Mercury and the crescent moon low in the western sky 40 minutes after sunset and about 6 degrees apart. Created with Stellarium
Let’s start with a quick reminder that the thin crescent moon will be low in the western sky during twilight this evening. Look several degrees (two or three fingers held at arm’s length) to its upper right to spot the planet Mercury. Since I’m writing much later than usual, I hope you’ll still have time to catch sight of them both.
Through a telescope at magnifications of 50x and higher, Mercury will look like a very tiny half moon.
Shackleton Crater, named after Antarctic explorer Ernest Shackleton is located at the lunar south pole. Because the moon’s axis is only slightly tilted, the crater’s floor is in perpetual shade. The average temperature there is 300 below zero F. Credit: NASA
The floor of the crater Shackleton, located in the chill shade of moon’s south pole, appears to harbor 22 percent ice among its rocks. That’s the story according to data from NASA’s Lunar Reconnaissance Orbiter (LRO). The craft shot laser beams into the 3-plus billion year-old dusty dark crater interior and measured the brightness of the light reflected back. The results showed that parts of the floor and walls are brighter than those of nearby craters, consistent with the presence of water ice.
Elevation (left) and shaded relief (right) image of the 12.5 mile-diameter crater Shackleton. The structure of the crater’s interior was revealed by a digital elevation model constructed from over 5 million laser elevation measurements made by the LRO. Credit: NASA/Zuber, M.T. et al., Nature, 2012
Shackleton might be one of the solar system’s best places to keep ice cream from melting. Because the tilt of the moon’s axis is a scant 5 degrees compared to Earth’s more generous 23.5 degrees, sunlight only grazes the rims of craters at the north and south poles. Their interiors remain in near-permanent shadow, making them ideal environments for preserving water and other ices that may have been delivered by long-ago comets.
Earth was bombarded by comets, too. That water has long since become one with the rivers, oceans and what pours from your faucet. To read more about Shackleton’s bounty of ice, click HERE.
