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Panspermia (also known as exogenesis) is a hypothesis that originated in the 19th century in opposition to the theory of spontaneous generation. Pansperia propounded that reproductive bodies (seeds) of living organisms exist throughout the universe and develop wherever the environment is favorable. The term is derived from the Greek word 'pan' meaning all and 'sperma' or seed. Exogenesis comes from the Greek words meaning outside origin. It is a hypothesis which maintains that microscopic living organisms came to our planet from outer space. It is largely distinguished in that it makes no prediction about how widespread life is in the cosmos.
The basic assertion of these hypotheticals is that primitive life, which originated elsewhere, was deposited on Earth’s surface by means of a collision with some other object that already harbored life. An asteroid or comet, perhaps containing primitive cells or simple bacteria, fell to Earth at some time in the past. Then over billions of years they evolved into the more advanced forms of life now spread across our planet. To date no meteorites have ever been shown to harbor bona fide life.
The search for extraterrestrial life (exobiology) has been repopularized upon the realization of the improbability that life formed through abiogenesis. Scientists have been unable to get a cell to form under any conceivable condition. Likewise it has also become clear that for the basic building blocks of life to form, oxygen must be absent, and yet oxides have been found in rocks supposedly 300 million years older than the first living cells.
Much of the research currently underway by NASA, such as the recent expedition to Mars, is aimed at finding proof that life might have begun elsewhere.
Objections to Panspermia
The full theory of panspermia requires two events to explain the presence of life on earth:
- The generation of life outside the earth
- The transfer of this life to earth
Many scientists have objected that the generation of life cannot occur, or have occurred, outside of a planetary environment, where heavier elements are plentiful. Almost the only elements present in interstellar space are hydrogen and helium--and the latter, being an inert or noble gas, is not a component of life in any form known to man.
The generation objection by itself would not destroy panspermia. But the transference event requires a transit through space, followed by a passage through the earth's atmosphere and then an impact on the ground or at sea. Either of these events is fraught with danger. The unprotected space outside of an atmosphere is subject to unfiltered radiation in various forms. These include the products of radioactive decay, cosmic rays (the highest-energy form of electromagnetic radiation known to man), and the stellar wind, a stream of particles that fly out from any star as it continuously burns. Even if any life forms could survive the spatial passage, it must then somehow penetrate the atmosphere and risk incineration from sheer friction, and then must survive the impact.
Recently a team of researchers at the Centre for Molecular Biophysics in France were able to simulate a meteoric entry by strapping rocks containing microfossils and laced with Chroococcidipsis, an unusually robust bacterium, to the heat shield of a rocket probe before it was launched and then ordered to re-enter the atmosphere. Though the microfossils remained after re-entry, the bacteria were all destroyed, and only their outlines remained. The investigators concluded that any bacteria or other micro-organisms in a meteorite would require at least 2 cm of rock covering to protect them. In fact, the experimental conditions seem to suggest that micro-organisms within an actual meteorite would require more shielding than 2 cm, because a typical meteorite enters the atmosphere at about twice the speed of the returning rocket probe.
In 1973, Francis H. Crick, co-discoverer of DNA, and Leslie E. Orgel proposed a new mechanism, which they called directed panspermia, to mitigate the hazards of transport and entry detailed above. They assume that an advanced civilization fired a brace of rocket missiles, each laden with a payload of bacteria and/or blue-green algae, in all directions. Crick and Orgel estimated that a payload of one metric ton could contain 1017 micro-organisms organized in ten or a hundred separate samples.
The theory has gained some attractiveness primarily by proposing to explain why so many life-forms on earth depend on the element molybdenum, which is rare on earth but might not have been so rare on the planet of origin of these micro-organisms.
However, this theory is subject to a number of logical objections:
- 1. Where and how did life form or come to this other world, for an intelligent race to build a civilization capable of launching guided missiles into interstellar, or even inter-galactic, space? Directed panspermia thus appears to be an example of the logical fallacy of infinite regression, and thus violative of Occam's razor.
- 2. Crick and Orgel totally ignore the question of the motive for firing this hypothetical brace of missiles. The attitude of such a civilization toward humanity would have to be one of four things:
- A. Irrelevant--that civilization was dying when it fired the missiles, and is now dead.
- B. Indifferent--having fired the missiles, they really don't care whether any of them landed intact or not, or whether any of them spawned a new civilization or not. But if so, then why bother with such a project? One can only imagine the sort of political debate that might have begun before the first launch-pad gantry crane was erected, and plagued the project for its duration. Such debates on alleged wastefulness ultimately curtailed Project Apollo, constantly threaten the abandonment of the International Space Station, and place the current plans for re-exploration of the moon by NASA in serious doubt. (They also invite disaster to themselves. Suppose, for instance, one of their "child" civilizations should decide to look for them and go to war with them to poach their technology, resources, and so on?)
- C. Friendly--that civilization plans a follow-up visit with a view to establishing trade and travel. Such a theory would no doubt have its appeal to non-believers hoping for a God-substitute to solve all the world's problems--which is a common theme in the science fiction of the twenty-first century. (Indeed, the intellectual heirs of the popular entertainer Gene Roddenberry explicitly proposed a race of "Progenitors" who were ultimately responsible for the spawning of humanity, "Vulcankind," and all the other hundreds of races that Mr. Roddenberry and his successors conceived for the longest-running franchise in the history of television.)
- D. Hostile--that civilization intended to create new planets for its own people to settle, in which case we are in the way, and "they" will follow up their life-seeding project with an expeditionary force consisting of warships. This theme pervaded the popular science fiction of the middle part of the twentieth century, especially in the early years of the Cold War between the United States of America and the Union of Soviet Socialist Republics.
For all the attention that Drs. Crick and Orgel pay to the design of one of those missiles, and the stresses and radiation bombardment it must have had to withstand while in transit, they say absolutely nothing in consideration of motive. Without such predictions, one cannot even make a decent public-policy recommendation--and indeed, they don't seem even to have considered that their theory has any public-policy implications at all.
In sum, directed panspermia is a remarkably sloppy theory to come from the co-discoverer of DNA. But more than that, Dr. Crick shows himself determined to reject God. So determined is he that he now indulges in a flight of fancy that is surely worse than any of which anti-creationists routinely accuse creation scientists.
- Did Life Come from Another World? New research indicates that microorganisms could have survived a journey from Mars to Earth. Scientific American Nov 2005.
- Exobiology: It's life...isn't it? Scientists find it hard enough to pin down evidence of early life on our own planet. How on Earth do we plan to determine whether life exists elsewhere? Nature 430, 288-290. July 2004
- Study May Cast Doubt On Some 1996 Evidence Of Past Life On Mars Debate over whether a meteorite contains evidence of past life on Mars continues to intensify. May 6, 2004
- ↑ Sarfati, Jonathan. "Panspermia theory burned to a crisp: bacteria couldn’t survive on meteorite." Creation on the Web, Creation Ministries International, October 10, 2008. Accessed October 31, 2008.
- ↑ Photo S94-032549 by the U.S. National Aeronautics and Space Administration
Crick, F. H. C., and Orgel, L. E. "Directed Panspermia," Icarus, 19, 341 (1973).
- Designed by aliens?: Discoverers of DNA’s structure attack Christianity by Gary Bates. Creation 25(4):54–55. September 2003
- Nature and Origin of Life on Planetary Bodies by Nicholas M. Short. NASA Remote Sensing Tutorial.
- Planet Quest NASA's Exoplanet Program.
- Origins NASA's Origin of Life Program.
- Astrobiology NASA's Astrobiology Program.