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Messenger’s Final Shot at Mercury

After almost 4,000 days in space, this probe died for science

This week Mercury shows its best face in homage to the Messenger spacecraft, which crashed into the planet early morning April 30.
    The craft was launched in August 2004 and reached Mercury in March 2011, the first to orbit the innermost planet. Since then it has circled Mercury more than 4,100 times, compiling more data in the process than everything combined before that.
    Thursday, April 30, scientists at Johns Hopkins Applied Physics Lab cut life support on their prodigy, and shortly thereafter the craft fell from orbit, plummeting to the surface at more than 8,750 miles an hour. Messenger was already running on borrowed time, having exhausted its traditional fuel supply, but programmers were able to supplement it with helium onboard for other reasons. Now that, too, is exhausted.
    “I guess the end is coming,” the Messenger team posted earlier on Twitter “After 10 years, spacecraft will end life as just another crater on Mercury's surface.” A big crater, more than 50 feet wide.
    The elusive planet is not only difficult to spot, it had been difficult to study before Messenger. Less than 45 percent of Mercury’s surface had even been photographed, and that decades ago. In its four years in orbit, Messenger sent more than a quarter-million photos back to earth. it found volcanoes, discovered polar caps of frozen water and studied Mercury’s chemical makeup.
    Mercury “is crucial to developing a better understanding of how the planets in our solar system formed and evolved,” NASA explains on its Messenger website. “Mercury is an extreme: the smallest, the densest, it has the oldest surface, the largest daily variations in surface temperature — and it’s the least explored.”
    Mercury reaches its greatest elongation from the sun on May 7, climbing 20 degrees above the horizon. Look for it low in the west just after sunset this week. You may need binoculars close to sunset when it’s at its highest, but by 9pm it should easily be visible as it prepares to set. Much-brighter Venus is 20 degrees higher, and Aldebaran, the red eye of Taurus the bull is 10 degrees to Mercury’s left.
    These are the last nights to see Mars, which is even deeper in the glare of sunset than Mercury. Jupiter shines high in the south at nightfall, while Saturn rises around the same time. Look for the just-past-full moon near Saturn Monday and Tuesday night.