PDA

View Full Version : Huge Asteroid Crater in Antarctica



Fraser
2006-Jun-06, 07:34 PM
SUMMARY: The asteroid impact that killed the dinosaurs 65 million years ago was big, but geologists have found a new asteroid crater that's even bigger: in Antarctica. This 482 km (300 mile) crater was discovered using NASA's GRACE satellites, which can detect the gravity fluctuations beneath Antarctica's ice sheets. This meteor was probably 48 km (30 miles) across and might have struck 250 million years ago - the time of the Permian-Triassic extinction, when almost all the animals on Earth died out.

View full article (http://www.universetoday.com/am/publish/bang_asteroid_hit.html)
What do you think about this story? post your comments below.

antoniseb
2006-Jun-06, 07:41 PM
Hudson & James Bays look like giant craters as well, but they are probably from well before the relatively recent 250 million years ago crater in Antarctica.

nrbdo
2006-Jun-06, 08:13 PM
If this were a large impact then why have we not heard of the iridium layers and shocked quartz that should go with it and that have been sought for around the globe in the effort to explain the permian extinction? It would be great if it could explain the event but I'll wait for the corraborating evidence to come in.

George
2006-Jun-07, 12:58 PM
Welcome to BAUT, nrbo. :clap:

Good point. What has been found during this era?

If it is verified, what a horrific event transpired. I trust no one will suggest Hell has frozen over? :)

Paul Verhage
2006-Jun-07, 02:20 PM
Does someone have a map of the earth during the PT event? Opposite of Yucatan is the Deccan Traps, a massive outpouring of basalt from fissures in India. The end of the Periman is marked with a larger outpouring in Siberia. I would be interested to know if the Siberian Traps are opposite of this possible impact site in Antartica.

George
2006-Jun-07, 02:47 PM
Welcome, Paul. :clap:

Perhaps this map of Pangea (http://www.scotese.com/newpage5.htm) will help.

Two years ago, NASA produced an article (http://nai.arc.nasa.gov/news_stories/news_detail.cfm?ID=286) showing evidence suggesting the Australian crater might be a cause for the PT event. Interestingly, evidence of meteoric fragments were found in Antarctica, and shocked quartz in Australia and Antarctica.

Apparently, no iridium anaomoly evidence has been found, at least as of the 2004 Nasa article. The 250 million year time frame seems to limit the existance of this layer, due to movement and erosion; albeit, some evidence of this boundary seems to exist in Pakistan and China, at least.

jhwegener
2006-Jun-07, 07:06 PM
Have scientists found any evidence of impacts on what is now deep ocean?
Most of earth are covered with water, so we should expect most impacts there. (Will the consequences be bigger or the opposite? But of course there may have been impacts all types of environments.
I guess the big objects made craters even on the bottom of oceans.

JonClarke
2006-Jun-07, 09:58 PM
It takes a lot more than a vaguely circular strucure and a gravity anomaly to demonstrate an impact. You need other geophtsial evidence - magnetic and seismic. Rocks would help too - shocked target rocks, crater fill, ejecta horizons. None of this has been tendered to date. This story is clutching at straws.

Jon

Svemir
2006-Jun-08, 06:55 AM
I recall reading somewhere that dino's didn't disappear over night, but over a period of several million years, which in my ears exclude the meteorit impact as a cause of their extinction.
Here it is presented as a fact. Is it?
And do we have now two major impact sites on the Earth on it's poles?

Ronald Brak
2006-Jun-08, 09:26 AM
Jhwegener, I'm afraid the ocean floor doesn't hang around as long as the continents. New ocean floor is always forming and old floor is always being subducted under continents so no ocean floor is supposed to be more than 200 million years old and most of it is much younger.

I do think it would be a little odd if we could tie every major extinction event to an impact crater on land.

Ronald Brak
2006-Jun-08, 09:34 AM
I recall reading somewhere that dino's didn't disappear over night, but over a period of several million years, which in my ears exclude the meteorit impact as a cause of their extinction.

The trouble is, we don't know. Accurate dating of fossils is not always possible, and dinosaur fossil sites are so rare that there are frequent gaps of millions of years for which we have no fossils.

So while it is possible that dinosaurs died out gradually, it could have been sudden. It is also possible that some dinosaurs survived the impact and hung around for a few million years or so years before something else extincted them.

Manybe someone else knows more on this?

Nerthus
2006-Jun-08, 07:42 PM
The trouble is, we don't know. Accurate dating of fossils is not always possible, and dinosaur fossil sites are so rare that there are frequent gaps of millions of years for which we have no fossils.

So while it is possible that dinosaurs died out gradually, it could have been sudden. It is also possible that some dinosaurs survived the impact and hung around for a few million years or so years before something else extincted them.

Manybe someone else knows more on this?

The dinosaurs didn't die out in millions of years but thousands. Everything didn't die out in the impact of course, but the intial impact wasn't the only thing about it that killed. Afterward Earth was an extremely hard place to live on, the impact created clouds of dust and ash that covered the planet changing global climates to extremes, some being in ice age conditions and others hot as hell. If you were a large animal (like a dinosaur) you couldn't survive because there just wasn't enough resources to sustain you and the impact changed life so drastically so quickly that no one had any time to evolve, so most died. Others died also because large animals usually rely on many many species for there own survival and some of those species must have gone extinct, became too rare, or migrated somewhere more suitable to theirselves. And through all this havoc diseases must have been very common as well. So if you didn't die in the impact, chances are you couldn't survive what it caused unless you were aquatic(like crocs and turtles) or small(like lizards, birds, and mammals).

