The international team of scientists, including the NASA glaciologist, discovered a large crater of a meteorite that was hidden under more than half a mile of ice in northwest Greenland.
The crater – the first of any size, located under the Greenland glacier – is one of the 25 largest craters on Earth measuring about 1,000 feet deep and more than 19 miles in diameter.
The group, led by researchers from the Copenhagen Center for Geogenetics at the Danish Museum of Natural History, has worked over the past three years to test their discovery, which they initially made in 2015 using NASA data. Their findings are published in the November 14 issue of Science Advances.
"NASA makes available data that it collects freely to scientists and the public around the world," says Joe MacGregor, a NASA glaciologist at Goddard Space Airport, which has begun investigating early stages. "It set a stage for our Danish colleague" Eureka. ""
Researchers first noted the crater in July 2015, while exploring a new topography map under the Greenland glacier that used ice-radar data primarily from Operation NASA Operation IceBridge – a multi-year air mission to monitor polar ice change – and former NASA aerial missions in Greenland. The scientists noticed a huge, unexplored, circular depression under the Hiawatha glacier, sitting at the very edge of the glacier in northwest Greenland.
Using satellite imagery from the NASA Terra and Aqua MacGregor Spectroradiometer, NASA Terra also examined the surface of the ice in the Hiawath glacier, and quickly found evidence of a circular pattern on the ice surface that corresponded to the condition observed in the bed topographic map.
To confirm their suspicion, in May 2016, the team sent a research aircraft from the German Institute of Alfred Wegener to fly over the Hiawatha glacier and mapped the crater and protruding ice to the state-of-the-art radar penetrating ice provided by the University of Kansas. MacGregor, an expert on radar ice measurement, helped design an aerial survey.
"The previous radar measurement of the Hiawath glacier has been part of NASA's long-term effort to map the change in Greenland's glacier coverage," says MacGregor. "What we really needed to test our hypothesis was dense and focused radar surveys." The survey surpassed all expectations and saw depression with stunning details: a distinctly circular edge, central stroke, disturbing and undisturbed layering of ice and basal debris – that's all . "
The crater formed less than 3 million years ago, according to a study, when an iron meteorite, more than half a mile wide, broke north-west Greenland. The resulting depression was subsequently covered with ice.
"The crater is exceptionally well preserved, and it is surprising, because ice ice is an incredibly effective erosive means to quickly remove traces of impact," says Kurt Kjær, professor of the Center for Geogenetics at the Museum of Natural History in Denmark and lead author of the study.
Kjær says the state of the crater suggests that the impact could even occur until the end of the last ice age, when the crater could be among the youngest on the planet.
In the years 2016 and 2017, the research team returned to the Hiawath glacier to map the tectonic structures in the rock near the glacier and collected samples of sediment washed out of the meltwater through depression.
"Some of the silica cracked sand had planar deformation elements that testify to a violent collision, a convincing evidence that depression under the Hiawatha glacier is a meteorite crater," says Professor Nicholas Larsen of Aarhus University in Denmark, one of the authors of the study.
Earlier studies have shown that major impacts can deeply affect the Earth's climate, with a major impact on Earth's life at the time. Scientists plan to continue working in this area and address the remaining questions about when and how the meteorite influence on the Hiawatha glacier affected the planet.
Recommended image: The Hiawatha impact crater is covered by Greenland's ice sheet, which flows just behind the crater's rims and forms a semicircular edge. Part of this edge (top of the photograph) and the tongue of the ice that violates the edge of the crater are listed in this photo taken during the NASA Operation IceBridge flight on April 17th.
Credits: NASA / John Sonntag