NASA probe spurs new view of Mercury's interior !!

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PostThu Mar 22, 2012 8:50 pm » by Matty26

NASA probe spurs new view of Mercury's interior
Mercury is a planet of many superlatives: speediest, smallest, nearly the hottest, and almost the most dense. It might also be the oddest. Scientists with MESSENGER (Mercury surface, space environment, geochemistry and ranging), a NASA mission that has just completed one year in orbit, today revealed their depiction of the radical and strange interior structure that they think lies beneath the planet’s cracked terrain. The proposal — that a thin, solid shell of iron sulphide envelopes the outer liquid core — would help to explainthe planet’s gravity field, but it presents problems in explaining the Mecury’s relatively recent geological upheavals.“It seems that Mercury has a novel internal structure,” says Steven Hauck, a planetary scientist on the team at Case Western Reserve University in Cleveland, Ohio, and part of the MESSENGER team. The researchers presented their latest findings this week at the Lunar and Planetary Science Conference in The Woodlands, Texas, and also published two papers in Science on 21 March. The first paper focuses on the high resolution topographic map created by the orbiter’s laser altimeter. Like all rocky planets, Mercury is pocked with deep, ancient impact basins. But the basins have been disturbed since then: basin floors have been tilted or uplifted, a sign that volcanic and tectonic activity persisted
well past Mercury’s first several hundred million years. “This points to the fact that Mercury had an active middle age,” says Maria Zuber, a science team member at the Massachusetts Institute of Technology in CambridgeThe second Science paper describes a new gravity model for the planet, one that was constructed by measuring tiny changes in the orbit of the spacecraft using NASA’s Deep Space Network. The model, when combined with topography data and measurements of the planet’s spin, suggests that as much as 85% of Mercury’s radius is taken up by its dense iron core — an upward revision. “We knew Mercury had a large core,” says Zuber. “Now we think it’s even larger.” The team further suggests that the liquid or partially liquid iron core is encased in a relatively thin shell of iron sulphide. This satisfies the gravitational data and would account for why the planet's crust is enriched in sulphur and depleted in iron, but it also makes it more difficult for much convection to occur witin the thin mantle that stis atop the shell. This presents problems for those that invoke convection as a driver of the observed tectonic and volcanic features at the surface. “There isn’t a whole lot of mantle to be doing this lifting up,” says Zuber. The team also announced the details of an additional year of extended mission operations. Next month, MESSENGER's 12-hour elliptical orbit will be shrunk slightly to an 8-hour orbit, giving the team many more close passes of the surface this ...this article and the original article can be found at ... l?spref=fb

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