Principal Investigator of the MESSENGER mission to Mercury Sean Solomon wrote a Science “Perspectives” article this week entitled “Hot News on Mercury’s Core,” describing the discovery of Mercury’s molten core by Margot, et al. in the Science article, “Large Longitude Libration of Mercury Reveals a Molten Core.” Some thirty years ago the Mariner 10 spacecraft flew by Mercury, detecting an internal magnetic field. Earth’s field is produced by a magnetic dynamo sustained by convective motions in the planet’s molten, iron-rich outer core. Mercury’s magnetic field was a mystery at the time, as its core characteristics were not yet determined.

According to Solomon, although Mercury’s high bulk density indicates that its mostly iron central core is the largest by fractional mass among the planets, the detection of its magnetic field was surprising because Venus has no field and Mars and the Moon show evidence only for ancient global fields. A necessary condition for Mercury’s magnetic field to arise from an active Earth-dynamo, Solomon writes, is that at least the outer shell of its core be molten. Using Earth-based radar, Margot, et al. provide strong evidence that Mercury’s outer core does meet this requirement.

Solomon is featured in a podcast on the Science Web site. He has also been quoted on these findings in several publications, including the The Washington Post, the Wall Street Journal (available online to subscribers), the New Scientist and National Geographic. For a full list of press coverage, see Google News.