After 33 years, a spaceprobe sent by man returns to the innermost planet... this image of Mercury, one of the first taken on this mission in order to check the accuracy of the navigation, was taken from 2.7 million km away; as I write, MESSENGER is 1.9 million km away, and closing fast. This, the first flyby, will reveal images of the whole of the Caloris Planitia, that huge 1300km diameter impact feature discovered by Mariner 10 back in 1974 (before I was born), and hopefully prove or disprove the existence of the putative Skinakas basin – an even larger impact basin that Earth-based imaging has been thought to have detected. Only 45% of the planet has ever been imaged close-up, and this flyby will reveal areas hitherto unknown. Images will be downloaded to Earth by the 16th and should be available on the MESSENGER website from the 18th or so.
(Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.)