用户名: 密码: 验证码:    注册 | 忘记密码?
首页|听力资源|每日听力|网络电台|在线词典|听力论坛|下载频道|部落家园|在线背单词|双语阅读|在线听写|普特网校
您的位置:主页 > 每日焦点 > 文化娱乐 >

视频围观:火星确定有液态水

2015-09-29    来源:网络    【      美国外教 在线口语培训

NASA finds "strong" evidence for liquid water on Mars
视频围观:火星确定有液态水

史上第一次,人类在其他行星上发现了存在液态水的确切证据!

据美国宇航局(NASA)于当地时间28日发布的消息称,美国NASA在火星上首次发现了存在液态水的“强有力”证据。在当天的发布会上,美国宇航局行星探测部门主管吉姆·格林正式宣布称:“美国宇航局确认,在某些特定情况下,火星地表存在液态水。”

事实上,人类早就发现火星的历史上存在液态水,比如20年前找到的极冠冰帽,甚至是大规模海洋,但已经消失很久了,现在是否依然隐秘地存在始终是个谜。

NASA的火星轨道探测器(MRO) 2011年就在火星上发现了一些暗黑条纹形状,但直到如今才确认,它们是季节性流水留下的痕迹。
WASHINGTON, Sept. 28 (Xinhua) -- U.S. space agency NASA announced on Monday it has found "strong" evidence that there is liquid water intermittently flowing on present-day Mars.

Images taken from the Mars orbit showed dark, finger-like markings that, typically less than five meters in width, appear on slopes during warm seasons, lengthen and then fade during cooler seasons on the Red Planet.

 


来自NASA能够证明火星有液态水的图片


These surface features, known as recurring slope lineae (RSL), have been hypothesized to form by the activity of brines, but direct evidence has been lacking.



Now, using an imaging spectrometer from NASA's Mars Reconnaissance Orbiter (MRO), researchers detected signatures of hydrated minerals on slopes where the mysterious streaks are seen on Mars.

"Our quest on Mars has been to 'follow the water,' in our search for life in the universe, and now we have convincing science that validates what we've long suspected," said John Grunsfeld, associate administrator of NASA's Science Mission Directorate in Washington.

"This is a significant development, as it appears to confirm that water -- albeit briny -- is flowing today on the surface of Mars."

These puzzling surface features were first noticed in 2010 by Lujendra Ojha, then a University of Arizona undergraduate student, using images from the MRO's High Resolution Imaging Science Experiment.

In the new study, Ojha, now a graduate student at Georgia Institute of Technology, and his colleagues analyzed spectra data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) aboard the MRO from four different locations where the RSL features were present.

They reported in the British journal Nature Geoscience that signatures of hydrated salts at these RSL locations existed only when the dark features were relatively wide.

"We found the hydrated salts only when the seasonal features were widest, which suggests that either the dark streaks themselves or a process that forms them is the source of the hydration," Ojha said.

"In either case, the detection of hydrated salts on these slopes means that water plays a vital role in the formation of these streaks."

The researchers interpreted the spectral signatures as caused by hydrated minerals called perchlorates, which are likely a mixture of magnesium perchlorate, magnesium chlorate and sodium perchlorate.

Some perchlorates have been shown to keep liquids from freezing even when conditions are as cold as minus 94 degrees Fahrenheit (minus 70 Celsius), NASA said. On Earth, naturally produced perchlorates are concentrated in deserts, and some types of perchlorates can be used as rocket propellant.

Perchlorates have previously been seen on Mars. For example, NASA's Phoenix lander and Curiosity rover both found them in the planet's soil, and some scientists believed that the Viking missions in the 1970s measured signatures of these salts.

"However, this study of RSL detected perchlorates, now in hydrated form, in different areas than those explored by the landers," NASA said. "This also is the first time perchlorates have been identified from orbit."

For Ojha, the new findings are more proof that the mysterious lines he first saw darkening Martian slopes five years ago are, indeed, present-day water.

"When most people talk about water on Mars, they're usually talking about ancient water or frozen water," he said.

"Now we know there's more to the story. This is the first spectral detection that unambiguously supports our liquid water-formation hypotheses for RSL."
  recurring slope lineae (RSL):季节性斜坡纹线,这种沟壑发育在比较陡峭的山坡上(坡度大于25°),有季节性的变化,一般在火星的春末开始发育或生长,在初冬之后变小或消失,往复如此。



顶一下
(2)
100%
踩一下
(0)
0%
手机上普特 m.putclub.com 手机上普特
[责任编辑:katee]
------分隔线----------------------------
发表评论 查看所有评论
请自觉遵守互联网政策法规,严禁发布色情、暴力、反动的言论。
评价:
表情:
用户名: 密码: 验证码:
  • 推荐文章
  • 资料下载
  • 讲座录音
普特英语手机网站
用手机浏览器输入m.putclub.com进入普特手机网站学习
查看更多手机学习APP>>