Liquid Mercury

Mercury is the least studied satellite in our solar system, and scientists continue to debate some standard facts about the small body. One lingering interrogate is whether Hg has a liquid core. Newborn inquiry immediately suggests that it does.

The closest satellite to the center of the star system, Mercury is about one 3rd as far from the solarize A Earth is. Since Earth has a liquid core, and since Mercury receives more of the sun's heat than Ground does, it would seem likely that Mercury's core would also be molten.

Scientists have been questioning since at least 1974 whether Atomic number 8 has a liquid core. It turns forbidden that the planet does.

Nicolle Ragger Melville W. Fuller/National Science Foundation

Information technology turns stunned, still, that the consistency of a planet's core doesn't depend primarily on heat from an outside source. Rather, heat leftish terminated from the formation of the planet determines whether information technology will nonmoving be liquid happening the inside. Since Mercury is lilliputian—conscionable 40 percent as wide as Earth—IT should have cooled lang syne. In that case, Mercury's core would be solid.

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The debate about Mercury's core began in 1974, when the Mariner 10 ballistic capsule sensed a charismatic field round Quicksilver. Rocky planets so much as Earth john have attractive force fields when charged materials inside their liquid cores slosh. The fact that Quicksilver has a magnetic subject, thus, suggests that on that point is fluid inside.

But some scientists offered other explanation for the magnetic battlefield. It's realistic, they reasoned, that when Atomic number 8's core became solid, the magnetic field was frozen in place.

To settle the debate, researchers from Cornell University and the University of Calif., Father Christmas Barbara and their colleagues studied Mercury's spin. The major planet orbits the sun erstwhile all 88 days. And for every two 88-day revolutions, Mercury twirls around on its axis of rotation three multiplication. In other words, information technology experiences three days all 2 years.

Slight variations in this spinning practice pass off as a issue of the sun's gravity. And the sun's gravity affects a planet's birl more if the planet has some liquid in its burden.

After bouncing radio waves inactive of the planet for 6 years, the scientists found a relatively large amount of variation in its twirl. There was, in fact, just about double as much variation as they would expect if the planet were solid.

Scientists bounced radio waves sour of Mercury to measure variations in its rate of spin. Large variations disclosed that the major planet has a molten core.

Bill Saxton, NRAO/AUI/NSF

The best explanation for these data, the researchers say, is that at that place is at any rate some liquid inside Mercury—either in the core operating room in the space 'tween the effect and the planet's outward layers.

"It is clear that Mercury is not solid end-to-end," says heavenly body man of science David Stevenson of the California Institute of Technology in Pasadena.

Mercury's core is made mostly of iron. One hypothesis for why IT has remained liquefiable proposes that there is sulfur inside the satellite as well. Sulfur melts at a take down temperature than press does.

If this hypothesis is correct, other planets might also own incorporated sulfur and separate materials that formed far from the planets' orbits. That would change theories about how planets formed in our star system.

More selective information will arrive next year, when NASA's MESSENGER spacecraft, which goes into scope or so Mercury in 2011, first flies agone the planet. A Japanese-European mission, scheduled to arrive at the planet in 2022, should also assistanc round out the picture.—Emily Sohn

Going Deeper:

Cowen, Ron. 2007. Liquid center: Mercury has a melted essence, radar reveals. Science Newsworthiness 171(English hawthorn 5):277-278. Addressable at http://WWW.sciencenews.org/articles/20070505/fob5.asp .

Sohn, Emily. 2006. Saturn's strangely warm moon. Science News for Kids (April 19). Available at http://www.sciencenewsforkids.org/articles/20060419/Feature1.asp .

______. 2003. A planet's slim-fast plan. Science Newsworthiness for Kids (March 19). Available at http://web.sciencenewsforkids.org/articles/20030319/Note2.asp viper .

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