Baqué Mickael, Napoli Alessandro, Fagliarone Claudia, Moeller Ralf, de Vera Jean-Pierre, Billi Daniela
German Aerospace Center (DLR), Institute of Planetary Research, Department of Planetary Laboratories, Astrobiological Laboratories, 12489-Berlin, Germany.
Department of Biology, Laboratory of Astrobiology and Molecular Biology of Cyanobacteria, University of Rome Tor Vergata, 00133-Rome, Italy.
Life (Basel). 2020 Jun 8;10(6):83. doi: 10.3390/life10060083.
Carotenoids are promising targets in our quest to search for life on Mars due to their biogenic origin and easy detection by Raman spectroscopy, especially with a 532 nm excitation thanks to resonance effects. Ionizing radiations reaching the surface and subsurface of Mars are however detrimental for the long-term preservation of biomolecules. We show here that desiccation can protect carotenoid Raman signatures in the desert cyanobacterium sp. CCMEE 029 even after high-dose gamma irradiation. Indeed, while the height of the carotenoids Raman peaks was considerably reduced in hydrated cells exposed to gamma irradiation, it remained stable in dried cells irradiated with the highest tested dose of 113 kGy of gamma rays, losing only 15-20% of its non-irradiated intensity. Interestingly, even though the carotenoid Raman signal of hydrated cells lost 90% of its non-irradiated intensity, it was still detectable after exposure to 113 kGy of gamma rays. These results add insights into the preservation potential and detectability limit of carotenoid-like molecules on Mars over a prolonged period of time and are crucial in supporting future missions carrying Raman spectrometers to Mars' surface.
由于类胡萝卜素的生物起源以及通过拉曼光谱易于检测，特别是由于共振效应，在532 nm激发下，它们是我们在火星上寻找生命的有希望的目标。然而，到达火星表面和次表面的电离辐射对生物分子的长期保存是有害的。我们在此表明，干燥可以保护沙漠蓝藻菌株CCMEE 029中的类胡萝卜素拉曼特征，即使在高剂量伽马辐射后也是如此。事实上，在暴露于伽马辐射的水合细胞中，类胡萝卜素拉曼峰的高度显著降低，而在用最高测试剂量113 kGy伽马射线照射的干燥细胞中，其保持稳定，仅损失其未照射强度的15-20%。有趣的是，尽管水合细胞的类胡萝卜素拉曼信号损失了其未照射强度的90%，但在暴露于113 kGy伽马射线后仍可检测到。这些结果为类胡萝卜素样分子在火星上的长期保存潜力和可检测极限提供了见解，对于支持未来携带拉曼光谱仪前往火星表面的任务至关重要。
