The Value of Panspermia

Chapter 6I

The Value of Panspermia

We have seen that Hoover’s claim to have found fossils of extraterrestrial cyanobacteria in meteorites does not really show that terrestrial life did not originate in our own planet. Even if those structures are indeed extraterrestrial fossils, such an admittedly extraordinary finding would only support the view that alien life has existed. The reasons are simple:

1. Fossils are dead things. Those meteorites did not bring living things to this planet.

2. Even if they had brought living things to this planet, and no one suggests they did, Hoover went to pains to argue that those structures were too different from terrestrial life, so they had to be extraterrestrial (e.g. only 8 amino acids in common out of 20, although for some reason some of the comments in the Journal of Cosmology referred to 8 out of 22). That is, Hoover gives no evidence that terrestrial life came from elsewhere.

We have also seen that the value of panspermia as an explanation for the origin of terrestrial life is quite low.

1. The motivation for the “impossibility proofs” against the idea that life could originate on Earth is often based on misunderstandings of biology, either of evolutionary biology, or genetics, or both.

2. By pointing to panspermia we have not explained the conditions under which life originate at all. That is, by saying that life must have started somewhere else we still have not explained the origins of life.

3. When this problem has been addressed by the advocates of panspermia, they have ultimately grounded their views on absurdities, either non-scientific fictions (e.g. Hoyle’s “superior beings”) or patently false claims (e.g. Klyce’s notion that life has always existed).

This is not to say that the idea of panspermia should not be entertained at all. We do not know yet how life originated. By elaborating different scenarios we challenge our imagination and our understanding. And we prepare ourselves for the fruitful exploration of other worlds where life might exist, or at least might have existed. Having trained our biological thinking on a variety of scenarios, for example, we will be better able to deal with the surprises such exploration is likely to offer.

Even the idea that living things might hitch rides inside meteorites or comets is not completely implausible. Spores can survive for long times. Extremophiles can withstand, it seems, extreme temperatures or radiation, and in addition to bacteria and lichens, even a very small animal, the Tardigrade, has been shown to survive in the vacuum of space! [1] Of course, as we have also seen in this blog, that life can survive in extreme conditions does not imply that life can originate in those extreme conditions. Nor should we infer either that those extreme conditions may persist for millions, let alone billions of years, as the interstellar journeys envisioned by some panspermia advocates would require, without destroying the extremophile voyagers.

A plurality of views may also help us determine what new types of observations and experimental investigations might be worth undertaking. All in all, the idea of panspermia might still prove useful as we search for life in the universe.

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[1]Jönsson, K. Ingemar; Rabbow, Elke; Schill, Ralph O.; Harms-Ringdahl, Mats; Rettberg, Petra (2008-09-09). "Tardigrades survive exposure to space in low Earth orbit". Current Biology 18 (17): R729–R731.

More on Meteorite Bacteria Fossils

Chapter 6f

More on Meteorite Bacteria Fossils

Some readers have expressed great interest in the controversy surrounding Richard Hoover’s claim to have found fossils of cyanobacteria in several meteorites. I have asked permission from the Journal of Cosmology, the online journal that published Hoover’s paper, to reprint the 24 commentaries on Hoover’s alleged discovery. Once I hear from the journal, I will let you know. I said “alleged” two sentences ago because I do not have the technical expertise to critique Hoover’s analysis. I could mention, however, that of the 24 commentaries, only about 8 are by people who do seem to be technically qualified to pass judgment on the quality of Hoover’s work. The others, which include pieces coming from Ph.D.s in many fields, mostly deal with what they take to be the implications of Hoover’s work. Several come from advocates of the panspermia hypothesis, i.e. that life is everywhere and spreads by hitching rides in meteorites, asteroids, comets, etc. Those advocates are also proponents of exogenesis, i.e. the view that Earth life did not originate on Earth but came from elsewhere. Those people believe that Hoover’s work confirms their views.

Of the commentators who actually take up the technical details of Hoover’s paper, about four give him a clean bill of health, mostly on the question of whether his findings could have been the result of contamination of the meteorites by Earth life, although some of them are also struck by the great physical resemblance between the structures he found and cyanobacteria. The reasons for concluding that there was no contamination were (1) lower levels of nitrogen than normally exhibited by modern bacteria, and (2) the presence of only 8 amino acids instead of the 22 employed by living things in this planet. The other four were rather skeptical about his experimental methods and his reasoning, even when expressing interest in his work.

A more definitive assessment would require the kind of peer review normally reserved for results of the upmost importance, a review that would include the experimental work proposed by some of the skeptical commentators. Unfortunately it seems that the major journals and NASA have grown gun shy after the bruising battles concerning the Martian meteorite I have discussed in previous blogs.

Perhaps in my next posting I will be able to include the 24 commentaries. Otherwise I will return to my regular line of thought derived from my manuscript in progress, The Dimming of Starlight. Today, however, I will bring up a couple of comments relevant to the panspermia and exogenesis hypotheses.

One of the commentators though that the meteorites in question were likely Martian. Another though that they could be from the Earth itself: they were thrown into space, and finally they came back. Unless this possibility is excluded, Hoover’s findings would not help the panspermia hypothesis. Now, it seems to me that if Hoover’s structures are indeed extraterrestrial fossils, then this extraordinary finding would support the view that life may be common in the universe. It does not support the exogenesis hypothesis all that much, for, after all, Hoover would have only found fossils, dead things, not living bacteria that survived the long journey through space to Earth (or even bacteria that made it alive to Earth and then died here). Dead is dead. Maybe live extraterrestrial bacteria could make it to Earth and survive, but we cannot infer that from the fact that dead ones made it. If they are indeed bacterial fossils to begin with.

Second, the confirmation of Hoover’s structures as fossils may actually seem to go against the exogenesis hypothesis, for the very strong reason already given to show that they are not the result of contamination, namely that they have only 8 amino acids instead of the earthlings’ 22 customary amino acids. That is, they are radically different from Earth life, even if they have enough similarity to call them life. But if they are radically different from Earth life, we have no evidence that life on Earth has an extraterrestrial origin.

Sometimes, I should mention, the words “panspermia” and “exogenesis” are used as synonyms. That is, panspermia is the flag around which the proponents of the extra-terrestrial origin of life on Earth gather. One of the commentators, the former Appollo 17 astronaut and U.S. senator, Harrison H. Schmitt, wondered why these people are adamant that life could not have evolved independently on Earth. Indeed I wonder too. But more on this next time.