why are all craters on the moon round? You would think that most would look elongated or elliptical depending on the angle of impact.
In: 498
Gravity. The moon is big enough to have pretty significant gravity, and it pulls objects towards its center. This has the effect of making the ankles of impact a lot more direct.
An impact crater doesn’t work like someone throwing a rock into the sand with the crater being the result of that rock shoving the sand away.
Meteors come in at speeds of several km per second. When it suddenly stops because it hits the ground all that kinetic energy is converted into heat and spreads outwards in a massive explosion that expands in a circle. In a way they’re more like bomb craters than “throw a rock into the sand” crater.
You very very rarely get elliptical craters if the meteor comes in at an extremely shallow angle of less than 5 degrees.
When a rock hits the moon at the kind of high speeds we’re looking at, the angle of attack doesn’t matter all that much. The rock just explodes immediately, creating a circular crater
Scientists were confused by the shape of craters for a while. After some math and tests they figured it out. If the energy an object hits something with is more than the energy holding the object together, the object breaks apart instantly and creates a circle instead of an elliptical or elongated impact. A similar example is a snowball. If a snowball hits a wall it breaks apart in a circle when it hits something rather than what you might expect.
I’ve seen nice explanation of this today on Veritasium: https://youtu.be/J_n1FZaKzF8?si=gndcLiNglKJw8Bwq&t=601
The same reason nuclear bomb leave a circular crater when they hit land. It’s not the warhead that’s dangerous it’s the kinetic energy of icbm. Whatever is in warhead is just a bonus.
The kinetic energy of the object impacting the moon is larger than the energy holding the object together. So the object explodes instead of deforming into the surface of the moon.
You can do this by throwing snowballs at walls. Regardless of the angle. As long as you throw it hard enough, it will always leave a circle of snow on the wall.
ELI5: The object is moving so fast that it shatters like glass instead of smushing like play-doh.
You would think, but that’s not how high velocity impacts work. It works more like throwing a pebble in a pond than in a pit of sand, the energies are so high the rock behaves like liquid and quite a lot of it outright vaporizes. Of course if the angle is very shallow you do get elliptical craters, but reasonably high angle impacts are all pretty circular.
I just want to say I appreciate this question. I don’t think It ever would have crossed my mind even after looking at the moon as many times as I have
I was watching the recent Apollo 11 documentary there there was a section of the moon where you could literally see where an impact had skipped several times across the surface. Just like a stone on water.
Latest Answers