Inter-Stellar meteors?

[Karls48 (Karl)]

I have an automated meteor detection camera. It works fine, but few times I have detected possible meteors that enter Earths atmosphere at very high speed. The software I’m using classifies anything with velocity over 72km/sec as flash and takes just snapshot of such an event, not the movie as it does with slower moving objects. It is reasonable to expect that inter-stellar object may enter Earths atmosphere faster then 72km/sec limit imposed on solar system meteors by solar system escape velocity and the Earths orbital speed.
Question. Do you think that inter- stellar objects hit the Earth occasionally, at what speed and is there any evidence of it?

Image of very fast object burning in the atmosphere. It is not any kind of electrical discharge – too straight for that. It is not reflection of light from an insect flying close to camera lens, again too straight for that. Laser pointer beam, possible but unlikely that someone would streak beam across the sky just once and switch it on and off in 0.08 sec. Exposure time of this image is 0.08sec.

[Blue Skies (Jacquie)]

You've answered your question in your first paragraph - anything travelling faster than 72km/hr has come from outside our solar system. I learned, while watching a video on just this subject, that there was an estimate that 15% of meteors have an interstellar origin, detectable by their faster-than-solar-system-escape-velocity speeds. I had just assumed that all meteors were of our solar system origin until I watched this. Now it seems obvious - after all, where to all those comets go that get thrown out by passing too close to the sun, like comet McNaught? And recently there was speculation that a comet from another solar system had been detected (its chemical make-up was quite different to what most comets are). So there is some exchange over stellar distances.

[Karls48 (Karl)]

Well, that raises interesting question – how well are we prepared for possible impact (however unlikely) of inter- stellar rock travelling at very high speed. It also raises the question if some of the past impacts were of massive body of Solar System origin or much less massive and faster meteors of inter-stellar origin. Because such meteor are travelling at high (unknown) speed the outer planets would provide much less protection against the Earth impact then they provide for bodies of Solar System origin

[Karls48 (Karl)]

There are few geologists on this forum. Question – can you distinguish impact crater from lets say, of body of 100000 tons travelling at 50km/sec from crater caused by body of 10000tons travelling at 500km/sec?

[citivolus (Ric)]

Above a certain point the impact with the atmosphere itself will likely destroy the object, such as with Tunguska.

There is a paper from 1991 on the subject here, unfortunately you would need to purchase it.

Here is another one from 1996, this one is free. Basically it concludes that anything moving over 28km/second will be vaporised in the impact with the atmosphere. It also goes into the likelihood of larger interstellar objects.

An interesting subject

Edit: High geocentric velocity meteor ablation from 2005
Edit 2: Meteoroids from outside the solar system (Click "Free fulltext article")

[Karls48 (Karl)]

Thank for the link. That clears few things up for me. I had thought that inter-stellar meteor could have a much greater velocity then indicated in the research paper.Currently I can detect meteors up to about 4 magnitude and that is not suficient to record inter-stelar dust.

[renormalised (Carl)]

Originally Posted by Karls48

There are few geologists on this forum. Question – can you distinguish impact crater from lets say, of body of 100000 tons travelling at 50km/sec from crater caused by body of 10000tons travelling at 500km/sec?

Yes, you can. For a start, that last body has 10x the KE of the first, even though the first one is much larger. So, upon impact with the ground, more KE will be transfered into the ground, hence it should, given the initial KE, create a larger crater even though it's a smaller object. If, however, they were traveling at the same velocity, the larger body would produce the larger crater.

A 10000 ton chunk of rock isn't very large...on the order of about 20 metres across. At 500kms, it would most likely shatter the moment it got too deep into the atmosphere and then flash vapourise in a large airburst. The larger body may even do so, depending on its composition and the strength of its internal structure. Actually, the same goes for all meteorites/asteroids. It's not only the speed of collision and what they're made of that's important. Their internal structures are also important.

Normally, for most impactors, there is a size relation between how big the impactor is and the size of the initial crater they leave. It's usually on the order of 10 to 20 times the size of the impactor. So, an impactor the size of the one that left the Chicxulub Crater (6 miles or 10km) will leave an initial crater around 100-110km across and about 15-25km deep. The crater floor rebounds after the impact, the crater walls collapse via faulting and the crater increases in size by about 50-100%, sometimes even larger. The Chicxulub Crater would've been about 200-250km across and about 3-4km deep in the end. The outer rings of faulting and collapse may have even extended out to 400km depending on what happened to the rocks in the vicinity of the impact, after the shockwaves and rebounding of the crust occurred.

Here's something for you to read...and think about just how massive an impact it was... http://en.wikipedia.org/wiki/Chicxulub_crater