Titan（泰坦）

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第三篇

“Life Form Found" on Saturn ' s Titan

Scientists say they have discovered hints of alien life on the Saturn'5 moon.The discovery of a sort of
life was announced after researchers at the US space agency,NASA,analyzed data from spacecraft Cassini,
which pointed to the existence of methane-based form of life on Saturn's biggest moon.
Scientists have reportedly discovered clues showing primitive alien beings are"breathing"in Titan's
dense atmosphere filled with hydrogen.
They argue that hydrogen gets absorbed before hitting Titan's planet-like surface covered with methane
lakes and rivers.This,they say,points to the existence of some"bugs"consuming the hydrogen at the surface
of the moon less than half the size of the Earth.
"We suggested hydrogen consumption because it's the obvious gas for life to consume on Titan,similar
to the way we consume oxygen on Earth,"says NASA scientist Chris McKay."If these signs do turn out to be
a sign of life,it would be doubly exciting because it would represent a second form of life independent from
water-based life on Earth."
To date,scientists have not yet detected this form of life anywhere,though there are liquid-water-based
microorganisms on Earth that grow well on methane or produce it as a waste product. On Titan,where
temperatures are around minus 17 Kelvin(minus 290 degrees Farenheit),a methane-based organism would
have to use a substance that is liquid as its medium for living processes,but not water itself. Water is frozen
solid on Titan'5 surface and much too cold to support life as we know it.
Scientists had expected the Sun'5 interactions with chemicals in the atmosphere to produce a coating of
acetylene on Titan'5 surface.But Cassini detected no acetylene on the surface.
The absence of detectable acetylene on the Titan's surface can very well have a non-biological explana-
tion,said Mark Allen,a principal investigator of the NASA Titan team.
"Scientific conservatism suggests that a biological explanation should be the last choice after all non-
biological explanations are addressed,"Allen said."We have a lot of work to do to rule out possible non-bio-
logical explanations.It is more likely that a chemical process,without biology,can explain these results."

Which of the following can replace the title of this passage?
A:Different Life Form,a Possibility.
B:Earthlike Living Beings Found on Titan.
C:Finding of One More Moon of Saturn.
D:Titan,a New Satellite Discovered.

共用题干
第三篇

“Life Form Found" on Saturn ' s Titan

Scientists say they have discovered hints of alien life on the Saturn'5 moon.The discovery of a sort of
life was announced after researchers at the US space agency,NASA,analyzed data from spacecraft Cassini,
which pointed to the existence of methane-based form of life on Saturn's biggest moon.
Scientists have reportedly discovered clues showing primitive alien beings are"breathing"in Titan's
dense atmosphere filled with hydrogen.
They argue that hydrogen gets absorbed before hitting Titan's planet-like surface covered with methane
lakes and rivers.This,they say,points to the existence of some"bugs"consuming the hydrogen at the surface
of the moon less than half the size of the Earth.
"We suggested hydrogen consumption because it's the obvious gas for life to consume on Titan,similar
to the way we consume oxygen on Earth,"says NASA scientist Chris McKay."If these signs do turn out to be
a sign of life,it would be doubly exciting because it would represent a second form of life independent from
water-based life on Earth."
To date,scientists have not yet detected this form of life anywhere,though there are liquid-water-based
microorganisms on Earth that grow well on methane or produce it as a waste product. On Titan,where
temperatures are around minus 17 Kelvin(minus 290 degrees Farenheit),a methane-based organism would
have to use a substance that is liquid as its medium for living processes,but not water itself. Water is frozen
solid on Titan'5 surface and much too cold to support life as we know it.
Scientists had expected the Sun'5 interactions with chemicals in the atmosphere to produce a coating of
acetylene on Titan'5 surface.But Cassini detected no acetylene on the surface.
The absence of detectable acetylene on the Titan's surface can very well have a non-biological explana-
tion,said Mark Allen,a principal investigator of the NASA Titan team.
"Scientific conservatism suggests that a biological explanation should be the last choice after all non-
biological explanations are addressed,"Allen said."We have a lot of work to do to rule out possible non-bio-
logical explanations.It is more likely that a chemical process,without biology,can explain these results."

Which of the following statements about Titan is true?
A:It is as large as the Earth.
B:There is acetylene on its surface.
C:Water on it acts as a life supporting medium.
D:Hydrogen consumption is reported to be on it.