Fred Hoyle An observer of the world and a ponderer on its problems ...
THE VINDICATION OF PANSPERMIA by Chandra Wickramasinghe
Throughout most of the 20th century Fred Hoyle remained the preeminent figure in theoretical astronomy. His contributions spanned an exceptionally wide range of topics from nuclear astrophysics, to planetary science and cosmology. In each of these areas he made lasting contributions that were pivotal to further developments. His endeavours relating to topic of panspermia and the theory of cosmic life were pursued mostly in conjunction with the present writer. Our work began with investigations into the nature of interstellar dust in the 1960s in which we challenged the prevailing dogma of inorganic ice grains, proposing instead dust grains comprised mainly of the element carbon. Following our first attempt to identify most of material with graphite, the progression to organic polymers and eventually biological dust eventually followed. From the outset this work provoked strong emotions and controversy in the scientific community.
The scientific consensus that we challenged was that life originated in a primordial soup on the Earth - possibly in its lakes and oceans. The organic molecules needed for the origin of life were supposed to have been formed from inorganic molecules by the action of electric discharges and solar ultraviolet rays and cosmic rays in terrestrial clouds, and then rained down into the oceans generating the canonical "primordial soup". The chemistry that preceded the emergence of the first self-replicating living cell was considered to be an extension of Darwinian evolution acting at a molecular level; so Darwinian evolution and the primordial soup origin of life were considered intimately linked as complementary processes. Discussions of panspermia that we were to engage in were thus perceived as a serious threat to one of the cornerstones of biology, and therefore had to be conducted against a rising tide of scientific hostility.
It transpired that a somewhat unlikely watershed in our work was reached in 1986 following observations of Comet Halley. Our predictions for organic material in comets were overwhelmingly validated by the new data, but reference to our work was conspicuously withheld in all the publications that followed. When we protested to the Editor of Nature that such conduct was a flagrant violation of generally accepted scientific etiquette, the magazine published a leading article attempting to defend their position. In it the Editor explained that we had only ourselves to blame for experiencing difficulties of an unusual kind in the referencing of our work1. Our crime was that we had become caught up in the eccentric doctrine of panspermiology, a doctrine for which it was claimed there was no evidence2.
The situation in relation to the acceptability of panspermia, the role of comets and the theory of cosmic life is now dramatically different from what it was scarcely two decades ago. Even in the past few months results from the Rosetta Mission to Comet 67P/C-G have shown that comets have an intimate connection with the origin of life. The following facts are widely conceded:
The logical beginning of the ideas described in this volume goes back to Fred Hoyle’s arguments of 1946 (ref. 3) that all the chemical elements in the universe heavier than H and He were synthesised in nuclear reactions in stars. The synthesis of 12C presented a problem to theoreticians because the only available route to its production (the triple-alpha reaction transforming 4He to 12C) required the existence of an hitherto undiscovered resonance in the carbon nucleus at E=7.162Mev without which no carbon could be synthesised. Hoyle inaugurated a principle that has come subsequently to be known as the "anthropic principle", a principle by which our existence in the world demands certain properties of the world to be true. Invoking this “anthropic principle” Hoyle predicted the existence of this resonance in the nucleus of 12C, later to be discovered in the laboratory by W.A. Fower. Thereafter Hoyle, Burbidge, Burbidge and Fowler (ref.4) wrote their seminal paper on the production of chemical elements in stars, showing also how supernovae can scatter the products of nucleosynthesis into interstellar space.
Hoyle’s work of the 1940’s and 1950’s and his espousal of the anthropic principle had a further important corollary. If life were to exist at all, not just on Earth but anywhere, the products of stellar nucleosynthesis had to be assembled into molecules that eventually led to life. We now know that the interstellar medium is choc-a-bloc with organic molecules, but these developments were preceded by long history of denials.
