The Messenger of fate: NASA spacecraft smashes into planet Mercury

Traci Watson, Special for USA TODAY | USA TODAY

Its fuel tanks empty and its options gone, NASA's Messenger spacecraft smashed into planet Mercury on Thursday afternoon after valiantly fighting off the inevitable.

Engineers calculated that the spacecraft, traveling a scorching 8,700 mph, bombed into the planet's heavily pockmarked surface at 3:26 p.m. ET Thursday. It was not a gentle goodbye: The impact was expected to pulverize the car-sized spaceship and gouge out a 50-foot crater -- big enough to accommodate a school bus -- near Mercury's north pole.

Engineers calculated that the spacecraft belly-flopped onto the cratered terrain on the far side of Mercury, when the ship was out of contact with Earth.

They confirmed its death when they could not pick up a signal from the craft.

"We monitored Messenger's beacon signal for about 20 additional minutes," said mission operations manager Andy Calloway of the Johns Hopkins University Applied Physics Laboratory. "It was strange to think during that time Messenger had already impacted, but we could not confirm it immediately due to the vast distance across space between Mercury and Earth."

"We're really sad to see this, because Messenger has been a fabulous mission," Brown University's James Head, a co-investigator on the mission, said before the impact. "It's an exhilarating time, but also really poignant."

At least Messenger went down with a fight and in a blaze of glory. Edging ever closer to Mercury because of the effects of the sun's gravity, the ship, its fuel tanks dry, was supposed to meet its destiny in March. But creative engineers bought their craft an extra month of life by repurposing Messenger's stockpile of helium, used to pressurize the fuel tanks. Leftover helium was expelled from the spacecraft's thrusters, nudging the ship away from the looming surface.

"We're beyond running on fumes at that point," Messenger mission systems engineer Dan O'Shaughnessy said before the slated impact time. "We're venturing into uncharted territory."

The spacecraft's new lease on life allowed scientists an intimate look at the tiny, scarred planet that Messenger has orbited for the past four years. The bad news, Head says, was that the ship would eventually get too close, but there's "good news about the bad news … the closer you are, the higher-resolution images you get." Scientists took advantage of the view by peering into craters that hide pockets of ice and searching for magnetic fields at the planet's surface.

Messenger is just the latest spacecraft to end with a bang. In 2012, NASA's twin Grail spacecraft were deliberately crashed into a lunar mountain. The space agency's LADEE spacecraft made a kamikaze dive in 2014 into a crater rim on the far side of the moon, a spot chosen to be well away from the Apollo landing sites. The graves are unmarked but not undetected, thanks to a NASA spacecraft orbiting the moon that spotted the tiny craters made by all three spacecraft.

Messenger managers hope their spacecraft's final resting spot will also be pinpointed after the European Space Agency's BepiColombo spacecraft launches for Mercury in 2017. Scientists are "quite confident that we are able to find the impact crater," says BepiColombo project scientist Johannes Benkhoff, who notes that his own craft will eventually suffer the same fate as Messenger.

"All good things must come to an end," said Ralph McNutt, Messenger's project scientist. "I guess it's time, but a little sad."

At least, "A crash is better than just failing spontaneously for an unspecified reason," said University of Michigan space physicist Jim Raines, who worked on Messenger. "At least we knew that this would happen and when."