首页
登录
职称英语
If you were on a distant planet, and if you had instruments that could tell
If you were on a distant planet, and if you had instruments that could tell
游客
2023-10-18
56
管理
问题
If you were on a distant planet, and if you had instruments that could tell you the composition of Earth’s atmosphere, how would you know there was life on this planet?
Water in the atmosphere would suggest there could be water on the surface, and as we all know water is considered crucial to life. But water would only suggest that life is possible. It wouldn’t prove it’s there.
Carbon? That basic component of "life as we know it?" Not necessarily. A diamond is pure carbon, and it may be pretty, but it isn’t alive.
What really sets Earth apart is nitrogen, which makes up 80 percent of the planet’s atmosphere. And it’s there only because there is abundant life on Earth, say scientists at the University of Southern California.
The report grew out of a class discussion two years ago in a course taught by Capone and Kenneth Nealson, professor of earth sciences. Students were asked to come up with different ideas about searching for life on other planets. What is a distinct "signature" , as Capone puts it, that would show there is life on another planet?
That’s a question that has been kicked around in many quarters in recent decades, especially since all efforts to find some form of life, no matter whether on Mars or in the distant reaches of space, have failed. At least so far.
The current effort to search for some evidence of life on Mars focuses primarily on the search for water, because it has long been believed that water, or at least some fluid, is necessary for the chemical processes that lead life to take place. But that’s probably the wrong approach, the USC group argues.
" It’s hard to imagine life without water, but it’s easy to imagine water without life," says Nealson, who was on the Mars team before moving to USC.
But nitrogen would be a much clearer signature of life. Only about 2 percent to 3 percent of the Martian atmosphere is nitrogen. That’s just a trace, and it probably means there is no life on Mars today, and if there was in the past, it probably ended many, many years ago.
But, the USC team adds quickly, that doesn’t mean there’s no life anywhere else in the universe. They don’t know where, of course, but they may have found a way to narrow down the search. Look first for nitrogen, then look for biological activity that should be there.
So if life exists elsewhere, and is similar to life as we know it, there should be nitrogen, and that’s what we should be looking for first, the researchers say.
If they don’t find nitrogen on Mars, Capone says, "that will probably bring us to the conclusion that there likely never was life on Mars. "
But how about elsewhere? Could this technique be used to search for life in other solar systems?
Maybe. It might be possible to detect a nitrogen - rich atmosphere around a planet orbiting another star, but not yet. Current instruments aren’t that sensitive.
If they ever are, the search for life might be narrowed down to the most promising prospects, chiefly because of the presence of nitrogen. And won’t that be fun! [br] What can probably prove there is no life on Mars today based on the new theory?
选项
答案
The small amount (2% to 3%) of nitrogen in the Martian atmosphere
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3110037.html
相关试题推荐
Newtechnologylinkstheworldasneverbefore.Ourplanethasshrunk.It’s
Newtechnologylinkstheworldasneverbefore.Ourplanethasshrunk.It’s
Ifyouwereonadistantplanet,andifyouhadinstrumentsthatcouldtell
Ifyouwereonadistantplanet,andifyouhadinstrumentsthatcouldtell
Ifyouwereonadistantplanet,andifyouhadinstrumentsthatcouldtell
Mercury,theplanetnearestthesun,isdifficulttoobservefromtheEarth
Mercury,theplanetnearestthesun,isdifficulttoobservefromtheEarth
Mercury,theplanetnearestthesun,isdifficulttoobservefromtheEarth
Newtechnologylinkstheworldasneverbefore.Ourplanethasshrunk.It’s
Newtechnologylinkstheworldasneverbefore.Ourplanethasshrunk.It’s
随机试题
Watchababybetweensixandninemonthsold,andyouwillobservethebasicide
What’stheonewordofadviceawell-meaningprofessionalwouldgivetoare
Scientistshavedevelopedanewcancerdrug.Sofar,theyhavetasteditonl
引起皮下蜂窝织炎的细菌最常见的为:()A.大肠杆菌 B.金黄色葡萄球菌
扩展不确定度是合成不确定度与一个大于1的数字因子的乘积。()
对婴儿智力发育有促进作用的脂肪酸为( )。A.n-6系列的花生四烯酸、DHA和
下列关于房产典当的说法,错误的是()。A:绝当的典当房产可以被拍卖 B:个人来
能把正电荷从低电位移向高电位的力叫()。
2008—2009年间某超市三种商品的价格和销售量数据如表7-5所示。 表
金融市场必须具备的要素有( )。A.交易价格 B.交易对象 C.交易主体
最新回复
(
0
)