Geologic map of the asteroid belt. Circles identify the asteroid families from which our ... Astronomers can measure how long ago these rocks were dug up from below the asteroid’s surface by measuring ...

"We now have the first outlines of a geologic map of the asteroid belt ... how long ago these rocks were dug up from below the asteroid's surface by measuring the level of radioactive elements ...

"We now have the first outlines of a geologic map of the asteroid belt ... how long ago these rocks were dug up from below ...

"We now have the first outlines of a geologic map of the asteroid belt." Ten years ago ... Astronomers can measure how long ago these rocks were dug up from below the asteroid's surface by measuring ...