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Lunar Giant

December 30, 2014

The Moon is scarred by billions of years of impacts. They blasted out big craters, and punched holes that filled with molten rock that bubbled up from below. Many of those scars are visible to the eye as the dark features on the lunar disk.

But the biggest scar of all is hidden from view — it’s on the far side of the Moon. Known as the South Pole-Aitken basin, it stretches about 1500 miles long — from the south pole to a crater named for astronomer Robert Aitken, who we’ll talk about tomorrow. And it offers both the highest and lowest spots on the entire Moon — from five miles above the average lunar altitude to about four miles below average.

The basin wasn’t discovered until the 1960s, and it wasn’t explored in any detail until the ’90s. And even today, much about it is unknown — including the details of its origin.

It certainly formed when a giant asteroid slammed into the Moon roughly four billion years ago. The asteroid may have hit with such force that it blasted through the lunar crust and excavated material from the mantle below. And in fact, the composition of the rocks in the basin appears to be different from those in other basins. But no one has ever gathered samples from the region, so we can’t be sure where the basin’s dark floor came from. A robotic mission to South Pole-Aitken basin could provide the answers, so it’s a top priority for lunar scientists — a mission that could probe far below the Moon’s battered surface.


Script by Damond Benningfield, Copyright 2014

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