The first detection of diatomic molecules goes back to the identification of the methylidyne radical CH in stellar spectra in 1937 (refs 5-7). Although molecules such as H2CO were not discovered until 1969, the existence of even larger and more complex molecules in interstellar space had been accumulating from earlier decades in the form of the so-called diffuse interstellar bands, the most prominent of which is centred on 4430A with a half-width of 30A (ref.8). Fred Hoyle, the present writer and some others saw this data as evidence of exceedingly complex molecules in space, even perhaps a molecule as complex as a chlorophyll (Johnson9). Whilst a publication of such statements in the scientific journals was barred by peer review censorship, Fred Hoyle was so convinced by the force of evidence that he published these ideas in his classic “Frontiers of Astronomy” in 1955 (ref.10) and two years later fictionalised them in his famous novel “The Black Cloud” published in 1957 (ref.11).
The collaborations of the present writer with Fred Hoyle that extended over nearly 4 decades began with an attempt to review and reassess the observational data and theoretical arguments for the composition of interstellar dust. It was widely held at the time that this was a futile exercise, it being 'proved beyond doubt' that the dust was made up of submicron-sized ice particles similar to the particles in the cumulous clouds of the terrestrial atmosphere. Very soon, however, our work showed clearly that the currently fashionable ice-grain theory (Oort and van de Hulst12) was seriously flawed, and we argued instead for refractory grains comprised mainly of the element carbon – the element for the synthesis of which Fred Hoyle’s predicted 12C resonance was crucial. We first argued the case for carbon dust in the form of graphite (Hoyle and Wickramasinghe13). This model had a considerable measure of success, but with the passage of time and with the deployment of new techniques of astronomical spectroscopy and with instruments carried above the atmosphere, things developed rapidly – unerringly it would seem in the direction of Fred Hoyle's The Black Cloud. In 1969 formaldehyde molecules as well as amino acid precursors were discovered in interstellar clouds, and in 1974 the present writer argued that polymers based on H2CO could make up the bulk of interstellar dust grains (Wickramasinghe14). Such grains arguably accounted for the newly-discovered spectral features of interstellar dust at ~ 10 μm, features which were earlier attributed to mineral silicates.
At this time we proposed an identification of the 2200A interstellar absorption feature of dust on the basis of complex organic molecules including PAH type structures of the type that are being discussed widely in the present day15. Between 1974 and 1980 we began suggesting that prebiotic molecular evolution takes place in the interstellar medium and that the inclusion of such material in the outer regions of the solar nebula led to the origin of life – life originating in comets in the outer solar system16.
Hoyle and the present writer were constantly striving for better agreements with astronomical data, as new observations with higher degrees of precision came along. We first argued for H2CO being assembled abiotically into cellulose chains17 (cellulose being overwhelmingly the most abundant biomolecule on Earth). Not long afterwards in 1980 we presented for the first time the theory that a large fraction of the interstellar dust was in fact generated biologically18. The carbonaceous interstellar material contained biological (bacterial cells) in various stages of degradation. Only a minuscule surviving fraction (< 10-24 was required for panspermia to the dominant process of spreading and evolving life in the universe. In a lecture delivered in Cardiff on 15 April 1980 entitled “The relation of biology to astronomy” Fred Hoyle concluded thus:
“Microbiology may be said to have had its beginnings in the nineteen forties. A new world of the most astonishing complexity began then to be revealed. In retrospect I find it remarkable that microbiologists did not at once recognize that the world into which they had penetrated had of necessity to be of cosmic order. I suspect that the cosmic quality of microbiology will seem as obvious to future generations as the Sun being the centre of our solar system seems obvious to the present generation….”
It was months after this declaration that D.A. Allen and D.T. Wickramasinghe19 obtained the first high resolution spectrum of the Galactic Centre infrared source GC-IRS7 over the 2.8 – 3.9μm waveband and obtained the stunning match with an earlier prediction for desiccated bacterial grains. This result clinched the case for us: a precise prediction made ahead of an observation was matched to an amazing degree of precision (Hoyle et al 20).
