(ORDO NEWS) — As rovers like Curiosity and Perseverance scour the surface for traces of ancient life, new data suggests we may have to dig much deeper to find them. Any traces of amino acids left over from when Mars might have been habitable are most likely buried at least 2 meters (6.6 feet) underground.
This is because Mars, with its lack of a magnetic field and fragile atmosphere, is exposed to a much higher dose of cosmic radiation on its surface than Earth. We know this, and we know that cosmic radiation destroys amino acids.
Now, thanks to experimental data, we also know that this process occurs in a very short time, from a geological point of view.
“Our results show that amino acids are being destroyed by cosmic rays in Martian surface rocks and regolith much faster than previously thought,” says physicist Alexander Pavlov of NASA’s Goddard Space Flight Center.
“The current Mars rover missions are drilled down to about 2 inches (about 5 centimeters). At such depths, it would take only 20 million years to completely destroy the amino acids. The addition of perchlorates and water further increases the rate of degradation of amino acids.”
Cosmic radiation is actually a huge problem for the exploration of Mars. The average person on Earth is exposed to about 0.33 millisieverts of cosmic radiation per year. On Mars, this annual exposure can exceed 250 millisieverts.
This high-energy radiation from solar flares and energetic events such as supernovae can penetrate rocks, ionizing and destroying any organic molecules it encounters.
Long ago, Mars had a global magnetic field and a much denser atmosphere like Earth’s. There is also evidence a lot of it that liquid water once existed on the surface of Mars in the form of oceans, rivers, and lakes.
This combination of features suggests that Mars could have been habitable (perhaps more than once). in his past.
One of the signs indicating the suitability of Mars for life is the presence of amino acids. These organic compounds are not biosignatures, but are one of the most basic building blocks of life.
Amino acids combine to form proteins and have been found in space rocks such as the asteroid Ryugu and in the Earth’s atmosphere. Comet 67P. Thus, they are not a definitive sign of life, but finding them on Mars would be another clue that life may have appeared there some time ago.
Pavlov and his team wanted to better understand the likelihood. After finding evidence of amino acids on the surface of Mars, they designed an experiment to test the stability of these compounds.
They mixed amino acids with mineral mixtures designed to mimic Martian soil, consisting of silica, hydrated silica, or silica and perchlorates (salts), and sealed them in test tubes that mimic the Martian atmosphere at various Martian-like temperatures.
The team then irradiated the samples with ionizing gamma rays to simulate the dose of cosmic radiation expected on the surface of Mars for about 80 million years. Previous experiments have only exploded amino acids without soil mimics. This may have led to inaccurate data on the lifespan of amino acids.
“Our work is the first comprehensive study that has examined the degradation (radiolysis) of a wide range of amino acids by various factors associated with Mars. (temperature, water content, perchlorate content) and radiolysis rates,” says Pavlov.
“It turns out that the addition of silicates, and especially silicates with perchlorates, greatly increases the rate of degradation of amino acids. .”
This means that any amino acids on the surface of Mars earlier than about 100 million years ago probably disappeared long ago, becoming nothing.
Given that the surface of Mars has not been hospitable to life as we know it for much longer billions of years, not millions the few centimeters that Curiosity and Perseverance can dig up are unlikely to use up amino acids.
Both rovers have found organic material on Mars, but since the molecules could have been produced by non-biological processes, they cannot be considered evidence of life. In addition, the group’s research indicates that these molecules may have been significantly altered since their formation by exposure to ionizing radiation.
There is other evidence that the research team may have found something. From time to time, material from beneath the Martian surface does make its way to Earth. In fact, amino acids have even been found in it.
“We have identified several straight-chain amino acids in the Antarctic Martian meteorite RBT 04262 at the Goddard Astrobiological Analytical Laboratory that we believe originated on Mars (rather than contamination from terrestrial biology), although the mechanism by which these amino acids are formed in RBT 04262 remains unclear,” says astrobiologist Danny Glavin of NASA Goddard.
“Since meteorites from Mars are typically ejected from depths of at least 3.3 feet (1 meter) or more, it is possible that the amino acids in RBT 04262 were shielded from cosmic radiation.”
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