The density of the asteroid Itokawa isn't the same all over. The peanut-shaped space rock is more compact on one side than on the other.
The idea that an asteroid's density could vary has been around for decades, but now telescope observations of Itokawa confirm it. Its interior varies from 2,850 kilograms per cubic meter on its smaller side to 1,750 kilograms per cubic meter on its round edge, astronomers report in the February Astronomy & Astrophysics.
The observations will help astronomers better understand how objects collide in the solar system, how planets form and possibly how to visit and land on asteroids in the future.