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There are places surprisingly close by that are the coldest known spots in the entire solar system: on our Moon’s south pole lie deep craters that never receive direct sunlight, in fact have never seen the Sun, and within these craters lie pockets of ice that contain the same frozen material they’ve had since forming over 4 billion years ago. This was the impetus behind NASA’s LCROSS mission, which sent a rocket to strike a permanently-shadowed lunar crater and observe via separate orbiter what sorts of material was kicked up by the impact. The result: water ice, and a surprising lot of it, as well as a considerable amount of other elements! Locked in a deep freeze for billions of years – at nearly -400º F – these craters are time capsules holding mementos from our solar system’s youth.
The animation above, produced by NASA’s Goddard Space Flight Center, shows just how these craters manage to hide from the Sun. As the Moon rotates and revolves around the Earth its angle never varies enough to allow light into its deepest southern craters. Anything in them would in effect have been shielded from direct light forever; the Moon, lacking an atmosphere, does not have scattered light like we have on Earth. Light is either direct or reflected off surfaces, but not diffused within a layer of air. And light on the Moon equals heat, so a shadowed area is freezing cold – much colder, in fact. If the light never comes, then anything in the shadow remains frozen.
The animation was made from image maps obtained by Japan’s Selene KAGUYA probe, a successful 2009 mission that mapped the lunar surface in astonishing HD. At the scheduled completion of its mission KAGUYA gradually lost altitude and eventually impacted the lunar surface on June 10, 2009.
Read more about this and other similar animations on the Goddard media site here.
Credit: NASA/Goddard Space Flight Center Scientific Visualization Studio. Digital Elevation Map (DEM) data of the lunar south pole provided by the JAXA/Selene.