July 13, 2026 · Tags: geology, antarctica, impact-crater, mass-extinction, permian
There's a hole in Antarctica. Not in the ice — in the planet itself. A ring-shaped gravitational anomaly 500 kilometers wide, buried under nearly two kilometers of ice, that looks exactly like the footprint of an asteroid impact. And if the leading hypothesis is right, it may have caused the worst day in the history of life on Earth.
It's called the Wilkes Land Crater, and you can't visit it. You can't drill into it. You can't even see it on the surface. What you can do is measure it — from space, with satellites that map the Earth's gravitational field in extraordinary detail.
The discovery #
The Wilkes Land Gravity Anomaly was first reported in 1959–60 by ground-based seismic and gravity surveys in East Antarctica. Early estimates pegged its diameter at about 243 km — already massive. But when NASA's GRACE (Gravity Recovery and Climate Experiment) satellites scanned the region from orbit, the picture got a lot bigger.
The GRACE data revealed a circular structure roughly 500 kilometers across — nearly three times the size of the Chicxulub crater that killed the dinosaurs. At its center sits a positive free-air gravity anomaly (a "mascon" — mass concentration), ringed by a negative anomaly. This pattern — central high, surrounding low — is the geophysical signature of a giant impact basin. The Moon has them. Mars has them. And apparently, so does Earth, hidden under the East Antarctic Ice Sheet.
Recent high-resolution gravito-topographic modeling published in 2018 used data from both GRACE and ESA's GOCE satellite to confirm the structure. The researchers found that "the Wilkes Land anomaly is a candidate for the greatest impact crater or the only one impact basin known till now on the Earth." At over 500 km in diameter, it would be the largest confirmed impact structure on the planet.
Why can't we just dig down and check? #
Because there's 1.6 to 2+ kilometers of ice sitting on top of it, deposited over the past 30–40 million years. The ice sheet makes direct geological sampling — the gold standard for confirming an impact (shocked quartz, meteorite fragments, impact melt) — effectively impossible with current technology. Every piece of evidence we have comes from remote sensing: gravity, magnetics, and subglacial topography from ice-penetrating radar.
The subglacial topography itself shows a basin-shaped depression at least 1,500 meters deep, with disturbed ice streams above it and a chaotically disrupted region of the continental ice sheet — exactly what you'd expect if a giant crater were messing with ice flow from below.
When did it happen? #
Two clues bracket the age.
First, the gravity anomaly still exists. If the crater were older than about 500 million years, isostatic relaxation — the slow redistribution of mass in the Earth's crust and mantle — would have smoothed it out by now. The fact that we can still see it means it's relatively young, geologically speaking.
Second, a giant rift valley that separated Australia from Antarctica about 100 million years ago cuts directly through the crater. So the impact happened before the continents split, but after about 500 million years ago.
The leading hypothesis narrows this further: the impact may have occurred around 250 to 260 million years ago, at the end of the Permian period. Why that specific date? Because of what was happening on the exact opposite side of the planet.
The antipodal connection #
Here's where it gets wild.
Take the Wilkes Land crater at 70°S, 120°E. Draw a line straight through the center of the Earth. Rewind plate tectonics to 260 million years ago. Where does that line come out?
The Siberian Traps.
The Siberian Traps are one of the largest volcanic events in Earth's history — a flood basalt province that covered millions of square kilometers in lava. And their eruption, dated to approximately 251–252 million years ago, coincides almost exactly with the Permian-Triassic mass extinction: the "Great Dying" that killed roughly 96% of marine species and 70% of terrestrial vertebrates. It was the worst mass extinction in the fossil record, worse than the one that got the dinosaurs.
The mainstream explanation is that the Siberian Traps were caused by a mantle plume — a rising column of hot rock from deep in the Earth. But the antipodal relationship with the Wilkes Land crater, first proposed by Ralph von Frese and colleagues at Ohio State University in 2009, suggests an alternative: the impact itself triggered the volcanism.
This isn't just speculation pulled from nowhere. Antipodal volcanism is a well-established phenomenon on other planetary bodies. The Moon's Mare Orientale basin has disrupted terrain at its antipode. On Mars, the massive Tharsis volcanic province — home to Olympus Mons, the largest volcano in the solar system — sits antipodal to the Hellas impact basin. And not just Hellas: the Argyre and Isidis impact basins also have their antipodes within the Tharsis region. The probability of three giant impacts randomly having their antipodes in the same volcanic province is vanishingly small.
On Earth, a 2005 study by Jonathan Hagstrum found that roughly 49% of Earth's large igneous provinces and hot spots have antipodal relationships to each other — far more than chance would predict.
The proposed mechanism: seismic energy from a giant impact converges at the antipode, disrupting the crust and upper mantle. This creates a zone of weakness that can develop into a hot spot, eventually producing flood basalt volcanism on the opposite side of the world.
The controversy #
To be clear: this is not the consensus view. The mantle plume model for the Siberian Traps is well-supported, and the impact-trigger hypothesis remains a minority position. The 2009 von Frese paper itself acknowledges a ~15° misfit in the antipodal alignment, which may be due to poorly constrained Late Permian paleolongitudes, an oblique impact trajectory, or the impact energy exciting volcanism at pre-existing crustal weaknesses rather than at the exact antipode.
The 2018 follow-up study was careful to state that "the exact geophysical interpretation of the continental dynamical process remains speculative" and that "gravity data alone... cannot provide the complete constraint to unravel the geophysical interpretation."
What's not controversial is the anomaly itself. The Wilkes Land structure is real. It's massive. It has the gravity signature of an impact basin. It sits antipodal to one of the largest volcanic events in Earth's history. And it falls within the time window of the worst mass extinction the planet has ever seen.
Whether those dots connect through an impact-triggered volcanic cascade — or whether they're a coincidence of plate tectonics and timing — is one of the more fascinating open questions in planetary geology. The only way to know for sure would be to drill through two kilometers of Antarctic ice and bring back a sample.
Until then, the largest crater on Earth sits silently under the ice, waiting.
Sources #
- von Frese, R. R. B., et al. (2009). "GRACE gravity evidence for an impact basin in Wilkes Land, Antarctica." Geochemistry, Geophysics, Geosystems, 10(2). doi:10.1029/2008GC002149
- Klokočník, J., et al. (2018). "On the detection of the Wilkes Land impact crater." Earth, Planets and Space, 70:135. doi:10.1186/s40623-018-0904-7
- Weihaupt, J. G. (1976). "The Wilkes Land Anomaly: Evidence for a possible hypervelocity impact crater." Journal of Geophysical Research, 81(32):5651–5663. doi:10.1029/JB081i032p05651
- Weihaupt, J. G., et al. (2015). "The Wilkes Land Anomaly revisited." Antarctic Science. doi:10.1017/S0954102014000789
- Hagstrum, J. T. (2005). "Antipodal hotspots and bipolar catastrophes: Were oceanic large-body impacts the cause?" Earth and Planetary Science Letters, 236(1–2):13–27. doi:10.1016/j.epsl.2005.02.020
- Burgess, S. D., et al. (2017). "Initial pulse of Siberian Traps sills as the trigger of the end-Permian mass extinction." Nature Communications, 8:164. doi:10.1038/s41467-017-00083-9