旧金山——对于那些为可能存在外星生命而高兴的人来说，土卫二，土星的一颗寒冷的卫星，是一个不断馈赠的礼物。
12月15日，哈佛大学的生物物理学家乔纳·彼得在美国地球物理联合会年会上报告说，在土卫二冰壳上喷口喷出的巨大水柱中，发现了可能支持外星微生物或帮助生命出现的关键化合物。其中包括氰化氢，它可能对人类有毒，尽管彼得指出，它也是“合成更复杂化合物的关键组成部分，包括氨基酸、糖和核碱基，而这些化合物又是蛋白质、RNA和DNA的前体。”
The findings are good tidings for the NASA team developing the Exobiology Extant Life Surveyor, or EELS, a snakelike robot that could one day crawl into Enceladus’ frozen crust to seek out signs of life in the ocean below.
Though that ocean has never been directly observed, it is thought to be the source of the huge water plume spouting from Enceladus’ south pole (SN: 6/9/23). Researchers had previously reported that the plume contains phosphorous in the form of phosphate, establishing Enceladus as the first alien ocean world known to possess all the elements essential for life (SN: 12/16/23). The detection of phosphorus bolstered the moon as a prime candidate for hosting extraterrestrial life, and the new findings from Peter’s team offer even more support.
With hydrogen cyanide and phosphate, “Enceladus might be seen as a favorable prebiotic system,” or a chemical setting capable of giving rise to life, said Christopher Glein, a geochemist at the Southwest Research Institute in San Antonio who was not involved in the study.
Peter and colleagues conducted a detailed analysis of data collected by NASA’s Cassini probe as it flew through Enceladus’ plume in 2011 and 2012. In addition to hydrogen cyanide, the spray contains acetylene, ethane and various alcohols, the team also reported December 14 in Nature Astronomy. These compounds fuel some microbes on Earth, Peter said, “and could supply large amounts of metabolic energy for any potential life” on Enceladus.
Though NASA has no missions scheduled for Enceladus, its habitability has already spurred the development of EELS. The 100-kilogram, 4-meter-long robot consists of ringed, cylindrical segments. These pieces can be angled and rotated in different ways to make EELS slither, sidewind or move vertically inside crevasses.
The robot’s most recent field test occurred in September, on the Athabasca Glacier in Alberta, Canada, reported technologist Masahiro Ono on December 13 at the meeting. On the glacier, Ono, of the Jet Propulsion Laboratory in Pasadena, Calif., and his colleagues tested the vertical mobility of EELS inside three ice shafts, or moulins. The robot first succeeded at holding itself steady in the moulins, unfurling its body to lodge itself between the frozen walls. Then, by carefully rotating treaded rings on its body, EELS safely completed multiple 1.5-meter descents.
Following further tests on the glacier, the next step for EELS might be Earth’s moon. For instance, a small version of the space snake could be deployed to assist stationary lunar landers, Ono said. This robot “is a game changer,” he said, “and not just for Enceladus.”
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