September 16, 2013
Was Life On Earth Jump-Started By Icy Comet Impact?
[ Watch the Video: Comets May Have Provided Earth The Building Blocks Of Life ]
Lawrence LeBlond for redOrbit.com - Your Universe Online
An international group of scientists has discovered that life on Earth may have been jump-started when icy comets bombarded the planet billions of years ago.
Scientists from University College London, the University of Kent and Lawrence Livermore National Laboratory have published a paper, appearing on the Nature Geosciences website on September 15. In this paper, the team describes how collisions between icy comets and rocky planets can jump start life.
First predicted in 2010 by LLNL chemist Nir Goldman, PhD, the evidence came to light after scientists shock compressed an icy mixture, which then created a number of amino acids -- the building blocks of life.
This icy mixture is very similar to the composition of comets, indicating that the icy cosmic travelers have the correct elements needed to bring life to otherwise vacant rocky worlds. In such the same manner, rocky meteorites can bring life to icy worlds.
Goldman first posited that impact by icy comets billions of years ago provided the right elements to allow a variety of prebiotic compounds, such as amino acids, to jump start life on planet Earth. Amino Acids are critical to life, and Goldman’s work predicted that simple molecules found in comets containing water, ammonia, methanol and carbon dioxide, among others, could have supplied the materials needed to jump-start life. Once an impact occurred, the abundant supply of energy produced by the impact could have forced this prebiotic chemistry into overdrive.
The researchers in the latest study, which also includes Goldman, suggest that this process adds another chapter to the story of how life originated on planet Earth some 4.5 to 3.8 billion years ago when the planet was heavily bombarded by comets and meteorites.
"These results confirm our earlier predictions of impact synthesis of prebiotic material, where the impact itself can yield life-building compounds," Goldman said. "Our work provides a realistic additional synthetic production pathway for the components of proteins in our Solar System, expanding the inventory of locations where life could potentially originate."
Dr Zita Martins, coauthor from the Department of Earth Science and Engineering at Imperial College London, said, "Our work shows that the basic building blocks of life can be assembled anywhere in the Solar System and perhaps beyond. However, the catch is that these building blocks need the right conditions in order for life to flourish. Excitingly, our study widens the scope for where these important ingredients may be formed in the Solar System and adds another piece to the puzzle of how life on our planet took root."
"This process demonstrates a very simple mechanism whereby we can go from a mix of simple molecules, such as water and carbon-dioxide ice, to a more complicated molecule, such as an amino acid. This is the first step towards life. The next step is to work out how to go from an amino acid to even more complex molecules such as proteins," added Dr Mark Price, coauthor from University of Kent.
For the latest study, the collaborators conducted a series of experiments similar to Goldman’s previous experiments in which a projectile was fired into a typical cometary ice mixture at speeds of 4.25 miles per second. Upon impact, several different types of amino acids began forming.
It is known that comets do contain simple ice mixtures and organic precursors of amino acids. The most recent discovery was that of Glycine – one of the simplest amino acids – in the comet Wild-2.
The team noted that it is possible that similar events may occur or likely have occurred elsewhere in the Solar System; Saturn’s moons Europa and Enceladus contain a mix of simple organics and water ice. The team concluded that if a rocky meteorite impacted either of these moons with enough force, enough energy should be produced to promote shock synthesis of more complex organic compounds, including life-building amino acids.
"This increases the chances of life originating and being widespread throughout our Solar System," Goldman said.
The team said this work underlines the importance of future space missions to these moons and other similar bodies to search for signs of life.