The Tanpopo project will hopefully confirm the survival of bacteria in the near-Earth environment at the distance of the ISS orbit and thus verify earlier results of Cockell et al (1). More importantly, perhaps it will sample the environment outside the ISS for ambient or in-falling microbes that may be of extraterrestrial origin. In this latter respect it would significantly extend earlier attempts to detect and isolate microbes in the stratosphere at heights of 41km (2-5). The relevance of this work towards confirming the Hoyle-Wickramasinghe theory of life as a cosmic phenomenon cannot be overlooked (6).
1. Exposure of phototrophs to 548 days in low Earth orbit: microbial selection pressures in outer space and on early earth
Charles S Cockell, Petra Rettberg, Elke Rabbow and Karen Olsson-Francis
The ISME Journal, 5, 1671–1682 (2011)
2. The detection of living cells in stratospheric samples
M.J. Harris, N.C. Wickramasinghe, D.Lloyd, J.V. Narlikar, P. Rajaratnam, M.P. Turner, S. Al-Mufti, M.K. Wallis, and F. Hoyle
Proceedings of the SPIE Conference, 4495, 192 (2002)
3. Microorganisms cultured from stratospheric air samples obtained at 41 km M. Wainwright, N.C. Wickramasinghe, J.V. Narlikar and P. Rajaratnam FEMS Microbiology Letters, 218, 1, 161 (2003)
4. Did silicon aid in the establishment of the first bacterium?
M. Wainwright, K. Al-Wajeeh, N.C. Wickramasinghe and J.V. Narlikar International Journal of Astrobiology, 2, 3, 227 (2003)
5. Progress towards the vindication of panspermia
N.C. Wickramasinghe, M. Wainwright, J.V. Narlikar, P. Rajaratnam, M.H. Harris and D. Lloyd Astrophysics and Space Science, 283, 403 (2003)
6. Astronomical Origins of Life: Steps towards Panspermia
F. Hoyle and N.C. Wickramasinghe (Kluwer Academic Publishers, 2000)
Aug 3, 2015 : Comet Evidence Supports Theory of Cosmic Life
It has long been hypothesized that comets are one of the main carriers of DNA/RNA and complex molecules of life inside the Solar System.
Surely 67P/Rosetta offers an important opportunity that ESA must seize – and on THIS mission! NOT on a new mission sometime in the future.
When Chandra Wickramasinghe attended early design meetings on Rosetta as a principal investigator, it was well known that he brought the view that “life detection” experiments should be carried on each of the two parts of the spacecraft.
But in those days, just 13 years ago, the field of astrobiology was of limited respectability to the astronomers, geologists, chemists and physicists who dominated the focus of the early team.
Since the 2013 consciousness change with the Kepler Mission breakthrough discoveries and announcements, current probabilities calculate that every star in the galaxy most likely has at least one exoplanet and perhaps a large number have an exoplanet in their “Goldilocks zone”.
This was strong evidence for the “life is a cosmic phenomenon” philosophy of Hoyle and Wickramasinghe. NASA astrobiologist Dr. Chris McKay, is often heard confirming his adoption of this theory.
So have the local Panspermia processes already seeded most of the inner Solar System with desiccated viruses, bacteria and algae?
I believe so.
As for “contamination by humans”, we know over 500 different species of bacteria can be found in a healthy human mouth, with at least ten times that many viruses. An experiment with a probiotic yoghurt counted the number of bacteria exchanged in a 10 second “intimate” kiss – and found a whopping 80 million passed from tongue to tongue.
If that surprises you, did you know every whale on the planet excretes 1013 viruses per day in their feces.
No wonder the Space Station is considered contaminated. MARS itself has likely already been contaminated, even without humans taking our biome with us there on manned landings.
Dr. Chris McKay talks about asteroid collisions causing the ejection of microbes from a given planet with the possible transfer of life planet to planet, comet to planet. McKay is guiding us to learn that “the theory of Panspermia” is the best current guess for NASA’s short and long term planning.
This is the reason that “Seeking the Signs of Life” is “Difficult”, because not only are viruses very small and hard to remotely detect and classify, but even the larger particles such as bacteria and algae (diatoms) have similar (if not quite as challenging) difficulties.
