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|作者：英语点津 文章来源：China Daily 点击数：40 更新时间：2017/4/26|
Saturn's icy moon Enceladus could theoretically be home to methane-producing alien life, NASA said Thursday.
Researchers made the announcement based on data from 2015, when the spacecraft Cassini detected the presence of hydrogen during a flyby through a plume of gas and ice erupting from Enceladus' south pole. The hydrogen, which is escaping into space from a hydrothermal vent on the moon's seafloor, could be a sign of methanogenesis, a form of anaerobic respiration in which microbes produce methane.
"This is a very significant finding because the hydrogen could be a potential source of chemical energy for any microbes that might be in Enceladus' ocean," Linda Spilker, a scientist at NASA's Jet Propulsion Laboratory, said Thursday at a press conference.
"We now know that Enceladus has almost all of the ingredients you would need to support life as we know it on Earth," she said.
The findings were published Thursday in the journal Science.
"This is the closest we've come, so far, to identifying a place with some of the ingredients needed for a habitable environment," Thomas Zurbuchen, associate administrator for NASA's Science Mission Directorate, said in a statement. "These results demonstrate the interconnected nature of NASA's science missions that are getting us closer to answering whether we are indeed alone or not."
NASA also announced that the Hubble Space Telescope observed what may have been a water vapor plume emerging from the surface of Jupiter's moon Europa in 2014, and again around the same area in 2016.
Confirming the existence of Europa's plumes would allow researchers to study that moon's chemical makeup without having to dig through miles of icy crust.
The Cassini and Hubble discoveries related to these "ocean worlds" will help scientists plan NASA's Europa Clipper mission, set to launch in the 2020s. The plan is for the unmanned spacecraft to orbit Jupiter and perform a detailed investigation of Europa, including measuring the depth and salinity of its ocean.
"These discoveries are coming just at the perfect time," Jim Green, director of NASA's Planetary Science Division, said Thursday. "It enables us to make the right set of observations that can tell us much more about these ocean worlds, Europa in particular."
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