|
| This photo made available by NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington on Tuesday, Nov. 27, 2012 shows a 68-mile-diameter crater, large indentation at center, in the north polar region of Mercury which has been shown to harbor water ice, thanks to measurements by the Messenger spacecraft. Scientists made the announcement Thursday, Nov. 29, 2012. |
CAPE CANAVERAL,
Fla. (AP) -- Just in time for Christmas, scientists have confirmed a
vast amount of ice at the north pole - on Mercury, the closest planet
to the sun.
The findings are from NASA's
Mercury-orbiting probe, Messenger, and the subject of three scientific
papers released Thursday by the journal Science.
The
frozen water is located in regions of Mercury's north pole that always
are in shadows, essentially impact craters. It's believed the south pole
harbors ice as well, though there are no hard data to support it.
Messenger orbits much closer to the north pole than the south.
"If
you add it all up, you have on the order of 100 billion to 1 trillion
metric tons of ice," said David Lawrence of the Applied Physics
Laboratory at Johns Hopkins University. "The uncertainty on that number
is just how deep it goes."
The ice is thought to be at least 1 1/2 feet deep - and possibly as much as 65 feet deep.
There's
enough polar ice at Mercury, in fact, to bury an area the size of
Washington, D.C., by two to 2 1/2 miles deep, said Lawrence, the lead
author of one of the papers.
"These are very exciting results," he added at a news conference.
For
two decades, radar measurements taken from Earth have suggested the
presence of ice at Mercury's poles. Now scientists know for sure, thanks
to Messenger, the first spacecraft to orbit Mercury.
The
water almost certainly came from impacting comets, or possibly
asteroids. Ice is found at the surface, as well as buried beneath a dark
material, likely organic.
Messenger was
launched in 2004 and went into orbit around the planet 1 1/2 years ago.
NASA hopes to continue observations well into next year.
Columbia
University's Sean Solomon, principal scientist for Messenger, stressed
that no one is suggesting that Mercury might hold evidence of life,
given the presence of water. But the latest findings may help explain
some of the early chapters of the book of life elsewhere in the solar
system, he said.
"Mercury is becoming an object of astrobiological interest, where it wasn't much of one before," Solomon said.
