SETI [Fwd: Panspermia and the Martian microfossils controversy]

Robert Owen (
Tue, 05 Oct 1999 15:46:46 -0400

Larry Klaes wrote:

> >From Science Week Digest
> October 8, 1999 -- Vol. 3 Number 41
> The techniques and data available to any generation in science
> differ more or less from the techniques and data available to the
> generation that preceded it. And so it makes sense for each
> generation to reexamine important still-unanswered questions in
> terms of possibilities. One such question concerns the origin of
> life on Earth: Did life originate here on Earth, or did "living"
> entities arrive here from elsewhere as the result of one or more
> natural cosmic processes? What are the possibilities to be
> reasonably considered, now that several decades of modern
> astronomy, astrophysics, and space exploration have occurred? In
> general, the term "panspermia" is the name given to the idea that
> life was introduced on Earth from elsewhere in the Universe. This
> is a classical notion, fostered by the chemist Svante A.
> Arrhenius (1859-1927) in the early part of the 20th century
> [*Note #1].
> ... ... Paul Davies (Imperial College London, UK) presents a
> review of current ideas concerning the seeding from elsewhere of
> life on Earth, the author making the following points:
> 1) In recent years, several experiments have been performed
> to test the viability of bacteria and viruses under space
> conditions. In one of these experiments, the bacterial species
> Bacillus subtilis was maintained nearly 6 years in space aboard
> the NASA Long Duration Exposure Facility, and a series of filters
> were used to determine separately the effects of vacuum, solar
> radiation, and cosmic rays. Another experiment simulated the
> effect of 250 years of space exposure in the laboratory. The
> results of these experiments indicate that microbes cope
> relatively easily with the cold and the vacuum, in effect
> becoming freeze-dried and this acting as a preservative. Some
> bacteria form *spores under these conditions. In general, under
> harsh conditions such as these, microbes apparently go into
> suspended animation, their metabolism ceases, and they merely
> remain inert until circumstances improve.
> 2) The most lethal form of radiation in interplanetary space
> is the ultraviolet radiation of the Sun. This radiation, however,
> can be screened by a thin layer of material, and it has been
> pointed out that cool *red giant stars spew out large quantities
> of carbon, and that space-faring bacteria in such a star system
> might therefore become coated in soot and be shielded from the
> worst of the ultraviolet radiation.
> 3) Another harmful radiation in space is galactic *cosmic
> radiation, the collection of high-energy subatomic particles that
> arises from the deeps of space. It is expected that over time the
> cumulative effects of such radiation would prove deadly to living
> systems. However it is possible to imagine scenarios in which
> microbes are at least partially shielded even from this
> ubiquitous hazard. In general, the long-term survival of bacteria
> or other microbes in space might occur because of rock-shielding
> from cosmic rays. A thin film of carbon affords protection from
> ultraviolet light, but a thick mantle of rock is needed to shield
> organisms from high-energy cosmic rays. Since this form of
> radiation creates a cascade of secondary particles upon impact,
> microbes embedded in small rocks would actually suffer higher
> radiation doses than those exposed directly to space. It has been
> estimated that for adequate shielding from cosmic radiation, the
> enclosing rock must be approximately 1 meter across.
> -----------
> Paul Davies: Interplanetary infestations.
> (Sky & Telescope September 1999)
> QY: Paul Davies, Imperial College London, UK.
> -----------
> Text Notes:
> ... ... *Note #1: As the author points out, the physicist William
> Kelvin (1824-1907), in a lecture at a meeting of the British
> Association in Edinburgh in 1871, speculated that from time to
> time an astronomical body might strike a planet with enough force
> to blast debris into space, and that as a result "many great and
> small fragments carrying seed and living plants and animals would
> undoubtedly be scattered through space... If at the present
> instant no life existed upon this Earth, one such stone falling
> on it might... lead to its becoming covered with vegetation."
> ... ... *spores: Only certain bacterial species form spores,
> which are specialized cell structures that may allow survival in
> extreme environments. In general, under conditions of nutritional
> depletion, each bacterium forms a single internal spore that is
> liberated when the mother cell undergoes destruction (autolysis).
> The spore is a resting system, highly resistant to desiccation,
> heat, and chemical agents; when returned to favorable nutritional
> conditions and activated, the spore germinates to produce a
> single bacterium.
> ... ... *red giant stars: A "red giant star" is a star in a late
> stage of evolution, having exhausted the hydrogen fuel in its
> core. It has a surface temperature of less than 4700 degrees
> Kelvin and a diameter 10 to 100 times that of the Sun.
