A map from the twin GRAIL spacecraft, which completed their mission in late 2012, shows differences in the Moon's surface gravity. Red areas have denser material, so their gravitational pull is slightly stronger, while blue areas are less dense and exert a slightly weaker pull. The image is centered on the lunar farside, with the nearside, which we see in the night sky, at the edges. [NASA/JPL-Caltech/GSFC/MIT]
The Moon is our closest astronomical neighbor, so you might think that scientists would know pretty much all there is to know about it. But they continue to learn new details about the Moon all the time.
In the last few years, for example, they’ve discovered that there’s quite a bit of water on the lunar surface. And a mission that finished its work just last year revealed that the lunar crust is a good bit thinner than earlier work had suggested - only a couple of dozen miles.
That discovery came from GRAIL, a pair of spacecraft that mapped the Moon’s gravitational field in great detail. The craft began their work last spring, and ended their mission when they were intentionally crashed into the Moon in December.
Scientists already knew that the Moon’s gravitational field is quite “lumpy” - there are regions where the gravitational pull is stronger or weaker than average. GRAIL mapped the lumps, revealing new details about the make-up of the lunar surface.
GRAIL also helped scientists probe the Moon’s interior and its bulk composition. Those observations support the idea that the Moon was born when a Mars-sized planet slammed into the young Earth, spewing molten rock that coalesced to form our close astronomical companion.
And the Moon is in good view this evening. It’s in the west at nightfall, with the brilliant planet Jupiter to its right or lower right. And the face of Taurus, the bull, looks on from below them.
Script by Damond Benningfield, Copyright 2013
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