And for this Antarctic impact, I was wondering myself why I had never heard of some large iridium layar in this era. Maybe there just wasn't enough iridium in the meteor and/or as someone said before, the layar is just too sparse across the planet today. It's very interesting though, the permian is one of my most favorite periods in Earth's history to study.

JESMKS
2006-Jun-08, 10:50 PM
Dinosaurs died out at the end of the Cretaceous Period, some 130 million years after the Permian Period. Probably from another meteor impact.
Jack

Nerthus
2006-Jun-08, 11:19 PM
Dinosaurs died out at the end of the Cretaceous Period, some 130 million years after the Permian Period. Probably from another meteor impact.
Jack

Its actually more like 185 million years between the end of the Permian and end of the Cretaceous.

Ronald Brak
2006-Jun-09, 03:28 AM
The dinosaurs didn't die out in millions of years but thousands.

That seems likely, but just from the fossil record as it currently stands we can't be sure. One could specualte that many species of dinosaur died soon after an impact, but some may have recovered and flourished for a million or more years until they were wiped out by something else. This might sound unlikely but we can't say it didn't happen because the fossil record is spotty and most dates have margins of error that cover large amounts of time.

Also if there is no irridium layer for this impact that is supposed to have happened 250 million years ago, could it have been caused by a big chunk of irridiumless ice?

katesisco
2006-Jun-12, 02:51 PM
Interesting............Remember the explanation for the genetic bottleneck of humans? That the Toba volcano in the Phillipines around 70,000 years ago may have caused a 4 year nuclear winter which dropped the human race in Africa (which had been previously dropped to near 50,000) and the entire race of current us is from the proberbial Eve and only as few as 150. Just think, all of us from everywhere belong to just one Eve and 150 people. I wondered if the Toba volcano could have caused a nuclear winter of 4 year duration, then why didn't we see evidence of this? Instead of drawing conclusions from the existing gelogic record, we have the genetic info. So why was the record not just shouting 'world wide cataclysm here!' Or is the record there just not being interpreted correctly, maybe the nuclear winter can be brought about by a lot less than we think should be there to indicate it.
Another question is if the crisis that reduced the African population previously to around 50,000, was the archaic humans (Neanders) population correspondingly dropped also? They must have had sufficient protection in their environment outside of Africa (more robust also) to prosper; some think they may have been responsible for keeping the remaining human population confined to the African continent. But when the Eve population of modern humans decamped into the rest of the world, they didn't have a chance.
All this has nothing to do with extinction based on meteorite impacts but the gelogic record is hard to interpret, for impacts from outer space and from our own planetary processes.

and I for one am skeptical that our seeming endless supply of ocean crust is on a one way conveyer belt of appearing and disappearing. I do not think it is inconcievable that all the ocean crust that was still is. That is a quote from Carey. What a strange concept permanent continent but roller coaster sea floor. Doesn't that sound goofy? Does anybody else see how odd this is?

katesisco
2006-Jun-12, 03:02 PM
Does someone have a map of the earth during the PT event? Opposite of Yucatan is the Deccan Traps, a massive outpouring of basalt from fissures in India. The end of the Periman is marked with a larger outpouring in Siberia. I would be interested to know if the Siberian Traps are opposite of this possible impact site in Antartica.
A previous news post has information you would like to read. It talks about volcanic gasses from the Deccan traps and the Siberian traps that could end life as if the impacts weren't enough.

http://www.universetoday.com/am/publish/earth_detox_extinction.html?932006

Blob
2006-Jun-12, 05:36 PM
Hum,
i have a google earth map that i have uploaded as an attachment..
(dated 240 million years ago)
Britain is near the centre of the world, Australia is that lump still attached to Antarctica bottom right... ;)

4cer
2006-Jun-23, 03:59 AM
250 million years ago, what is the latitude and longitude of the impact site? Within time-frame, need to know speed of Earth rotation, Earth axis to Solar Eliptic, and orientation of the Gondwana supercontinent.

The mass of the Earth was less than it is now, and the mantle thickness was thinner. The impact caused the mantle to fracture like an eggshell and initiated plate techtonics which we experience today. I expect the meteor to be more massive, mostly ice, with a near-surface explosion.

antoniseb
2006-Jun-23, 01:25 PM
Hi 4cer, welcome to the BAUT forum.

I'm curious to know what you mean by The mass of the Earth was less than it is now. I suspect that the Mass of the Earth might actually be the same or less now, given the continual loss of atmosphere.

GOURDHEAD
2006-Jun-23, 02:14 PM
What do we know about the balance between the accretion of mass by infalling dust, asteroids, and comets versus the loss of hydrogen from the upper atmosphere of Earth? How is this balance affected by the absorption of particles, mostly hydrogen, from the solar wind? If any planets are left in the solar system after the sun "goes out" some billions of years from now, will they continue to accrete mass until they "turn on"? How much mass will the sun have to lose in order for Jupiter or Saturn to wander off into their own separate orbits within the MW? How many times may this have already happened with respect to other stellar systems?

antoniseb
2006-Jun-23, 03:22 PM
What do we know about the balance between the accretion of mass by infalling dust, asteroids, and comets versus the loss of hydrogen from the upper atmosphere of Earth?

I don't thing we do know this balance. 4cer seemed to be implying that the balance was so much tipped toward accretion that the Earth was significantly more massive now than then. I was asking where he got the idea, and throwing in an opposing viewpoint, partly as devil's advocate to spur him to a quicker and more thorough response. Oops, my secret motive is out.