On Monday afternoon, around 5:30 p.m. EST, NASA will crash the GRAIL spacecrafts into this mountain on the moon:
GRAIL stands for Gravity Recovery and Interior Laboratory and was launched last September. The two spacecrafts, called Ebb and Flow, have been circling the Moon since New Years Day last year and are running out of fuel. They were mapping the gravity of the moon and made several interesting discoveries, including finding hidden volcanoes on the Moon.
The gravity measurements will be useful in landing spacecraft on the moon, enabling them to target landing areas very precisely.
Everything's been working perfectly for this mission, and it actually came in more than $8 million under budget.
"In my wildest dreams I couldn’t imaging that this mission would have gone any better than it has," Maria Zuber, GRAIL principal investigator, said in a press conference today. "In terms of the science measurements we achieved everything we could have hoped for."
They chose the site to avoid any "Lunar Historical Sites" seen in the image below, including the Apollo landing sites. The orbits of the spacecrafts are seen here in red and purple. When they crash, the Lunar Reconnaissance Orbiter will be watching, and will be looking to see if they kick up any interesting compounds, and the impacts should help researchers better understand the mechanical properties of the lunar surface.
They should land about 20 to 40 kilometers apart on the mountain ridge. They will make a crater and break apart. They will be going about 1.5 kilometers per second, or 3,355 miles per hour. Their debris will add to the 400,000 pounds of stuff that's already on the Moon.