After seeing today's APOTD

Vision · Post by **Vision** » Mon Sep 17, 2007 9:12 am

If our own atmosphere burns up a large amount of any in bound impact, why is it that on other moons and planets lacking such 'atmosphere' (I use that term loosely

) , there are for the most part no remnants other than impact craters?

I realize there is some 'atmosphere' on these planets, but even looking at the moon, its clear this miniscule solar system(in the vastness of it all), has seen a lot of impact activity.

Anyways, just realized this forum existed, and curious as to why we dont see a big chunk of space rock at the center of a lot of these impacts. Buried? Destroyed from the force of the impact? Richochet?

Anyways glad to be here, sorry if its a stupid question.

Case · Post by **Case** » Mon Sep 17, 2007 10:44 am

Destroyed from the force of the impact. All that kinetic energy that was the velocity of the mass, will be transformed to pressure, then into heat and displacement of debris - explosion-like.

FieryIce · Post by **FieryIce** » Mon Sep 17, 2007 1:23 pm

LPOD, February 12, 2007, A REALLY TALL PEAK

“Explosion-like” only if there is something to make it explosive, impact is just that, an impact. Don’t make it more grandiose than it is. Research what Eugene Shoemaker was investigating regarding crater geology, heat, melted glass, explosive catalyst and you might discover there is a different between an impact crater and an explosion crater (above surface, surface and below surface). Melting different surface material results in different coloured glass. Central peaks are interesting; there should be impacter remnants (maybe) and fall back.

bystander · Post by **bystander** » Mon Sep 17, 2007 1:37 pm

You don't think that high kinetic impacts have enough energy to be explosive?

FieryIce · Post by **FieryIce** » Mon Sep 17, 2007 3:08 pm

Do you think it's "high kinetic impacts"?

Pete · Post by **Pete** » Mon Sep 17, 2007 4:01 pm

FieryIce, you avoided bystander's question. Also, what's your alternative explanation to high kinetic impacts?

Chris Peterson · Post by **Chris Peterson** » Mon Sep 17, 2007 4:31 pm

FieryIce wrote:“Explosion-like” only if there is something to make it explosive, impact is just that, an impact.

There's nothing wrong with calling it an explosion- that's what a high speed impact produces. An explosion is just a rapid release of energy; it doesn't matter if the cause is chemical, nuclear, or kinetic.

BMAONE23 · Post by **BMAONE23** » Mon Sep 17, 2007 4:51 pm

The only real difference is the method of transferring kinetic energy. For an Impact the transferrence is caused by Direct Contact between the objects of impact. For an explosion, the means is more of an Indirect Contact and therefore dependant on several factors such as size/velocity of impactor and altitude at the time of explosion. The kinetic energy will still transfer but damage is dependant on the above mentioned factors. Like Tunguska.

mick_malkemus · Post by **mick_malkemus** » Mon Sep 17, 2007 5:24 pm

I've never seen flat rocks like this anywhere, except where they were purposefully laid down by masons. What is the reason these rocks are so even with the surface? I'm not a geologist, so I'm sure there must be a reasonable explanation from an expert out there. Thanks.

craterchains · Post by **craterchains** » Tue Sep 18, 2007 12:04 am

Where are any of the impactors? Good question Vision!

This thread may help with your questions, , ,

http://asterisk.apod.com/vie ... t=impactor

Personaly I think these craters, for the most part, are caused by weapons.

Norval

Chris Peterson · Post by **Chris Peterson** » Tue Sep 18, 2007 12:26 am

craterchains wrote:Personaly I think these craters, for the most part, are caused by weapons.

You're joking, right?

The craters are just exactly as you would expect for high velocity collisions, which are the only kind of collisions possible on a body with any significant gravitational field. Very little of the original mass survives, and on small bodies, much of what does is thrown back into space at greater than escape velocity. I can't imagine any collision mechanism that would produce impactor fragments around craters.

craterchains · Post by **craterchains** » Tue Sep 18, 2007 12:34 am

uh huh, , ,

explain Hyperion then, , FOCLMAO

Chris Peterson · Post by **Chris Peterson** » Tue Sep 18, 2007 12:45 am

craterchains wrote:uh huh, , , :roll: explain Hyperion then, , FOCLMAO :P

Explain what?

craterchains · Post by **craterchains** » Tue Sep 18, 2007 12:50 am

Chris Peterson wrote:
craterchains wrote:Personaly I think these craters, for the most part, are caused by weapons.
You're joking, right?

The craters are just exactly as you would expect for high velocity collisions, which are the only kind of collisions possible on a body with any significant gravitational field.

Think of ALL the smaller objects that are so heavily cratered, but they have very little gravity to cause the hyper velocity speeds.

NO, I am not joking, all these craters and NOT ONE IMPACTOR can be found around them. Just fragments? FOCL, , ,

Chris Peterson · Post by **Chris Peterson** » Tue Sep 18, 2007 1:21 am

craterchains wrote:Think of ALL the smaller objects that are so heavily cratered, but they have very little gravity to cause the hyper velocity speeds.

The gravity of an object doesn't determine the collision speed, but the minimum collision speed. The dynamics of the all the objects in the Solar System mean that collisions tend to be much faster than this minimum. This is very obvious on Earth, where the average meteor has a speed about four times higher than the minimum speed as determined by the Earth's gravity. Furthermore, the rate of cratering has not been constant. Much of the cratering we see on Solar System bodies occurred about 4 billion years ago, during a period of instability when material was flying around in strongly elliptical or even parabolic/hyperbolic orbits. Such material will be close to Solar escape velocity, which even at Saturn is still very fast (about 14 km/s).

NO, I am not joking, all these craters and NOT ONE IMPACTOR can be found around them. Just fragments?

There is increasing evidence that most asteroidal bodies are probably not rigidly solid, but rather made up of loosely bound collections of material. What would you expect a collision with something like that to look like? And what makes you so certain there isn't a certain amount of impactor debris around some craters? It isn't like we've seen them at the necessary resolution, or been able to sample surrounding material. Parent material is found around craters on the Earth.

Nereid · Post by **Nereid** » Tue Sep 18, 2007 1:36 am

Two threads on the same APOD merged.

Pete · Post by **Pete** » Tue Sep 18, 2007 2:44 am

craterchains wrote:uh huh, , , explain Hyperion then, , FOCLMAO

Amazing. In one sentence (featuring more than enough commas), you've managed to refute current generally accepted theories of crater formation and open readers' eyes to the now-obvious true origin of craters.

Seriously, I shouldn't feed the trolls...

Vision · Post by **Vision** » Tue Sep 18, 2007 5:00 am

craterchains wrote:uh huh, , , explain Hyperion then, , FOCLMAO

This sight had a good theory about Hyperion. I assume you were talking about its surface.

http://ciclops.org/view.php?id=1507&js=1

I didnt find one on laser beams *pew pew* yet though

Starship Asterisk*

After seeing today's APOTD

After seeing today's APOTD

Re: After seeing today's APOTD

Inside Victoria Crater on Mars (APOD 17 Sep 2007)