Did comets spark life on Earth?

Billions of
years ago, comets may have ferried life-sustaining water to our planet's
surface, but that may not be all that we should thank these dirty snowballs for.
Researchers are simulating comet impacts to see if they might help proliferate
the left-handedness in molecules that life on Earth depends upon.There is
evidence from meteorite studies that amino acids may have been delivered
to Earth from space."There is interest in how these building blocks came to be on primordial Earth,"
says Jennifer Blank of the SETI Institute.She and her
colleagues study comets as a second avenue for depositing these biological compounds
on Earth. Their current work, which is supported by NASA's Exobiology and
Evolutionary Biology Program, is looking at how the fire
and brimstone of a comet impact may benefit the formation of complex
molecules of a particular handedness.