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Scientists are now claiming they have found a second crater buried under Greenland’s icecap.
To confirm his suspicion about the possible presence of a second impact crater, MacGregor studied the raw radar images that are used to map the topography of the bedrock beneath the ice, including those collected by NASA’s Operation IceBridge. What he saw under the ice were several distinctive features of a complex impact crater: a flat, bowl-shaped depression in the bedrock that was surrounded by an elevated rim and centrally located peaks, which form when the crater floor equilibrates post-impact. Though the structure isn’t as clearly circular as the Hiawatha crater, MacGregor estimated the second crater’s diameter at 22.7 miles. Measurements from Operation IceBridge also revealed a negative gravity anomaly over the area, which is characteristic of impact craters.
“The only other circular structure that might approach this size would be a collapsed volcanic caldera,” MacGregor said. “But the areas of known volcanic activity in Greenland are several hundred miles away. Also, a volcano should have a clear positive magnetic anomaly, and we don’t see that at all.”
It must be emphasized that this conclusion remains very uncertain. What they have found is a depression that has features indicative of an impact crater, data that is far from sufficient to definitively prove the crater is real.