A map of the north pole of the moon showing where the spacecraft Ebb and Flow will make impact on their controlled descent Monday evening. (NASA)

NASA’s twin moon-orbiting probes - Ebb and Flow - have reached the end of their lives. They’ve literally run out of fuel so they will be intentionally run into the ground.

At 5:28 p.m. today, NASA will engineer a “controlled descent and impact” on a mountain near the moon’s north pole.

Before their death swoon reaching speeds of 3,760 mph, NASA will fire their main engines until the fuel tanks are empty.

“This will help NASA engineers validate fuel consumption computer models to improve predictions of fuel needs for future missions,” NASA says.

Image of the free-air lunar gravity globe, centered on 120 degrees west longitude. ( NASA )

“The map will provide a better understanding of how Earth and other rocky planets in the solar system formed and evolved,” NASA says.

The spacecraft orbited the moon from March to May at a altitude of 34 miles above the lunar surface before being lowered to just 20 miles in recent months.

“Data from the GRAIL twins are allowing scientists to learn about the moon’s internal structure and composition in unprecedented detail,” NASA says.

An image from the Ebb spacecraft ( NASA )

The mission promises to end with a bang. NASA will broadcast the play by play of the surface impact live on NASA Television and on Ustream later today.

Related links:

Grail website

HD Animations of today’s crash

Grail Gravity Map Animations