LAWRENCE, Kan. (AP) — Researchers at the University of Kansas had a hand in uncovering what might have been about a mile-wide iron asteroid that crashed into Greenland perhaps as recently as 12,000 years ago.
Details of the impact crater beneath the Hiawatha Glacier in remote northwest Greenland were recently published in Science Advances, a multidisciplinary journal.
The crater — the first of any size found under the Greenland ice sheet — is one of the 25 largest impact craters on Earth, measuring roughly 1,000 feet deep and more than 19 miles in diameter, an area slightly larger than that inside Washington's Capital Beltway, according to a NASA release.
John Paden, co-author of the report, is a courtesy associate professor of electrical engineering and computer science and a researcher at KU's Center for the Remote Sensing of Ice Sheets, or CReSIS.
While Paden said the asteroid impact wasn't as cataclysmic as the "dinosaur" asteroid that hit the Yucatan Peninsula some 66 million years ago (that one was 1,000 times more massive), it did leave a massive crater, which has been hidden under the ice.
Although the report on the impact crater was just published earlier this month, evidence for the crater began to surface in 2015, the Lawrence Journal-World reported.
Scientists had been collecting radar-sounding data in Greenland over several decades, Paden said. Meanwhile, glaciologists put the radar-sounding data sets together to produce maps of what Greenland is like under the ice. They began to see big, crater-like depressions, and because the site was on the edge of the ice sheet, they also saw a circular pattern, Paden said.
The researchers studying the radar data suspected that this was a crater, but they still needed more data to confirm it, according to the NASA release.
That's where CReSIS came in.
The center was tapped to build an ice-penetrating radar system that could accurately map the area. Paden himself helped develop the signal processing software for the radar system, which was dubbed the Multichannel Coherent Radar Depth Sounder, or MCoRDS.
Also involved in the project were Carl Leuschen, associate professor of electrical engineering and computer science and director of CReSIS; Rich Hale, chair of KU's department of aerospace engineering and associate director of CReSIS; and Fernando Rodriguez-Morales, professor of electrical engineering and computer science.
In May 2016, the KU team went to Greenland to scope out the area. Rodriguez-Morales and Paden went into the field and did surveys on the impact crater site.
"Just being a part of it was an amazing series of events," Paden said.
"The crater is located in a remote location in the very far north of Greenland," he said. "We almost couldn't go because of weather; we waited two weeks."
The fog was very bad for most of the time they were in Greenland, which meant they couldn't do any flying. However, the weather improved toward the tail end of the trip, and they finally got clearance to operate out of Thule Air Base. They were able to do three days of flights.
"That was the exciting part of the trip," Paden said. "I didn't think we would get data."
The crater was buried under ice, and it was hard to see from the airplane. However, as the plane went over the rim where the ice bottom drops out once over the crater, they were able to see it.
"There was a conspicuous edge on the ice sheet — it was very unusual, almost a perfect semicircle," Paden said. "Once NASA scientist Joe MacGregor pointed it out to me, it seemed obvious that it was a crater, and the detailed survey verified that."
MacGregor co-led the research project with Danish scientist Kurt Kjaer.
"We were able to put to rest (that) it definitely had an impact-crater shape," Paden said. "The imagery was so clear; there was nothing like that we have seen."
In the NASA release, Kjaer noted that the "crater is exceptionally well-preserved, and that is surprising because glacier ice is an incredibly efficient erosive agent that would have quickly removed traces of the impact."
Kjaer said that the crater's condition indicates the impact might even have occurred toward the end of the last ice age, which would place the resulting crater among the youngest on the planet.
Earlier studies have shown large impacts can profoundly affect Earth's climate, with major consequences for life on Earth at the time. The international research team plans to continue its work in this area, addressing remaining questions on when and how the meteorite impact at Hiawatha Glacier affected the planet.