During the period 1981-1991 correspondences between further predictions of the theory of cometary panspermia and new observations unfolded uncannily in a manner that should have convinced even the most hardened skeptic that we were on the right track. No “wrong theory” could produce unerringly such close correspondences with a wide range of predictions, as for instance the discovery in 1986 that the dust from Comet Halley had a spectrum that also matched the prediction of bacterial-type dust. Yet the entrenched geocentric position of most scientists remained stubbornly difficult to shift. We put out a stream of scientific papers and books, some of which were issued first as preprints. These preprints, in the days before the internet, constituted the only secure way of communicating our ideas to colleagues and the public. The Editor of Nature, John Maddox, referred to these as “samizdat” publications, despite the fact that some of the key papers were in fact later published in Nature.
We developed our ideas relating to the cosmic nature of life in a series of papers in scientific journals, including Nature, and in popular books such as Lifecloud (1977), Diseases from Space (1978) and Evolution from Space (1980). Many strident rebuttals of a polemical nature were published by prominent scientists of the day. The following remark by W.W. Duley and D.A. Williams in Nature is one example:
“….We conclude that no spectroscopic evidence exists to support the contention that much of the interstellar dust consists of organic materials…….” Nature, 277, 4 January 1979.
The facts as they continued to unfold have proved that such opponents were mistaken. Today a wide range of data in a variety of fields – astronomy, geology and biology are beginning to converge on establishing the validity of the hypothesis that life is a cosmic phenomenon. Of particular relevance are recent studies of exoplanets – planets outside our solar system – which lead to estimates of some 140 billion habitable planets in our galaxy alone21. With an average separation of such planetary systems of only a few light years it would be impossible to prevent the exchange of biological material between these systems. The emerging picture, described in several recent books22,23,24 is of a single connected biosphere extending at least across our Milky Way within which Darwinian evolution occurs. This is exactly the position that Fred Hoyle and the present writer had reached over 3 decades ago.
1. Maddox, J., 1986. Nature, 321, 723
2. Hoyle, F and Wickramasinghe, N.C., 1986. Nature, 322, 509-511
3. Hoyle, F., 1946. The synthesis of the elements from hydrogen, Mon.Not.Roy.Astr.Soc, 106, 343
4. Burbidge, E.M., Burbidge, G.R., Fowler, W.A. and Hoyle, F., 1957. Synthesis of the elements in stars, Rev.Mod.Phys, 29(4), 547
5. Herbst, E., 2001. The chemistry of interstellar space, Chem. Soc. Rev., 30, 168-176
6. Dunham, T., Jr., Adams, W.S., 1937. Publ.Astron.Soc.Pacific, 49, 26
7. Swings, P. and Rosenfield, L., 1937. Astrophys.J., 86, 483
8. Herbig, G.H., The diffuse interstellar bands, Ann.Rev.Astron.Astrophys., 33, 359
9. Johnson, F.M., 1967. Diffuse interstellar lines and chemical characterisation of interstellar dust, in Interstellar Grains (ed J.M.Greenberg and T.P. Roark) NASA-SP 140
