Looking for life high in the atmosphere, the Indian Space Research Organisation found colonies--12 bacterial and six fungal--in the
stratosphere. U R Rao, former ISRO chairman and project advisor, explained the implications to Sumana Narayanan.
Why did ISRO embark on the study?
We wanted to ascertain the validity of the Hoyle-Wickramasinghe theory. The English astronomer Fred Hoyle along with the astrobiologist
Chandra Wickramasinghe proposed the theory of panspermia. It states that life (simple bacteria-like organisms) originally came from outer
space, piggybacking on asteroids or comets. It refutes the primordial soup theory which says life originated in a broth-like liquid on earth. A chain
of reactions in the broth led to the formation of amino acids which gave rise to the first proteins and eventually life.The catch lies in the big jump
from the formation of amino acids to genetic matter capable of replication (DNA and RNA).
How was it carried out?
We shot a balloon probe with 16 cubes, 40 km into the atmosphere. The probe measured 0.76 million cubic metres. Before launching it, air was
sucked out of the cubes to create a vacuum. The cubes were then immersed in liquid neon, a decontaminant. Once the probe reached the
stratosphere, the cubes were released at different heights, using remote control, to allow air into them.
What did you find?
The cubes were analyzed at the Centre for Cellular and Molecular Biology, Hyderabad and at the National Centre for Cell Science, Pune. The air
samples obtained from the cubes were filtered to trap the microorganisms. The sides of the cubes were washed with a solution. This solution
was also filtered. The filtered samples were transferred to different growth mediums and cultured under different temperatures. We had to cover a
basic range of mediums because we did not know what environmental conditions would induce growth. Different species were isolated from the
cultures and their genetic material was sequenced for identification. Of the life forms discovered, three bacterial species are new and highly
resistant to UV radiations.
Have you done this before?
Such experiments were developed to sample aerosols to understand climate change. Contamination is not an issue in aerosol sampling but in a
study like this it is. In 2001 we conducted a similar experiment but we were not sure if the samples were uncontaminated. For the current study,
we modified the probe so that it could be sterilized. The modified balloon was created in Hyderabad.
Does it substantiate Hoyle's theory?
Not really. We cannot be certain the bacteria came from outer space. Erupting volcanoes and the gases spewed out of them might have carried
bacteria into the stratosphere. Moreover, there is no method to prove the hypothesis. Nevertheless, the interesting fact is that life has been
discovered in the stratosphere which includes new species of microorganisms with previously unknown levels of UV resistance.