A large impact crater beneath Hiawatha Glacier in northwest Greenland

• Published in: Science Advances
• Main Authors: Kjær, Kurt, Larsen, Nicolaj, Binder, Tobias, Björk, Anders, Eisen, Olaf, Fahnestock, Mark, Funder, Svend, Garde, Adam, Haack, Henning, Helm, Veit, Houmark-Nielsen, Michael, Kjeldsen, Kristian, Khan, Shfaqat, Machguth, Horst, Mcdonald, Iain, Morlighem, Mathieu, Mouginot, Jérémie, Paden, John, Waight, Tod, Weikusat, Christian, Willerslev, Eske, Macgregor, Joseph
• Other Authors: Abteilung Klinische Sozialmedizin, Berufs- und Umweltdermatologie, Universität Heidelberg Heidelberg, Centre for Star and Planet Formation (STARPLAN), Globe Institute, Faculty of Health and Medical Sciences, University of Copenhagen = Københavns Universitet (UCPH)-University of Copenhagen = Københavns Universitet (UCPH)-Faculty of Health and Medical Sciences, University of Copenhagen = Københavns Universitet (UCPH)-University of Copenhagen = Københavns Universitet (UCPH), Jodrell Bank Centre for Astrophysics (JBCA), University of Manchester Manchester, Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 ), University of California Irvine (UC Irvine), University of California (UC), Center for Remote Sensing of Ice Sheets (CReSIS), University of Kansas Lawrence (KU), Section for GeoGenetics, Institute for Geophysics, University of Texas at Dallas Richardson (UT Dallas)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: [SDE]Environmental Sciences; [SDE.MCG]Environmental Sciences/Global Changes; Greenland; glacier; Ice Sheet
• Online Access: https://hal.archives-ouvertes.fr/hal-02392102; https://hal.archives-ouvertes.fr/hal-02392102/document; https://hal.archives-ouvertes.fr/hal-02392102/file/eaar8173.full.pdf; https://doi.org/10.1126/sciadv.aar8173

International audience We report the discovery of a large impact crater beneath Hiawatha Glacier in northwest Greenland. From airborne radar surveys, we identify a 31-kilometer-wide, circular bedrock depression beneath up to a kilometer of ice. This depression has an elevated rim that cross-cuts tributary subglacial channels and a subdued central uplift that appears to be actively eroding. From ground investigations of the deglaciated foreland, we identify overprinted structures within Precambrian bedrock along the ice margin that strike tangent to the subglacial rim. Glaciofluvial sediment from the largest river draining the crater contains shocked quartz and other impactrelated grains. Geochemical analysis of this sediment indicates that the impactor was a fractionated iron asteroid, which must have been more than a kilometer wide to produce the identified crater. Radiostratigraphy of the ice in the crater shows that the Holocene ice is continuous and conformable, but all deeper and older ice appears to be debris rich or heavily disturbed. The age of this impact crater is presently unknown, but from our geological and geophysical evidence, we conclude that it is unlikely to predate the Pleistocene inception of the Greenland Ice Sheet.