Viewing a single comment thread. View all comments

ryoon21 t1_ixr21ro wrote

Why does the moon have so many craters but not the earth? Is it because the moon has no atmosphere to incinerate meteorites?

10

Ralphie99 t1_ixrbjiy wrote

Most of the craters were made millions of years ago. The moon does not have the atmosphere that Earth has, so more objects will hit the surface of the moon than will hit the surface of the Earth. Earth’s atmosphere burns up most objects that enters it.

Also, the moon does not have the same systems as Earth has that erode surface features over time. On Earth, a crater might get filled with water, and sediment and vegetation might fill it over time. None of these things happen on the moon.

22

_kst_ t1_ixrvmiq wrote

i don't think Earth's atmosphere significantly reduces the number of craters that are formed on Earth. Anything big enough to form a crater that's visible from space is going to get through the atmosphere reasonably intact.

Earth has fewer visible craters than the Moon because it erases them.

−1

enderjaca t1_ixs3aqh wrote

Mmm I dunno about that. There are plenty of moon craters you can see in these photos that would not form on earth because those small meteoroids would burn up in Earth's atmosphere. And the moon's surface is relatively light and dusty.

5

Ralphie99 t1_ixs48d4 wrote

Even the craters that are from objects that are big enough to also impact Earth would be smaller on Earth as some of the material from the object would burn up in Earth’s atmosphere, even if a portion of it reached the ground.

2

_kst_ t1_ixs4j9a wrote

A quick Google search found this article which says:

> Typically, though, a meteoroid would have to be about the size of a marble for a portion of it to reach the Earth's surface. Smaller particles burn up in the atmosphere about 50 to 75 miles (80 to 120 kilometers) above the Earth.

A crater is typically about 10 times the diameter of the meteorite that created it.

Any crater that's big enough to be visible from space would have formed either on the Moon or Earth.

Unless (and I neglected to allow for this) it hits in the ocean.

According to this article, the smallest meteorite crater on Earth is about 7cm in diameter and 3cm deep. That wouldn't be visible from space.

2

enderjaca t1_ixs7hym wrote

Good to know, thanks for the resourced info!

2

Ralphie99 t1_ixs401w wrote

I mentioned craters getting “erased” as one reason we don’t have nearly as many visible craters on Earth. However, I stand by my contention that the smaller craters on the moon are from objects that would have burned up in Earth’s atmosphere. These objects smash unimpeded into the moon.

1

_kst_ t1_ixs4tng wrote

The smaller craters yes -- but only the ones that are so small that they can't be from orbit. See my other comment.

1