Shocking start to life from cometary impacts

Complex amino acids, the basic building blocks of life, might have been produced by the impact of icy comets onto planets or moons, say scientists who have mimicked their formation in lab experiments. They prepared frozen mixtures of ammonium hydroxide, carbon dioxide and methanol in proportions similar to those found in icy comets and blasted them with a stainless steel ball travelling at up to 7.15 km s^–1.

A GC/MS analysis of the products confirmed that several amino acids were formed, including glycine, D,L-isovaline and equal amounts of the isomeric pairs D- and L-alanine and D- and L-norvaline. Some of the products are the essential amino acids which are needed to synthesise the proteins required for life, as described in Nature Geoscience. This was not a rogue result. Two experiments carried out a year apart with different ice mixtures produced the same group of amino acids.

The same processes could have taken place in space by the impact of icy comets onto the surfaces of planets, moons and other bodies, or by the collisions of rocky bodies with icy moons such as satellites of Jupiter and Saturn. The research team commented "It is highly probable therefore that there are conditions on the surfaces of bodies in the saturnian system where ammonium compounds, simple alcohols, CO₂ and water ice coexist in an intimately mixed solid form. Impact of a body travelling with sufficiently high velocity (5-20 km s^–1) would impart enough energy to promote shock synthesis of more complex organic compounds, including amino acids, from these ices."

Although the amino acids might be formed in these collisions, the right conditions for Life to flourish still need to be in place. However, the work shows that the basic building blocks can be produced within the Solar System, and possibly beyond.