March 28, 2012
New Evidence Suggests Comets Carried Life To Earth
New evidence has come up that supports the idea that comets bombarding Earth billions of years ago carried and deposited the key ingredients for life.
Scientists reported at the 243rd National Meeting & Exposition of the American Chemical Society (ACS) that the research is part of a broader scientific effort to understand how amino acids and other ingredients for the first living things appeared on Earth billions of years ago.
"Our research shows that the building blocks of life could, indeed, have remained intact despite the tremendous shock wave and other violent conditions in a comet impact," Jennifer G. Blank, Ph.D., who led the research team, said in a statement.
Comets are chunks of frozen gases, water, ice dust and rock that astronomers consider a "dirty snowball." They orbit the Sun in a belt located far beyond the most distant planets in the solar system, but periodically break loose and hurtle inward.
"Comets really would have been the ideal packages for delivering ingredients for the chemical evolution thought to have resulted in life. We like the comet delivery scenario because it includes all of the ingredients for life – amino acids, water and energy," Blank said.
Evidence suggests that life on Earth started at the end of a period 3.8 billion years ago, which was known as the "late heavy bombardment" that involved comets and asteroids. Before this event, Earth was considered to be too hot for living things to survive.
The team set out to determine whether amino acids could remain intact after a comet's descent through Earth's atmosphere.
They used gas guns to simulate the temperatures and powerful shock waves that amino acids in comets would experience when entering the planet's atmosphere.
The gas guns hit objects with high-pressure blasts of gas moving at supersonic speeds, shooting the gas at capsules filled with amino acids, water and other materials. The amino acids began linking together with proteins, forming "peptide bonds."
The scientists said the pressure from the impact of the crash offset the intense heat and also supplied the energy needed to create the peptides.
Blank suggested that there may have been multiple deliveries of seedlings of life through the years from comets, asteroids and meteorites.