At 8 pm, on May 14, 1864—a mere five years after Darwin proclaimed his theory of evolution to a highly skeptical and rather hostile scientific community—a giant fireball screamed along the horizon of southwestern France and crashed to the Earth near the village of Orgueil. It was also 50 years after the recognition of the extraterrestrial origin of meteorites. And this one carried some travellers aboard—according to some scientists. Observers claimed that the bolide (the visible fireball) was the size of the moon in the sky before it exploded. Over twenty fragments scattered in an area of 10 square kilometers.
Historical Analysis of the Orgueil Meteorite
A retired professor of physics described its visible explosion in the air, followed by a detonation similar to a platoon fire or a cannonade. After the fall, the air grew palpably warmer and took on a sulfur smell and a whitish cloud persisted for a quarter of an hour. The physicist picked up a stone the size of an orange, which he described as “black with some veins of a lighter colour, as well as here and there some shiny points.” He noticed that the stone was very tender inside the strong varnish of half a millimeter thickness that covered it, and that, when plunged into water, it dissolved and turned to “a mud, black as shoeshine.”
Orgueil is arguably one of the most important meteorites, write Gounelle and Zolensky, who provide an excellent review of the history of its study. “Not only does it serve as a reference for the cosmic composition, but its richness in water and other volatile compounds indicates that it came from an ice-rich body that might have originally contained one of the most complete set of phases condensed from the solar protoplanetary disk (SPD).” They add: “Its diversity in organic molecules has been perplexing [researchers] since the year 1864.”
Studies of the meteor when it landed some 150 years ago revealed that the organic matter in the meteorite contained carbon, hydrogen, oxygen, and organic material. France, at the time, was embroiled in the debate about spontaneous generation: that life can spontaneously come into existence inside inanimate substances. Some strongly supported and others strongly opposed. This provided fertile ground for passionate debate that resulted in attempts at scientific maleficence and, of course, elaborate hoaxes. But I’ll come to that later…
Shortly after the meteor landed and a month after Louis Pasteur attempted to debunk the concept of spontaneous generation, French chemist François Stanislaus Cloëz—on examining Orgueil meteor samples—detected the presence of materials resembling humic acid or peat; for him this implied the existence of fossil life—indigenous fossils—in the meteorite’s parent body.
Several months later in his paper in La Revue des deux Mondes, physicist Jules Jamin was struck by the meteorite’s high carbon content and similarity to peat, which he noted “on Earth originates from the decomposition of aquatic plants in our swamps.”
Orgueil Meteorite Composition and Provenance
In their 2014 article in Meteoritics & Planetary Science, Gounelle and Zolensky use the Orgueil meteorite’s minerology and hydrothermal alteration to suggest that it likely originated from a volatile-rich “cometary” outer solar system body, a comet of the Jupiter family type. Because the meteorite bears strong similarities to other carbonaceous chondrites that originated on dark asteroids, this cometary connection supports the idea of a continuum between dark asteroids and comets.
An X-ray diffraction analysis done in 1970 showed that Orgueil is mainly an assemblage of clay minerals (mostly saponite and serpentine) and these are, of course, water-bearing minerals found in many terrestrial environments. The implications, Gounelle and Zolensky tell us, is that “wherever Orgueil had originated, that body must once have supported liquid water for a period sufficiently long for anhydrous minerals to have partially dissolved and reformed into the clay minerals.” The Orgueil parent body underwent hydrothermal circulation.
“Despite the fact that the bulk composition of Orgueil is the closest match we have to the solar photosphere, its mineralogy has been very thoroughly altered by the activity of liquid water early in solar system history, resulting in an apparent contradiction.”
Gounelle and Zolensky (Meteoritics & Planetary Science, 2014)
Gounelle and Zolensky go on to describe how the textures shown by foliation directions of Orgueil’s phyllosilicates can also be observed in terrestrial permafrost soils, caused by alternating freeze-thaw cycles:
“The Orgueil parent body must have experienced similar alternating temperatures … It is interesting to think of the extraterrestrial parent body operating as a permafrost soil.”
Gounelle and Zolensky (Meteoritics & Planetary Science, 2014)
Organized Elements in the Orgueil Meteorite
In 1961 and 1962 Nagy et al. published several findings in Nature on an Orgueil meteorite fragment that had been sealed in a glass jar in Montauban since its discovery. Nagy’s study showed ‘organized elements’ embedded in a specimen of the Orgueil meteorite that resembled biological structures; they found and discounted some recognizable terrestrial contaminants in each sample (e.g., bacteria, diatoms, sponge spicules, starch granules and cellulose fibres) and confirmed their findings with detailed soil and rock analysis of the Orgueil area. They concluded that the unidentifiable ‘organized elements’ were of extraterrestrial origin and were microfossils indigenous to the carbonaceous chondrite.
