Traces of an ancient meteorite impact in Greenland

A small rock proves that a meteorite struck Greenland about a billion years ago. The traces of the crater are among the oldest found on Earth.

Today there are around 200 confirmed craters left by meteorites that have crashed into the Earth. Eight of them are in Sweden and twelve in Finland. This means that ten percent of all known impact craters in the world. One reason may be that the bedrock is relatively old and well preserved in the two countries.

Now an international team of researchers has found a piece of rock that is a trace of a crater after a meteorite impact in Greenland. It’s an unusual find because almost 80 percent of the island is covered in ice.

The stone was discovered along the edge of the ice sheet in the Inglefield Land region of northwestern Greenland.

– The small stone stood out among all the other stones and boulders that cover the mostly flat landscape. It is a molten rock formed by the enormous temperatures and pressures that arise during a meteorite impact. It can compare with those found inside the earth’s core, says geologist Gavin Kenny at the National Museum of Natural History.

Scientists have found traces in the form of a small stone, which can be seen in the inset image. The piece of rock from an impact crater was discovered on the ice sheet in Greenland. Image: William Hyde/Pierre Beck.

The sample was collected in Greenland in 2019. When the rock was analyzed using modern electron imaging techniques, the researchers were able to confirm that it was formed in an impact crater.

A billion years old

Laboratory investigations showed that the impact occurred approximately one billion years ago. Back then the earth looked very different compared to today. Most of the Earth’s land mass was gathered in the supercontinent Rodinia.

– We looked for zircon grains in the sample, as these uranium-bearing minerals can provide precise radiometric ages. Zircon is usually used to determine the time of geological events, but during a meteorite impact, the enormous pressures and temperatures can cause zircon grains to “reset” and record the exact time of an impact, says researcher William Hyde, now a researcher at Lund University.

Unclear where the crater is

There is much evidence that the rock sample comes from a meteorite crater inland, hidden under ice sheets. But the small stone could possibly originate from another crater, which researchers previously found traces of, in northwestern Greenland.

According to the researchers, the current finding is both surprising and exciting.

– The study shows that it is possible to discover new impact craters by looking for loose material on the ground. This is especially needed in inaccessible places on Earth, such as the mostly ice-covered areas of Greenland and Antarctica, says William Hyde.