Ancient Water From Afar
It streaked across the sky on a warm March evening last year, then crashed
into a street in the small town of Monahans, Texas. When seven boys quit their
basketball game to inspect the damage, they found a shiny, black grapefruit-size
rock settled in the asphalt (沥青). Word of the “flaming rock” traveled quickly in
newspapers and on TV. The next day, NASA scientist Everett Gibson arrived and
took the meteorite(陨石) , later named Monahans 1998, back to a lab in Houston.
There researchers broke open the extraterrestrial (地球外的)rock with a hammer and
chisel (凿子). To their surprise, they struck water. A team led by Michael
Zolensky of the Johnson Space Center reports this discovery in a journal. It’s
the first time anyone has found liquid water in an object from space—and a
suggestion that life may exist out side our planet.
Meteorites
containing water are probably not scarce, Zolensky says. But by the time
researchers get their hands on the rocks, minerals that trap the water have
dissolved away, and the water have evaporated. Worse, some researchers destroy
the evidence by cutting meteor ites open with rock saws and water. “I’m betting
this isn’t such a rare finds it’s just that people have been mistreating their
meteorites,” Zolensky says.
Of course, Zolensky’s team did get a
bit lucky. Monahans 1998 was safe in their lab less than two days after it hit
the Earth, so they examined an unusually fresh sample. The scientists were keen
to find vivid purple crystals of halite (岩盐)inside the meteorite, since halite
is a salt mineral usually formed from liquid water. Even more curious were the
hundreds of tiny bubbles suspended in the halite crystals. Zolensky’s team
analyzed the bubbles by shining a laser beam through them and confirmed they
were made of salty brine (盐水).
By dating the halite, Zolensky’s
team found the water trapped inside it formed at least 4.5 billion years ago,
back when most scientists believe our solar system was born. That means the
briny object amy help researchers learn about the gaseous nebulas(星云)that gave
rise to our sun and planets.
But how did the meteorite get wet
One possibility is that a passing comet smashed into the rock, dropping off a
load of liquid water. Or the rock might have chipped off an asteroid (小行星)that
holds pools of fluid. Zolensky’s team still needs to study whether the water
comes from our own solar system. One thing is certain, however: the Monahans
meteorite will fuel the debate on extraterrestrial life, “Water is a life-giver,
so if you want to study where life came from in the solar system, you have to
follow where water came from,” Zolensky says. A wet rock from space doesn’t mean
little green men are coming soon to a planet near you, but it does raise hopes
that we’re not alone in the universe. |
