Message: Hi there, Please could you tell me how safe the LCROSS experiment is? The reason I ask is due to a lot of comments I have read over the internet stating that it will throw our moon out of orbit and all other dreadful things will happen. Thank you in advance

Thank you for asking this question rather than adding to the ridiculousness that is currently ongoing throughout the internet (and even several major news networks!). The problem is that the major networks are not checking facts and then people on the internet are taking that information and letting their imaginations run completely wild with no rhyme or reason to their thought processes. The main (non-scientific) things you need to know about the LCROSS mission are 1) there are no “bombs” associated with the spacecraft, 2) impacts of this size occur on the Moon (and on Earth!) about once every 3-5 weeks, 3) no chemicals/nuclear weaponry of any kind are being used on the spacecraft to contaminate the Moon’s surface, and 4) the amount of material that will be excavated by the impact will be on the order of 10′s of tons… or about a few 10′s of cubic meters.

To expand on those items just a little. The upper stage of the Centaur rocket is what is being used as the “impactor.” Basically this is a large hollow canister which weighs about 5000 lbs. It has been outgassed after the launch to render it completely empty, as if it still retained any fuel from the launch, it would contaminate the plume of dust that we are trying to measure so carefully! So basically, we are very accurately throwing a big metallic rock at the Moon. The resultant crater will likely be approximately 3 meters deep and about 20-30 meters across (about 1/4 the size of a football field). As I mentioned before, the Moon actually experiences meteorite impacts this size on a regular basis. On any square kilometer of the Moon, you can find 30-100 similarly sized craters. The only difference is that we know exactly when and where our impact is going to take place so that we can point all of our telescopes at it and monitor the plume of dust, water (cross your fingers) and other compounds that previously weren’t thought to have existed on the Moon! I highly recommend that you look at the website for the mission as it’s going to be incredibly informative and useful to not only understand the nature of our Moon, but also for future exploration of our own solar system!

Brad Bailey
NLSI Staff Scientist

October 8, 2009

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