From: Discovery News
A pair of robotic space probes circling the moon to reveal what is inside will make suicidal plunges to the lunar surface next week, a planned — albeit dramatic — finale to a mission that is giving scientists new insights into how the solar system evolved.
The Gravity Recovery and Interior Laboratory, or GRAIL, mission will come to an end at 5:28 p.m. EST Monday (Dec. 17) when the twin spacecraft crash into a mountain near the moon’s north pole after nearly a year in lunar orbit.
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The duo have been formation-flying to map the moon’s gravity, an innovative technique that has revealed a lunar crust that is thinner and far more deeply fractured than scientists expected and an extensive underground system of lava-filled cracks, the first direct evidence that the moon expanded after it was formed.
The information applies not just to the moon, but to the other solid bodies in the inner solar system, including Earth and Mars.
Seeing the extent of the damage from impacting comets and asteroids, for example, makes it easier to visualize how water on the surface of ancient Mars might have made it way inside the planet, where it might still exist today.
“There’s a lot of questions about where did the water that we think was on the surface of Mars go. Well, if a planetary crust is that fractured these fractures provide a pathway deep inside the planet. It’s very easy to envision now how a possible ocean on the surface could have found its way deep into the crust of the planet,” GRAIL lead scientist Maria Zuber, with the Massachusetts Institute of Technology, told reporters on a conference call Thursday.
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The GRAIL spacecraft, nicknamed Ebb and Flow, completed their primary mapping mission in May, flying about 34 miles above the lunar surface. By precisely and continuously measuring the distance between the two probes, scientists were able to map the moon’s gravity, revealing its interior structure. The distance changed slightly as the leading spacecraft and then the following one sped up or slowed down as they flew over denser or less-dense regions of the moon in response to the gravitational tugging.
This summer, the pair’s orbit was lowered to about…
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