At the Astrobiology conference in Sri Lanka last week, I talked with Professor Milton Wainwright, the biologist from Sheffield University in the UK. I was struck by his reaction when I pointed out new lens-free microscope technology which offers real-time bio-imaging (from a small and light device) which could allow much easier detection of viruses.
“Our tests in the stratosphere have been focused on larger particles typically algae (aka plankton; diatoms). The benefit of our focusing on these larger-sized particles has been that they are much less likely to have been lifted from the surface of Earth. Plus the particles we are finding are spectacularly interesting”, Professor Milton Wainwright .
But comets as carriers? Many of us will recall reading that Sir Arthur C. Clark was most impressed with the Hoyle-Wickramasinghe Model but cautioned us that we would have to wait for the return of the short-period comet, Halley, in 2061, to confirm the theory.
Little did Clark know how quickly humans would be able to dance around the solar system jumping from one comet to another, taking samples and transmitting the results back to our control centres on Earth!
Chandra left the Rosetta team in frustration, around 2002, saddened that his advice seemed to have been ignored. But it now seems that many quietly heeded his input and raised their game. So we actually have a very sophisticated set of “seeds of life” detection instruments on Rosetta and Philae.
We do NOT have an instrument that actually detects a “moving” microbe. At least this is not overtly stated (MIDAS is very close). But the experiments on Philae and Rosetta together detect almost everything else you might wish to seek.
Chandra has been particularly intrigued with the MIDAS experiment which is operating at the virus–size level. It might not be able to deliver conclusive proof of microbes on this voyage, but this technology augurs well for the next comet visit.
Long Period Comets
My own particular request is for us to visit a long-period comet –similar to ISON 2 years ago. Unlike 67P, which orbits over just 8 years and in the plane of the Galaxy, the long-period comets have orbits of over 100,000 years and might well come in from adjacent stars. They also come in at a steep angle to the plane of the Galaxy.
The Solar System is at an angle to the plane of the galactic disk. This is almost certainly because the Solar system is not from the Milky Way. Rather it is now believed to be part of the Sagittarius Galaxy passing through the Milky Way. I believe the long period comets, if they come in from an adjacent star, or even from the Oort Cloud, can come in at any angle to the ecliptic – ie to the plane of the solar system. Whereas short period comets are always IN the plane of the solar system.
Typically the bulk of the long period comets, have been moving in the plane of the Milky Way (at the constant angle to the solar system). So they usually come in at a steep angle.
I believe it is highly likely we will confirm life in the short period comets – as Hoyle and Wickramasinghe predicted. But finding life in a long-period comet would be even more significant, as this would be life not just from another star system but even from another galaxy – the Milky Way.
According to Wickramasinghe’s predictions, the whole Galaxy is a homogenized life pool, so it would be an exciting experiment to seek and discover life in a long-period comet, and to compare any of its RNA/DNA with our known Solar System RNA/DNA. Although we might predict differences in the life-form roots from the two separate galaxies, the inter-galactic contamination has been going on for a very long time, so it is unlikely there is any major differences between life in the two galaxies.
I have recently learned much about the iBOL Project (International Barcode of Life – DNA classification project) and believe this will become very important. I will cover this in my next “Letter from Canada”.
At AbReCon 2015
Astrobiology Research Conference
University of Peradeniya, Sri Lanka
21-23 August 2015
I am happy to be able to report the rapid acceptance of Panspermia into academia. A new generation of astrobiologists have embraced panspermia especially as it relates to the solar system.
Well worth scanning is this 1-page PDF from last Friday’s New Scientist. New Scientist – 2015-8-8
Dr. Chris McKay, Astrobiologist at NASA AMES gives animated explanation of panspermia.
As we visit short period comets like 67/P, the Rosetta Mission catches glimpses of the “seeds of life” without having a complete set of experiments on board.
The good news : as we have predicted, the complex molecules found are consistent with Panspermia.
We await MIDAS results from the Rosetta Orbiter, by PI Mark Bentley. Even though he is seeing particles down at the virus size level, he is being conservative (encouraged by his peers) calling the specks “Dust”.
If only ESA scientists would “dare to dream”, and announce the “dust” is consistent with the theory of Panspermia. Consistent with the proposal that viruses and bacteria are carried by Comets like 67P. Let’s face it, accepting the existence of microbes in short period comets is not too far a leap from accepting the interchange of microbes between planets. 67P is on a short 7 year orbit. Not much more mysterious than an asteroid.
