lunar crater history

[moony]

If given a photo of the moon, how do i deduce the lunar crater history? what graph should i draw or what equation should i use? thanks!

[zong]

I don't understand your question. You want to know which craters were formed when, in chronological order?

[chrisyeo]

Do you mean which crater is older and which is younger?

[weixing]

Hi,

I don't understand your question. You want to know which craters were formed when, in chronological order?

I think he mean how to know the age/history of a lunar crater is through photo.

Have a nice day.

[moony]

Yah what I meant was looking at the photo that I have taken, try to get the crater density and deduce some relationship between the lunar history? like generally more small craters are formed than big ones..

[zong]

Wow.. hmm. Just curious, what made you want to learn about this? Not a very popular topic.. haha

As far as I know there isn't such a formula to deduce any relationship. As for crater counts, you probably can't get very far with your own photos due to a limiting resolution (unless you're remus, lol). You could still do a rough gauge by counting the craters in your photos. For more accurate results, try learning how to zoom in to small parts of the moon, and track the moon while taking your pictures, so that you can mosaic them together for higher resolution.

If there were any reports that could date a crater, it would probably require advanced techniques or complex simulations.

[ChaosKnight]

There is an equation relating crater diameter to ke of impactor, some sort of power law iirc. So given the crater size, you know something of the ke of whatever hit it.

Now, if you make an assumption that when the impactor is far away, its ke is very small compared to the ke when it hits the moon, then you can say the ke of the impactor just before it hits is purely due to conversion from GPE.

Therefore for a particular crater diameter D -- > ke of impactor.

And the ke of impactor ke = GMm/r, where M is mass of moon.

Here note that you have 2 unknowns: m and r. So you plot a graph of m vs r. You end up with straight lines that pass through the origin at different gradients. Do this for many craters and impactors.

Now look at r = distance to the asteroid belt, and the density of lines passing through this r. Read off the values of m.

Compare the mean and variance values of m to statistical studies of known mass distribution in the asteroid belt. We know that the asteroid belt was dynamic in the past, with changes in mass distribution due to the formation of Jupiter.

So, if the mass distribution from your graph is similar to that of the mass distribution of the asteroid belt, you can conclude it is likely the moon was cratered by impactors from the asteroid belt in its present state, which is an indication of the epoch of cratering.

If the distribution from your graph is different, it could be because the moon was cratered when the asteroid belt composition was different from its present state, in which case you also have a time scale over which cratering took place, or the impactors were from elsewhere and not related to the asteroid belt.

Don't mind me. i'm sending you on a fool's errand.

[ChaosKnight]

btw, GPE is gravitational potential energy, not Great Polaris Economy

[ChaosKnight]

Apologies, i stated a wrong assumption.

An object from the asteroid belt has ke several orders of magnitude larger than GPE, so the assumption GPE >> ke is wrong. Rather we can assume ke >> GPE, and GPE can be neglected.

Hence if we assume the impactor is from the asteroid belt, we assume the crater diameter gives a measure of its original ke.

To obtain the mass of the impactor, we can assume the asteroid had an original velocity of between 13000m/s to 24000m/s, but an average of 19000m/s is good. After that you can do your statistical analysis of mass distribution.