Two Moon Questions

[TopHouse]

me and my wife were looking at the moon tonight through my 200p, it's a first scope so we're total newbies and it's the first time the scope has been used, but we have 2 questions.

1) What are the very light spots, the ones that look like it's a little led light on the surface.

2) We noticed a few of the smallish craters had what we call a 'pimple' right in the middle of them, like a little raised bit, just looked on a moon atlas and crater alphonsus has one, but we noticed several, what are these 'little lumps'.

Thanks

[Merlin66]

The bright white spots are cause by highly reflective material ( a bit like cat's eyes on the road) and are far more obvious near Full moon.

The central peak in craters is quite common ( as you're probably noticing) and could be the remnants of volcanic activity ( the old volcanic plug) or the residual bulge caused by an impact meteor..your choice.

[TopHouse]

Thanks Merlin, now all that's left is to explain to my wife why the area from around crater maginus looks like a watermelon! And i have to agree, it does!

[Talitha]

TH, the lunar soil is called 'regolith' and the stuff right up on the surface is continually being darkened by radiation. When the most recent impacts occurred, the brighter regolith from below the surface was exhumed and ejected, causing those bright rays we see splashed on the surface. That's how we know they're younger craters.. because of the brighter ejecta like Copernicus has. Older craters like Langrenus also have a large ray system, but it's been darkened over time. You can still see them, though.

The small bright craters lacking an ejecta pattern were excavated deeply enough to expose the brighter regolith, but the impactor wasn't large enough to cause a big splash like we see around Copernicus and extending (very far) away from Tycho.

Yep, i'm a MoonGeek.

[TopHouse]

WOW, thanks, that really was a brilliant explanation.

[SteveP]

Thanks Talitha

What a great explanation

Steve

[Talitha]

Glad to be of help.

[The Warthog]

Volcanic theories of crater formation have been mostly abandoned in favour of impact theories. The central peak of some craters is thought to be a 'rebound' artifact as the central area of the impact 'bounces back.'

This article gives a good, brief picture of crater formation.

Have a look at the picture of King crater. It looks like a dome to me, an example of the illusion some crater photos give of being reversed.