Just shy of a full year encircling the moon, NASA’s twin lunar probes are bidding farewell on Monday, crashing in a controlled fashion into a small mountain-like formation at the moon’s north pole. The GRAIL twins, nicknamed Ebb and Flow, are almost out of fuel and their lives would come to an end anyway–but rather than let them fall out of the lunar sky, as it were, NASA is performing a kind of spacecraft euthanasia.
“It’s kind of sad for me,” said David Lehman, GRAIL’s project manager at the Jet Propulsion Laboratory in Pasadena, in a phone call with journalists. “I’m hoping tonight a gas station will pull up next to our spacecraft, refuel it, and we can continue another 6 months. But I don’t think that’s going to happen.”
Ebb and Flow, which were named by schoolchildren and are about the size of washing machines, will receive commands Friday morning to fly from south to north on their final trajectory. Ebb, which reached the moon on New Year’s Eve, will be the first to go down, impacting at 2:28:40 p.m. Pacific time on Monday. Flow will hit about 20 seconds later.