And to add more grist to the mill here is Carl Sagan giving his...

And to add more grist to the mill here is Carl Sagan giving his opinion on Crick's Directed Panspermia Ideas.

I also apologise if this is seen as a diversion from this threads intent . Sagan and Crick though have been discussed through these threads.

https://www.nytimes.com/1981/11/29/books/is-there-life-elsewhere-and-did-it-come-here.html

Carl Sagan, professor of astronomy and director of the Laboratory for Planetary Studies at Cornell, is the author of ''Cosmos.''

LIFE ITSELF Its Origin and Nature. By Francis Crick. 192 pp. New York: Simon & Schuster. $12.95.


By CARL SAGAN''ONCE the scale and nature of the galaxy is appreciated, it is intolerable not to know whether we are its sole inhabitants. It may even be very dangerous not to do so. ... To show no interest in these topics is to be truly uneducated.'' In this book, Francis Crick, the doyen of modern molecular biology, considers the grand panorama of cosmic evolution and offers the highly unorthodox proposal that life on earth originally came from other planetary systems.Just 10 years ago it was my task to organize, for the National Academy of Sciences, the Western delegation to a joint U.S./U.S.S.R. Conference on Communication with Extraterrestrial Intelligence. It was natural for me to ask Leslie Orgel, one of the leading researchers on the organic chemical steps that led to the origin of life on Earth, to attend, along with his colleague Francis Crick.

About halfway through the conference, at lunch in the refectory of the Byurakan Observatory in the Armenian S.S.R., Messrs. Crick and Orgel asked me about the panspermia hypothesis, the old 19th-century view that if the universe is infinitely old, perhaps life is also infinitely old, and if life and matter are coeternal, there is no problem of the origin of life to be figured out. But then life must have been transported to newly arising worlds. Around the turn of the century, the Swedish chemist Svante Arrhenius had proposed that stellar radiation pressure propelled little spores of life from world to world, but I had calculated that the radiation dose accumulated during the ejection of an unprotected microbe from an alien solar system would kill the little beast long before it could arrive on some virgin world. If you imagined a bigger microbe, I argued, surrounded with radiation shielding, it would be too heavy to be ejected. Yes, Messrs. Crick and Orgel replied, but why couldn't life on Earth and other planets have been deposited by intelligent beings - an idea they proposed calling Directed Panspermia - rather than accidentally wafted by radiation pressure through interstellar space?

Something like this had been proposed a decade earlier by the astronomer Tommy Gold of Cornell University, who, in a lighthearted mood, imagined picnickers from some distant planetary system briefly alighting on the early Earth, and their detritus - the microbes in their cookie crumbs was one of Mr. Gold's images - slowly evolving to become us. But Directed Panspermia was different in one major respect: Messrs. Crick and Orgel imagined the Earth to have been seeded not accidentally but intentionally, in an effort by intelligent beings much more advanced than we to spread their form of life through the cosmos. Subsequently, Messrs. Crick and Orgel wrote this idea up for the scientific journal Icarus, of which I was then editor, and after being refereed, their article was published. ''Life Itself'' is a somewhat fleshed-out version of that original paper.

Francis Crick is the co-discoverer, with J.D. Watson, of the molecular structure of DNA, the master molecule of life on Earth. He is also the person primarily responsible for discovering the nature of the genetic code. The sequence of nucleotide building blocks in our genes (made of DNA) somehow determines the sequence of amino-acid building blocks in the proteins that our cells busily synthesize. This translation of nucleic-acid information into protein information is called the genetic code. Mr. Crick found that every set of three nucleotides specifies a particular amino acid (or, e.g., specifies the end of a protein message). He has continued to make important contributions on topics ranging from the physiology of thinking to ''selfish DNA'' - the proposal, again made with Mr. Orgel, that sections of DNA are devoted to perpetuating their own existence rather than that of the organism they inhabit and control. When Mr. Crick writes about the nature and origin of life, it is always prudent and often a delight to pay attention.The central theme of his book is Mr. Crick's suspicion that life may not have originated spontaneously on Earth, and his conclusion by default that life may have come from somewhere else.