A year later, Fitch & Anders identified pollen and fungal spores of Earth origin in an Orgueil sample that they later showed was intentionally placed there in 1865 as part of the debate on spontaneous generation of life that pitted Louis Pasteur against Félix Archimède Pouchet in the mid 1800s. Museum Hoaxes.com suggest the following explanation: ‘It could be that someone decided to play a joke on the French scientists by placing plant and coal fragments inside of the meteorite, hoping that the fragments would soon be found. If found, they could have been used as evidence to suggest that life had spontaneously generated within the meteorite… If this is the case, then the carefully planned hoax backfired, because the meteorite was sealed inside a glass jar and forgotten until 1962, almost a century later.”
Despite the clear disconnection between the Anders et al. hoax revelation and Nagy’s ‘organized elements’, the discovery of the contamination helped cast doubt on the reality of extraterrestrial life forms and indigenous fossils.
Harold Urey, in his 1962 paper in Science, took Nagy’s findings seriously and suggested that if the hydrocarbons and ‘organized elements’ were indeed the residue of living organisms indigenous to the carbonaceous chondrites, this would represent an astounding discovery. Urey argued that, “The objects looked somewhat like pollen grains, to the amateur at least, but they were firmly embedded in the silicate matrix and thus could hardly have been introduced into the meteorite mechanically, and pollen grains do not grow in such places. These objects … taken together, make an interesting argument.”
(photo: Harold Urey)
Acknowledging the possibility that some of the organized elements could be mineral artifacts or biological contaminants, Urey emphasized that, “In order to reach a positive decision relative to indigenous fossils in these meteorites it is only necessary that we be sure that some of these specimens are biogenic in character and indigenous to the meteorites.”
The debate among scientists and interested parties continues to this day as maverick scientists fervently support the theory of panspermia and conservative scientists rule it out as fringe science.
But let’s look at some interesting reasons why we should consider the possibility of biological material landing on Earth from space in what is called panspermia (see below) and the possibility of seeding the Earth with viable extraterrestrial biomaterial.
Microbial Extremophiles
Scientists have found microbial life inside some types of rock, beneath the seafloor, in the Antarctic ice sheet, in extreme acidic environments such as the Rio Tinto Basin in Spain, in extreme saline environments such as the concentrated lithium pans in Argentina, and in the driest deserts in the world. Extremophilic (halophilic) diatoms thrive alongside the brine shrimp Artemia monica amid limestone tufa towers of Mono Lake, California, two and a half times as salty and 80 times as alkaline as the ocean.
Many scientists and astrobiologists agree on the possibility of extremophilic and extremotolerant bacteria in the icy worlds of other planets and moons of the Solar system. Ice appears rather common in the Solar system: examples include Mars, Mercury, Uranus and Neptune, Pluto, Earth’s Moon, Europa, Ganymede and Callisto, Titan, Mimas, Enceladus, Triton, Umbriel, and Miranda.
Rock-Eating Bacteria
In 1967, W.C. Tan and Sam L. VanLandingham published findings and electron microscopic photos in the Journal of the Royal Astronomical Society of what they described as “filamentary microstructures” in the Orgueil meteorite sample they studied. In 1998, Russian bacteriologist Mikhil Vainshtein recognized the structures as magnetotactic bacteria. These endolithic bacteria (called lithotrophs) ingest iron and retain it in particles which cause the bacteria to align themselves with a magnetic field, just as the Orgueil photos indicated. Endolithic organisms (sometimes called extremophiles) are able—and may even thrive—in extreme temperatures, intense pressures, total darkness, and anoxic conditions. This supports the possibility of panspermia: not only the travel of life forms through space in spatial ices from one planetary body to another; but their continued propagation or ‘seeding.’
Lichens in Space
De Vera et al (2002) showed that lichen symbiotic organisms Fulgensia bracteata and Xanthoria elegans and their isolated photobionts and mycobionts withstood outer space conditions that included vacuum and ultraviolet radiation.
Sessile Benthic Extremophiles
In 2021, sessile benthic community far beneath an Antarctic ice shelf suggested that organisms of higher cellular complexity could survive the harsh environment of an extraterrestrial ocean world.
