Asteroids, Proteins and Life on Earth

Posted by: Mike Pallante on April 3, 2011 at 2:45PM
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Was Life on Earth Seeded By Objects From Space?

In an interview with prominent author Ben Stein well known philosopher and atheist Richard Dawkins posited that aliens may have seeded life on Earth. While Dawkins didn't invent this theory his comments garnered extra criticism due to his celebrity as a rationalist. However, new research from NASA suggests elements of life came from orbit. And it all has to do with left-handed Amino Acids.

What are Amino Acids, Why are they important and what does “left handed” mean?

Amino Acids are molecules containing a amine and carbide group. What makes Amino Acids unique is how the amine group, NH2 (Nitrogen and two hydrogens) are built. Its best to think of molecules like a set of Lego building blocks. Take three Lego blocks, call one Nitrogen and two of them Hydrogen. You can snap these blocks together in any number of ways. But if you need to put these Legos into an existing structure, call it a Carbide wall, only one orientation will fit. Amino Acids contain a specific grouping of atoms, or Legos, that fit well with the wall, or carbide group. Amino Acids are one of twenty fundamental elements in proteins. Proteins not only are responsible for things like teeth and nails but more importantly regulate the chemical processes in your body. You can't have life without proteins and you can't have proteins without amino acids.


But scientists have been considering a curious anomaly. While all life uses a specific grouping of amines to build Amino Acids there's simply no reason why another grouping wouldn't work. The mirror image of the Amino Acids should be just as capable of building life. The kind of Amino Acids found in all life today are dubbed “Left Hand” types and the other kind, which exists but is not found in Earth life, are called the “Right Hand” variety. The titles are arbitrary but the essential point is that we have an abundance of “left hand” amino acids. But why?

Earth Seeded from Space with Left Handed Amino Acids

In 2009 NASA researchers at the Goddard Space Flight Center made a telling discovery. Samples taken from carbon-rich asteroids contained an excess of amino acid isovaline (L-Isovaline) or "left handed" amino acids. From this discovery scientists began to posit that primordial meteor impacts may have provided an excess of L-isovaline when life was forming on Earth. This suggests an environmental bias towards life built with this type of Amino Acid. Further discoveries at Goddard showed the same prevalence of high levels of l-Isovaline in a wide variety of carbon rich asteroids and meteors. Dr. Daniel Glavin of NASA Goddard, author of a recently published paper on the issue commented, “This tells us our initial discovery wasn’t a fluke; that there really was something going on in the asteroids where these meteorites came from that favors the creation of left-handed amino acids.”

The variety of meteors showing high levels of l-isovaline all show signs of having at one point been changed by liquid water. Whenever mineral deposits show evidence of meteors being altered by liquid water high levels of l-isovaline are also present. Galvin commented, “The more these asteroids were altered, the greater the excess L-isovaline we found. This indicates some process involving liquid water favors the creation of left-handed amino acids.”

The amount of l-isovaline in these meteors is telling. Galvin explains, “In the meteorites with the largest left-handed excess, we find about 1,000 times less isovaline than in meteorites with a small or non-detectable left-handed excess. This tells us that to get the excess, you need to use up or destroy the amino acid, so the process is a double-edged sword.”

So, while many viewers felt Dawkins performed a philosophical handstand by suggesting the Earth was seeded for life NASA may have come to his rescue, in a way. This research does not suggest life was actually seeded by asteroids. However, it does suggest that the type of life on Earth may have been impacted by chemicals developed in space and introduced to earth by meteor impacts.