The [KT] layer is thought to be the fallout from the fireball.

328

The argument is silly.

199

We think comets make up a huge amount of stuff out in the solar system. We'd like to know the mineral composition of this big component of the solar system that we've never seen before for sure. Various particles have been measured that have been inferred to be from comets, but nobody's sure. This would finally provide some ground truth.

160

When you vaporize rock, there is very little hydrogen -- whereas 50 percent of the atoms in a rock are oxygen.

133

That vapor is very hot and expands outward from the point of impact, cooling and expanding as it goes. As it cools the vapor condenses as little droplets and rains out over the whole Earth.

123