Dormancy is a common strategy of organisms that live in harsh and unstable environments and has been documented in crustaceans, rotifers, tardigrades, phytoplankton and ciliates. “Dormant forms of some planktonic invertebrates are among the most highly resistant … stages in the whole animal kingdom,” writes Jacek Radzikowski in a 2013 review in the Journal of Plankton Research.
Bdelloid rotifers can go into quiescent dormancy at practically any stage in their life cycle in response to unfavourable conditions. Early research noted that dormant animals could withstand freezing and thawing from −40°C to 100°C and storage under vacuum. They also tolerated high doses of UV and X radiation. Later work reported that some rotifers could survive extreme abiotic conditions, such as exposure to liquid nitrogen (−196°C) for several weeks or liquid helium (−269°C) for several hours. Desiccated adult bdelloid rotifers apparently survived minus 80°C conditions for more than 6 years. The dormant eggs of cladocerans and ostracods also survived below freezing temperatures for years.
In 2021 a living Adineta sp bdelloid rotifer was discovered in the 24,000 year old Arctic permafrost. It was shown to have effective biochemical mechanisms of organ and cell shielding to survive low temperatures.
Tardigrades in Space
Fossils of invertebrate tardigrades date to the Cambrian period, over 500 million years ago. Over nine hundred species are known. They are a cosmopolitan group found anywhere from mountain tops of 20,000 metres to ocean depths of 3,000 metres, in Japanese hot springs, and 80 metres under the surface of a glacier. Tardigrades are true extremophiles. They have shown the ability to survive impact shocks, able to withstand extreme pressures, temperatures and salinities, lack of oxygen and water, toxic chemicals, and levels of X-ray radiation 1000x the human lethal dose. In 2007 a European team of researchers exposed tardigrades to the vacuum of space on the outside of a FOTON-M3 rocket for 10 days and over two thirds remained viable after.
The Argument for Travelling Diatoms
In 2017, NASA scientist Richard B. Hoover and colleagues studied an Orgueil sample fractured from a 0.3 g fragment of the Orgueil meteorite (MNHNP #2838) provided to the NASA/Marshall Space Flight Center by the Musée Nationale d’Histoire Naturelle de Paris. Inside the sample they discovered what they described as indigenous fossils of diatoms. Here is part of their account:
Complete frustules of fossil diatoms were discovered in sample “Org_2838_A1” in Dubna (Fig. 1a). Calibrated measurements of the Orgueil diatoms show the cells have lengths of 20.1 μm (upper) and 19.6 μm (lower). The cells are about 4–5 μm broad but tilt of cells prevent precise measurements. Energy Dispersive X-Ray Spectra and 2-D Element X ray maps did not detect nitrogen indicating it was below the 0.5% detection limit and 2-D X-ray maps indicate the Orgueil diatoms are coated with sulfates of calcium and magnesium. The valves of the Orgueil diatoms are linear-lanceolate with rounded apices and there is a broad transverse facia in the central area. Raphe details of the Orgueil diatoms are not discernable. The Orgueil diatoms have about 15 transapical striae per 10 μm and the striae are radiate towards the middle of the valve and convergent toward the apices.
Diatoms Forever…
Diatoms are pigmented single-celled photosynthetic eukaryotes that comprise a major component of the food chain in marine, estuarine and freshwater habitats. Living diatoms cover themselves with tough glass-like bio-mineralized composites of bio-silica (called frustules) and these outer shells are mechanically resilient. The diatom’s sophisticated structure challenges predators, which must generate large forces and invest large amounts of energy to break a diatom’s frustule. In their 2022 paper, Aitken et.al. note that the diatom shell has the highest specific strength of all previously reported biological materials. Fracture analysis and finite element simulations also suggest mechanisms to mitigate fracture of the shell architecture.
When the diatom dies, its tough shell of inorganic silica does not decompose; the silica cells remain preserved over time–up to millions of years. While everyone calls them fossils, they are not true fossils in that their original material–silica–is not replaced by another mineral.
This is how taxonomists identify most diatoms: removal of the living material allows the researcher to clearly see the diatom’s extensively designed shell–its best diagnostic feature. The frustule of each diatom species has unique markings that include ribs, spines, ridges, grooves, nodules, and pores. This is the work I did for my biology degree when I studied the colonization of periphyton communities: I took live colonies that had settled on my submerged glass slides placed in various streams, incinerated them to remove all masking biological material to reveal the diatoms’ clearly marked frustules before identification and counting.
