June 6, 2013
Ancient Comets Brought Organic Ingredients Needed For Life On Earth
April Flowers for redOrbit.com - Your Universe Online
When it came to jump-starting life, the early Earth was not a very hospitable place. New research from the Lawrence Livermore National Laboratory (LLNL) and the University of Ontario Institute of Technology (UOIT) reveals that life on Earth may indeed have come from outer space.
LLNL scientist Nir Goldman and UOIT´s Isaac Tamblyn — a former LLNL postdoctoral researcher — found that billions of years ago icy comets crashed into the Earth. These comets could have produced life-producing organic compounds, including the building blocks of proteins and nucleobase pairs of DNA and RNA.
Comets like these contain a variety of simple molecules, such as water, ammonia, methanol and carbon dioxide. An impact with a planetary surface would provide an abundant supply of energy to drive chemical reactions, the study found. The results of this study were published in The Journal of Physical Chemistry A.
"The flux of organic matter to Earth via comets and asteroids during periods of heavy bombardment may have been as high as 10 trillion kilograms per year, delivering up to several orders of magnitude greater mass of organics than what likely pre-existed on the planet," Goldman said.
Goldman´s previous research is based on computational intensive models that were only able to capture 10-30 picoseconds of a comet impact event. New simulations have been developed on LLNL´s supercomputers Rzcereal and Aztec using much more computationally efficient models. The new simulations were able to capture hundreds of picoseconds of the impacts — much closer to chemical equilibrium.
"As a result, we now observe a very different and a wider array of hydrocarbon chemical products that, upon impact, could have created organic material that eventually led to life," Goldman said.
Comets can range in size from just under a mile to approximately 35 miles. Though passing through Earth´s atmosphere heats the exterior of the comet, the interior remains cool. A shockwave is generated when the comet impacts with the planet´s surface due to the sudden compression. These shockwaves create sudden, intense pressures and temperatures, which could affect chemical reactions within a comet before it interacts with the ambient planetary environment. In the case of an oblique collision, where the comet strikes a glancing blow rather than head on, thermodynamic conditions conducive to organic synthesis could be generated. Both processes could result in significant concentrations of organic species being delivered to Earth.
Higher shock conditions — about 480,000 to 600,000 atmospheres of pressure and at 6,200 to 8,180 degrees Fahrenheit — can result in the synthesis of methane and formaldehyde, and may also cause some long-chain carbon molecules to form. These compounds are known by scientists to be precursors to amino acids and complex organic synthesis. At these conditions, all shock compression simulations have produced significant quantities of new, simple carbon-nitrogen bonded compounds upon expansion and cooling, which are known as prebiotic precursors.
"Cometary impacts could result in the synthesis of prebiotic molecules without the need for other 'special' conditions, such as the presence of catalysts, UV radiation, or special pre-existing conditions on a planet," Goldman said. "This data is critical in understanding the role of impact events in the formation of life-building compounds both on early Earth and on other planets and in guiding future experimentation in these areas."
Other recent studies have corroborated these results results. Researchers from the University of Washington and the University of South Florida reported yesterday that meteorite impacts brought the reactive phosphorus essential for the development of life on Earth.