(JSC/NASA)
A group of scientists came to the conclusion that the organic substances in the Martian meteorite ALH 84001 were formed due to two different mechanisms of abiotic organic synthesis.
Those mechanisms could take place on ancient Mars in the late Noachian period.
The rock ALH 84001 was found in 1984 in Antarctica and is one of the few meteorites that hit Earth from Mars.
It is considered one of the oldest known Martian rocks, having formed during the Noachian period, approximately 4.09 billion years ago.
The meteorite is mainly orthopyroxene and contains carbonate globules, the formation of which is associated with the presence of liquid water on Mars 3.9 billion years ago.
ALH 84001 gained worldwide fame in 1996, when structures similar to microbial fossils were found in its composition, but this was later recognized as a mistake.
There are a number of hypotheses that explain the origin of organic compounds (including nitrogen-containing ones) found in the meteorite
Those are abiotic processes (impacts, eruptions, hydrothermal processes), the result of the vital activity of potential ancient Martian organisms, or pollution by terrestrial substances.
Now a group of planetary scientists led by Andrew Steele of the Carnegie Institution published the results of studies of thin meteorite samples cut
The team used an ion beam using transmission electron microscopy, scanning transmission x-ray microscopy and nanoscale mass spectrometry of secondary ions.
The scientists concluded that the substance of the meteorite was indeed exposed to liquid water, which was not too long.
Moreover, the phase associations found in the sample, such as amorphous silica, talc-like phases, magnetite, and carbonates rich in iron, magnesium, and calcium, are similar to those observed in terrestrial rocks that have undergone serpentinization and/or mineral carbonization
All of this means that similar processes were at work on ancient Mars.
The simplest explanation is that these substances are the reaction products of orthopyroxene with neutral to high pH hydrothermal fluid.
The deuterium-rich organic material is combined with nanophase magnetite; it is assumed that its synthesis occurred similarly to the serpentinization of terrestrial rocks
This led to the formation of aromatic, aliphatic, carbonyl, carboxyl, and carbonate compounds.
The similarity of the organics in ALH 84001 to that of the 600-million-year-old Tissint meteorite indicates that abiotic organic synthesis reactions took place on Mars throughout most of its history, which are not associated with the activity of any microorganisms.
Similar reactions can explain the presence of methane in the Martian atmosphere.
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