A binary asteroid is two asteroids that are orbiting each other, as well as orbiting the Sun.
The Clearwater lakes in Canada are a double crater, but geologist Martin Schmieder of the University of Western Australia, and colleagues, now believe that the craters were formed in two separate events.
The rock sample is heated to release both the argon-39 and argon-40, so that the two isotopes can be measured at the same time.
During an impact, rocks from the Earth’s crust can be uplifted to form a central peak, or ring, within the center of the crater.
In the West Lake, this is evident as a ring of islands in the middle of the lake.
The amount of argon-39 that it is released indicates how much potassium-40 was originally in the rock.
For the Clearwater dating study, this method was applied at the University of Heidelberg in Germany.
The study is important because lunar craters tell us a lot about our satellite, and others like it in the solar system, including its surface age.