Mars rovers may have to dig deeper to find signs of ancient life.
New research shows that certain protein-producing amino acids that could be evidence of ancient life on March are more sensitive to radiation than scientists thought, meaning that amino acids left behind by life forms might only have survived if buried deep below the planet’s surface.
“Our results suggest that amino acids are destroyed by cosmic rays into Martian surface rocks and regolith at much faster speeds than previously thought,” said Alexander Pavlov, a space scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, in a statement. “Current Mars rover missions go down to about two inches (about five centimeters). At those depths, it would only take 20 million years to completely destroy amino acids.”
Related: Possible sign of life on Mars? Curiosity rover finds ‘tempting’ organic material on Red Planet
While 20 million years may seem like an incredibly long time, it is a brief period in the development of planets and life. This is especially true when one considers that the signs of life that vagrants such as Curiosity research on Mars would have been present billions of years ago, when Mars was more like Earth.
The team found that the presence of liquid water, abundant on Mars billions of years ago, and perchlorate (charged ions of one chlorine atom surrounded by four oxygen atoms) could have accelerated the destruction amino acids. The results were delivered by the first amino acid mixing experiment with simulated Martian soil.
Research suggests we’re not digging deep enough below the Martian surface to discover signs of life. To solve this problem, research could focus on places where geological processes have brought buried rocks to the surface.
“Missions with shallow borehole sampling should look for recently exposed outcrops — for example, recent microcraters with ages less than 10 million years or the material ejected from these craters,” Pavlov said.
How Mars lost its magnetosphere
One of the main reasons Earth is more hospitable to life than Mars is that a strong magnetic field, the magnetospheresurrounds our planet.
The magnetosphere protects earth’s atmosphere from solar wind (charged particles from the sun) and fragments of other stars ( cosmic rays) by making them travel along magnetic field lines and behind the Earth, similar to how a boat creates a bow shock when moving through water.
These charged particles can degrade or destroy organic molecules as they penetrate meters of solid rock, ionizing and destroying everything in their path. The radiation of the Sun can also remove a planet’s atmosphere key factor in its ability to retain liquid water.
Billions of years ago, Mars lost its magnetic field, its atmosphere, and ultimately much of its vital liquid water. This means that the look for lifeon Mars is to look for signs of ancient biological activity in Martian rocks via indicators such as amino acids.
To test the effectiveness of our current research, the team of scientists mixed several types of amino acids in silica, hydrated silica, or silica and perchlorate to simulate Martian soil conditions, then sealed the samples in vacuum test tubes to simulate thin Martian air.
While some of these samples were kept at temperatures similar to those on the surface of Mars, others were cooled to minus 67 degrees Fahrenheit (minus 55 degrees Celsius). All samples were exposed to high-energy gamma rays to simulate the cosmic ray exposure that rocks on the surface of Mars would have experienced around 80 million years ago.
“Our work is the first comprehensive study where the destruction (radiolysis) of a wide range of amino acids has been investigated under a variety of Mars-relevant factors (temperature, water content, perchlorate abundance) and radiolysis rates. were compared,” Pavlov said. “It turns out that adding silicates, and particularly silicates with perchlorates, dramatically increases the rates of amino acid destruction.”
Researchers have yet to find amino acids on Mars, but they have found these molecules in meteorites, including one from the red planet. But how did these complex chemicals form in the Martian Meteorite RBT 04262 which was discovered in Antarctica in 2004, is still unclear.
Since meteorites are typically ejected at least 3.3 feet (1 meter) below the Martian surface, this new research implies that the amino acids in RBT 04262 may have been shielded from sunlight and cosmic rays.
The results also indicate that the complex organic molecules that the Mars rovers Curiosity and Perseverancediscovered, which intrigue scientists but are not indicators of life, may have been altered over time by radiation exposure.
The team’s research was published June 26 in the journalAstrobiology.
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