July 16, 2002
In the grand ledger of cosmic time, a human life is breathtakingly brief. But brevity is not insignificance.
Outbound from Mercury
Birthday · July 16, 2002
A little universe, just for you
Your date.
Ready to give.
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APOD published July 16, 2002. Full image credits are on the original APOD entry below. A publication-date match, not a photo taken on your date. Independent of NASA.
After just passing Mercury, the robot spacecraft Mariner 10 looked back. The above picture is what it saw. Mercury, the closest planet to the Sun, is heavily cratered much like Earth's Moon. As Mercury slowly rotates, its surface temperature varies from an unbearably cold -180 degrees Celsius in the half facing away from the Sun, to an unbearably hot 400 degrees Celsius in the half facing toward the Sun. Mercury is slightly larger than Earth's Moon and much denser. The Mariner 10 spacecraft swooped by Mercury three times in its journey around the inner Solar System in the mid-1970s. This outbound view has similarities to the inbound view. Nearly half of Mercury's surface has yet to be photographed in detail.