> ... ... *cosmic radiation: Cosmic rays are highly energetic
> particles moving at close to the speed of light and continuously
> bombarding the Earth's atmosphere from all directions. The
> energies of the particles are enormous and range from 10^(8) to
> over 10^(19) electronvolts. The term "highest energy cosmic rays"
> refers to cosmic rays with energies of the order of 10^(20)
> electronvolts or greater, apparently from extra-galactic sources,
> but the origins are not clear.
> -------------------
> Summary & Notes by SCIENCE-WEEK [] 8Oct99
> Ultimately, the labeling of a system as "living" or
> "nonliving" is an anthropocentric question and perhaps not of
> paramount importance in the effort to unravel the workings of
> nature. But labels and the categories they name do have utility:
> in particular, labels and categories do help us conceptually
> organize the enormous variety that nature presents to us. During
> the past few years, there has been a strong debate in progress
> concerning the use of the label "nanobacteria" to characterize
> certain inclusions found in samples of Martian rock, and also
> recently in kidney stones. (For details, see the related
> background material appended below.)
> These nanobacterial entities are extremely small, an order
> of magnitude smaller than the systems biologists classify as
> "bacteria", but not smaller than a number of small viruses. Are
> these entities bacteria? Biologists do not use the term
> "bacteria" loosely, and the defining parameter of bacteria is not
> size. For example, there are protozoa, which as a group consists
> of organisms considerably more complex structurally and
> dynamically than bacteria, that are smaller than certain
> bacteria. There are also fungi that are smaller than certain
> bacteria. In biology, structure and dynamics are the criteria for
> differentiating bacteria, protozoa, fungi, and viruses -- not
> size. Biologists, for example, never use the term "microbacteria"
> to characterize living systems which are not bacteria but which
> are smaller than bacteria. Again, the term "bacteria" puts no
> constraint on the size of a system, except that the system must
> be at least large enough to contain those molecular entities and
> structures that differentiate bacteria from other known living
> forms.
> So when several years ago a group of NASA space researchers
> announced to the world in a press conference that they had
> discovered "nannobacteria" (their first spelling of the term) in
> a Martian rock, and that these inclusions were of the order of 20
> to 50 nanometers in diameter, a host of biologists rose up to
> complain (and even effectively shout) that these inclusions could
> not be "bacteria" because they were simply too small as systems
> to include the molecular and structural repertoires known to
> exist in bacteria, which repertoires differentiate bacteria from
> viruses, protozoa, fungi, etc. To provide an analogy that might
> be helpful in understanding the uproar among biologists, if a
> team of sociologists would call a press conference to announce to
> the world that a group of six people holding hands in a closed
> loop would thenceforth be called by them a "benzene ring", and
> they would further announce their intent to seek the financial
> support of various funding agencies for research in chemistry --
> given such a scenario, one might understand a few thousand
> chemists rising to their feet to shout that a benzene ring is
> much more than six entities joined in a closed loop. "Never
> mind," the sociologists reply: "We know chemistry when we see
> it."
> Considering the use of labels, one wonders whether to label
> this affair as out of Harold Pinter or Groucho Marx. Certainly,
> at the outset, it would have been advisable to have called the
> Martian rock inclusions something other than "nannobacteria".
> Apparently, rather than dissipate, the debate has now become
> more structured. A Finnish scientist has now formally requested
> the University of Kuopio to investigate the work of one of its
> senior researchers, Olavi Kajander, the accuser charging that
> Kajander is making misleading but widely publicized claims that
> he has discovered a new form of life, known as "nanobacteria".
> This has some international ramifications, since Kajander is now
> formally associated with the NASA Institute of Astrobiology, a
> "virtual institute" involving 11 research centers in the US, and
> collaborating with David McKay of the Johnson Space Center in
> Texas on Mars rock research (details of the work of both Kajander
> and McKay is included in the related background material below).
> In brief, Kajander claims that he has identified DNA in
> nanobacteria. Jouni Issakainen (Turku University, FI), the
> Finnish scientist (mycologist) who is requesting investigation,
> says this cannot be substantiated because controls were not
> shown, and because Kajander increased the normal concentration of
> a DNA stain by an order of magnitude, as well as increasing the
> reaction time. Under these conditions, says Issakainen, the stain
> can become nonspecific.
