Comets and other icy celestial bodies have some basic building blocks for life, but it takes violent impacts to take them to the next level, according to researchers who claim to have successfully created amino acids in the lab by recreating icy interplanetary collisions.
First the researchers created mixtures of water ice and light organic chemicals roughly based on what has been observed on comets and what is suspected to exist on the Saturn's moons. Then they shocked the ice by firing at it with a steel projectile at very high, interplanetary planetary collision speeds approaching 16,000 miles per hour (7 kilometers per second).
They found that the hypervelocity impact shock of a typical comet ice mixture produced several amino acids, including equal amounts of D- and L-alanine (that means right and left-handed versions of that amino acid molecules). Meanwhile, analyses of the non-shocked "control" samples of the same ice contained none of these important steps towards genuine proteins needed for life. The results suggest that icy impacts within our solar system may play an important role for making ingredients for life.
The team ran the experiment twice, a year apart, to show that their amino acids were not flukes. They also went to great pains to keep their ice mixtures and equipment free of earthly contamination.
"We needed everything to be extremely clean and we needed to show that the results were reproducible," said Zita Martins of Imperial College London and lead author on the paper published in the Sept. 15 issue of Nature Geoscience.
The study is an important step forward because it goes beyond simulations of impacts, of which there are many, she said.
"There are lots of theoretical studies," said Martins. "But every time they publish they get criticized for not being experimental." But with the success of this work, it's likely others will follow.
"It's an exciting paper and it's definitely going to spur ancillary work," said icy impacts researcher Michael Mumma of NASA's Goddard Space Flight Center. He is especially interested in what will happen if the experiments are done with a wider range of icy mixtures -- including those that match some of the latest discoveries about the composition of comet ices. "It suggests a whole range of mixtures."
As for what it has to do with life on Earth, that requires going back in time a few billion years and reversing the collisions a bit: instead of rocks slamming into ice, it would be icy comets slamming into Earth's rocky crust. Another implication of the work is that it increases the chances of life originating and being widespread throughout our Solar System, the researchers wrote.