雅思课外读物--Water on Mars? Life on Mars?

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今天给大家带来的是一篇关于火星的雅思阅读文章。Water on Mars? Life on Mars?最近，美国航空航天局再次发声，信誓旦旦地表示已经掌握火星上有水合物存在的证据。这会不会引起新一轮火星热?无论如何，按照人类地球消耗的速度，人类必须要尽快找到未来栖身的地方!

NASA(美国航空航天局)on Monday announced the strongest evidence yet for liquid

water(液态水)on the red planet, increasing the possibility that astronauts

journeying to Mars could someday rely on the planet's own water for their

drinking needs.

You may feel like you've heard about the hunt for liquid water on Mars before

-- and the researchers involved know it may seem played out. But science has yet

to truly prove that water flows on Mars once and for all, and doing so could

completely change the way we view the planet. This new data is a big step in the

right direction.

"Liquid water is a sexy topic, and we’re like the thousandth time someone has

discovered water on Mars," Lujendra Ojha, the Georgia Tech PhD candidate who led

the research announced Monday, told The Post. But there's a good reason that

liquid water is so "sexy": Mars is now the only planet in our solar system to

show evidence of the stuff on its surface, other than our own. Other worlds have

it in subsurface oceans, or scattered around as vapor in the atmosphere. But

Mars is the only place where we have solid evidence for liquid that sits right

there in the open air.

While it would be a major leap to suggest that Mars might harbor(怀有，拥有)life

-- even microbial life -- liquid water at least makes it possible that parts of

the planet are habitable(可居住的).

The study builds on research from April, when scientists using data from the

Curiosity rover noted that the planet had the seasonal potential for liquid

water. We know that because of the extremely low pressure on Mars, water has a

boiling point of just a few degrees Celsius, after which it evaporates(蒸发). The

April study noted the presence of perchlorates -- a kind of salt -- which could

make the boiling point of Mars's water much higher, theoretically allowing it to

remain liquid. They posited(假定，推测) that the planet's temperature would be right

for liquid, perchlorate-filled water to form every day during winter and

spring.

In theory, water that periodically turned liquid before evaporating could

form geographic features often spotted on the planet that look like the slow

crawl and retreat of dark, damp sand, which are called recurring slope lineae

(RSL).

In the new study, published Monday in Nature Geoscience, a different group of

researchers took the search for perchlorates one step further: They went looking

for them in the very RSL features thought to be formed by salty liquid. They

found perchlorates in abundance -- and it seems like they've been getting

hydrated.

Ojha and his colleagues used the Mars Reconnaissance Orbiter (MRO) to check

out the chemical composition of the wet looking streaks. They used a technique

called spectroscopy, which keeps track of what spectra of light an object

absorbs in order to make conclusions about its composition. With this technique,

scientists can identify glass, ice, and other substances from miles above the

surface.

"We’re going to places where we thought we were seeing the presence of water

and finding chemical evidence of perchlorates," Ojha said. And the correlation

goes further than that: The hydrated(水合物的)salts seem to disappear in areas where

RSL weren't forming anymore, or were shrinking.

"We're observing the leftover molecules of water in the salt," Ojha said.

"We're finding evidence that they're getting hydrated."

Morten Bo Madsen of the University of Copenhagen -- who co-authored the April

study, but wasn't involved in the latest work -- said the new results were

significant.

"[The] flow of liquid salty water is no longer just a possibility; it does

actually occur," he told The Post. "The results show that liquid does indeed

flow on Mars today."

Ojha's work confirms that hydrated salts seem very likely to have something

to do with the formation of the wet looking streaks on Mars. But there's more

work to do to confirm the presence of liquid water itself. Ojha pointed out that

the MRO's resolution is too low to pick up many of the smaller "wet" features on

Mars, and that a new orbiter could get even more information -- especially since

the MRO allows us to examine Mars's surface only at what Ojha believes is the

driest point in the day. Eventually, the hope is that a rover can take a closer

look at the streaks themselves.