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As you watch the Moon over the course of a month, you'll notice that different
features are illuminated by the Sun at different times. However, there are some
parts of the Moon that never see sunlight. These areas are called
permanently shadowed regions, and they appear dark because unlike on the Earth,
the axis of the Moon is nearly perpendicular to the direction of the
Sun's light. The result is that the bottoms of certain craters, like here at
the Moon's south pole, are never pointed toward the Sun, with some remaining dark
for over two billion years. However, thanks to new data from NASA's Lunar
Reconnaissance Orbiter, we can now see into these dark craters in incredible
detail. Seeing the shape of the crater is important, and LRO has used its LOLA
instrument to make the best yet topographical maps of these craters by
reflecting lasers off the lunar surface. This has allowed us to see the shapes of
the craters' interiors from any angle, and by making 3D models, we can light up the
crater floors as if we had a giant flashlight. And although the Sun never
illuminates these craters, other stars still cast a faint light into the
permanent shadows. LRO's LAMP instrument can actually measure this light, giving
us yet another view of this unique region on the Moon. LRO's DIVINER
instrument can also measure temperature, revealing the extreme cold within the
craters. Finally, LRO's LEND instrument can measure the speed of neutrons to
detect elements like hydrogen in the lunar soil. So, while there are some areas
on the Moon that never see the light of day, LRO will keep collecting data so
that we can learn more about them. And as we continue to study the Moon, we'll
improve our understanding of Earth's original satellite, and, pun fully
intended, bring new discoveries to light.
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