> Kajander, in turn, states: "In fact, I don't care whether
> nanobacteria have genetic material or not -- we have shown that
> they are automatically replicating particles that produce
> apatite, and that they are involved in disease. And I want to
> cure disease."
> Apparently despite the controversy, the medical and
> scientific sections of the Academy of Finland have continued to
> support Kajander's work. Reviewers of a US$120,000 (FM706,000) 3-
> year grant application for work on nanobacteria "combining
> microbiology, geology, and astrobiology" recommended rejection,
> but the grant was approved after the publication of Kajander's
> paper in the _Proceedings of the National Academy of Sciences
> US_, and evidently funded with money from the Academy's "risk
> fund". An academy spokesman states: "Although we recognize that
> there are no solid elements of a scientific basis, the academy
> decided to take a risk with the work."
> -----------
> Alison Abbott: Battle lines drawn between "nanobacteria"
> researchers.
> (Nature 9 Sep 99 401:105)
> QY: Alison Abbott []
> -------------------
> Summary by SCIENCE-WEEK [] 8Oct99
> -------------------
> Related Background:
> In 1984, a 1.9 kilogram meteorite the size of a potato
> (designated ALH84001) was found in Antarctica, and because of its
> chemical composition the consensus is that this meteorite (and a
> dozen similar meteorites) originated from the planet Mars. The
> basis for the consensus is the detailed quantitative
> correspondence of the trapped gases in the meteorites to Martian
> atmospheric gases, and the specific distributions of oxygen
> isotopes. In 1996 a group of researchers, D. McKay et al
> (National Aeronautics and Space Administration Johnson Space
> Center, US; Stanford University, US) reported they had concluded
> that unusual characteristics of the meteorite ALH84001 can be
> most reasonably interpreted as vestiges of ancient Martian
> bacterial life. In particular, the authors noted the presence of
> tubules 20 to 40 nanometers in diameter (called by some
> "nannobacteria"), and they proposed these structures were
> fossilized bacteria or parts of microorganisms. The report was
> first delivered at a press conference in August 1996 (published
> as a paper 9 days later) and provoked considerable media
> attention and controversy when it appeared. The controversy has
> continued, with many biologists objecting to the interpretation
> of the rock data, and in particular objecting to the idea of
> "bacteria" 20 to 40 nanometers in diameter.
> ... ... Allan Treiman (National Aeronautics and Space
> Administration, US) presents a review and update of the ALH84001
> meteorite controversy, the author making the following points: 1)
> Early hopes for a fast resolution of the controversy concerning
> meteorite ALH84001 have evaporated: no agreement has emerged on
> whether or not the meteorite ever contained Martian life. 2)
> There is no disagreement that ALH84001 formed on Mars
> approximately 4.5 billion years ago, that the meteorite was
> probably ejected into space approximately 16 million years ago by
> an asteroid impact, that the meteorite fell in Antarctica 13,000
> years ago, and that the meteorite remained in Antarctica until
> found on the ice in 1984. 3) ALH84001 is an igneous rock (i.e., a
> rock congealed from a molten mass) that apparently crystallized
> slowly from molten lava and which contains globules of carbonate
> minerals scattered along fractures. All the evidence for life is
> in the carbonate globules or their rims. 4) The 4 lines of
> evidence originally proposed by the McKay group were a) the
> presence in the meteorite of carbon compounds (polycyclic
> aromatic hydrocarbons) suggestive of decayed organic matter; b)
> the presence in the meteorite of unusual small crystals of
> magnetite (an iron oxide) matching identical crystals believed to
> be produced only by Earth bacteria; c) the presence in the
> meteorite of apparently incompatible minerals (e.g., iron-sulfide
> and iron-oxide) close together whose proximity would suggest
> organic action if the rock were from Earth; and d) the presence
> in the meteorite of bacteria-shaped formations. 5) The author
> [Treiman] suggests that a) The polycyclic aromatic hydrocarbons
> may or may not be Martian, and if they are, they may or may not
> be related to life. b) The magnetite crystals are indeed Martian,
> but there is evidence that some of these crystals formed without
> life and the origin of the others remains unclear. c) The mineral
> associations in the carbonate globules do not prove life, but
> also do not exclude it. d) The bacteria-shaped objects in
> ALH84001 are not fossil bacteria but could be fossils of bacteria
> fragments. (McKay's group now agrees that the objects are too
> small to be fossil microbes.) 6) The author concludes: "McKay's
> original hypothesis (as expressed in the 1996 paper) depended on
> all four lines of evidence working together... The evidence has
> not been verified, so the hypothesis has not succeeded... Despite
> world attention, significant spending, and the work of the best
> laboratories on Earth, the question [of life on Mars] is
> unresolved."
