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Emily LakdawallaJuly 3, 2008

MESSENGER Scientists 'Astonished' to Find Water in Mercury's Thin Atmosphere [TEASER]

I've just posted a news story on the latest results of the MESSENGER mission, announced in a telephone news conference held today. The timing may seem strange, as it's the day before a major holiday in the U.S., exactly the right time to hold a press conference if your goal is for people to ignore or overlook the news. However, the mission had no choice; the timing was dictated by the editors of Science magazine, who selected Independence Day for the first publication of peer-reviewed research (a total of eleven papers!) from MESSENGER's first flyby of Mercury. Sigh.

Anyway, much of the content of the press briefing consisted of updates or refinements to the discoveries announced shortly after the flyby in January -- there's a dipolar magnetic field and not much in the way of small-scale magnetic field structure, both of which indicate that Mercury's core is still partially molten and generating the field via a dynamo, just like Earth's; there's lots of stuff in the MESSENGER images that looks like volcanic constructs, settling a 30-year-old-debate; there's interesting stuff to be seen in the composition of the neutral species in Mercury's extended atmosphere. The biggest and newest news this week came out of the FIPS instrument (the Fast Imaging Plasma Spectrometer), which found water -- water?!? -- in Mercury's exosphere, and quite a lot of it. Go read my news article for the rest of the story.

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Emily Lakdawalla

Solar System Specialist for The Planetary Society
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