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NASA Finds Major Ice Source In Moon Crater
coondoggie writes with news that a NASA survey of the moon's Shackleton crater by the Lunar Reconnaissance Orbiter has provided data indicating as much as 22% of the crater's surface may be covered in ice.
"The team of NASA and university scientists using laser light from LRO's laser altimeter examined the floor of Shackleton crater. They found the crater's floor is brighter than those of other nearby craters, which is consistent with the presence of small amounts of ice. ... The spacecraft mapped Shackleton crater with unprecedented detail, using a laser to illuminate the crater's interior and measure its albedo or natural reflectance. The laser light measures to a depth comparable to its wavelength, or about a micron. That represents a millionth of a meter, or less than one ten-thousandth of an inch. The team also used the instrument to map the relief of the crater's terrain based on the time it took for laser light to bounce back from the moon's surface. The longer it took, the lower the terrain's elevation. ... The crater, named after the Antarctic explorer Ernest Shackleton, is two miles deep and more than 12 miles wide. Like several craters at the moon's south pole, the small tilt of the lunar spin axis means Shackleton crater's interior is permanently dark and therefore extremely cold."
Ah, so the prism is actually ice, and the white beam is actually six laser beams combined. That explains a lot.
0 if you move it in solid form.
I just wish the editors would do their job and change headlines to what the article actually says;
ASA's Lunar Reconnaissance Orbiter (LRO) spacecraft has returned data that indicate ice may make up as much as 22 percent of the surface material in a crater located on the moon's south pole.
They found the crater's floor is brighter than those of other nearby craters, which is consistent with the presence of small amounts of ice.
In addition to the possible evidence of ice,...
Nowhere did they state they found ice or in what quantity. As for quantity, it could be a small quantity spread over a wide area.
You are mixing up albedo / reflectivity with ranging. Skin depth / surface detail info is not the same as geodetic accuracy (which is at the 10 cm level at best without a corner cube retroreflector).
Here is an example - suppose I shine a flashlight on my car at night. Can I tell if it is wet ? Yes, because I can see specular reflection from a thin layer of water if it is. That layer may be 100 microns thick; seeing it doesn't mean that I know where I am, or where my car is, or the relative distance between us, to anything like 100 microns.
The LRO has a multi-beam altimeter, with fiber optics to send out 5 shots simultaneously from each laser pulse - see Dave Smith's LEAG presentation, page 6. Each spot is 5 meters across (actually, less now as the orbit has been lowered); with 5 spots they can get the local slope and estimate the terrain roughness per shot. They estimate that they can get 10 cm height accuracy with these multiple beams, when the local slope is less than 3 degrees.
Never have had to think about solar cells on the moon's poles :)
Lots of people have been. There are regions of the rim of Shackleton Crater which are never out of the Sun*, so solar power could be collected there and beamed down into the crater. This is the reason why NASA selected power beaming for a Game Changing Technology award.
* Well, maybe never, or maybe never except for a few days every few years. There are still arguments about the terrain models, so I believe the point is still uncertain. And, of course, you will lose the Sun every time there is a Lunar eclipse (i.e., when the Earth gets in the way).