美國宇航局13日宣布了土星探測器卡西尼號和哈勃望遠鏡的發現，為土星第六大衛星“土衛二”和木星第四大衛星“木衛二”存在地球以外生命跡象提供了最新證據。研究人員認為，土衛二幾乎具備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.
美國宇航局（NASA）13日表示，冰冷的土星衛星土衛二理論上可能存在釋放甲烷的外星生物。

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，土星探測器卡西尼號在飛過土衛二南極區域噴射的一股氣流和冰物質時，發現了氫氣的存在。研究人員基于當時的數據宣布了該消息。氫氣是從土衛二海床的熱液噴口飄入太空的。這可能是產甲烷反應的標志。產甲烷反應是微生物進行無氧呼吸時產生甲烷的過程。

"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噴氣推進實驗室的科學家琳達?斯皮爾克13日在新聞發布會上表示：“這是一個非常重要的發現，因為氫氣或許是土衛二海洋中可能存在的微生物的潛在化學能量來源。”

"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.
她說：“我們現在知道，土衛二上幾乎具備所有已知的地球生命必需物質。”

The findings were published Thursday in the journal Science.
這些發現13日被發表在《科學》雜志上。

"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科學使命理事會副主任托馬斯?澤爾布肯在一份聲明中表示：“在我們尋找擁有宜居環境所需物質的星球期間，迄今為止，這是離這一目標最近的一次。這些觀測結果觸及NASA科學任務互通的本質：弄清我們是否為宇宙中唯一的生命。”

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還宣布，2014年哈勃太空望遠鏡觀測到木星衛星木衛二表面出現了疑似水汽羽狀物，并在2016年在同一區域附近再次出現。

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.
確認木衛二存在羽狀物后，研究人員不必穿越數英里厚的冰層，就可以對該星球上的化學成分進行分析。

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.
卡西尼號和哈勃望遠鏡關于“海洋星球”的發現有助于科學家籌備NASA的“木衛二快艇號”任務，該計劃將于本世紀20年代啟動。該計劃是讓木衛二快艇號無人航天器繞木星飛行，并對木衛二進行海洋深度、海水鹽分濃度測量等詳細調查。

"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行星科學部主任吉姆?格林13日表示：“這些發現來的正是時候。它使我們能夠作出正確的觀察，可以讓我們更了解海洋星球，特別是木衛二。”

英文來源：赫芬頓郵報
翻譯&編輯：董靜
審校：丹妮