NASA - National Aeronautics and Space Administration

MESSENGER Settles Old Debates and Makes New Discoveries at Mercury



Scientists have argued about the origins of Mercury's smooth plains and the source of its magnetic field for more than 30 years. Now, analyses of data from the January 2008 flyby of the planet by the Mercury Surface, Space Environment, Geochemistry and Ranging (MESSENGER) spacecraft have shown that volcanoes were involved in plains formation and suggest that its magnetic field is actively produced in the planet's core.

The controversy over the origin of Mercury's smooth plains began with the 1972 Apollo 16 moon mission, which suggested that some lunar plains came from material that was ejected by large impacts and then formed smooth "ponds." When Mariner 10 imaged similar formations on Mercury in 1975, some scientists believed that the same processes were at work. Others thought Mercury's plains material came from erupted lavas, but the absence of volcanic vents or other volcanic features in images from that mission prevented a consensus.

NASA will host a media teleconference Thursday, July 3, at 2 p.m. EDT, to discuss analysis of data from the Mercury Surface, Space Environment, Geochemistry and Ranging (MESSENGER) spacecraft's flyby of Mercury earlier this year.

The spacecraft is the first designed to orbit the planet closest to the sun. It flew past Mercury on Jan. 14, 2008, and made the first up-close measurements since Mariner 10's final flyby in 1975.

Analyses of the data show volcanoes were involved in the formation of plains. The data also suggest the planet's magnetic field is actively produced in its core. In addition, the mission has provided the first look at the chemical composition of Mercury's surface. The results will be reported in a series of 11 papers published July 4 in a special section of Science magazine.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

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> Johns Hopkins Applied Physics Lab Media Telecon website for the MESSENGER Mercury discovery will be available at 2 pm on July 03, 2008.