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Mercury’s Water Ice Find a Boon for Astrobiology

(From left) Sean Solomon, David Lawrence, Gregory Neumann and David Paige participate in a news briefing to discuss new observations from Messenger that offer compelling evidence that the planet harbors abundant water ice and other frozen volatile materials within its permanently shadowed polar craters. Credit: NASA photo

SEATTLE — The discovery of huge amounts of water ice and possible organic compounds on the heat-blasted planet Mercury suggests that the raw materials necessary for life as we know it may be common throughout the solar system, researchers say.

Mercury likely harbors between 100 billion and 1 trillion metric tons of water ice in permanently shadowed areas near its poles, scientists analyzing data from NASA’s Messenger spacecraft announced Nov. 29.

Life on sun-scorched Mercury remains an extreme long shot, the researchers stressed, but the new results should still put a spring in the step of astrobiologists around the world.

“The more we examine the solar system, the more we realize it’s a soggy place,” Jim Green, the director of NASA’s Planetary Science Division, said during a press conference.

“And that’s really quite exciting, because that means the amount of water that we have here on Earth — that was not only inherent when it was originally formed but probably brought here — that water and other volatiles were brought to many other places in the solar system,” Green added. “So it really bodes well for us to continue on the exploration, following the water and its signs throughout the solar system.”

The observations by Messenger, which has been orbiting Mercury since March 2011, provide compelling evidence that reflective patches first spotted near the planet’s poles by the Arecibo Observatory’s radio telescope in Puerto Rico two decades ago are indeed water ice, researchers said.

In the coldest parts of Mercury — permanently shadowed regions where temperatures drop to perhaps minus 223 degrees Celsius — this ice can lie bare and exposed. But Messenger’s data also show that much more frozen water is found in slightly warmer areas, buried beneath a strange dark material that acts as an insulator.

This dark stuff is likely a mixture of complex organic compounds, the carbon-containing building blocks of life as we know it, researchers said during the news conference.

“This organic material may be the same type of organic material that ultimately gave rise to life on Earth,” said Messenger participating scientist David Paige of the University of California, Los Angeles.

Mercury probably acquired much of its water and organic material the same way Earth did, researchers said — via comet impacts and asteroid strikes. Ice and organics are common on the frigid bodies in the solar system’s outer reaches.

“There’s a lot of water out there, as there is a lot of water around other stars, but at substantial distance,” said Messenger principal investigator Sean Solomon, of Columbia University’s Lamont-Doherty Earth Observatory.

With its ultrathin atmosphere and proximity to the sun, Mercury is probably not a good bet to host life. But finding ice and organics there should still inform the hunt for organisms beyond Earth and aid scientists’ quest to learn more about how life took root on our planet.

“The history of life begins with the delivery to some home object of water and of the building blocks, the organic building blocks, that must undergo some kind of chemistry, which we still don’t understand on our own planet,” Solomon said.

“And so Mercury is becoming an object of astrobiological interest, where it wasn’t much of one before,” Solomon added. “That’s not say to say that we expect to find any life forms — I don’t think anybody on this table does — but in terms of the book of life, there are some early chapters, and Mercury may indeed inform us about what’s in those chapters.”

Built and operated by the Johns Hopkins University’s Applied Physics Laboratory in Laurel, Md., the Messenger spacecraft was launched in April 2004 aboard a Delta 2 rocket from Cape Canaveral Air Force Station, Fla.

Messenger’s one-year primary mission ended earlier this year. Its extended mission is scheduled to last until March 2013.

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