LCROSS Team Changes Target Crater For Impact

Matt_dk sends word that NASA has chosen a new target crater into which to crash the Lunar Crater Observation and Sensing Satellite (LCROSS) mission vehicles. "The decision means that when NASA's LCROSS probe and its spent Centaur rocket stage slam into the moon on Oct. 9, they will crash into the large crater Cabeus, and not the nearby (and smaller) Cabeus A crater that was previously targeted. ... The data suggests the new target Cabeus has a concentration of hydrogen — an indication of possible water ice — that's higher than anywhere else at the lunar south pole. ... A small valley etched into the otherwise tall crater ridge of Cabeus should allow sunlight to shine on the ejecta cloud kicked up when LCROSS and its Centaur rocket stage crash into the moon in successive impacts."

Comments

Re:Why not remotely?

[solafide]

It's hard to dig deep into rocks without some variety of explosive. It's pretty hard to plant explosives well. The Mars rovers have a rock-digging tool, the RAT: it regularly measures its dig depths in millimeters. This project wants to dig in and learn about well below the surface: we don't really have a good way of doing this right now without smashing stuff.

We can always recycle this variety of space junk once we get there: this is patently untrue of genuine junk in space. The usefulness of a ridiculously high-tech junkyard cannot be underestimated.

Google Maps of Cabeus crater

[BadAnalogyGuy]

http://maps.google.com/moon/#lat=-83.215692&lon=-38.320312&map=visible&apollo=&q=Cabeus

Re:Why not remotely?

[wizardforce]

We can even detect the composition of stars many light years away from the Earth.

spectral lines from a gas are easy to identify as we only need to match the lines to the lines characteristic of various elements. Solid bodies like the moon are different. You can't just take a look at the light reflected off the moon and know whether there is water there. You can use cosmic radiation generated neutrons to probe the moon's composition but it only tells you what elements are in the soil, not the chemical form they are in. If we were to slam a probe into a section of the moon where we think there's water, the impact could vaporize some water fro mthe regolith if there is any which gives us a higher chance of detecting gaseous water spectrographically. Granted it would be easier still for us to send a probe to the surface and take some actual samples of these areas but when you've got a probe in the area that isn't really doing much else useful, you may as well get your money worth by using it in this fashion.

Re:Why not remotely?

[compro01]

We cannot spectroscopy through the moon's surface.

That's why we're throwing a heavy object at it so we can see the stuff we're wanting to look at.

What is crashing into the moon is the spent rocket. The sensors are on the orbiter which will fly through the plume created by that impact. To go through that, it needs to get very close to the surface and there's no way to recover that, so it crashes shortly afterwards.

Also, rovers would not cut it for this. You would either need heavy digging equipment (Which is far too large/heavy to be feasibly boosted into space with current techniques) or (literally) a ton of TNT.

As for cluttering, this is just another meteor impact among thousands of others, aside from that we're aiming this one for an area we're interested in examining.

Orbiter simulation

[Amiralul]

Here's a simulation of the impact, done with Orbiter software and a bunch of plugins: http://www.youtube.com/watch?v=mXTc47x4HDk