NASA新消息：若有外星人，最可能在这里

美国宇航局13日宣布了土星探测器卡西尼号和哈勃望远镜的发现，为土星第六大卫星“土卫二”和木星第四大卫星“木卫二”存在地球以外生命迹象提供了最新证据。研究人员认为，土卫二几乎具备所有存在外星生命的已知要件。

Saturn's icy moon Enceladus could theoretically be home to methane-producing alien life, NASA said Thursday.
美国宇航局（NASA）13日表示，冰冷的土星卫星土卫二理论上可能存在释放甲烷的外星生物。

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.
2015年，土星探测器卡西尼号在飞过土卫二南极区域喷射的一股气流和冰物质时，发现了氢气的存在。研究人员基于当时的数据宣布了该消息。氢气是从土卫二海床的热液喷口飘入太空的。这可能是产甲烷反应的标志。产甲烷反应是微生物进行无氧呼吸时产生甲烷的过程。

"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.
NASA喷气推进实验室的科学家琳达•斯皮尔克13日在新闻发布会上表示：“这是一个非常重要的发现，因为氢气或许是土卫二海洋中可能存在的微生物的潜在化学能量来源。”

"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.
她说：“我们现在知道，土卫二上几乎具备所有已知的地球生命必需物质。”

The findings were published Thursday in the journal Science.
这些发现13日被发表在《科学》杂志上。

"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科学使命理事会副主任托马斯•泽尔布肯在一份声明中表示：“在我们寻找拥有宜居环境所需物质的星球期间，迄今为止，这是离这一目标最近的一次。这些观测结果触及NASA科学任务互通的本质：弄清我们是否为宇宙中唯一的生命。”

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.
NASA还宣布，2014年哈勃太空望远镜观测到木星卫星木卫二表面出现了疑似水汽羽状物，并在2016年在同一区域附近再次出现。

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.
确认木卫二存在羽状物后，研究人员不必穿越数英里厚的冰层，就可以对该星球上的化学成分进行分析。

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.
卡西尼号和哈勃望远镜关于“海洋星球”的发现有助于科学家筹备NASA的“木卫二快艇号”任务，该计划将于本世纪20年代启动。该计划是让木卫二快艇号无人航天器绕木星飞行，并对木卫二进行海洋深度、海水盐分浓度测量等详细调查。

"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."
NASA行星科学部主任吉姆•格林13日表示：“这些发现来的正是时候。它使我们能够作出正确的观察，可以让我们更了解海洋星球，特别是木卫二。”