> -----------
> Allan Treiman: Microbes in a Martian meteorite?
> (Sky & Telescope April 1999)
> QY: Allan Treiman []
> -------------------
> Related Background:
> The formation of discrete and organized inorganic crystalline
> structures within macromolecular extracellular matrices is a
> widespread biological phenomenon generally referred to as
> biomineralization. Mammalian bone and dental enamel are examples
> of biomineralization involving *apatite minerals, but the
> molecular basis of such mineralization remains largely unknown.
> Recently, bacteria have been implicated as factors in
> biogeochemical cycles for mineral formation in aqueous sediments.
> The principle constituent of modern *authigenic phosphate
> minerals in marine sediments is carbonate apatite. Microorganisms
> are capable of depositing apatite in sea water, and they can
> segregate Ca from Mg and actively nucleate carbonate apatite by
> means of specific *oligopeptides under conditions of pH < 8.5 and
> an Mg/Ca concentration ratio of greater than 0.1. Such conditions
> are also present in the human body. ... ... Kajander and
> Ciftcioglu (University of Kuopio, FI) report a study of biogenic
> apatite production by "nanobacteria", identified by the authors
> as "the *smallest cell-walled bacteria, only recently discovered
> in human and cow blood and commercial cell culture serum." The
> authors report that nanobacteria can act as crystallization
> centers for the formation of biogenic apatite structures, and
> that nanobacteria can produce apatite in media mimicking tissue
> fluids and *glomerular filtrate, and provide a unique model for
> in vitro studies of calcification. The authors suggest that
> nanobacteria may play a key role in the formation of all kidney
> stones, and they report they have found nanobacteria in all 30
> human kidney stones that they have screened. The authors suggest
> their findings are of concern in medicine because nanobacterial
> *bacteremia occurs in humans, and nanobacterial crystallization
> centers might initiate pathological calcification.
> QY: E. Olavi Kajander <>
> (Proc. Natl. Acad. Sci. US 7 Jul 98 95:8274)
> (Science-Week 7 Aug 98)
> -------------------
> Related Background:
> ... ... *apatite minerals: A group of phosphate-containing
> minerals.
> ... ... *authigenic phosphate minerals: Authigenic minerals
> (authigenes) are minerals that came into existence with or after
> the formation of the rock of which they constitute a part. The
> principal constituent of modern authigenic phosphate minerals in
> marine sediments is carbonate (hydroxy)fluorapatite:
> Ca(sub10)(PO(sub4))(sub6-x)(CO(sub3))(subx)(F,OH)(sub2+x).
> ... ... *oligopeptides: A peptide composed of no more than 10
> amino acids.
> ... ... *smallest cell-walled bacteria: The electron micrographs
> in this report show various forms with diameters 0.2 to 0.5
> microns. See related reports below concerning the reported size
> of nanobacteria.
> ... ... *glomerular filtrate: A glomerulus is a tuft-like
> structure composed of blood vessel capillaries or nerve fibers,
> and in this context, a glomerulus is a blood vessel capillary
> structure and part of the nephron, the fundamental filtration
> unit of the kidney. The filtrate from kidney glomeruli consists
> of small solute molecules filtered under pressure from blood.
> ... ... *bacteremia: This is a general term referring to the
> presence of bacteria in blood.
> -------------------
> Related Background:
> As the subunits that compose protein polymers in living systems,
> the detection of certain amino acids in a material is often
> interpreted as indicating a possible biological origin. The
> meteorite ALH84001, along with a number of other discovered
> meteorites, has a composition that suggests it was apparently
> ejected from the surface of Mars, and during the past year it has
> been proposed that microanalysis of this meteorite indicates the
> possible presence of bio-organics and biogenic fossils. This
> proposal, however, has met with considerable controversy, and the
> controversy is still in full force. ... ... Bada et al (4 authors
> at 3 installations, US) now report that the amino acids present
> in a sample of the ALH84001 meteorite appear to be terrestrial in
> origin and similar to those found in the ice where the meteorite
> was discovered, although the possibility remains that minute
> amounts of endogenous amino acids are preserved in the meteorite.
> The authors suggest that radiocarbon studies (cf. contiguous
> report: Jull et al, Science 279:366 1998), coupled with their own
> amino acid results, indicate that major and minor organic
> constituents in the Martian meteorites are contaminants.
