There is a theory that says life could have intergalactic origin
In the mid 1970s two British astronomers, Fred Hoyle and Chandra Wickramasinghe, proposed a scenario under which bacteria could come to Earth from deep space and trigger life. According to them, when bacteria, encased in comets in frozen form, travel in the vicinity of the sun, a cometary tail develops out of the evaporated materials. Some bacteria spread out onto the cometary tail and in the event of a tail brushing the Earth’s atmosphere, as happens not infrequently, get transferred to it. Physicists and biologists criticised this concept saying microorganisms would not survive in the ultraviolet (UV) and possibly X-ray background. However, the hypothesis has received support in recent times, with experiments demonstrating the survival of bacterial species like Deinococcus radiodurans under a dose of radiation.
In 2001, ISRO sponsored its first balloon flight to sample air from heights, ranging from 19 km to 41 km. Analysis of the contents showed the presence of live cells and bacteria. Two bacterial species, B Simplex and Staphylococcus pasteurii, as well as a fungus, Engyotontium album were found. Four new species of Bacillus, namely B aerius, B aerophilus, B strospericus and B altitudinus, from air samples in the upper three strata, were found to be more UV-resistant than their nearest phylogenetic neighbours. This may be linked to their survival in the stratosphere where UV intensity is considerably more than on Earth.
In the samples from the next launch, held on April 20, 2005, a total of 12 bacterial and six fungal colonies were detected. Three strains—PVAS-1, B3W22 and B8W22—were identified as new species. All the three new species are more UV-resistant than their nearest phylogenetic neighbours.
While the study does not conclusively establish extragalactic origin of the microorganisms, it highlights the need to consider that alternative Nuclear isotopic analysis of a microorganism collected in such a sample should tell us whether it is extraterrestrial and the test is still under preparation.
(Jayant Vishnu Narlikar is professor emeritus at the Inter-University Centre for Astronomy and Astrophysics, Pune)
(This article was first published in Down To Earth's print edition dated May 1-15, 2019)
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