Ancient Martian Lake Contained Different Types of Microbes

An ancient Martian lake has recently been analysed by scientists. The new information makes room for the existence of different types of microbes on the red planet. The paper is published in the journal Science.

A Martian rock with even layers, an image captured in 2014 by NASA’s Curiosity Mars rover, indicates sedimentary deposit of a lake-floor near the inlet of flowing water into the water body. Photo credits: NASA/JPL-Caltech/MSSS

A long-lasting lake on ancient Mars has been described by a team of researchers from DOE/Los Alamos National Laboratory. The research is based on findings from NASA’s Curiosity rover mission whereby 3.5 years-worth of data had been analysed. While previous studies had already unveiled the existence of such a water body over 3 billion years ago in Mars’ Gale Crater, the new findings expose unprecedented information about the lake: its chemical conditions and stratification.

Curiosity was able to determine that the ancient Gale lake was stratified. This type of water features (on Earth) are known to be characterised by a stark contrast between its deep water and shallow water in terms of their chemical or physical composition, and the Martian lake conformed to this principle: its shallow water was found to be richer in oxidants than its deeper counterpart. This means that parts of the lake consisted of more oxygen than others—something common in lakes on Earth. This oxidant stratification constituted very different, co-existing environments in the same water body, says lead author Joel Hurowitz.

Co-author Roger Wiens points at the pertinence of this piece of information pertaining to Mars, explaining that it determines which minerals formed part of the sedimentary deposits. Furthermore, pursues Wiens, while oxygen is otherwise crucial for life, Gale Lake existed at a time when life on our planet had not yet started using oxygen (photosynthesis did not yet happen), implying that certain elements like manganese and iron might have been fuelling life, if they occurred on Mars, that is; the oxidation states of these substances would be regulated by the dissolved oxygen found in the water.

If life did flourish in the lake, the diverse environments in it might have allowed for the survival of different forms of microorganisms, suggests Hurowitz.

However, we still have no clear information about whether life did exist on Mars or not. One step towards finding out is in reconstructing the environment that once existed there: if it was one that would support life or not. This is one of the main purposes behind Curiosity: to explore the ancient environment of the red planet for habitable regions.

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