MEHULENTERPRISE

The origins of life...

Where did I come from? It is a multi-billion dollar question. Where did life begin, on the Earth or on some other planet? It is another quest, another frontier, and another space odyssey. Cassini Huygens mission is the goal of the largest interplanetary spacecraft is to study Titan. It might teach us about the origins of life on our planet. In January 2005, the Huygens probe will be released from Cassini, descend to Titan’s surface and carry out science tasks. Cassini entered into the orbit around the Saturn in July 2004, on a four-year mission and will make more 40 visits to Titan. It is a project between NASA, the European Space Agency, and the Italian Space Agency. Cassini’s trysts with Titan, the Saturn’s largest moon, and is the second biggest in the solar system, will hopefully answers questions about the origins of life. It is believed to be the only body other than the Earth with liquid on the surface. Titan’s diameter size is 5,150 kilometres and mass is 1.35x10^23 kilogram. Its distance from the Saturn is 1,221,850 kilometres. It takes 15.945 Earth days time to orbit the Saturn. It has thick nitrogen atmosphere. Its surface has orange colour. It has probably rocky iron core. Titan is a cold world. At 1,200 million kilometres away from the Sun, the surface is a chilly, 180º C. Once upon a time, Titan may have been a lot warmer. Liquid water may have flowed across its surface. As the world began to freeze over, these could have survived beneath the surface. In several billion years, our Sun will become a red giant. Then the temperature on Titan’s surface will rise to a more hospitable, 100º C. So as the Earth becomes too hot to inhabit, Titan may start a whole new lease of life. There seem to be methane clouds, a large crater, deposits of ice, and lines and circles of unknown origin. Temperatures rarely venture above 179º C; the atmosphere is dominated by nitrogen and carbon based compounds. It has a hazy atmosphere. Its atmosphere and surface are believed to be dynamic and active. It is rich in hydrocarbons and resembles post big-bang cosmic conditions before life began some 3.5 billion years ago. Titan is the only moon in the solar system with an atmosphere. Its surface could be rich in methane and carbon molecules, a pre-requisite for the creation of life itself. Scientists hope to find pre-biotic conditions here that preceded the evolution of life. Several scientific theories have been mooted about our origins, the most popular one being the panspermia theory. It was propounded by Fred Hoyle and N Chandra Wickremasinghe in the 1970s. According to it, we are born of inter-stellar seeding when microbes got transplanted to the Earth as they piggy-backed on comets and meteors that collided with the planet. That would make us out to be the aliens we are looking for. “Not all microbes in inter-stellar space would survive of course,” said Wickremasinghe. “But the survival of even a minute fraction of microbes leaving one solar system and reaching the next site of planet formation would be enough for panspermia to be overwhelmingly more probable than starting life from scratch in a new location.” Scientists are attempting to simulate cosmic conditions prevalent at the time following the big-bang. The explosion stirred up primordial soup that somehow spawned life. In this soup, simple molecules combined to form more complex ones. As the basic molecules of life moved from space to a planetary environment, they began to interact and undergo chemical reactions that produced more complicated molecules. They were energized by lightning or volcanic heat to form amino acids. These went on to form proteins, life’s building blocks. For life to evolve, simple chemicals must combine to form more complex ones. Liquid water is an appropriate medium for these chemicals to dissolve, act, and react. Chemical building blocks like carbon, oxygen, and hydrogen. Carbon can form long chain like molecules, integral for the creation of organic life. Hydrogen and oxygen can bond with carbon and they are present in water. Nitrogen, too, is carbon friendly and stable. Other chemical ingredients that make life include sulphur, phosphorus, sodium, potassium, magnesium, calcium, manganese, iron, cobalt, copper, and zinc. Energy source has to drive the chemical reactions. The Sun is the primary source of energy, but extremophile organisms living deep inside ocean beds and polar ice manage without the Sun. They have survived like this for millions of years. All these ingredients are mixed to make primordial soup. Adding energy, letting them to react, forming molecules; once these begin to copy themselves, life has begun. If life evolved outside the Earth, the panspermia theory would explain how the Earth got inhabited. If not, the same chemical processes could well have taken place on this planet, as pre-biotic conditions here are believed to have been exactly what it is in Titan now. Scientists therefore hope the Titan probe will confirm the primordial soup theory. To prove that life can be created from scratch, researchers at Harvard University have undertaken a multi-million dollar project that seeks to simulate life-friendly chemical conditions in the laboratory. “We are trying to create a primordial organism in the lab,” said Jack Szostak of Harvard Medical School. He and his team have successfully started an evolutionary cycle by randomly stringing together nucleotides to create trillions of RNA molecules, pre-cursors of self-replicating DNA. But they are yet to create a brand new RNA, a task that once achieved, could be the link to the creation of life in the laboratory. What is the catalyst that takes inert matter and transforms it into a process capable of replicating itself, no matter how rudimentary? Even the lowest form of algae represents a process that can turn sunlight into nutrition and propagate the species. Over time, the humble algae will go up the evolutionary spiral onto more complex processes of life forms, unlike crystals, which can replicate but are struck in the same evolutionary groove forever. One day, we might stumble upon that magical something that breathes life into inert matter. It could be as ubiquitous and unglamorous as clay; or it could be a mystical particle of faith. Either way, life will never be the same again. Until then, we will continue to grapple with the question: Did the life originate in the stars or on the Earth? Speculations abound. Astronomer Carl Sagan estimated that there were a million technical civilisations in our galaxy alone. Sceptics like astronomer Ben Zuckerman insist we are alone in this galaxy, if not in this universe. Still others, exobiologists, are delving deep into the Earth to study extremophile organisms that they believe will tell us more about origins, possibly on the Earth itself. They survive in a functioning ecosystem that has neither sunlight nor photosynthesis drawing energy from chemicals in hydrothermal vents beneath ocean floors. How do a bunch of chemicals organise themselves into life? What are the conditions necessary to create this magic? Will the Cassini probe help us find answers to the question: Where did I come from? Time will tell.

* Compiled by NARAYANI GANESH (Times of India).