostile and frigid to life, NASA's robotic explorers have been finding clues about whether the planet supported life in the distant past. 

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The instruments on board Curiosity have been used by the researchers for measuring the isotopic composition of carbon-rich minerals (carbonates) which were discovered in the Gale crater and found new insights into how the ancient climate of the Red Planet transformed.

Here's what happened to ancient Mars

"The isotope values of these carbonates point toward extreme amounts of evaporation, suggesting that these carbonates likely formed in a climate that could only support transient liquid water," said David Burtt, who is lead author of a paper and works at NASA's Goddard Space Flight Center in Greenbelt, Maryland. 

The research was published in the Proceedings of the National Academy of Sciences.

"Our samples are not consistent with an ancient environment with life (biosphere) on the surface of Mars, although this does not rule out the possibility of an underground biosphere or a surface biosphere that began and ended before these carbonates formed," Burtt said. 

Isotopes are different versions of an element which have different masses. With the evaporation of water, light versions of carbon and oxygen escaped into the atmosphere while the heavy versions remained behind, accumulated in high abundances and were eventually incorporated into the carbonate rocks.

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In the paper, the researchers proposed two ways in which carbonates present at Gale were formed.

In the first case, carbonates were created in a series of wet-dry cycles that took place in the Gale Crater. In the second way, carbonates were formed in very salty water that was under cold, ice-forming (cryogenic) conditions in the Gale Crater.

"These formation mechanisms represent two different climate regimes that may present different habitability scenarios," said Jennifer Stern, who is co-author of the paper and is from NASA Goddard.

"Wet-dry cycling would indicate alternation between more-habitable and less-habitable environments, while cryogenic temperatures in the mid-latitudes of Mars would indicate a less-habitable environment where most water is locked up in ice and not available for chemistry or biology, and what is there is extremely salty and unpleasant for life," he added. 

(With inputs from agencies)