We are not asking for misrepresentations nor inaccurate statements BUT the facts are that these specks on MIDAS do seem to be consistent with viral and bacterial clumps. If they are not microbial clumps and 67P has no microbes, then this really would be worthy of a paper.
Long Period Comets
But what if these were inter-stellar comets?
Email from Bill Smith to Haley Sapers 2015-7-10
Dear Haley :
Chandra writes : I will certainly send you (Bill and Haley) the meteorite sample – a porous piece of rock about 2-3 cm across.
Before I send Chandra the shipping details, please confirm you are still ready to undertake this project. It would help if you could summarize the experiments you felt necessary. I am hoping you will use additional equipment and techniques.
I am concerned over contamination and will ask Chandra to discuss the status of contamination of the rock with you by email.
Once you are ready and have OK’d the project, I would like to track your progress in a BLOG. I think the global community will be very interested.
The following six (6) peer-reviewed papers represent what was completed, documented and published in 2013 :
1) Vol 21 No. 37 (a) published 10-1-2013 Fossil Diatoms in a new Carbonaceous Meteorite
Abstract : We report the discovery for the first time of diatom frustules in a carbonaceous meteorite that fell in the North Central Province of Sri Lanka on 29 December 2012.
Contamination is excluded by the circumstance that the elemental abundances within the structures match closely with those of the surrounding matrix. There is also evidence of structures morphologically similar to red rain cells that may have contributed to the episode of red rain that followed within days of the meteorite fall. The new data on “fossil” diatoms provide strong evidence to support the theory of cometary panspermia.
2) Vol 21 No. 38 (b) published 13-1-2013 On the Cometary Origin of the Polonnaruwa Meteorite
Abstract : The diatoms discovered in the Polonnaruwa meteorite are interpreted as originating in comets and the dust in interstellar space. The exceptionally porous structure of the Polonnaruwa meteorite points to it being a recently denuded cometary fragment. Microorganisms that were present in a freeze-dried state within pores and cavities may have survived entry to be added to the terrestrial biosphere.
We conclude by reporting that an extract from the interior of a Polonnaruwa meteorite sample, studied under a light microscope at the Medical Research Institute in Colombo, was found to contain living diatoms (See Fig.4). If this result is confirmed in future studies and contamination is excluded, the meteorite would have been shown to contain both fossil as well as living microbes, and panspermia thus demonstrated in real time.
3) Vol 21 No. 39 © published 4-2-2013 Authenticity of the Life Bearing Polonnaruwa Meteorite
Abstract : We show that the Polonnaruwa stones that were collected on 29 December 2012 following a witnessed fireball, in which we found biological structures, do not possess properties that are consistent with fulgurites on the basis of X-ray diffraction studies, and other data. The existence of distinct diatom frustules fused into the rock matrix makes recent contamination unlikely. Contamination
4) Vol 21 No. 40 (d) published 8-2-2013 Living Diatoms In Polonnaura Meteorite – Possible Link to Red and Yellow Rain
Abstract : Meteoroids belonging to a cometary meteor stream, upon entering the atmosphere, could undergo hierarchical fragmentation, and the smallest micron-sized dust might serve to nucleate rain. The larger fragments that survive passage through the atmosphere may end up as the spray of meteorites such as were collected in Sri Lanka on 29th December 2012 and 3rd January 2013. We show tentative evidence for the presence a wide range of genera and species of diatoms which are living, in addition to those discovered in SEM studies that are fossilised.
5) Vol 22 No. 2 published 5-3-2013 Oxygen Isotope, Crystalline and Biological Composition
Abstract: Results of X-Ray Diffraction (XRD) analysis, Triple Oxygen Isotope analysis and Scanning Electron Microscopic (SEM) studies are presented for stone fragments recovered from the North Central Province of Sri Lanka following a witnessed fireball event on 29 December 2012.
The existence of numerous nitrogen depleted highly carbonaceous fossilized biological structures fused into the rock matrix is inconsistent with recent terrestrial contamination.
Oxygen isotope results compare well with those of CI and CT-like chondrites but are inconsistent with the fulgurite hypothesis.
6) Vol 22 No. 1 published 5-3-2013 INCIDENCE OF LOW DENSITY METEOROIDS OF THE POLONNARUWA-TYPE.
