The Deep Plunge Sunward

Mercury Winter 2007 Table of Contents

Illustration courtesy of NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.

by Bruce Dorminey

As elusive as Venus is forgotten, enigmatic Mercury only seems to capture our imaginations when making one of its rare solar transits (see "Mercury's Time to 'Shine,'" September/October 2006, p. 12). Its very presence in an eccentric orbit deep in the gravity well of our own G-dwarf star only underscores Earth’s privileged position in the heart of the habitable zone.

Mercury itself is a puzzle, in large part, because its exploration has arguably been in stasis since NASA's Mariner 10 spacecraft made multiple flybys more than thirty years ago. As a result, the tiny planet still holds the dubious distinction of being the least explored planet of the inner Solar System.

Given its lethal proximity to the Sun's particle flux and extreme radiation, this will take some time to undo. But with NASA's $420 million MESSENGER orbital mission en route, and development of the European Space Agency's €650 million ($850 million) BepiColombo mission in cooperation with Japan, this iron-rich runt of a planet is finally going to get its due.

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