Narrator: This is Science Today. To better
understand asteroids, scientists must have some idea
about their basic composition and structure. Mark
Hammergren, a planetary scientist at the Lawrence
Livermore National Laboratory, has recently discovered
that very elongated asteroids are weaker in centrifugal
force than circular ones. This finding supports a
theory that most asteroids are not solid chunks of
rock, as formerly thought - but rather loosely held
piles of rubble.
Hammergren: It's a theory that's growing in
popularity among asteroid researchers - that asteroids
could be rubble piles, that they might be held together
- not by material strength, but only by gravity.
Narrator: This can give researchers an idea
of how asteroids have changed since the formation
of the solar system over four and a half billion years
Hammergren: And also it helps us figure out
how we're going to deal with these things if one ever
happens to come towards the Earth because how you
deal with a solid object is different than how you
deal with a loosely-held pile of rubble.
Narrator: For Science Today, I'm Larissa Branin.