Crick (1973) advanced the idea that life was originally seeded on Earth from space - the idea of Panspermia. The British astronomer Fred Hoyle and Srilankan Chandra Wickramsinghe have further raised the possibility of Panspermia (1981).
The whole idea of Panspermia is the outcome of inability to satisfactorily explain origin of life on Earth despite accumulation of vast amount of data since Alexander Oparin (1924) first published his paper on this subject. He speculated that early Earth had reducing atmosphere. He considered it essential for Origin of life on Earth.
Even demonstration of origin of amino acids under physico-chemical influences by Miller - Urey (1953) has not resolved the question of spontaneous origin of life on Earth. In fact much work has been done after Miller - Urey to bridge the gap between inanimate and animate but still spontaneous transformation of inanimate into animate remains a matter of faith and belief. Till date, it is not possible to even conjecture spontaneous origin of a single polypeptide chain, what to talk about spontaneous origin of the simplest biological cell.
The gap between inanimate and animate remains as wide as ever.
Demonstration of amino acids, purine and pyrimidine bases in meteorites bombarded on earth, specifically Murchison meteorite; and presence of polycyclic aromatic hydrocarbons in space does not tell us anything about origin of life, whether on Earth or elsewhere. These findings only indicate feasibility of spontaneous origin of these chemicals under physico-chemical influences and nothing more.
All the work done so far demonstrates only one or more aspect of 'life like activity' but does not explain origin of life itself. Known properties of RNA are far from constituting life. Even recent analytical study by Bokov and Steinberg (2009) indicating feasibility of step-by-step evolution of ribosome at structural level beginning from a small core leaves much to be desired to constitute life.
Theory of extraterrestrial origin of terrestrial life, i.e. Theory of Panspermia may provide some relief from the question of explaining origin of life on Earth but it lands us into the question of explaining origin of life in extra-terrestrial space. So, we aren't in any better position with our original question.
Theory of extraterrestrial origin of life leads to further questions. If life was seeded from space, than how could it be found 5 Km below the surface of Earth in the form of extremophiles bacteria or 9000 meters below sea level on the ocean floor of Galapagos rift in the form of Poganophora. Barophillic Marine microbes have been found at more than 10 Km depth in Marianas Trench. Therefore, distribution of life on Earth is inconsistent with extraterrestrial origin of life.
Theory of Panspermia also raises the question of adaptation or survival of alien life under the conditions seen on Earth. All the available evidence indicates that alien life if any, must have originated under quite different environmental conditions than seen on Earth. So, how could alien life survive on Earth and evolve to the present state? Gradual adaptation over an immense period of time in line with Darwinism is more easily said than can be done.
Hence, Theory of Panspermia or Extraterrestrial Origin of life is nothing but scientific fiction created with the sole purpose, to divert attention from the question of origin of life.
Author: Dr Mahesh C. Jain is a practicing medical doctor and has written the book "Encounter of Science with Philosophy - A synthetic view". The book begins with first chapter devoted to scientifically valid concept of God and then explains cosmic phenomena right from origin of nature and universe up to origin of life and evolution of man. The book includes several chapters devoted to auxiliary concepts and social sciences as corollaries to the concept of God. This is the only book which deals with origin of nature and universe from null. Twenty-ninth chapter of the book deals with the subject matter of 'Origin of Life'.