NASA discovers a massive crater under the ice of Greenland

Two views of the Hiawatha crater region: one covered by the Greenland Ice Cap, the other showing the topography of the rock beneath the ice cap, including the crater. Credits: NASA / Cindy Starr

An international team of researchers, including a NASA glaciologist, has discovered a large meteorite impact crater concealed under more than half a kilometer of ice in northwestern Greenland. The crater – the first of any size under Greenland's icecap – is one of the 25 largest impact craters on Earth. It is approximately 1,000 feet deep and more than 30 kilometers in diameter, slightly larger than Washington's Capital Beltway.

The group, led by researchers from the Center for GeoGenetics at the University of Copenhagen in the Natural History Museum of Denmark, has been working for the last three years to verify their discovery, which they made in 2015 using NASA data. Their discovery is published in the Nov. 14 issue of Science Advances.

An international team of scientists met to unravel the mystery of the Hiawatha crater in Greenland. This video shows how this discovery is made. Credits: NASA / Jefferson Beck

"NASA is making the collected data available to scientists and the public free of charge," said Joe MacGregor, a NASA glaciologist at the Goddard Space Flight Center in the Greenbelt of Maryland, who was involved in the investigation in its early days. . "This paved the way for the moment" Eureka "of our Danish colleagues."

The researchers first discovered the crater in July 2015, while inspecting a new map of the topography beneath the Greenland ice cap, which used radar data penetrating the ice mainly from the ice. NASA's IceBridge operation – a multi-year airborne mission to track changes in polar ice – and NASA's previous airborne missions to Greenland. Scientists have noticed a huge circular depression previously unexamined under the Hiawatha Glacier, located at the edge of the ice cap in northwestern Greenland.

Using satellite images of the medium-resolution imaging spectroradiometer on NASA's Terra and Aqua satellites, MacGregor also examined the ice surface in the Hiawatha Glacier region and quickly found the trace of a circular pattern on the surface of the ice that corresponds to that observed in the topographic map bed.

To confirm their suspicions, the team sent in May 2016 a research aircraft from the German Alfred Wegener Institute to fly over the Hiawatha Glacier and map the crater and ice above with an ice-penetrating radar. ultramodern provided by the University. from Kansas. MacGregor, expert in ice radar measurements, participated in the design of the airborne survey.

Radar data from an intensive aerial survey of the Hiawatha crater in May 2016 are presented here as aqua-colored curtains. A blue arrow points to the central summit of the crater. Credits: NASA / Cindy Starr

"Previous radar measurements from the Hiawatha Glacier were part of NASA's long-term effort to map the evolution of Greenland's ice cover," MacGregor said. "What we really needed to test our hypothesis was a dense and focused radar survey. The survey surpbaded all expectations and allowed the depression to be imagined with a breathtaking level of detail: distinctly circular edge, central uplift, disturbed and undisturbed layer of ice, and basal debris – everything is there. "

According to the study, the crater was formed less than 3 million years ago, when an iron meteorite of more than one kilometer wide s & rsquo; is crushed in northwestern Greenland. The resulting depression was then covered with ice.

"The crater is exceptionally well preserved, which is surprising because glacier ice is an incredibly effective erosive agent that would have quickly eliminated traces of impact," said Kurt Kjær, professor at the Geogenetics Center at Natural History. Museum of Denmark. and lead author of the study.

Kjær said the state of the crater indicated that the impact may have occurred near the end of the last ice age, which would place the crater among the youngest on the planet.

In the summer of 2016 and 2017, the research team returned to the Hiawatha Glacier to map tectonic structures in the rock at the foot of the glacier and collect sediment samples removed from the depression through a meltwater channel. .

"Part of the quartz sand from the crater had flat deformation characteristics indicating a violent impact. it's conclusive evidence that depression under the Hiawatha Glacier is a meteor crater, "said Associate Professor Nicolaj Larsen of the Aarhus University in Denmark, one of the authors of the study.

Previous studies have shown that significant impacts can profoundly affect the Earth's climate, with major consequences for life on Earth at this time. The researchers plan to continue their work in this area, wondering when and how the impact of meteorites on the Hiawatha glacier affected the planet.

Publication: Kurt H. Kjær, et al., "A Large Impact Crater Under the Hiawatha Glacier in Northwestern Greenland," Science Advances, November 14, 2018, vol. 4, no. 11, eaar8173; DOI: 10.1126 / sciadv.aar8173