This hypothesis, of course, postpones rather than solves the problem of the origin of life. It arises from the same sort of despair that motivated Hermann von Helmholtz and Svante Arrhenius to propose the panspermia hypothesis theory in the 19th century. But consider how much progress has been made since then. We know that the Earth, far from being infinitely old, is 4.5 billion years old. From the fossil record we know that life had to arise within the next few hundred million years. We understand that the atmosphere of the early Earth was more hydrogen-rich than the present atmosphere, and that the application of energy to such a mixture of gases produces all the fundamental building blocks of nucleic acids and proteins. We find from Voyager spacecraft data that the atmosphere of Titan, the largest moon of Saturn - something like the atmosphere of the early Earth - is generating complex organic molecules today, and that complex organic matter is covering many objects in the outer solar system. We know that the interstellar medium, the thin gas between the stars, is filled with many dozens of varieties of complex organic molecules. In addition, work done partly in Mr. Orgel's own laboratory shows that there are plausible means for the spontaneous formation of short chains of nucleotides to synthesize molecular systems that know how, under the right conditions, to make identical copies of themselves.

The origin of the genetic code remains a deep mystery. But we have been at this sort of research for only a few decades. Nature has had a four-billion-year head start. It seems premature, in the face of so much heroic progress, to despair.Mr. Crick believes that the commonality of the genetic code among all organisms on Earth points to our all having descended from a single and common instance of the origin of life.

This is by far the orthodox view. But is that instance an indigenous origin or an exogenous experiment? He wonders why, if the origin of life occurred readily on the primitive Earth, there are not many different sorts of genetic codes in operation in different organisms today. One plausible answer seems to be that the first organism to get going had an enormous selective advantage over the latecomers; whatever characteristics - genetic code, stereoisomerism, choice of amino acids or nucleotides -were incorporated into the first organism should have been preferentially proliferated. The characteristics of lately arising forms of life would be overwhelmed by those of the first varieties, multiplying in the absence of competitors for long periods of time.Mr. Crick admits that there are no anomalous concentrations of comparatively rare elements in terrestrial biology that are so striking as to suggest an extraterrestrial origin; in fact the distribution of chemical elements in Earthly life is very much like - although not identical with - the distribution of elements in seawater, from which life is conventionally thought to have emerged. He points to the fact that there was a comparatively short period of time between the epoch in which the Earth was first suitable for the origin of life and the time of the oldest fossils.

This might be thought consistent with a discontinuous arrival of life from some extraterrestrial spacecraft, but it is also consistent with the idea that the origin of life out of the organic chemicals of the early Earth was a likely event and happened fast. Mr. Crick says that if he had been in charge of seeding the Earth, he would have included eukaryotes (organisms with fully formed nuclei) as well as prokaryotes (organisms without nuclei), while the fossil record seems clearly to show a long period of prokaryote evolution preceding the advent of eukaryotes. In short, while there is nothing we know that rigorously excludes the idea of Directed Panspermia, there is likewise nothing that strongly supports it.

''Life Itself'' is a kind of romp, a presentation of an entertaining and enchanting speculation not strongly supported by the facts. I would not, however, agree with Mr. Crick's own assessment that it is unimaginative. It is also filled with a passionate devotion to large questions. For example: ''People are happy to contemplate the limitless powers of God - a doubtful proposition at best - but quite unwilling to meditate creatively on the size of this extraordinary universe in which, through no virtue of their own, they find themselves. Naively one might have thought that both poets and priests would be so utterly astonished by these scientific revelations that they would be working with a white-hot fury to try to embody them in the foundation of our culture.'' Or: ''I find it a curious symptom of our times that those who derive deep satisfaction from brooding on their unity with nature are often quite ignorant of the very unity they are attempting to contemplate. Perhaps in California there already exists a church in which the genetic code is read out every Sunday morning.''

