Love and Light.
Microbes Beyond Earth
By Nandkumar Kamat
THERE were three different discoveries recently which could excite the exobiologists. The first was about Titan, the giant orange coloured satellite of Saturn which is made up of an unique hydrocarbon soup imitating the conditions required for pre-biotic chemical evolution.
The second discovery was the concrete evidence of a dried ocean on Mars with signatures of the sea salts in the frozen sediments.
The third discovery was of a novel species of a bacterium isolated from a frozen pond exposed at the side of the Fox tunnel in Alaska.
Dr Richard B Hoover, a biologist at National Aeronautics Space Agencys, Marshall Space Flight Center had visited the refrigerated tunnel when he noticed a discoloured patch in a layer that froze 32,000 years ago. The age was determined from radiocarbon data. Taking samples back to his laboratory, Dr Hoover and his colleague Dr Elena V Pikuta noticed bacteria that started moving as soon as the ice thawed. The cold loving presumptively ancient bacteria resembled a group of similar microbes called carnobacteria that can tolerate cold and are often isolated from refrigerated food.
The NASA researchers established that the microbes belonged to a new species, which they have named Carnobacterium Pleistocenium in honour of its age. Now what is the significance of these three unrelated discoveries in the solar system? Let us take the discovery of the ancient Carnobacterium first. There are still some doubts about its antiquity because DNA cannot survive for such a long time. But since the bacterium is a novel species the contamination is ruled out. The only conclusion that can be drawn from the Rip van Winkle bacteria is that certain cold loving microbes, could suspend their metabolism in such a way that they can regrow when the conditions are right. Or in other words the clock is frozen for these cells.
The biochemistry behind this process is not easy to explain. There would have to be special kind of metabolic processes, proteins and enzymes to keep the bacteria in suspended animation. If such bacteria can exist in Alaska then many other species could be found on earth. The cold ocean floor could also harbour a life teeming with bacteria. Siberian permafrost and frozen sediments could yield novel microbes. If microbial life can be found on earth under extreme conditions then logically the frozen sea sediments on Mars could harbour similar life. Already minerals which are formed in the presence of water have been located on Mars. But no directed searches for organic life were conducted by the twin rovers-Spirit and Opportunity. The indirect evidence shows that life could have evolved on Mars in the past but no traces are left. The future missions to Mars would carefully scan the red planet for organic life.
The next example is Titan. It has such a low temperature that the biologists see no possibility for evolution of life. But below the thick hydrocarbon ice there could be warmth which could favour some kind of microbial activity. Superficial surface scans of Titan do not reveal any biogenic processes. But the astrobiologists have not given up their hopes just because Titan has absolutely unfavourable thermal conditions for life. After all, Eskimoes on earth live in houses built with snow-the igloos. The Snow cushions the external cold. If microbes could survive in a frozen pond in Alaska then there may not be any limits for such cold loving species. Perhaps we do not know everything about behaviour of DNA under extremely cold conditions.
The Alaskan discovery also brings in focus the neo-panspermia theory of Hoyle and Wikramsinghe. They had speculated that the life on earth was seeded from outer space, possibly by comets. It is true that the comets brought phenomenal amounts of water on earth in the early days after the planet came into existence. But could there be microbial life in the comets? Could it lay dormant for indefinite period? A global influenza epidemic of 1910 was attributed to apparition of Halleys comet. There were concerns that if Earth passed through the large tail of the Halleys comet then people would die of monoxide poisoning.
The famous British writer H G Wells wrote a science fiction In the Days of Comet. The Comet mania passed with time but the debate continued. The Earth is constantly bombarded by interstellar dust and cometary material. Even the isotopic-ejecta from distant supernova has been found in the deep ocean sediments. If microbes can survive stressful conditions such as low temperatures then the astrobiologists would have to re-examine the data.
The standard view does not favour panspermia theory. Evolution of life on earth is seen from fully a geocentric context, as a one time event, a chance occurrence. We are told that the first cell, the first prokaryote evolved biochemically from an organic soup under highly reducing atmosphere. But so far it has not been possible to synthesize a crude prokaryote in the laboratory.
The minimum set of life giving genes has been identified. Models using Von Neumans Cellular automatons have been tried to explain phylogeny. But the mysteries of earths first biosphere are not yet solved. It is difficult to go beyond 3. 6 billion years. If the comets or the interstellar dust seeded the earth with unknown life forms, then this evidence has been already obliterated by the natural upheavals on our planet.
If there are still extra terrestrial living fossils of very ancient origins then we still do not have the probes to identify these. However the deep sea floor may store some surprises for biological oceanographers in future. Astrobiologists are also interested in exploring Europa, Jupiters icy satellite. It looks more promising than Titan because it has liquid water. The Stardust mission and other missions to various comets may also reveal new data about their composition.
In the meantime, the new discoveries of microbes under exceptional circumstances on earth would offer certain clues to biochemists about the intricacies of DNA. Without intact DNA there can be no life. A space mission which can detect DNA on a planetary soil or satellite or in a cometary sample would revolutionise astrobiology.
I withdraw the lines written about the Wonder boy Saurabh Singh in my previous article, as his claim of giving a NASA examination has turned out to be a fraud. I regret for not verifying the facts.
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