LCROSS/LRO and Their Effect on the Moon

[HeLiXe]

I asked this on another thread, but I think it might need a thread of its own. If this has already been covered, can you please insert the link to the appropriate thread?

I am wondering about the effect the LCROSS and LRO missions had on the moon. I've searched, but the most I can find is the estimation of the matter displacement of the impact before it occurred and details about the plume from the impact. I've also found a few different estimations of the magnitude of the impact. Was the libration of the moon affected at all? If so, how was it affected? Was the moon's path of orbit affected? If so, how? If you have an answer for any of these questions (whether it be yes or no or whatever), can you please give me a detailed answer, including any magnitude of force, etc, and major equations which may be involved. I would like to research them as a point of interest. Thx!

 

[Mu naught]

What do you see in this image? The moon has been impacted by meteors thousands of times in it's life, if such a small impact could have any measurable affect on the moon, then all the thousands of much greater impacts it has suffered would have had a far greater effect. The moon is a heavy object, it doesn't get bounced around every time a fly lands on it.

 

[HeLiXe]

Thanks for your answer Mu Naught. I was hoping for something a bit more scientific than what you have offered, but it is possible that I did not convey what I was looking for clearly enough. You are saying the impact is so small it could not have any effect on the moon. How small was the impact? How many metric tons of matter were displaced? What do you consider no effect?(libration not affected, orbit not affected, surface not affected etc.) Are there any equations to detail the magnitude of force of impact as it relates to the libration of the moon, orbit of the moon, etc.? If the larger impacts the moon has suffered would have had a far greater effect, what would that effect be? What was the force of those larger impacts, how much matter was displaced, etc.

Your tone is a bit condescending, possibly because you have misunderstood my intent, maybe because I am just starting my physics education, or maybe you did not read my post in its entirety. I could care less about your tone so long as you can provide a more detailed and scientific answer. Thanks for your time and effort!

 

[brother time]

I found a good link that claims that the crater is about 28 meters in diameter. Compared to some of the moons hits this is relatively small. The same article also says that 300 - 400 tonnes of rock and water was kicked up into space following the collision.
hope this helps answer the question,
brother time.

 

[HeLiXe]

Thanks brother time. This is more along the lines of what I am looking for. Do you have a link to the article you referenced?

Prior to impact, it was noted that the impacts would displace 500 metric tons of matter*. Prior to impact, it was also estimated the LCROSS would hit the moon at a speed of 9000+ km/h**, and from what I have gathered, the speed at the time of impact was 10,300+ km/h. I also understand that the destination of impact was changed from crater Cabeus A to Crater Cabeus B.***
[PLAIN]http://science.nasa.gov/media/medialibrary/2009/09/11/11sep_lcrosstarget_resources/385735main_NMSU_LCROSS_medium-1_strip.gif
Which is a larger crater than Cabeus A. Cabeus B is said to be 61km in diameter and Cabeus A is 40km in diameter. Which is why I am interested to know how much matter was displaced because so far I have not gathered any information about the size of the crater after impact...although I am sure it is the same and would not be a good way to determine the magnitude of impact. I have tried searching NASA's site and many other sites, but I am not really getting the details I need about the impact and post impact. Thanks for your info! I would really appreciate it if you are able to link the article!

*http://www.news.com.au/nasa-launches-mission-to-bomb-the-moon/story-0-1225737622591"

**http://lcross.arc.nasa.gov/impact.htm"

***http://www.msnbc.msn.com/id/33064495/ns/technology_and_science-space/"

 

[D H]

http://lcross.arc.nasa.gov/faq.htm#q4

 

[HeLiXe]

Thank YOUUUUUUUUUUUU! I've been searching for this for months and never came across this on NASA's site. This is the answer I have been looking for. Thank you very much I really appreciate this!

 

[HeLiXe]

Here is the answer Janus provided me on another thread...in case anyone else may be interested but uninformed as I was:

LCROSS masses about 585 kg. It hit at about 9000 kph. This equates to a momentum of 1462500 kgm/s The Moon masses 7.35e22 kg. If we divide the Moon's mass into the momentum of LCROSS, we get a fair estimate of what type of velocity change the impact could have on the Moon. It works out to be 2e-17 m/s. This is the equivalent of 1 meter per 1,000,000 yrs. Pretty darn insignificant.

And that's not all. You can't even count all of that 9000 kph impact speed. The vast majority of it is due to The Moon's gravity pulling the craft in. Since gravity is a two way street, as the Probe falls toward the Moon, the Moon falls toward the probe. The upshot is that any part of the probe's momentum on impact that is due to the gravitational attraction between it and the Moon is canceled out by the moon's own momentum. That means that any momentum change to the Moon is due to the small amount of the probe's momentum that is in excess of that. This makes the change in velocity to the Moon is even smaller than the last figure I gave.

This really explains so much and is beautifully detailed. Thanks again so much. This is what I really needed!