Did our great ancestors — microbes — hitchhike to Earth on meteorites? Yes, say researchers from Columbia University who have discovered traces of amino acids — building blocks of life — on meteorites that landed in Australia and the US as recently as 100 years ago. These extraterrestrial amino acids probably mixed with moisture in Earth’s ancient atmosphere to produce an acidic ‘soup’, which nourished the planet’s first organisms. This gives a leg-up to the theory of panspermia, which says comets seeded life on Earth some four billion years ago and that micro-organisms still continue to arrive here. Many scientists, however, believe that life arose spontaneously out of a chemical ‘soup’ on infant Earth.
If panspermia is the reality, the ‘miracle’ of life could happen anywhere, and our microbial ancestors — or more evolved cousins — are scattered like chaff throughout universe. This idea goes back to the time of Greek philosopher Anaxagoras. In the 19th century, Louis Pasteur proved that spontaneous generation didn’t work, sparking interest in the possibility of life having spontaneously begun on Earth. But panspermia never found favour with scientists till the 1970s, when the late Sir Fred Hoyle and Chandra Wickramesinghe came across “traces of life” in interstellar dust. When cultured, two species of bacteria and a microfungus found in space rocks turned out to be similar to terrestrial organisms — as panspermia predicted.
About a tonne of microbial material enters Earth’s atmosphere every day, and this has been happening for the last four billion-odd years. Much of this is sterile due to exposure to the sun, or is burnt in the higher reaches of the atmosphere. But a fraction of the incoming dust — evaporated from comets, and possibly containing microbes — could survive the fiery descent. Discoveries of microfossils in a Martian meteorite found in Antarctica, and data from the 1976 Viking space probes (which confirmed the presence of Martian micro-organisms, but was overlooked for 25 years) bear this out. We still don’t know how, or where, life began. But if the latest findings hold up, we might all be aliens.