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."