On Sept. 10, 2011, NASA’s GRAIL spacecraft launched on a mission to the moon!
GRAIL, which stands for Gravity Restoration and Inside Laboratory, was despatched to the moon to map its gravitational fields. Scientists may examine the moon’s inside construction by taking a look at maps of the moon’s gravity.
Asteroid impacts from billions of years in the past left dense pockets of fabric beneath the lunar floor, which might exert additional gravitational pull on spacecraft orbiting the moon. So by measuring that gravitational pull, the GRAIL mission could reveal information about what lies beneath the surface.
The mission actually consisted of two twin spacecraft named Ebb and Flow, which would fly in tandem around the moon to map variations in its gravitation field. Both lifted off on the same Delta II rocket from Cape Canaveral, Florida and arrived in lunar orbit almost four months later.
They mapped the moon for about nine months before NASA decided it was finished with the mission, and the two orbiters crashed into the moon.
Why it mattered
The moon is a weird place. It may look like a cold, gray ball of solid rock, but its density varies from location to location due to odd “mass concentrations” (or mascons for short) buried under the lunar surface. That leads to a strange, lumpy gravity that’s not uniform across the lunar surface.
That’s where GRAIL’s Ebb and Flow probes came in. Each of the twin spacecraft carried three instruments to map the interior of the moon. Those included a Lunar Gravity Ranging System, a Radio Science Beacon and a camera called MoonKam Lunar-Imaging system.
Together, the instruments mapped the mascons on the moon in extreme detail to monitor where lunar gravity increased from the norm. Astronomers had long suspected that mascons on the moon and other planets formed during violent asteroid impacts.
(Image credit: NASA/JPL)
“GRAIL data confirm that lunar mascons were generated when large asteroids or comets impacted the ancient Moon when its interior was much hotter than it is now,” Jay Melosh, a GRAIL co-investigator at Purdue University, said in a NASA overview.
The MoonKam instrument was really a scholar experiment (MoonKam is brief for Moon Data Acquired by Center Faculty College students). It was constructed by undergradutate college students on the College of California, San Diego in partnership with the Sally Journey Science basis to encourage youthful college students to review science and area. (The names Ebb and Circulate as GRAIL probe names had been additionally urged by 4th grade college students at Emily Dickinson Elementary Faculty in Bozeman, Montana, as a part of a nationwide competitors.)
The $496 million GRAIL probes orbited the moon in an especially low orbit, coming inside 30 miles (50 km) of the lunar floor at their closest method. They had been separated from one another at distances that ranged from 109 miles to 140 miles (175 km to 225 km).
NASA crashed the GRAIL probes into the moon on Dec. 17, 2012 as soon as its gasoline reserves reached the purpose that it couldn’t keep its low lunar orbit. They crashed right into a crater rim close to the moon’s north pole to stop them from randomly crashing uncontrolled into someplace like an historic Apollo moon touchdown web site.
Need more room historical past? Take a look at our full On This Day In House Story archive and watch our On This Day In Space videos on YouTube.
On today in area! Sept. 9, 1982: The first non-public rocket Conestoga 1 launches from Texas ranch