> QY: Jeffrey L. Bada <>
> (Science 16 Jan 98) (Science-Week 30 Jan 98)
> -------------------
> Related Background:
> ... ... Gibson et al (National Aeronautics and Space
> Administration Houston, US; University of Georgia, US), the
> group including some of the authors of the 1996 McKay report, in
> a review of the evidence for relic life on Mars, consider the
> ALH84001 meteorite not only the strongest evidence for Martian
> relic life, but also for the possibility of present Martian
> microbial life. The authors are hopeful that in 2005 a "sample
> return" mission will be launched to robotically collect Martian
> rocks and soil and return them to Earth.
> QY: Everett K. Gibson <>
> (Scientific American December 1997) (Science-Week 28 Nov 97)
> -------------------
> Related Background:
> The term "nanofossils" (originally spelled "nannofossils" by the
> group that introduced the term) refers to elongated microscopic
> forms found in the Martian meteorite ALH84001. Several groups in
> the space and geology communities have proposed these forms are
> fossilized bacteria, but most biologists have rejected the idea
> on the basis that the forms are too small to be bacteria and
> should not be classified as such. Bradley et al (3 installations,
> US) now report that new analysis of material from the ALH84001
> meteorite indicates the majority of the elongated microscopic
> forms can be resolved as either emergent substrate layers or
> magnetite whiskers, rather than biogenic nanofossils. Their
> report is followed by a response from McKay et al (3
> installations, US CA), some of the original proponents of the
> nanofossil idea, and in their response McKay et al say the
> artifact possibilities mentioned by Bradley et al are already
> known to them, but are not related to their own observations.
> They add that living bacteria as small as 70 nanometers in
> diameter have been observed in mammalian blood, and that soil
> bacteria as small as 80 nanometers have also been observed. The
> references for these bacterial forms are one unpublished paper
> and two recently published papers in Proc. Soc. Photo-Opt.
> Instrum. Eng. 3111:420,429 (1997). It is evident that the
> nanofossil controversy has not yet been resolved.
> QY: J.P. Bradley, Georgia Inst. Technol. 404-894-2000; David S.
> McKay <>
> (Nature 4 Dec 97) (Science-Week 26 Dec 97)
> -------------------
> Related Background:
> Apart from their heuristic significance, scientific controversies
> can be either amusing or irritating. In recent months, a
> controversy between some geologists and many biologists has
> developed, and it is apparently irritating the biologists. The
> issue concerns the minimum possible dimensions of bacteria. The
> geologists are led by Robert L. Folk (University of Texas, Austin
> TX US), and they have proposed that certain microscopic entities
> found in the Martian meteorite ALH84001 are fossils of what they
> term "nannobacteria" (their own unique spelling of the prefix
> nano-), which they say are similar to those found in Earth
> travertine and limestone rocks, and which have dimensions of 30
> to 50 nanometers. This has caused a furor among biologists, whose
> understanding of bacteria and life forms in general is that the
> smallest dimensions possible for a life form with a bounding
> plasma membrane is about 200 nanometers. In fact no membrane-
> bound bacterium with dimensions less than 340 nanometers has ever
> been identified, and one can make simple calculations that a 50
> nanometer bacterium would not have enough internal volume to
> sustain its chemistry. Folk published papers on the subject in
> several geological journals in 1996, starting the debate, and in
> the Letters section of the 20 June 1997 issue of *Science* the
> debate continues, and this week it is being reported in the
> popular media as a "debate about life on earth". What evidently
> irritates biologists is the apparent misunderstanding by these
> geologists of experimental methods in biology. Characterizations
> of "living" vs. "non-living" by biologists are made on the basis
> of experimental laboratory replicability of an organism, and not
> on the basis of the visible structure of an entity. Which means
> the geologists involved need to attempt to culture their
> Earth-rock entities, and which means decisions that the Martian
> meteorite's so-called "nannobacteria fossils" are actually such
> will require demonstration of cultured entities with those
> dimensions. Biologists are not unwilling to admit the existence
> of new species of life forms, of which they have already
> recognized several million entities, but they argue that one does
> not classify pieces of rock as a life form on the basis of
> structure alone.
> (New York Times 29 Jul 97) (Science-Week 1 Aug 97)

Robert M. Owen
The Orion Institute
57 W. Morgan Street
Brevard, NC 28712-3659 USA

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