Bài thực hành nghe Tiếng Anh nâng cao - Bài 22 - Thẩm Tâm Vy - Năm 2018 (Có âm thanh)

 Thẩm Tâm Vy’s, December 25th, 2018 PRACTISE LISTENING FOR ADVANCED LEARNERS – LESSON 22 
PRACTISE LISTENING FOR ADVANCED LEARNERS 22 
The Search for life on Mars 
Whiffs of Reality 
 WASHINGTON , D C 
 The latest results suggest no methane on Mars. Biology is thus less likely 
 On earth, most of the methane in the atmosphere has been belched by living 
organisms, so finding the gas on Mars would be happy news for seekers after extra-
terrestrial life. Sadly, news announced on December 12
th
 at the annual meeting of the 
American Geophysical Union (AGU), in Washington, DC, was anything but happy. 
Preliminary results from ExoMars Trace Gas Orbiter, a European craft that has been 
circling Mars for the past two years, give a thumbs-down to the idea that there is 
methane in its atmosphere. 
 Previous observations, from orbit and by telescopes on Earth, suggested Mars might 
sport traces of the gas. These were backed up by data from Curiosity, an American 
Mars rover. In its six years crawling around a crater called Gale (picture). 
 Curiosity has both detected methane and recorded seasonal ups and downs of the stuff 
that cycle from a modest 0.25 parts per billion during the winter to 0.65ppbn in the 
summer, with spikes up to 7.0ppbn. That cyclical pattern has intrigued researchers back 
on Earth. Broadly speaking, there are two possible sources for Martian methane. One is 
outer space, whence carbon-rich molecules, some of which are likely to break down into 
methane, arrive constantly on meteors of various sizes. The other is from under the 
planet’s surface. 
 Methane from both sources will mix eventually into the atmosphere. But if the gas is 
coming from underground, it will be more concentrated near its source, and might well 
appear on a seasonal basis. The process could be a geological or geochemical one that is 
encouraged by the relative warmth of summer. That would be interesting. Or it could be 
biological, with methane-generating bugs waking up during the summer months. That 
would be headlinegrabbing. For either to be the explanation of the seasonality 
observed by Curiosity, the rover would have to have had the luck to land in an area of 
such methane seeps. But such lucky breaks do happen. 
 Regardless of their source, any methane molecules in Mars’s atmosphere would, on the 
basis of experiments on Earth, be expected to hang around for centuries. It was to find 
signs of this more widespread material that a spectroscopic instrument called NOMAD 
(Nadir and Occultation for MArs Discovery), which is on board ExoMars Trace Gas 
Orbiter, was designed. And, as Ann Carine Vandaele of the Belgian Institute for Space 
Aeronomy told the AGU, NOMAD has failed to find the slightest hint of methane in the 
Martian atmosphere. Since NOMAD is 20 times more sensitive than the methane 
detector on board Curiosity, this is bad news. 
 The findings are still under review, pending publication in a journal, and are therefore 
preliminary. But they do not surprise Kevin Zahnle of the Ames Research Centre, in 
California, a laboratory belonging to NASA, America’s space agency. Dr Zahnle has 
long argued that Curiosity’s reports of Martian methane are artefacts. They are only 
marginally higher than control readings, and those readings indicate the rover itself may 
be a source of methane (though nobody knows how), which further complicates taking 
accurate readings. The optimists will not be deflected, though. They note that NOMAD 
can probe only the upper part of Mars’s atmosphere. 
 Air with an altitude of less than 5km is beyond its range. Moreover, when ExoMars 
Trace Gas Orbiter flew over Gale, a dust storm obscured nomad’s view of anything 
within 30km of the surface. Such optimists thus argue that the idea of methane seeping 
from the crater cannot be discounted. 
 What NOMAD does seem to show is that, if methane exists at all in Mars’s air, it is 
rare and confined to low levels of the atmosphere. But for now, neither side is willing to 
give way. [Source: The Economist, Dec. 22nd, 2018] 
~***~ 
 Notes. 
 - give a thumbs-down to = disagrre with = phản bác; tương phản 
 - spikes up to = rises/increases up to: tăng vọt lên tới 
 - headline-grabbing (<= to grab the headlines) = becoming important item of news (trở thành tin 
 sốt dẻo, đăng ‘titre’ lớn) [titre <= “tít”: tiếng Pháp] 
 - artefacts: an object that is made by a person, such as a tool or a decoration, especially one that is of 
 historical interest (đồ tạo tác thời kỳ tiền sử - (nghĩa bóng) = sự bịa đặt) 
**>** 
Gale