Both Curiosity and Persistence they use Raman spectrometers to recognize organic compounds and possibly biological molecules Marssurface. A Raman spectrometer uses a laser to excite molecules, and then the way those excited molecules scatter light tells scientists what kind of molecules they are. In particular, they are sensitive to organic compounds, which is why they are a key tool for both rovers. However, new research in International Space Station led by Mickael Baqué of the German Aerospace Center (DLR) has cast doubt on how useful the instruments might be on Mars. Because of its thin atmosphere and lack of magnetic shielding, Mars is bombarded by a torrent of ultraviolet light from The sunwhich can be harmful to biological cells. Baqué’s team exposed a sample of seven different types of biomolecules to Mars-like conditions for 469 days at the Biology and Mars Experiment (BIOMEX), which is installed on the Expose-R2 platform on the outside of the ISS. Temperature, diurnal light cycles, and ionizing radiation levels were adjusted to mimic Mars, and the sample was placed among simulated Martian regolith. The biomolecules involved in the experiment were all those commonly found in organisms: 𝛃-carotene (which is an antioxidant and a light-responsive pigment), chlorophyllin (derived from the chlorophyll that plants use to process sunlight) , naringenin (a common antioxidant), quercetin (another common antioxidant), melanin (a pigment that provides protection from UV light), cellulose (a component of cell walls in plants), and chitin (found in the skeletons of bugs). Typically, Raman spectroscopy can detect all seven of these biomolecules. However, by the end of the experiment, Baqué’s team found that only three—chlorophyllin, quercetin, and melanin—remained detectable, and even their signal had weakened by 30% to 50%. The ultraviolet light to which the molecules had been exposed had degraded them to the point where Raman spectroscopy could not identify them. Importantly, the technique could still detect the biomolecules from a control sample shielded from radiation by deeper layers of regolith. These detections suggest that the Perseverance missions or future rover missions could still detect biomarkers buried on the surface. “Ultraviolet [radiation] only penetrates the first few micrometers to millimeters of the Martian surface, so organic compounds and possible biomolecules should be protected beyond these depths,” Baqué told Space.com. (A micrometer is about 1% the width of a human hair, 1 millimeter is smaller than a grain of sand.) Dig a little deeper and the Martian regolith should provide adequate radiation shielding.
The Expose-R2 platform outside the International Space Station houses biological material and organisms for testing in space conditions. (Image: Roscosmos) Meanwhile, the European Space Agency Rosalind Franklin ExoMars The rover will carry a robotic drill to Mars that will be able to dig 6.6 feet (2 meters) down into the surface. The launch of this rover was delayed because a Russian lander was to deposit it on the surface and Europe will no longer cooperate with Russia because of its invasion of Ukraine. Even as it faces a launch no earlier than 2028, the Rosalind Franklin rover delivers the best chance of finding life on Mars since the Viking missionssay the scientists. If the Rosalind Franklin rover finds evidence of microbial lifethen these microbes will have evolved in a very harsh environment. “The surface of Mars appears very harmful to organic compounds due to ultraviolet radiation, but also [because of] oxidizing substances and finally – but most importantly for long-term preservation for billions of years – ionizing radiation,” said Baqué. Curiously, the results differ from those of similar BIOMEX experiments that exposed intact organisms, living and dead, to similar UV-bathed conditions. These experiments found that the biomolecules within the organism remain intact. Baqué said he puts this difference down to life’s ability to protect its cells. “Just as regolith can protect directly exposed molecules from UV photodegradation, other cellular components can play the same role in organisms,” he said. The results mean, however, that Raman spectroscopy may play less of a role in the search for life on Mars, part or present, than scientists expected. Baqué’s team concludes that any biomarkers on the surface will degrade within a few years at most, meaning that if Mars isn’t teeming with enough life to continually replenish such biomarkers, the surface will appear dead—which may may or may not be the real picture. The research was published on Wednesday (September 7) in the Advances in Science. Follow Keith Cooper on Twitter @21stCenturySETI. Follow us on Twitter @Spacedotcom and up Facebook.
