Although life has not been found on Mars just yet, an astrophysicist thinks there could be life...under it.
Dimitra Atri, research scientist at the Center for Space Science at NYU Abu Dhabi, believes that the sub-surface conditions of Mars could be home to organic molecules.
Above the surface, Mars is not very hospitable. Aside from small amounts of water in brines, polar caps, and hydrated minerals, the Red Planet lacks the necessary resources to support life. Oxyidants and chemical compounds known as perchlorates, when activated by heat, destroy potential biomolecules and chemical biosignatures.
Below the surface of Mars, however, may be where to look for life.
One reason to dig deep on the planet: There's more water down there.
Although the Martian sub-surface environment has not yet been directly probed, satellite observations and rover measurements have shown large deposits of water ice. The ice deposits occur as shallow as 1 meter below the surface, extending down to several kilometers in depth.
Another reason to explore the sub-surface: There's radiation.
The Martian surface is bombarded by Galactic Cosmic Rays (GCRs), energetic charged particles that penetrate a few meters below the surface.
According to Atri, the steady bombardment of penetrating Galactic Cosmic Rays (GCRs) provides the energy needed to catalyze organic activity there.
One of the most important requirements for life to exist is chemical disequilibrium, says Atri, and the radiation from GCRs offers that kind of disruption, initiating a chemical process known as radiolysis.
"A system is in equilibrium when a substance A converts to substance B, at the same rate as substance B converts back to substance A — overall nothing new is being produced in the system." Atri told Tech Briefs. "The system is in disequilibrium when this equilibrium gets disrupted."
And below the surface of Mars, the radiation from Galactic Cosmic Rays continuously creates a "GCR-induced radiolytic zone" below the surface of Mars — an area of disequilibrium that is potentially supportive of life.
Atri proposes that galactic cosmic radiation, which can penetrate several meters below the surface, will induce chemical reactions that can be used for metabolic energy by extant life, and host organisms using mechanisms seen in similar chemical and radiation environments on Earth.
Atri’s findings are reported in the study Investigating the biological potential of galactic cosmic ray-induced radiation-driven chemical disequilibrium in the Martian subsurface environment in the journal Scientific Reports, Springer Nature.
“Based on the results of radiation chemistry experiments, and observations of interstellar ices and comets, it is highly likely that prebiotic molecules are present below the surface,” Atri says in the introduction of his report.
Using a combination of numerical models, space mission data, and studies of deep-cave ecosystems on Earth for his research, Atri proposes mechanisms through which life, if it ever existed on Mars, could survive and be detected with the upcoming ExoMars mission (2022) by the European Space Agency and Roscosmos Space Corporation.
The ExoMars will send the Rosalind Franklin rover to dig two-meters deep into the Martian surface and pull samples for study.
In a short Q&A with Tech Briefs below, Atri explains why answering the question of life on Mars is such an important one to answer.
Tech Briefs: The Perseverance rover launched this month, where it will eventually take surface samples and hopefully return them to Earth. What parts of the Mars 2020 mission are you especially excited about and paying attention to, and that can help to support your study's hypotheses? Will Perseverance be reaching the subsurface levels that your study focuses on?
Dimitra Atri: The sample return aspect is certainly very exciting, but those samples will be available to study on Earth several years from now. At present, the most interesting instrument on board the rover for me is SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals) which is going to analyze the surface and shallow subsurface of Mars.
Although it does not go deep enough in the Martian subsurface, I am hoping that it will provide us with new and useful information about the chemical environment there. It will certainly help with validating the chemistry part of my research and hopefully signs of present or past life on the planet.
Tech Briefs: How can the upcoming ExoMars mission (2022) by the European Space Agency and Roscosmos potentially detect the life that you're talking about?
Dimitra Atri: The ExoMars mission's Rosalind Franklin rover has a drill capable of retrieving samples from up to 2 meters below the Martian surface and studying them with sophisticated instruments such as:
- The Mars Organic Molecule Analyzer (MOMA) for the study of organic molecules and biosignatures.
- The close-up imager (CLUPI) for high-resolution color images.
- The MicroOmega instrument for imaging crushed sample material.
- The ADRON neutron and gamma ray detector to measure the subsurface hydrogen content.
- The Raman Laser Spectrometer (RLS) for the detection of organic functional groups.
These instruments would assist in detecting signs of possible microbial life and/or chemical biosignatures.
Tech Briefs: Why is answering this question about the proof of life below the surface of Mars such an important one to answer?
Dimitra Atri: All of us have wondered whether life exists beyond earth. It is also one of the biggest questions in modern science. If we detect life on Mars, it will help us understand how life fits in a broader astrophysical context and hopefully help us understand the physical underpinning of life!
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