Comets and the Origin of Life

STEP by step, the case for an extraterrestrial origin of life has got stronger. But though the case for planetary panspermia - the idea that micro-organisms transfer between planets - is now widely accepted, interstellar panspermia remains controversial.
A key element in the scheme, promoted by Chandra Wickramasinghe and the late Fred Hoyle, are comets, the bodies in which the desiccated bacteria of interstellar space are claimed to come to life before being ferried to planetary surfaces। The recent discovery of amino acids and clays in comets, which could have formed only if comets once had liquid-water interiors, bolsters the case for interstellar panspermia. Yet most scientists require more evidence. Here, the fascinating case that we are all ETs is spelled out in semi-technical rather than popular form.