These larger questions in fact enter, although indirectly, into the main argument. Mr. Crick contends that an advanced extraterrestrial society would have sent microbes rather than themselves because ''bacteria go farther.'' But radio waves go farther still. They are much less expensive to launch, and they travel at the speed of light. It would be possible to send by radio a description of the genetic code and all the genes of hundreds or thousands of different organisms.

If the only objective of the extraterrestrials were to propagate their kind of life, why not just broadcast the structure of that life to anyone who will listen? Presumably Mr. Crick would argue that this is not a reliable method, since the senders might not know beforehand if anyone was listening. But in that case, why would they accept some comparable uncertainty about the survival of containers of microbes taking tens of thousands of years to reach their destinations? Even if every such canister were automatically guided to a suitable untenanted world, would there not be many major crises in the subsequent evolution that would need some guiding through? Could it really be, as Mr. Crick the molecular biologist suggests, that the extraterrestrials are only interested in propagating their molecular biology? Would they have no interest in communicating the equivalent of their brain structure or their culture? It seems unlikely that merely sending the simplest organisms would satisfy such a civilization intent on colonization. If they have no scruples about infecting a ripe but hitherto lifeless world, why should they scruple at repeated intervention in the subsequent evolution of life on the seeded planet?But this natural consequence of Mr. Crick's hypothesis does not, I suspect, sit well with him; it is much too close to the old-time Western religion he decries as a sign of our backwardness and superstition. (After creating life, the God of the Judeo-Christian-Islamic myths repeatedly intervened in human affairs when He was dissatisfied with the flow of events.)

For myself, the idea that life arises on many worlds through the interaction of matter and energy - that is, by the consequences of the laws of physics and chemistry - seems a sufficiently ennobling prospect to satisfy anyone's predilections for the holy, and embraces that awe for the intricacy and subtlety of the cosmos which Einstein described as the deepest of religious feelings. But it is very hard to approach the question of the origin of life without coming to grips with religious sentiments of one sort or another.One of the criteria for a successful scientific theory is that it be, at least in principle, falsifiable - that there be some experiment that has the potential of disproving the theory. But the theory of Directed Panspermia, because it attributes critical events to extremely powerful beings in remote times and places, tends, like many varieties of conventional Eastern and Western religions, to resist any attempt to test its validity. It's too easy to say: ''The extraterrestrials could have made life any way they wanted to.'' A theory that is consistent with any possible datum is not much better than a theory that is consistent with none of the data. Only a real failure in our ability to explain the origin of life through prebiological organic chemistry on the primitive Earth would point us toward Directed Panspermia. Nothing like such a failure exists today; indeed, my reading of the evidence makes the prospect of understanding the origin of life by indigenous processes quite hopeful.

The book has an occasional disconcerting tendency to describe the extraterrestrials as ''people,'' which carries a distinctly anti-Darwinian implication; there are a few errors of fact and a few excesses of conservatism, as when the universe is said to be ''at least three billion light-years'' in radius; for a popular book, there are a great many technical terms that are not explained when first introduced: e.g., neutron star, angular momentum, tetrahedron, levo, dextro, polymerization, tRNA, and the ''temperature'' of space. There are also many easily accessible insights into molecular biology which are both felicitous and instructive as, for example, Mr. Crick's description of the interwined double helix of DNA as ''two lovers.''Darwin got the hereditary mechanism wrong (although his contemporary Gregor Mendel was on the correct track) but, in my opinion, the origin of life right; while for Mr. Crick, I believe it is just the other way around. Darwin wrote: ''But if (and oh what a big if!) we could conceive in some warm little pond, with all sorts of ammonia and phosphoric salts, light, heat, electricity, etc., present, that a protein compound was chemically formed ready to undergo still more complex changes.''

Darwin and Mr. Crick are probably the two most eminent personages in the history of British biology, and it is interesting that Darwin was not considered fit to be knighted, and Mr. Crick has not yet been - their devotion to reason in matters of religion being perhaps a contributory cause. I recommend ''Life Itself'' highly for its stimulating and provocative thesis, but not as a work to be read uncritically