![\"Photo](\"https:\/\/de40cj7fpezr7.cloudfront.net\/bda58539-4e34-4501-a2cd-882e63f48ae4.jpg\")
\nPhoto of a piece of the Murchison meteorite. (Image Source: NASA\/ edited in Canva by Starlust team))<\/p>\n
To date, several NASA rovers have wandered across Mars, inspecting rocks and searching for molecules of past life. But how could future rovers distinguish the organic molecules of long-extinct organisms from those produced by lifeless, geological processes? Scientists have pinned their hopes on two stable hydrocarbons\u2014pristane and phytane\u2014which come from living organisms on Earth and are common constituents of petroleum. \u201cIf life once existed on Mars, then molecules like pristane and phytane represent important molecular biosignatures that could have survived to this day,\u201d said MPS scientist and lead author Guillaume Leseigneur in\u00a0a statement<\/a>.<\/p>\n Pristane and phytane stand out as signs of life because they are chiral. This means that they can exist in different configurations, known as enantiomers, which mirror each other like the fingers of your left and right hands. \u201cChirality is a valuable tool in the search for past extraterrestrial life,\u201d said co-author Uwe Meierhenrich of C\u00f4te d\u2019Azur University. With regard to the same, living organisms are remarkably picky and almost exclusively use one specific configuration over the other. Conversely, non-biological processes produce an equal, 50\/50 mix of both forms. Such rules are true on Earth and should also apply to any alien life, scientists hypothesize.<\/p>\n The Rosalind Franklin rover carries the Mars Organic Molecule Analyzer (MOMA), an instrument that can distinguish between organic molecules of different chirality. MOMA, built as a joint partnership between MPS and NASA, consists of a gas chromatograph, a mass spectrometer, small furnaces, and an excitation laser. The instrument probes volatiles in heated rock samples by using the gas chromatograph and mass spectrometer. \u201cThe resulting gas mixture then passes through various capillary tubes that have been coated on their inner surfaces. Since chiral variants of the same type of molecule react at different rates with the coatings, they can be separated in time,\u201d MPS explains in a statement.<\/p>\n For this particular study, researchers tested MOMA\u2019s efficiency in separating the extremely unreactive enantiomers of pristane and phytane. \u201cChiral separation of pristane and phytane requires high instrument sensitivity and measurement accuracy, both of which we show MOMA can achieve\u201d, explained co-author and MOMA team member Fatma Yesil Sahan from the MPS. The researchers collected rock samples from the Murchison meteorite, which fell in Australia in 1969, to use as a substitute for Martian rock. The\u00a0meteorite<\/a> contains a variety of organic molecules, some of them are indigenous to the space rock, while others have been added through terrestrial contamination. Given the rock’s exposure to Earth soil, the team wondered if the pristane and phytane trapped inside came from microbes at the crash site.<\/p>\n The results, however, surprised the researchers. They found that the meteorite contained chiral variants of pristane and phytane in an exactly equal ratio. This finding definitively ruled out the possibility of recent biomass contaminating the space rock at the discovery site, thereby demonstrating MOMA’s ability to spot false-positives. Instead, the researchers determined the meteorite picked up the hydrocarbons during its descent through the Earth\u2019s atmosphere when it came in contact with aerosols from fossil fuel burning. Other studies have shown that these hydrocarbons are preserved in oil shales, sedimentary rocks that contain a petroleum precursor. \u201cPetroleum forms in these rocks over millions of years at great depths under the influence of heat and pressure\u201d, said co-author Manuel Reinhardt from the University of G\u00f6ttingen. Such extreme conditions destroy the chiral imbalance, effectively “resetting” the molecules to a 50\/50 mix. This explains why the researchers found the hydrocarbons in equal parts within the meteorite. The success of this trial shows that the ESA rover is more than ready to explore the dusty, bone-dry\u00a0surface of Mars<\/a>.<\/p>\n More on Starlust:\u00a0<\/p>\n Ancient crystals in Chile’s salt flat may offer hints about life on Mars<\/a><\/p>\n![\"A](\"https:\/\/de40cj7fpezr7.cloudfront.net\/aa483a6c-c9f5-47c5-b2c8-9d7a84af7fd4.jpg\")
\nA self-portrait of NASA\u2019s Curiosity rover taken on June 15, 2018, when a Martian dust storm had reduced sunlight and visibility at the rover\u2019s location in Gale Crater. (Image Source: NASA\/JPL-Caltech\/MSSS)<\/p>\n![\"This](\"https:\/\/de40cj7fpezr7.cloudfront.net\/c34293b2-8207-4171-b3ee-648ebec32cfd.jpg\")
\nThis illustration shows Jezero Crater \u2014 the landing site of the Mars 2020 Perseverance rover (Image Source: NASA\/JPL-Caltech)<\/p>\n![\"Artist\u2019s](\"https:\/\/de40cj7fpezr7.cloudfront.net\/e46da813-eca2-4f19-a9d8-03aaf07b4841.jpg\")
\nArtist\u2019s visualization of the Rosalind Franklin rover on the Martian surface. (Image Source: NASA)<\/p>\n![\"An](\"https:\/\/de40cj7fpezr7.cloudfront.net\/3d6ff0bc-8279-4cee-9783-dc5009cd030a.png\")
\nAn illustrated image of Mars. (Representative Image Source: Getty | Westend61)<\/p>\n