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Mars(火星) appears to be flowing with small
streams of salty water, at least in the summer, scientists reported Monday.
"It suggests that it would be possible for there to be life today on
Mars," NASA's science mission chief, John Grunsfeld, said at a news
conference on September 28, 2015.
The streams are about 12 to 15 feet wide
and 300 feet or more long, scientists said. "What we're dealing with is
wet soil, thin layers of wet soil, not standing water," said Aifred McEwen
of the University of Arizona at Tueson, the principal scientist for the Mars
Reconnaissance Orbiter's high-resolution imaging experiment.
Because liquid water is essential to life,
the findings could have major implications for the possibility of Martian life.
The researchers said further exploration is needed to determine whether
microscopic life exists on the planet.
The presence of liquid water could also
make life easier for astronauts visiting or living on Mars. Water could be used
for drinking and for creating oxygen and rocket fuel. NASA's goal is to send
humans there in the 2030s.
The evidence of flowing water consists
largely of dark, narrow streaks(条痕) on the surface that tend to appear
and grow during the warmest Martian months and fade the rest of the year.
Mars is extremely cold even in summer, and
the streaks are in places where the temperature is as low as minus 10 degrees
Fahrenheit. But salt can lower the freezing point of water and melt ice.
The source of the water is a mystery.
Scientists noted it could be melting ice. It could be an underground aquifer,
which is rock or sand that can hold water. It is possibly water vapor from the
thin Martian atmosphere. Or it may be a combination Michael Meyer, lead
scientist for NASA's Mars exploration program, said the only definitive way for
now to determine whether there's life on Mars is to collect rocks and soil for
analysis on Earth—something a U. S. lander set for lift-off in 2020 will do.
（1）According to John Grunsfeld, there seems to be on Mars.
A . salty water
B . standing water
C . rocket fuel
D . human beings
（2）Scientists are uncertain about the of the water on Mars.
A . state
B . source
C . temperature
D . taste
（3）What matters to the existence of liquid water on Mars?
A . The distance from the sun
B . The favorable climate
C . The gravity of the earth
D . The salt in it
（4）What would be the best title for the text?
A . Streams of Water Spotted on Mars
B . Astronauts will Land on Mars
C . NASA's Mars Exploration Program
D . A Breakthrough in the Exploration of Mars
