Odd Impact Crater found in the North Sea

An anonymous reader writes "Just noticed this on MSNBC. It seems they discovered an impact crater in the North Sea that doesn't look like anything else seen on Earth. Supposedly it looks like something usually seen on moons of Jupiter."

Comments

Re:So what's the difference between what's seen on

[dev0n]

the article says that they're 99 percent sure that it was an impact crater, though.

AP Story

[ELCarlsson]

Here's another story about it Nandotimes.com . I think that this is pretty neat. I'm glad to see how technology is able to detect stuff like this even deep under the sea.

That's called a caldera.

[EMDischarge]

A good example of a caldera is Crater Lake National Park in Oregon.

Re:Multiple impacts?

[dodald]

I would guess not, I am not a scientist, so this is purly a slightly educated guess.

Inorder to gut concentric rings like that with multiple impacts I would assume that the impacts would need to be a couple of hours apart, because the initial impact would still be hot, so it would just make the crater bigger.

Since Earth is rotating (15deg/hour) the asteroids would need to come from different directions, and the chances of that would be very high like, say 1 in 2^276709, so I would say that it was probably not multiple impacts.

Did that make sense?

What *is* odd about this is...

[Randym]

...the concentric circles. Most asteroids, because of their angle of impact, leave an elliptical footprint, with a bit of a "splash" [ejecta], sometimes forming a hill or mountain beyond the impact point. Concentric circles seem to indicate a "straight-in" impact, which leads to the idea that the object was going pretty darned fast (not slowed down much by atmosphere) *and* at just the right angle to compensate for the rotational speed of the Earth.

Concentric circles would be more common on worlds with little atmosphere to slow the object. Since we know that Earth at that time had a (relatively) thick atmosphere, it just makes the puzzle all the more interesting. What would be interesting to find out is the metal composition at the center of the impact site -- that could tell us a great deal about what hit. Probably iron, but it *could* be something as heavy as uranium.

Re:What *is* odd about this is...

[Mr.Sharpy]

ah, but what if it was a meteor composed of iridium. or perhaps a fragment of or part of a group of iridium bearing meteors. the density of iridium is 17% higher than uranium, so it would definitely have enough energy to give the earth a good whack. maybe enough to make those interesting rings.

the (at least partial) disintegration of such meteorites might help explain the iridium layer. perhaps the earth passed through a field of iridium bearing objects during that time. who knows. it will be interesting to see what they dig up.

Almost all impact craters are circular

[dmatos]

I remember seeing a study on this on Discovery or TLC. The fired rifle bullets into sand at high velocities and at many different angles, and the resulting crater was almost always circular. A quick google search turns up this link, a section from some lecture notes at University College Worcester.

Craters are not always circular as they may have been created from impacts which hit the surface at oblique angles forming elliptical craters however as impact craters are formed by very high velocity impacts which act essentially like an explosion rather than a distortion of the surface so unless the impact is very shallow and ploughs along the surface the craters will tend to be circular.

Here is another interesting quote from the same page that may explain the concentric rings:

If the crater is larger and the same order of magnitude as the thickness of the lithosphere then shock waves will penetrate the more plastic athenosphere resulting in the formation of multiringed basins.

Map URL

[ke4roh]

See a map of the crater accompanying the National Geographic story.