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Moon crater central peak

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#1 Alderman

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Posted 21 July 2018 - 12:19 PM

Having fun with this scope and was wondering why the craters on the moon often have a raised portion in the middle of them. Excuse the poor pics but the best I could do with my phone. 314e8ac5b7e026f420fbf6524131e31c.jpgecdfe4debe409713c6f2255f3cb574ff.jpg46cb7276b62981da843ef9b5be993b79.jpg0c267c3bf131c170c43ca0a37c1f2cf1.jpg


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Edited by Alderman, 21 July 2018 - 12:20 PM.


#2 aeajr

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Posted 21 July 2018 - 02:44 PM

Can't answer with certainty, but I would guess there was another smaller impact some time after the primary impact.  They just keep coming.

 

I suppose there could also be a bit of a water drop effect. Drop a stone into water and you get a hole, like a crater, which then comes back in on itself and sends a spout/splash up the center.   If a large impact occurs it likely liquified the impact area and you might be seeing the center splash.


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#3 sg6

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Posted 21 July 2018 - 03:06 PM

That is the way that the mechanics of an impact work, well fluid mechanics.

The impact will send out a shockwave and eject material outwards as a crater wall, but the is "rebound" at the impact site and that leaves a small raised central lump.

 

Have a search for slow motion impacts of rain on water and you should see the outward spreading wave(s) and a central pillar raising up. Same on the moon but as it is not quite a fluid in the liquid water sense the central bit remains, and without an atmoshere for rain and wind it basically stays there for a huge time. Enough for use to evolve, discover the fun of a telescope and observe them.


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#4 Tony Flanders

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Posted 21 July 2018 - 06:03 PM

I suppose there could also be a bit of a water drop effect. Drop a stone into water and you get a hole, like a crater, which then comes back in on itself and sends a spout/splash up the center.   If a large impact occurs it likely liquified the impact area and you might be seeing the center splash.

That's precisely the reason. It's certainly not due to secondary impacts, in view of the fact that almost all craters larger than a certain size have mountains very near their centers. The chances of that happening once or twice by accident are high; the chances of its happening in 95% of all cases are essentially zero.

Things are actually a bit more complex, because in addition to the initial splash, you have residual effects as the walls of the craters collapse, sending waves of debris inward. And then there's subsidence, as the underlying rock layers compress and bend under the weight of the crater walls. In really big craters, there are almost always multiple rings of terraces as well as the central peak.



#5 rowdy388

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Posted 21 July 2018 - 08:52 PM

The variety is nice. Sometimes one peak, sometimes two, sometimes a mini-mountain range,

or nothing at all.




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