why are there more impact craters at the top and bottom of the moon than .....

[Mick UK]

there are around the Middle?

[pvaz]

More recent volcanic eruptions re-paved those areas and "erased" the craters that ware there.

[Mick UK]

Thanks for that pvaz, i suppose it now begs the question, why was there only volcanic eruptions around the middle of the moon and not the top and bottom!

[pvaz]

Thanks for that pvaz, i suppose it now begs the question, why was there only volcanic eruptions around the middle of the moon and not the top and bottom!

Hehe! I'm clueless. Whe need Thalita here! She's the lunatic!

[Mick UK]

..the wait will be worth it!

[PeterW]

.... why are there no 'maria' on the back of the moon..... time to dig out the copy of Charles Wood's book or go read the Geological History of the Moon again.

Cheers

PEterW

[Talitha]

Yep, i'm a lunatic and proud of it.

When large impactors hit the Moon they actually cracked the crust and allowed lava to flow up and fill in lower areas. Seeing as the impactors punched the crust down so much, it's logical that the pole areas remained higher in elevation and remained unflooded for the most part.

The large Mare Imbrium was from a huge impact and there are theories of an even larger one calld (iirc?) Gigantus or something like that.. you can see the huge rounded outline of it defined by the western shores of Oceanus Procellarum.

Regarding the large marias on the near side, i seem to recall reading that it was because that half's crust was thinner during the 'great bombardment'. The crust was thinner because the underlying lava fields melted the crust from the inside. When the impactors hit, the crust easily cracked and allowed the lava to flow out.

Mare Orientale is the result of a huge impact on the far side, but as you can see, the lava was contained within the circular rebound mountain chains of Rook and Cordillera.

[pvaz]

And the master as spoken!

Thanks

[Smoore]

I had heard somewhere that Earth had an influence on volcanic activity and that is why Mares are mostly on the near side where Earth had more influence, is there any truth to this at all then? I'd wonder if the Moon was even tidally locked to us back then or not.

[GazOC]

I had heard somewhere that Earth had an influence on volcanic activity and that is why Mares are mostly on the near side where Earth had more influence, is there any truth to this at all then? I'd wonder if the Moon was even tidally locked to us back then or not.

Thats correct.

[Mick UK]

Thank you for that Talitha, very interesting...those poor Clangers, first they get bombarded by asteroids, then they are swamped by hot Lava..no wonder they are extinct:sad:

[LukeSkywatcher]

When the Moon finally breaks away from Earths gravity/orbit does that mean that our seas will cease to have high/low tides?.

[pvaz]

When the Moon finally breaks away from Earths gravity/orbit does that mean that our seas will cease to have high/low tides?.

The sun also causes tides (half the force of the moon due to the distance). The largest high tides are caused when they are aligned.

As to the moon breaking away, that won't happen as the sun will die 1st.

[LukeSkywatcher]

Thanks Paulo. I was under the impression that the Moon will only orbit Earth for another few million years before it is too far away to be held by earths gravity and go off on its merry way wandering through the solar system. Whereas the Sun is gonna be around for a few BILLION yrs more before it dies.

[George Jones]

Thanks Paulo. I was under the impression that the Moon will only orbit Earth for another few million years before it is too far away to be held by earths gravity and go off on its merry way wandering through the solar system. Whereas the Sun is gonna be around for a few BILLION yrs more before it dies.

Due to a combination of tides and the Earth's rotation, the Moon currently is moving away from the Earth at the rate of about 4 centimetres per year, but this rate is gradually slowing down. The rate of rotation of the Earth also is slowing down gradually. Eventually, things will reach an equilibrium. The Earth-Moon distance and the rate of rotation of the Earth will both remain constant. When this happens, the length of a day for Earth will be the same as the time the Moon takes to orbit once. The Moon remain at a fixed position in our sky!

If I can find an appropriate image and if anyone is interested, I can try to explain why tides cause the Earth-Moon distance to increase, and cause the Earth's rotation rate to decrease.

[Talitha]

Due to a combination of tides and the Earth's rotation, the Moon currently is moving away from the Earth at the rate of about 4 centimetres per year, but this rate is gradually slowing down.

From what i read, we're able to determine the distance by bouncing laser beams from a mirror (mirrors?) left on the lunar surface by one of the Apollo missions. Something else i read was that as the Moon recedes, we won't have any more total eclipses of the Sun, they'll all be annular. No idea how long that'll take to happen, though.

If anyone would like a good read, try 'The Once and Future Moon' by Paul Spudis. Very informative, and easy to understand.

[George Jones]

From what i read, we're able to determine the distance by bouncing laser beams from a mirror (mirrors?) left on the lunar surface by one of the Apollo missions.

Another reason that the moon landings were not a hoax. For an image, see

File:Lunar Laser McDonald Observatory.jpg - Wikimedia Commons.

The mirrors left were corner-cube reflectors like those in bicycle reflectors, so that the reflected beam goes back along the same path as the incident beam. This is how car drivers see the bicycle reflectors: light travels from headlights to reflector and back to the driver's eyes, no matter the angle between bike and car.

Something else i read was that as the Moon recedes, we won't have any more total eclipses of the Sun, they'll all be annular. No idea how long that'll take to happen, though.

I hadn't thought about that. It has to happen eventually.

[LukeSkywatcher]

From what i read, we're able to determine the distance by bouncing laser beams from a mirror (mirrors?) left on the lunar surface by one of the Apollo missions. Something else i read was that as the Moon recedes, we won't have any more total eclipses of the Sun, they'll all be annular. No idea how long that'll take to happen, though.

If anyone would like a good read, try 'The Once and Future Moon' by Paul Spudis. Very informative, and easy to understand.

I had never thought of that. As the Moon moves further away there will be no more total solar eclipses (and fewer lunar eclipses also). Thats a good few million yrs away though.

As for measuring the distance from Earth to Moon.............yep that is done with lasers and mirror(s) left on the Moon during an Apollo mission. If there was no man made mirror there we could simply not take those measurements.............................this single fact alone proves without doubt that man went to the moon.

[RobH]

Here's an interesting article on new discoveries regarding why the moon has maria on our side and not on the other.....life on earth nearly didn't get started, and although I curse the moon when I'm imaging, I'm rather glad it's there

Spaceflight Now | Breaking News | 'Man in the moon' origin may have been found

Cheers

Rob

[ollypenrice]

Back on the location of lunar volcanic activity, would we not expect it to be more equatorial than polar anyway? The tidal forces affecting planets are strongest on their equators because there you have the greatest distances between that side near the gravitating companion and that which is further away. Therefore the flexing of the crust is greatest there, weaking it and leaving it prone to fissure. (I don't know If this is so, it just struck me as reasonable.)

Another nice observation on the Moon is to note that small craters overlap large ones but not the reverse, tracing the reducing size of the impactors. Quite reassuring when you think about it...

Still resent the darned thing making my booking schedule such a nightmare though!!

Olly