Abstract : The ingress of micrometeorites of cometary origin with densities below ~ 1 g cm-3 into the Earth could average at least 5 tonne per day. Although much of this is burnt upon entry through the atmosphere as meteors, a non-trivial fraction (~10%) which have sizes of ~ 1
Notes on 2013 experiments on the the Polonnaruwa meterorite
From: Richard Hoover [mailto:email@example.com]
Sent: May 21, 2013 3:32 PM
To: <firstname.lastname@example.org>; <email@example.com>
Subject: Re: Confidential – Jan/Feb 2013 Polonnaruwa Meteorite analysis results
Your summary is not entirely correct.
1. Nitrogen analysis.
I personally conducted the study of nitrogen levels present in diatoms, cyanobacterial filaments, Hystrichospheres and actriarch fossils that I found embedded in the Polonnaruwa stones that O personally collected in Sri Lanka. These studies were carried out at NASA/MSFC and at Cardiff University in collaboration with Prof. Wickramasinghe and other members of the team.
The stones contained clearly biological forms that did not contain detectable nitrogen levels.
1. This is not Necessary for the forms to be indigenous to the stones rather than contaminants. If the diatoms & Cyanobacteria had lived on the parent body and died in the last hundred thousand years or so, then they could contain nitrogen and still be extraterrestrial.
2. The absence of nitrogen in Biological remains in the stones is SUFFICIENT to establish that these remains are NOT MODERN CONTAMINANTS.
The Polonnaruwa stones fell on Dec. 29, 2012. Any microbes that entered the stones after they fell would contain detectable levels of Nitrogen. That also applies to the other carbonaceous meteorites that I have examined. Alais fell in 1806— only a little over 200 years ago. The loss of Nitrogen requires geological time periods (millions of years) rather than weeks or centuries.
The other tests 2, 3, and 4 are not necessary to conclude that the fossils in Polonnaruwa are indigenous. Those studies have been performed by many other researchers on a wide variety ofCI1 and CM2 meteorites that also contain fossils that lack nitrogen. Those remains have also been dismissed as recent contaminants—with no effort to answer the problems posed by the missing biomolecules—which would certainly be present if the stones contained post arrival biological remains.
You did not answer my question in the prior e-mail. Did you ask Caleb or any of the other critics how they can explain the absence of these life critical biomolecules in stones contaminated after they landed by living terrestrial microbes? I have discussed this problem with prominent biochemists and microbiologists and have yet to hear any Answer whatsoever.
William E. (Bill) Smith
Institute for the Study of Panspermia and Astroeconomics
c/o KBP, 4-1-7/8F
No.801, Kagano, Ogaki-City
Gifu 503-0006, Japan
2014-10-15 : Just 4 days to go to Mars Obiter MAVEN turning from MARS to observe Comet Siding Spring. A short summary video is well worth watching http://youtu.be/AwMjoy_02Ic
It should be noted that unlike short-period Comets Halley and 67P/G-C (Rosetta target) which are short period Comets (75 years and 7 years respectively), Comet Siding Spring is a long-period comet – just as was Comet ISON last year. Although it is generally accepted that these long-period comets have very long orbit periods (>100,000 years) and come in from the Oort Cloud, our hypothesis includes the proposition that many such comets are effectively parabolic and are “sling shot in” towards our solar system from nearby stars.
The Hoyle-Wickramasinghe Panspermia Model of the Panspermia Hypothesis predicts that the short period comets and even some asteroids orbiting the sun are carriers of “solar system life” including the RNA/DNA that we find in within living cells in every nook and cranny of earth, and that we are now finding in the stratosphere; inside meteorites; and even outside the windows of the International Space Station. With the overwhelming dominance of viruses in our terrestrial biosphere, viruses are also most likely included in the cosmic cargo being transported in these objects. Within just a few years we expect to confirm that microbial life across the solar system, from deep under the ice and rock of Mars, to under the ice of Europa and Enceladus is largely the same – with viruses, bacteria and archaea largely “similar” as solar system life has been homogenized over the last 4.5 billion years (4.5 bya).
But what about life in other solar systems and across the galaxy? We have recently published a paper at http://www.hypothesisjournal.org which calculates the time to seed the galaxy from a single point source which was likely NOT Earth. Included in this “thought experiment”, is the assumption that “the seeds of life”, are carried from star to star by the long-period comets like ISON and SIDING SPRING.
