Moon craters

[bendiddley]

I was out yesterday evening observing the moon, and I was reminded of a question I have had for a while now but never sort an answer, so I decided I'm going to post it now. In the middle of many of the craters there seems to be a tiny lump that looks like a raised mound of rock or something, is that the remains of the meteor or asteroid that impacted the surface to form the crater?

[wxsatuser]

Try this....

http://www.lpi.usra.edu/education/explore/shaping_the_planets/impact_cratering.shtml

[michaelmorris]

No, the impactor is usually vaporised in the impact.  The uplift is caused by an effect sometimes called rebound   For larger craters, the crust in central part of the crater rises above the crater floor. A similar same effect can be seen when a peeble is dropped into water. 

[bingevader]

Top answer, but please stop dropping those peebles in the water, they really don't like it. 

Cheers

[bendiddley]

Great that explains it thanks! I can now look at them and know what they are. Nice image by the way of the water droplet that helps to visualise it more.

[michaelmorris]

If you are interested, the pebble in water analogy is also useful for explaining crater rays.  In larger 'plops' interference patterns in pressure waves in the water cause water spray out in lines. (see picture below).   It's my understanding that in lunar impacts, these pressure waves proproagte in the gas/dust/rock 'fluid' temporarily present during/immediately after the impact causing ejecta to fall in lines

[Qualia]

Great question, Ben and thank you for raising it

[bendiddley]

Great question, Ben and thank you for raising it

You're welcome

[MarkMayf]

Great question that is well well answered. Brief and to the point.

[Dave73]

This is a great site for finding information.

I was looking at the same thing on Sat evening and wondered what these objects were.

Is there any relationship between the size of the crater and the size of the rebound ?

I shall be looking for more examples now - when the cloud clear.

[michaelmorris]

Is there any relationship between the size of the crater and the size of the rebound ?

Yes.  Central uplift tends to be found in craters with diameters in the region of 30km to 300km.  Above this multi ring impact basins are formed.  There is an intermediate form where a central ring of peaks is formed.  An example of this on the near side of the Moon is the crater Antoniadi.

If you want to find out more about the processes of cratering and other lunar geological rpocesses, I can thoroughly recommend getting hold of a copy of Charles Wood's excellent book, A Modern Moon.

http://www.amazon.co.uk/The-Modern-Moon-Personal-View/dp/0933346999/ref=sr_1_6?ie=UTF8&qid=1382442469&sr=8-6&keywords=charles+wood+moon

Sadly it's appears to be presently out of print

[Dave73]

Yes.  Central uplift tends to be found in craters with diameters in the region of 30km to 300km.  Above this multi ring impact basins are formed.  There is an intermediate form where a central ring of peaks is formed.  An example of this on the near side of the Moon is the crater Antoniadi.

If you want to find out more about the processes of cratering and other lunar geological rpocesses, I can thoroughly recommend getting hold of a copy of Charles Wood's excellent book, A Modern Moon.

Thanks for this information. It will provide some more points of interest when observing the moons features.