YM COLUMN ARCHIVE

February 6, 2008

Flyby observation by Mercury Explorer

Mercury Explorer MESSENGER that left Kennedy Space Center in August 2004 swung by earth once and Venus twice on its space journey of eight billion kilometers and this time encountered Mercury for the first time.

The first visitor to Mercury was Mariner 10, NASA’s explorer, which was launched in 1973. Mariner 10, after flyby observation of Venus, swung by Mercury three times from March 1974 to March next year and produced more than four thousand images.

MESSENGER that headed for Mercury for the first time in over thirty years since Mariner 10 encountered Mercury on January 14, 2008 and transmitted the images of craters never seen before. The craters are informally named “spider”. More than 50-odd cracks, “spider”, radiating from the center of gigantic impact crater are reported to have the land features never seen in Solar System.

MESSENGER also discovered, contrary to our common knowledge so far, that Mercury is a gigantic dipolar magnetic field just like earth. Strong magnetic field of earth has been considered to be caused by the movement of molten metals at innermost earth, while Mercury was long believed to have no such molten metals inside. In this respect, MESSENGER presented a new valuable problem by discovering magnetic field on Mercury.

MESSENGER is expected to become the first Mercury orbiter in mankind’s history in 2011 after approaching Mercury on the second visits in October this year and the third access there in September next year. Incidentally, Mercury Exploring Mission, “BepiColombo”, to be jointly developed between Japan and Europe is scheduled to depart earth for Mercury in 2013.

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                                   (Translated by The Planetary Society of Japan)