Many years ago I concluded that “Life is a Cosmic Phenomenon”, so I wait with baited breath the results of MAVEN’s observations this coming Saturday. I have written that the inside of long-period comets should be ideal places to incubate evolving viruses and bacteria. Then again it could simply house dormant viruses or DNA pieces or even prions with no associated cells (ie no bacteria or archaea) to cause activation. Now we have a chance to point sophisticated instruments at both Mars and at this long-period comet approaching the red planet. It is for me a breath-taking moment.
In 2001 Sir Arthur C. Clarke predicted “2061 Halley’s Comet returns – first landing by humans, And the sensational discovery of both dormant and active life forms vindicates Wickramasinghe and Hoyle’s century-old hypothesis that life exists through space.”
Well, little did Sir Arthur or any of us, know just 13 years ago, that on October 19th, 2014 we would have a long-period comet (way more significant than Halley’s Comet), Comet Siding Spring, pass close to Mars just when NASA had positioned an amazing set of scientific instruments in orbit around Mars (The MAVEN Mission). These instruments will point to Comet Siding Spring in just a few days. The same experiments planned to run on the upper atmosphere of Mars, by serendipity of timing, can now be pointed and run on a long-period comet.
As we conjecture what complex molecules MAVEN might discover in Comet Siding Spring, we should recall the recent discovery by ALMA scientists of the molecule i-propyl cyanide which has a branched backbone of carbon atoms. “There seems to be quite a lot of it, which would indicate that this more complex organic structure is possibly very common, maybe even the norm, when it comes to simple organic molecules in space. It’s a step closer to discovering molecules that can be regarded as the building blocks or the precursors… of amino acids.”
The hope is that amino acids will eventually be detected outside our Solar System. “That’s what everyone would like to see,” said Prof Griffin. “If amino acids are widespread throughout the galaxy, life may be also”.
“So far we do not have the sensitivity to detect the signals from [amino acids]… in the interstellar medium,” explained Dr Belloche. “The interstellar chemistry seems to be able to form these amino acids but at the moment we lack the evidence.
The catalog of discoveries of complex molecules is well maintained in Wikipedia at : http://en.wikipedia.org/wiki/List_of_interstellar_and_circumstellar_molecules
After years of using remote spectroscopy looking into the Inter-Stellar Medium (ISM) from earth 27,000 light years distance, we now have an amazing close-up opportunity to analyze a Comet. On Saturday Maven will be just 132,000 km away from the COMET Siding Spring.
Prof. Bruce Jakosky, MAVEN’s Principal Investigator of CU-Boulder, CO, told Universe Today in an exclusive interview “NASA’s MAVEN Mars Orbiter is “ideally” instrumented to uniquely “map the composition of Comet Siding Spring” in great detail when it streaks past the Red Planet during an extremely close flyby on Oct. 19, 2014 – thereby providing a totally “unexpected science opportunity … and a before and after look at Mars atmosphere”
The probes state-of-the-art ultraviolet spectrograph will be the key instrument making the one-of-a-kind compositional observations of this long period “Oort cloud comet“ making its first passage through the inner solar system on its millions year orbital journey. “MAVEN’s Imaging Ultraviolet Spectrograph (IUVS) is the ideal way to observe the comet coma and tail,” Jakosky explained. “The IUVS can do spectroscopy that will allow derivation of compositional information.” “It will do imaging of the entire coma and tail, allowing mapping of composition.”
Conservative statement we suggest.
We see this as a “historic moment” in space exploration and the “search for life”. Perhaps even an opportunity to test one of the main propositions of Panspermia. The Hoyle-Wickramasinghe Model of Panspermia hypothesized that long period Comets are the source of life in the solar system.
Maven’s observations of Comet Siding Spring could/should deliver the evidence consistent with this hypothesis. These would be momentus results in “NASA’s Difficult Endeavour of Seeking the Signs of Life”.
If long-period Comets are the source of the “seeds of life”, then this weekend NASA’s Maven spectroscopy should detect not just the molecule i-propyl cyanide but amino acids and the molecules of RNA/DNA
- Guanine (G) : C5H5N5O
- Adenine (A) : C5H5N5
- Thymine (T) : C5H6N2O2
- Cytosine (C) : C4H5N3O
COMET Siding Spring, whose source is at least as far as the very edge of our solar system, could be the first confirmation that Comets do indeed carry the “seeds of life”. It might be a long time before we are as close again as this to an Exocomet with such an array of powerful scientific capability pointing at the Comet.