10. Hoyle, F., 1955. Frontiers of Astronomy (Heinemann, Lond.)
11. Hoyle, F., 1957. The Black Cloud (Heinemann, Lond.)
12. Oort, J.H. and van de Hulst, H.C., 1946. Gas and smoke in interstellar space, Bull Astron. Inst. Netherlands, 10, 187
13. Hoyle, F. and Wickramasinghe, N.C., 1962. On graphite particles as interstellar grains, Mon.Not.Roy.Astr.Soc, 124, 417
14. Wickramasinghe, N.C., 1974. Formaldehyde polymers in interstellar space, Nature, 252, 462
15. Hoyle, F. and Wickramasinghe, N.C., 1977. Identification of the λ2,200A interstellar absorption feature, Nature, 270, 322
16. Hoyle, F. and Wickramasinghe, N.C. 1980. In Comets and the Origin of Life (ed C. Ponnamperuma) (D. Reidel, Dordrecht)
17. Hoyle, F. and Wickramasinghe, N.C., 1977. Polysaccharides and the infrared spectra of galactic sources, Nature, 268, 610
18. Hoyle, F. and Wickramasinghe, N.C.,1979. On the nature of interstellar grains, Astrophys.Sp.Sci., 66,77
19. Allen, D.A. and Wickramasinghe, D.T., 1981, Nature, 294, 239
20. Hoyle, F., Wickramasinghe, N.C., Al-Mufti, S., Olavesen, A.H. and Wickramasinghe, D.T., 1982. Infrared spectroscopy over the 2.9-3.9μm waveband in biochemistry and astronomy Astrophys.Sp.Sci., 83, 405
21. Kopparapu, R.. 2013. A revised estimate of the occurrence rate of terrestrial planets in thehabitable zones around kepler m-dwarfs, astro-ph, arXiv:1303.2649
22. Wickramasinghe, J.T., Wickramasinghe, N.C., Napier W.M., 2011. Comets and the Origin of Life (World Scientific and Imperial Coll.Lond. Press)
23. Wickramasinghe, C., 2014. The Search for Our Cosmic Ancestry (World Scientific and Imperial Coll.Lond. Press)
24. Vindication of Cosmic Biology: A tribute to Sir Fred Hoyle, 2015 (World Scientific and Imperial Coll.Lond. Press)
Status Report (1999) by Hoyle and Wickramasinghe
Living material contains about twenty different sorts of atom combined into a set of relatively simple molecules. Astrobiologists tend to believe that abiotic material will give rise to life in any place where these molecules exist in appreciable abundances and where physical conditions approximate to those occurring here on Earth. We think this popular view is wrong, for it is not the existence of the building blocks of life that is crucial but the exceedingly complicated structures in which they are arranged in living forms. The probability of arriving at biologically significant arrangements is so very small that only by calling on the resources of the whole universe does there seem to be any possibility of life originating, a conclusion that requires life on the Earth to be a minute component of a universal system.
Some think that the hugely improbable transition from non-living to living matter can be achieved by dividing the transition into many small steps, calling on a so-called 'evolutionary' process to bridge the small steps one by one. This claim turns on semantic arguments which seek to replace the probability for the whole chain by the sum of the individual probabilities of the many steps, instead of by their product. This is an error well known to those bookies who are accustomed to taking bets on the stacking of horse races.
But we did not begin our investigation from this point of view. We began by attempting to understand the data on the scattering and absorption of starlight by interstellar dust particles. As the observations improved over the years we were led gradually to a cosmic view of the origin of life, led first to clear evidence that a major fraction of the dust is of an organic composition and then to the result that the dust actually contains a biological component in the form of bacteria. Much of this work appeared in the Cardiff Blue Preprint Series and was later published in journals, mainly in Astrophysics and Space Science.
Microorganisms reproduce themselves at astonishing rates when the physical and chemical conditions are favourable, so great indeed that there is no difficulty in seeing how the entire universe could be suffused by microbial life. Those with a dislike for this conclusion often argue that interstellar microorganisms would be destroyed by ultraviolet light from stars. But there are several effective replies. First, organisms are not so much destroyed by ultraviolet as deactivated. Their genetic arrangements survive, and reactivation can be achieved simply by a redirecting of the switching of thymine bonds. Second, microorganisms are easily shielded against ultraviolet light. Indeed molecular clouds in the galaxy are highly effective in this respect, both in cutting out the glare of ultraviolet radiation and permitting the growth of protective mantles around the bacterial particles. And third, the replicative power of microorganisms is so great that only a minute fraction of them are required to survive in each generation. These replies seem collectively more than adequate to answer this objection.
With the genetic components of life distributed widely throughout the universe, it is a matter for each local environment to pick out the arrangements that fit the particular circumstances. In a case like the Earth a complicated fitting together of the components has occurred over the last several hundred million years, by a process which biologists refer to as evolution. However the basic genes have not been produced here. For those who believe otherwise there are problems. The interclass differences between bears and horses are much greater than the interspecies differences among bears and horses taken separately. Yet it is the latter that dominate the fossil record. Yet it is the latter that dominate the fossil record. Because the latter have indeed occurred on the Earth, whereas the genes responsible for the class differences of bears and horses have been externally driven and the record of their origin is not local.