Icy organics help understanding of origin of life

Posted by Emma Woollacott

NASA scientists are zapping organics with lasers in an attempt to discover how life arose on Earth.

It's considered likely that the basic ingredients of life, including water and organics, originated in the frozen outer reaches of our solar system, making their way here on comets and asteroids.

And NASA says it's now established that organic material can begin the processing it needs to become prebiotic - while still frozen in ice.

"The very basic steps needed for the evolution of life may have started in the coldest regions of our universe," saysJet Propulsion Laboratory scientist Murthy Gudipati. "We were surprised to see organic chemistry brewing up on ice, at these very cold temperatures in our lab."

The team studied polycyclic aromatic hydrocarbons (PAHs): carbon-rich molecules that can be found on Earth, in candle soot and the like. They've also been spotted throughout space in comets and asteroids; and NASA's Spitzer Space Telescope has even found them in the swirling planet-forming disks around stars, in the spaces between stars and in remote galaxies.

At temperatures as low as 5 Kelvin - minus 450 degrees Fahrenheit - the team bombarded the particles with ultraviolet radiation similar to that from stars. Then, to discover the products of the chemical reaction, they zapped the ice with both infrared and ultraviolet lasers.

The results revealed that the PAHs had transformed, incorporating hydrogen atoms into their structure and losing their circular, aromatic bonds to become more complex organics.

According to Gudipati, this is the type of change that would need to occur if the material were to eventually become amino acids and nucleotides - bits and pieces of protein and DNA, respectively.

"PAHs are strong, stubborn molecules, so we were surprised to see them undergoing these chemical changes at such freezing-cold temperatures," he says.

The results may explain why, while organics are widely found as gases and hot dust, their signatures don't show up on ice. The new findings show that PAHs, once they stick to the ice surface, are chemically transformed into other complex organics, and therefore might not be seen.