A new study explains why it´s so hard to find traces of life on Martian clays


The Curiosity rover in Gale Crater, where it has found organic molecules hidden in sediments rich in clays formed 3 billion years ago. Credits: NASA/GSFC.

The clay minerals discovered in the Gale crater of Mars by the Curiosity rover are very interesting for being able to preserve organic compounds for long periods of time. A scientific team led by the Center for Astrobiology (CAB, CSIC-INTA) has assessed whether this capability can be influenced by brief exposure to both acidic and alkaline fluids, which could serve to more accurately direct future efforts in the search for life on Mars.

If there was ever life on Mars, he probably found the best chance of thriving during the first 1.5 billion years of the planet's history. At that time, Mars had large amounts of water on its surface. At the same time, the oceans had also settled on Earth, and life was prevalent in our world. However, these were exclusively single-celled life forms. It is therefore reasonable to assume that, if there was life on Mars during the same period, it also did not evolve beyond single-celled life.

Finding the traces of this possible primordial Martian life is no easy task. The surface and subsurface of Mars are not ideal places for the preservation of organic compounds that can retain information on possible preterite living forms. Radiation is intense, dryness absolute and also contain significant amounts of oxidizing compounds. However, NASA's Curiosity rover has managed to identify some organic clay compounds analyzed in Gale Crater on Mars. This crater housed a small lake for a few million years of Mars' early geological history, and the organic compounds discovered by Curiosity could represent remnants of living forms that inhabited that lake.

A scientific team led by researchers from the Center for Astrobiology has just published in the journal Scientific Reports a study that adds a new condition for the preservation of organic compounds on Mars that had gone unnoticed until now: exposure to acids.

For Carolina Gil-Lozano, CAB researcher and lead author of the study, "the results and this work once again confirm the importance of conducting similar experiments in planetary simulation chambers to support the search for signs of life on Mars."

It is known that, once Mars lost its seas, lakes and rivers, there were small amounts of water that continued to leak among the rocks, in specific episodes separated by millions of years of absolute dryness, according to Alberto G. Fairén, cab researcher and study director. According to Fairén, "the chemical nature of these fluids that circulated between the rocks has largely determined that organic compounds have been preserved on Mars to this day. Our study describes how exposure to acidic fluids greatly complicates the preservation of organics in clays. Therefore, the results of the study provide information on the nature of the water that has circulated in the subsoil of Gale Crater over the past 3 billion years." 

This type of study will certainly help scientists in designing future strategies in the search for life on Mars.

This work has been funded by the European Research Council (ERC), through the Projects "MarsFirstWater" (ERC Consolidator Grant 818602) and "IcyMARS" /ERC Starting Grant 307496).


Fuente: UCC-CAB

Fecha: 2020-09-15


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