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They found a possible crater that could be about 250 million years old. The Permian extinction happened that long ago and killed off an estimated 70% of land species and 90% of marine species. The crater is under the ice in Wilkies Land in eastern Antarctica. It was found with gravity mapping and radar. Gravity mapping works by measuring how variations in local gravitional fields made by different densities of materials affect satellites.
The feature is 300 miles across, over twice the size of the Chicxulub crater. It is estimated that meteors that could create craters that big would be 30 km across. The one that created the Chicxulub crater was estimated to be 6 miles across. The feature has a circular ridge with a more dense mass in the center, much like some impact basins on the Moon. Those form when the more dense mantle bounces back after an impact and the material gets held in place by the crust. The crater can be as young as 250 million years old because the more dense material haven't yet been eroded away.
They hope to go out there to get any rocks that may have been affected by the impact to better determine the feature's age and to look for the signs of an impact event such as the little cracks in shocked quartz and various sorts of materials that only impacts have enough energy to create on Earth.
It is in the area where Antarctica and Australia separated. Maybe the big impact helped to create the rift that ended up separating Antarctica, Australia and I guess, India too, since that was joined near there too.
It's interesting that the feature was antipodal, or across the Earth from, Siberia a quarter billion years ago when the Permian extinction happened. It was known that there was massive volcanic eruptions in Siberia at that time. So, it looks like it's possible that the impact, the volcanic eruptions plus the stress from the formation of the supercontinent of Pangea, caused the Permian extinction. It's stressful when a supercontinent forms because plenty of shallow water habits disappear between the continents when they come together and the interior of the supercontient becomes a vast desert. Having a huge impact that spawns massive volcanic activity won't be too nice when you're stressed like that.
Here's a map of the Earth during the late Permian. It can be seen that Siberia and Antarctica were on opposite sides of Earth.
There are other examples of antipodal effects. The Chicxulub crater was on the other side of Earth from India at the end of the Mesozoic. There were massive volcanic eruptions at that time too in India. Here's a map of Earth at that time.
On Mercury, there is a very rough area on the opposite side of the planet from the 1300 km across Caloris impact basin. Only part of it is visible in the pictures because part of it was on the night side. Look for the concentral circles on the left.
On Mars, the 2100 km across Hellas impact basin is on the opposite side of the planet from the Tharsis highlands where there are several huge volcanos, including the 27 km high Olympus Mons, the highest mountain in the solar system. The Argyre basin is across from Elysium Planitia, which has some more volcanos.
Here's a topographic map of Mars. The Tharsis highlands is the large red and white area on the left. Hellas basin is the dark purple area on the lower right. Argyre basin is the light blue circle on the lower left. Elysium Planitia is the area with the smaller volcanos on the upper right.
I also find this interesting because I studied Mare Humorum for an astronomy project at RIT and it has the same sort of overdensity of the material that shows up in gravity maps of the Moon.
The Times
Ohio State Research News
BBC
Space.com
The Age
They found a possible crater that could be about 250 million years old. The Permian extinction happened that long ago and killed off an estimated 70% of land species and 90% of marine species. The crater is under the ice in Wilkies Land in eastern Antarctica. It was found with gravity mapping and radar. Gravity mapping works by measuring how variations in local gravitional fields made by different densities of materials affect satellites.
The feature is 300 miles across, over twice the size of the Chicxulub crater. It is estimated that meteors that could create craters that big would be 30 km across. The one that created the Chicxulub crater was estimated to be 6 miles across. The feature has a circular ridge with a more dense mass in the center, much like some impact basins on the Moon. Those form when the more dense mantle bounces back after an impact and the material gets held in place by the crust. The crater can be as young as 250 million years old because the more dense material haven't yet been eroded away.
They hope to go out there to get any rocks that may have been affected by the impact to better determine the feature's age and to look for the signs of an impact event such as the little cracks in shocked quartz and various sorts of materials that only impacts have enough energy to create on Earth.
It is in the area where Antarctica and Australia separated. Maybe the big impact helped to create the rift that ended up separating Antarctica, Australia and I guess, India too, since that was joined near there too.
It's interesting that the feature was antipodal, or across the Earth from, Siberia a quarter billion years ago when the Permian extinction happened. It was known that there was massive volcanic eruptions in Siberia at that time. So, it looks like it's possible that the impact, the volcanic eruptions plus the stress from the formation of the supercontinent of Pangea, caused the Permian extinction. It's stressful when a supercontinent forms because plenty of shallow water habits disappear between the continents when they come together and the interior of the supercontient becomes a vast desert. Having a huge impact that spawns massive volcanic activity won't be too nice when you're stressed like that.
Here's a map of the Earth during the late Permian. It can be seen that Siberia and Antarctica were on opposite sides of Earth.
There are other examples of antipodal effects. The Chicxulub crater was on the other side of Earth from India at the end of the Mesozoic. There were massive volcanic eruptions at that time too in India. Here's a map of Earth at that time.
On Mercury, there is a very rough area on the opposite side of the planet from the 1300 km across Caloris impact basin. Only part of it is visible in the pictures because part of it was on the night side. Look for the concentral circles on the left.
On Mars, the 2100 km across Hellas impact basin is on the opposite side of the planet from the Tharsis highlands where there are several huge volcanos, including the 27 km high Olympus Mons, the highest mountain in the solar system. The Argyre basin is across from Elysium Planitia, which has some more volcanos.
Here's a topographic map of Mars. The Tharsis highlands is the large red and white area on the left. Hellas basin is the dark purple area on the lower right. Argyre basin is the light blue circle on the lower left. Elysium Planitia is the area with the smaller volcanos on the upper right.
I also find this interesting because I studied Mare Humorum for an astronomy project at RIT and it has the same sort of overdensity of the material that shows up in gravity maps of the Moon.
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