A possible impact crater in Antarctica is back under scrutiny.
Beneath the ice of Wilkes Land, in the eastern part of the continent, NASA satellites have detected a ring-shaped gravitational anomaly measuring 310 miles in diameter. If it turns out to have been carved by a meteorite, it would be the largest impact structure ever identified on Earth.
What the Gravity Data Shows
The anomaly sits at coordinates 70°S, 120°E, in the north-central part of Wilkes Land, buried beneath roughly a mile of ice.
Satellite data reveal a positive gravity anomaly at the center of the structure, encircled by a ring of negative anomalies. Researchers compare the resulting pattern to a donut: a dense core surrounded by a depression.
That central core is thought to be a mascon — a mass concentration — formed when Earth’s mantle rebounds after the impact of a massive object, forcing dense material back up beneath the crater like a plug.
The structure is not perfectly circular.
A 2018 study described it as U-shaped, with its northern rim fragmented, possibly due to the tectonic forces that pulled Australia away from Antarctica.
How the Anomaly Was Detected
The first hint appeared in 1962, when Richard A. Schmidt, a geologist at the University of Wisconsin, first put forward the idea of a hidden crater based on seismic and gravimetric data collected in 1959 and 1960 during the American Victoria Land Traverse expedition.
At the time, the estimated diameter was roughly 150 miles.
The picture shifted in 2006, when the NASA GRACE satellite allowed scientists to map Antarctica’s gravitational field with far greater precision.
The new data revealed a structure nearly three times larger: approximately 310 miles across — roughly triple the size of the Chicxulub crater in Mexico.
A study published in 2018 in the journal Earth Planets Space used higher-resolution gravity-topographic models to confirm the circular pattern and detected possible traces of the same structure in southern Australia, a landmass that remained joined to Antarctica until roughly 35 million years ago.
The authors suggested that the anomaly-forming event occurred before the two continents separated.
Impact, Volcano, or Sedimentary Basin: The Competing Hypotheses
The meteorite impact explanation is the most widely accepted, but it is far from the only one.
A 2015 study published in Antarctic Science, using satellite remote-sensing techniques, laid out several alternative explanations.
Among them: a volcanic structure, a sedimentary basin, or a valley scoured by glaciers over millions of years.
That same study noted that the anomaly’s size is consistent with the large asteroids that bombarded Earth between 4.1 and 3.8 billion years ago, during the period known as the Late Heavy Bombardment.
The authors were careful to note, however, that the limits imposed by the region’s ice cover mean that every other hypothesis remains very much alive.
Why It Remains Unconfirmed
No one has yet drilled through the ice to extract direct samples from the bedrock beneath Wilkes Land.
All available evidence comes from indirect measurements: satellite gravimetry, ice-penetrating radar, and topographic modeling.
Without a physical sample confirming shocked minerals or impact glass — the standard indicators used to classify a crater — the meteorite hypothesis remains just one of several possible interpretations, even though it is the interpretation most strongly supported by the available gravity data.
The region’s extreme conditions and the cost of drilling to depths exceeding 4,900 feet help explain why, more than sixty years after the first hypothesis was proposed, Wilkes Land remains a crater that exists only on gravity maps.
