Today, an international team of scientists describes what they say is a huge new impact crater that lies under northwestern Greenland’s Hiawatha Glacier. If confirmed, it would be the first impact crater on Earth discovered under ice, the team reports in the journal Science Advances. At an estimated 19 miles wide, it is larger than Washington, D.C., and would rank among the top 25 known craters in the world.

“Until 2015, no one had paid much attention to this part of the planet,” says study coauthor Joseph MacGregor, a glaciologist with the NASA Goddard Space Flight Center in Maryland. But that year, scientists began flying over the area with highly sensitive scanning instruments, such as lasers and radar,