Perseverance detects traces of organic compounds in Mars

sarahjay1 (69)memberin Popular STEM • 2 years ago (edited)

(NASA/JPL-Caltech/MSSS http://bit.ly/3VbsCqv)

Geologists from Texas A&M University and Caltech have published new results from their study of rock samples in the Lake Lake crater on Mars using the Perseverance rover.

Two teams led by Michael M. Tice and Eva L. Scheller found that the primary igneous rocks at the bottom of the crater had repeatedly been exposed to salt water at low temperatures.

This process led to the formation of carbonates, sulfates and perchlorates, as well as aromatic organic compounds.

Liquid water existed for a long time on Mars several billion years ago and played an important role in the mineralogical, chemical and geological evolution of the planet's surface.

In particular, planetary scientists have found various minerals on the planet formed with the participation of water, such as carbonates or clays.

Currently, scientists are interested in compiling a detailed picture of the geological evolution of various regions of Mars

This requires a thorough analysis of various rocks in order to determine their composition, structure and possible geochemical processes and reactions.

(NASA/JPL-Caltech http://bit.ly/3iaSfcd)

THE FIRST WORK
The Lake Crater, where the Perseverance rover has been operating for nearly two years, is a 45-kilometer impact crater thought to have formed about 3.9 billion years ago.

Geologists and planetologists believe that in ancient times there was a lake there, from which vast accumulations of sedimentary rocks remained at the bottom of the crater.

The rover is equipped with a range of scientific instruments that allow detailed exploration of various rocks, allowing scientists to trace the geological history of selected samples.

Now, Tice’s team published the results of studying a thin section of a Martian rock using the PIXL X-ray fluorescence microscope and the SHERLOC instrument.

The sample was named Dourbes and was located in an outcrop in the Séítah Formation, where olivine and carbonate minerals had previously been discovered.

In the composition of the rock, the researchers found

olivine
augite pyroxene
feldspar mesostasis
Fe, Cr, Ti-spinels
merrillite

In addition, the team found (Fe,Mg)-carbonates, silicates with a low content of Fe and Mg, magnesium and calcium sulfates, and also, possibly, perchlorates.

The scientists proposed a step-by-step model for the formation of the studied rocks in this region of the Seit Formation.

Initially, the region contained cumulative coarse-grained rocks of igneous origin, which could have formed due to the slow cooling of lava.

The rocks were then repeatedly exposed to liquid water at temperatures well below 200 degrees Celsius.

This led to the dissolution and successive replacement of primary minerals with amorphous or finely crystalline secondary minerals such as carbonates, sulfates, oxides, chlorates and oxychlorides.

The water could have been brought by meteorites or from the ground.

THE SECOND RESEARCH
Scheller’s group analyzed data from the rover's SHERLOC instrument, as well as PIXL and SuperCam, three polished rock samples breeds.

One of the thin sections belonged to the Seit Formation at the bottom of the Jezero crater, the other two belonged to the overlying and, therefore, younger basalt formation of the Máaz, dated 2.3–2.6 billion years ago.

Scientists have determined that in the case of these rocks also there was a gradual modification of the primary igneous rock rich in olivine, liquid salt water.

This led first to the formation of carbonates, and then sulfates and perchlorates.

In the latter case, it is worth noting that these are sodium perchlorates found inside the rock.

Another important result was the discovery of traces of aromatic organic compounds in rocks containing one or two fused aromatic rings and/or aromatic heterocycles.

Specific compounds have not yet been identified, but may include naphthalene and benzene.

It is assumed that these compounds arose during the mineral rearrangement of primary igneous rocks under the influence of water.

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