from 2015, when the spacecraft Cassini detected the presence of hydrogen during a flight through a cloud of gas and ice erupting from Enceladus' south pole. The hydrogen could be a sign of methanogenesis, a form of breath in which microbes (微生物) 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 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." The findings were published 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 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 water vapor 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 gas would allow researchers to study that moon's chemical makeup without having to dig through miles of icy crust (表面). 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.

　　"These discoveries are coming just at the perfect time，" Jim Green, director of NASA's Planetary Science Division, said. "It enables us to make the right set of observations that can tell us much more about these ocean worlds, Europa in particular."

　　1．The new discovery made the scientists feel more ________.

　　A．confident　　　　　　　 B．doubtful

　　C．worried D．confused

　　解析：选A　细节理解题。由第二段中的"This is a very significant finding"，第三段中的"This is the closest we've come"及最后一段中的"These discoveries are coming just at the perfect time"可知，新的发现让科学家们对探测外星生命的任务更加有信心。

　　2．According to the text, NASA's science missions aim to ________.

　　A．make space travel a reality

　　B．analyze Jupiter's chemical makeup

　　C．find out whether life exists outside Earth

　　D．explore the resources on Saturn's icy moon

解析：选C　细节理解题。由第三段中的"These results demonstrate the nature of NASA's science missions that are getting us closer to answering whether we are indeed alone or not"可知，NASA科学任务的本质是弄清是否只有地球上存在生命。