NASA’s Messenger spacecraft fell silent Thursday April 30, wrapping up four years of studies of the Solar System’s innermost planet with a crash landing into Mercury. Out of range from Earth-based observatories, Messenger’s demise came as predicted at 17:26 UTC. Flight controllers were able to confirm the end of operations at 17:40 UTC when tracking radars failed to see the spacecraft emerge from behind the planet on its 4,105th orbit.
“We bid a fond farewell to one of the most resilient and accomplished spacecraft ever to have explored our neighboring planets,” Messenger’s lead scientist Sean Solomon, director of Columbia University’s Lamont-Doherty Earth Observatory, said in a statement.
The MErcury Surface, Space ENvironment, GEochemistry, and Ranging, or “Messenger”, spacecraft spent six years getting itself to Mercury, the first and so far only robotic probe to orbit the planet closest to the Sun.
NASA’s Mariner 10 probe conducted three flybys in the mid-1970s, mapping about 45 percent of the planet. Until Messenger’s arrival, the other half of Mercury had never even been seen.
During four years in orbit, the probe sniffed out an unexpected mix of materials on its surface, including volatiles that weren’t considered likely to exist on a world where daytime temperatures can exceed 800° Fahrenheit (427°C.) It confirmed water ice on the floors of permanently shadowed craters on Mercury’s poles and raised the intriguing prospect that some of the ice is covered with organic material.
Scientists using Messenger data also learned that Mercury’s internal magnetic field is asymmetrical, though they can’t yet say why.“The Messenger mission has surpassed all expectations and delivered a stunningly long list of discoveries that have changed our views not only of one of Earth’s sibling planets but of the entire inner Solar System,” Solomon said.Flight engineers predicted Messenger, traveling at more than 8,700 mph, would pass over several miles of lava-filled basin known as Shakespeare before smashing into a ridge.The impact likely left a new 52-foot wide crater that future science probes will look for.Europe and Japan are collaborating on a Mercury orbiter called BepiColombo that is due to launch in 2017 and arrive in 2024.Scientists expect to continue analyzing Messenger’s data for years to come.
“Mercury was a poor, neglected planet,” astronomer Bob Berman said during a webcast Messenger tribute on Slooh.com.“It was the darkest planet in the known Universe and the one with the greatest temperature change from day to night, and yet we had no intimate knowledge of its surface until we finally sent something to have a closer look, to orbit around it, so this MESSENGER has been very exciting,” he said.