Science

Space station experiment suggests rovers will have to dig deep to find life

NASA rovers shouldn’t have to wait to detect biomarkers on the surface of the Red Planet, according to a new study based on an experiment aboard the International Space Station (ISS) that suggests ultraviolet radiation would destroy such molecules in just a year or more. two.

Both Curiosity and Perseverance use Raman spectrometers to identify organic compounds and possibly biological molecules on the Martian surface. A Raman spectrometer uses a laser to excite molecules, and then how those excited molecules scatter the light tells scientists what those molecules are. In particular, they are sensitive to organic compounds, which is why they are a key tool for both rovers.

However, a new study on the International Space Station led by Mikael Backe of the German Aerospace Center (DLR) has cast doubt on how useful these tools could be on Mars. Due to its thin atmosphere and lack of magnetic shielding, Mars is flooded with solar ultraviolet light, which can be harmful to biological cells.

On the subject: 12 amazing photos of the first year of the Perseverance rover on Mars

Backe’s team exposed a sample of seven different types of biomolecules to Martian-like conditions for 469 days as part of the Biological and Martian Experiment (BIOMEX), which is installed on the Expose-R2 platform outside the ISS. Temperature, diurnal light cycles, and ionizing radiation levels were adapted to mimic Mars, and the sample was placed in a simulated Martian regolith.

The experiment involved biomolecules commonly found in organisms: 𝛃-carotene (antioxidant and pigment that reacts to light), chlorophyllin (derived from chlorophyll, used by plants to process sunlight), naringenin (common antioxidant). , quercetin (another common antioxidant), melanin (a pigment that provides protection from ultraviolet light), cellulose (a component of plant cell walls), and chitin (found in insect skeletons).

Typically, Raman spectroscopy can detect all seven of these biomolecules. However, by the end of the experiment, Backe’s team found that only three of them – chlorophyllin, quercetin and melanin – remained detectable, and even their signal was attenuated by 30-50%. The ultraviolet light that the molecules were exposed to corrupted them to the point that Raman spectroscopy could not recognize them.

Importantly, this method was still able to detect biomolecules from a control sample that was shielded from radiation by deeper layers of regolith. These findings imply that Perseverance or future rover missions can still identify biomarkers buried in the surface.

“ultraviolet [radiation] penetrates only the first few micrometers or millimeters of the Martian surface, so organic compounds and potential biomolecules must be protected beyond these depths,” Backe told Space.com. less than a grain of sand.) Dig a little deeper and the Martian regolith should provide enough protection from the radiation.

The Expose-R2 platform outside the International Space Station contains biological material and organisms for space testing. (Image credit: Roscosmos)

Meanwhile, the European Space Agency’s Rosalind Franklin ExoMars rover will deliver a robotic drilling rig to Mars that can dive up to 6.6 feet (2 meters) into the surface. The launch of this rover was delayed because a Russian lander was supposed to take it to the surface, and Europe would no longer cooperate with Russia due to its invasion of Ukraine. Even launching the Rosalind Franklin rover no earlier than 2028 gives us the best chance of finding life on Mars since the Viking missions, scientists say.

If the Rosalind Franklin rover does find evidence of microbial life, then these microbes evolved under very harsh conditions.

“The Martian surface seems to be very harmful to organic compounds due to ultraviolet radiation, but also [because of] oxidizing agents and, finally, most importantly for long-term preservation for billions of years, ionizing radiation,” Baquet said.

Curiously, the results differ from those of similar BIOMEX experiments in which intact organisms, both living and dead, were exposed to similar conditions bathed in ultraviolet radiation. These experiments showed that the biomolecules inside the body remain intact. Baquet said he attributes this discrepancy to life’s ability to protect its own cells.

“Just as regolith can protect directly exposed molecules from photodegradation by ultraviolet radiation, other cellular components can play the same role in organisms,” he said.

However, the results mean that Raman spectroscopy may play a smaller role in the search for Martian life, partial or real, than scientists expected. Backe’s team concludes that any biomarkers on the surface degrade within a few years at the most, meaning that unless Mars is teeming with enough life to continually replenish such biomarkers, the surface will appear dead – which may or may not be the case. not be a true picture.

The study was published Wednesday (September 7) in the journal Science Advances.

Follow Keith Cooper on Twitter @21stCenturySETI. Follow us on Twitter @Spacedotcom and on Facebook.

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