Our best wishes go out to the NASA teams of ALMA, HiRise and MAVEN, as you follow the new NASA directive to “follow the difficult endeavour of seeking the signs of life” in Comet Siding Spring.
This could well be the paradigm changing moment.
Prof. Chandra Wickramasinghe
Director, Buckingham Centre for Astrobiology and Honorary Professor, University of Buckingham, UK
Visiting Professor University of Peradeniya, Peradeniya, Sri Lanka
Member of the Board of Trustees and Director of Research of the Institute for the Study of Panspermia and Astroeconomics, Gifu, Japan
William E. Smith, Director of CardioCommSolutions Inc. and Student of Prof. Chandra Wickramasinghe
Associate of the University of Peradeniya, Peradeniya, Sri Lanka
Further thoughts on the ISS discovery news. FYI – From WIKIPEDIA : Diatoms are a major group of algae, and are among the most common types of phytoplankton. Diatoms are traditionally divided into two orders:
- centric diatoms (Centrales), which are radially symmetrical – this seems to be what has been identified but we are not sure
- pennate diatoms (Pennales), which are bilaterally symmetrical. The former are paraphyletic to the latter.
Richard Hoover is a world expert on diatoms and is seeking further information from the Russians to determine the classification of what has been found.
Question #1 : Are diatoms Eukaryotes? Yes, they are because they have at least one nucleus. So what has been found on the ISS seems to have been identified as large size diatoms.
Question #2 : did they also test for bacteria or archea (or even viruses?) ? Don’t know.
Question #3 : could a particle the size of a diatom rise up from earth to the ISS where there is no air to even “lift” the diatom? There is no way that a particle as large as a diatom could have been carried up to the the space station . It is a defiance of physics. As Richard Hoover wrote this morning :
The famous Russian Cosmonaut Vladimir Solovyev just announced that diatoms and other marine plankton were discovered alive on the outside of the windows of the Russian Section of the International Space Station—surviving in the hard vacuum, thermal, and radiation environment of space. This is consistent with the detection of diatoms embedded in the interior of the Polonnaruwa meteorite stones described in a paper with Chandra Wickramasinghe and Jamie Wallis published last year (2013) in the SPIE Astrobiology Volume. In 1986, the late Sir Fred Hoyle and I proposed in a paper in the Journal Earth, Moon, and Planets that planktonic diatoms could be spewed into space along with water and ice ejected from Europa or from comets and transferred to The Earth.
I do not think there is any possibility they could have been carried to the Space Station by air currents as was suggested, since air currents do not work in a vacuum.
Some critics may say that the diatom found on the space station is too closely related to well-recognised species of diatoms that exist on the Earth. An origin of such an organism in a comet, they could say makes no sense from an evolutionary biology standpoint as life strives always to be ideally adapted to its particular environment.
The reason why the space incident diatom is similar to a terrestrial diatom is that they both came from space. All life comes from space in the first place, and continues to do so. Life on Earth is an expression on the Earth of a Darwinian evolutionary scheme that has taken place over a vast cosmological scale. Not so long ago it would have been thought impossible to find the same species in opposite hemispheres of the Earth. The connected biosphere of the Earth has now to be regarded as being connected to a vast cosmological biosphere within which frequent exchanges of genes and genotypes have established a unity of all life in the cosmos.
I BELIEVE THIS IS STAGGERING NEW EVIDENCE FOR ONGOING PANSPERMIA.
PS. I thought it a good time to dig out two old papers on “Diatoms in Space” which I make available FREE here to my BLOG Readers.
Hoyle, F., Wickramasinghe, N.C., and Al-Mufti, S : Organo-Siliceous Biomolecules and the Infra-Red Spectrum of the Trapezium Nebula, Astrophysics and Space Science, 86, 63-69 (1982), Kluwer Academic Publishers. Diatoms1
Hoover, R.B., Hoyle, F., Wickramasinghe, N.C., Hoover, M.J., and Al-Mufti, S.: Diatoms on Earth, Comets, Europa and in Interstellar Space, Kluwer Academic Publishers, 1985. Diatoms2