The Why Files The Why Files --

Comets: the universal recipe?

Love those leftovers
Reach deep into your fridge. Past the green cottage cheese and the bunch of blackened radishes. Yes, grab that formless lump inside the crinkly tin foil! What exactly is it? Half Ma's meatloaf and half seventh-grade science experiment, those are leftovers -- the bites and bits that didn't rate as Dinner, but might pass as Tomorrow's Lunch.

Leftovers. Everybody got 'em. But what to do with 'em? NASA says whack them hard and watch what happens next. That's the mission of Deep Impact, which just sent a daughter spacecraft into impact-oblivion against comet Tempel 1.

Rock-like formation floats through space. Close-up view of comet's surface.

Above left: Serene and unaware of its impending migraine, Tempel 1 speeds through space, about 5 minutes before Deep Impact's... July 4 impact. All images on this page from NASA/JPL-Caltech/UMD

Above right: 30 seconds to impact, in an image from the impactor's targeting sensor. Tempel 1 never saw it coming.

Below: Moments after Deep Impact's probe smashed Tempel 1, the crash site was bathed in light. Will Tempel 1 ever recover?

Seen from a distance, a bright light at impact.

In an analogy we will reheat and reuse ad nauseum, comets are the leftovers of the cosmos, the tin-foil-wrapped crud from the back shelves of the solar system.

In peeling back the tin foil from a common comet, Deep Impact is part of an effort to answer common comet questions:

Tempel 1 is clearly not the only comet in space. What have we learned from three other close encounters with cosmic leftovers?