Probably about once in almost every decade a scientific discovery is reported that brings out passionate debate concerning the possible existence of extraterrestrial life, and panspermia theory [Bhattacharya-2009] , past or present. Nagy et al. (1961)  reported the occurrence of biogenic hydrocarbons in the Orgueil meteorite and then subsequently went on to describe possible relict microstructures that looked similar to microbial life forms on Earth (e.g. Nagy et al., 1963) . Levin and Straat (1976)  reported the results of experiments performed during the Viking Mission to Mars that could be interpreted as possible evidence for extant microbial life in the outer space. Engel and Nagy (1982)  reported the occurrence of non-racemic amino acids in the Murchison meteorite (L-enantiomer excess) that could be interpreted as possible evidence for past extraterrestrial life. McKay et al. (1996) [ 6] reported possible evidence for fossil microbial life in the Martian meteorite ALH84001. The question was whether life started first in Rocks or in ocean?
For last decade, geologists also have looked at water droplets entangled in ancient Rocks — called fluid inclusions – of thousands years old trapped in the rocks found in death valley or saline valley of California USA and from Michigan, Kansas and Italy[ temperature in these locations are 130 degree Fahrenheit or more] and they wondered that microbes could be extracted from them. Fluid inclusions have been found inside salt crystals ranging in age from thousands to hundreds of millions years old. But there had always been a question about whether the organisms cultured from salt crystals are genuinely ancient material or of extraterrestrial origin or whether they are modern-day world contaminants,[science daily 22nd November-2010] and research on reviewed existing literature and they confirmed that microbes or allege DNA were over 100,000 years back and could survive as the conditions inside these water droplets are ideally suited to preserving their DNA
Richard Hoover  very recently had discovered evidence of microfossils similar to Cyanobacteria, as we discussed early in the article, in freshly fractured slices of the interior surfaces of the Alais, Ivuna, and Orgueil CI1 carbonaceous meteorites and in ALH 84001 meteorite based on Field Emission Scanning Electron Microscopy (FESEM) and other measures, This me- teorite seemed to have been ejected from the Planet Mars on earth, a few billion years ago and after a long and circuitous journey fell to Earth and remained buried in the Antarctic region for a few thousand years. Woo ! it proves pan-spermia theory and life in this planet appeared from Asteroids [1,13] Richard Hoover  has concluded they are indigenous to these meteors and are similar to trichomic cyanobacteria and other trichomic prokaryotes such as filamentous sulfur bacteria. He concludes these fossilized bacteria are not Earthly contaminants at all but are the fossilized remains of living organisms which lived in the parent bodies of these meteors, e.g. comets, moons, and other astral bodies. The implications are that life is everywhere, and that life on Earth may have come from other planets. [1,13]. Based on a genomic analysis, that DNA-based life has a genetic ancestry leading backwards in time over 10 billion years [8,9,10] (Joseph, Wickramasinghe, Wainwright 2011; Sharov 2009), which is twice the age of Earth.
Comet / asteroid was a source of origin of life in this planet the earth? A comet is a dirty icy snowball and much of the dirty materials are organic material formaldehyde, hydrogen and more complex substances. In cold interstellar molecular clouds gaseous species such as H2O2, CO, CO2, CH3OH, H2O and NH3 are believed to condense on to sub micron carbonaceous grain to form these icy mantes. By a combination of process that included gas grain, chemical reactions, ultraviolet photolysis and cosmic ray bombardment these components could meet further to produce small amount of complex organic compound. Icy planetismals that probably formed through successive aggregation and agglomeration of such ice-coated grain might have carried significant amount of pre-biotic organic molecules to this earth during its early history. But these organic substances must had been destroyed by the heat generated of impact as comet bombarded in the early earth? If these fragile compounds had some how survived, they could have provided the starting point for the chemical evolution that led to more complex molecules like amino acids, nucleic acids and ultimately giant molecule “The RNA or DNA’. So in that case there needed extra terrestrial source of organic compounds. Carl Sagon [Science 27th July 1990, P366] told that only small parts of comets flowing in the earth atmosphere would stay cool enough to preserve the organic chemicals. J.Mayo Greenberg was however in favoring of comet as source of compounds as origin of life in this planet the earth. According to Greenberg the Icy particles make up the comets. In his laboratory, he made icy particles that make up comets. To create them he condensed mixture of water vapor, methane, CO, and other gases present in the interstellar spaces on a glass plate cooled to~100K. The Icy was amorphous like a comet ice, having a disorderly molecular structure rather then crystalline one. Amorphous ice conducts heat more slowly then the crystalline ice. Greenberg found that when ice was deposited very slowly as it would be in the interstellar grains it’s thermal conductivity become slower and slower by a factors 10,000-100,000, because of lesser connectedness’ of water molecules that had accumulated slowly. The effect of this lower thermal conductivity might have to insulate the organic materials against the heat of a cometary’s impact. While the outer layer of grains were vaporized during the comet collision on earth atmosphere, the inner part might survived unscalled and floated gently on sea of earth. But one of the most mysterious feature of present day is the fact that ribose and deoxyribose sugar in RNA and DNA are all right handed while amino acids that make up proteins are all south. This is a puzzle because sugars and amino acids are chiral molecule i.e. they can exist in two different mirror image. But on earth they do not exist as chiral. No one could answer how this enantiomeric excess came about on earth.