Mistastin (Kamestastin)

Key facts

Country

Canada

Diameter

28 km

Age

about 36 million years

Location

55.88° N, 63.30° W

Mistastin Lake, known to the Innu as Kamestastin, lies in the tundra and forest of northern Labrador, in eastern Canada. It fills the eroded remains of an impact crater about 28 km across, and it has become one of the most important places on Earth for understanding the Moon.

The impact. About 36 million years ago, an asteroid struck the region, forming a crater about 28 km wide. Erosion, including the work of ice-age glaciers, has removed much of the crater, and the lake now fills the central part. Horseshoe Island, near the centre of the lake, is the remains of the crater's central uplift.

A Moon on Earth. What makes Mistastin special is the rock it struck. Much of the target was anorthosite, a rock made mostly of the mineral plagioclase feldspar. Anorthosite is rare on Earth but makes up much of the bright highlands of the Moon. That means the impact rocks at Mistastin are similar to the rocks in lunar highland craters. Scientists, including NASA researchers, study Mistastin to understand how lunar rocks were changed by impacts, and astronauts and engineers have used it as a training and testing site.

Melt rock cliffs. The impact melted large volumes of rock, which cooled to form impact melt rock. Along the lake shore, at a place called Discovery Hill, cliffs of melt rock about 80 m high are exposed. These cliffs are among the best exposures of impact melt anywhere on Earth, and they allow scientists to study how melt sheets form and cool.

Record temperatures. In 2017 scientists studying zircon crystals in the impact melt reported evidence that the rock had been heated to at least 2,370 °C. At that temperature zircon breaks down, and tiny grains of new minerals formed in their place. This is one of the highest temperatures recorded in rocks from the Earth's crust, showing how much energy an impact can release.

The Innu. The lake and the surrounding land are part of the traditional territory of the Innu, who have hunted caribou and fished in the area for thousands of years. Archaeologists have found evidence of long human use of the area. Research at Kamestastin is carried out in partnership with Innu communities.

Visiting. Mistastin is remote and reached by floatplane. A small number of research teams and visitors go there each summer. The area is culturally important to the Innu, so visits should be arranged with respect for their rights and traditions.

Why it matters. Mistastin's anorthosite target makes it one of the best Earth analogues for lunar craters, helping scientists interpret samples brought back from the Moon and plan future missions.

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