"When the scientists overlaid their gravity image with airborne radar images of the ground beneath the ice, they found the mascon perfectly centered inside a circular ridge some 300 miles wide -- a crater easily large enough to hold the state of Ohio.
...
He and Potts would like to go to Antarctica to confirm the finding. The best evidence would come from the rocks within the crater. Since the cost of drilling through more than a mile of ice to reach these rocks directly is prohibitive, they want to hunt for them at the base of the ice along the coast where the ice streams are pushing scoured rock into the sea. Airborne gravity and magnetic surveys would also be very useful for testing their interpretation of the satellite data, they said."
http://www.freerepublic.com/focus/f-news/1641966/posts

If you search "Permian-Triassic extinction + impactor" you will find other candidates. But this one sound like a pretty good candidate. In biological history Permian-Triassic is the famous big extinction event, where practically everything thing dies, unlike the more limited extinction which killed the dinosaurs. Once it was accepted that impactor have hit earth recently- the 65 million year ago impact- then it became somewhat obvious that eariler extinctions events were probably caused by impactors- it just became a matter of finding the impact crater. It's possible that this isn't the Permian-Triassic extinction crater, but it's at least probably evidence of impactor. With 70% of the planet covered with ocean you might think that the chances favor finding this type of crater on the ocean floor- but perhaps if one has an impactor which is 30 miles in diameter slamming into a ocean area it's affect is such that a once ocean area becomes transformed into a land area.