Diatoms have been extensively used in palaeo-environmental studies. For instance, as a lake ages, it lays down seasonal layers of sediment over time, creating varves that act like tree rings–undisturbed annual sediment laminations that provide accurate chronology that can date back thousands of years. Such a study was done on several meromictic lakes in the Kawartha Region of Ontario. Laminations of sediment accumulation dated back to the late Pleistocene and Holocene 10,000 to 12,000 years ago. Seasonal sedimentation creates varve couplets (summer-winter layers per year). Elk Lake varves consisted of a dark layer of organic sludge with algal filaments, iron sulfides, and clay that graded upward into a lacy network of diatom frustules and organic matter; this was be overlain by a light layer of diatom frustules and calcite that turned into pure calcite at the top.
Ubiquitous and Sexy Diatoms
The diatoms that Hoover et al. discovered inside the Orgueil meteorite were, of course, the silica remains of diatoms (diatom fossils), not living diatoms capable of doing any kind of seeding. Having said that, the notion that diatoms also occur on extraterrestrial habitats, is not ridiculous; diatoms occur just about everywhere on Earth. Why wouldn’t they exist beyond our planet?
Diatoms exist in all phases of water throughout most biogeoclimatic zones wherever there is light, water, carbon dioxide ad necessary nutrients. They live as plankton in the ocean and freshwater lakes; they attach to anything from dust to cobbles, sand and plants in water, creating underwater forests. They live in many moist habitats, on tree trunks, soil and sediment, even brick walls! They travel through the air on the air currents. Some were even discovered in the stratosphere and one study suggests these diatoms are residents of the stratosphere. Wherever there is water and movement, there will be diatoms. They are the dominant eukaryotes in polar regions (including ancient Antarctic ice), in fumaroles, hot springs and geysers, and in hypersaline and hyperalkaline lakes and pools. One species of diatom Pinnularia braunni lives in sulfuric acid habitats of pH 1 to 3. Aquatic diatoms have also shown an immunity to UV radiation. Some scientists speculate that diatoms may exist on Europa and in interstellar dust.
Cryophilic species such as Fragilaria sublinearis and Chaetoceras fragilis can carry out respiration at extremely low rates at low temperatures in darkness.
Diatoms in Space
The survival of diatoms in space is another matter. While they are ubiquitous, living diatoms are not exactly extremophiles, able to withstand space and radiation and tremendous pressures. As unicellular eukaryotes, most are mesophytic photoautotrophs that require optimum temperatures and light to live. Even the cryophilic species have their limitations.
Or could they travel safely inside a meteorite ‘spaceship’?…
Sanyal et. al. (2021) showed that diatom resting spores could survive in nature for several millennia and were still viable. Both recent and ancient spores of the diatom Chaetoceros muelleri var. subsalsum buried in sediments in the Baltic Sea were revived. The researchers revived resting spores deposited in sub-seafloor sediments from three ages (recent: 0-80 years; ancient: `1250 (Medieval Climate Anomaly) and ~6600 (Holocene Thermal Maximum) calendar before present.
Panspermia Hypothesis
The Panspermia Hypothesis argues that microscopic forms of life can migrate naturally through space, in spatial ices, and distributed to planets that can support life by comets and meteorites (lithopanspermia). The theory argues that the seeds of life exist all over the Universe and can be propagated through space from one location to another. The lithopanspermia theory involves the movement of impact ejecta from one planet with subsequent arrival on a new body at high speed; both ejection and arrival involve accelerations and shocks.
While the concept of panspermia, first introduced by the Swedish chemist Svante Arrhenius at the turn of the century, was met with much skepticism, recent advances in astrobiology and discoveries from different fields of research (including the study of extremophiles on Earth) have given it more credence. Scientists have proven that some microorganisms can survive the rigours of space travel including the high impact and velocity experienced during the ejection from one planet, the journey through space, and the impact process onto another world. Ramplelotto (2010) discusses a body of evidence suggesting that microbes can survive the conditions of interplanetary transfer from Mars to Earth or from any Mars-like planet to other habitable planets in the same solar system (e.g., Io, Europa, Ganymede, Callisto, Titan, and Enceladus).
Spaceflight experiments have demonstrated that with minimal UV shielding, several types of microbes can survive for years at exposures in space (Rettberg et al., 2002). Horneck et al. (2002) estimated that if shielded by 2 meters of meteorite, a substantial number of spores could survive after 25 million years in space. Microbes were brought back to life after 250 million years (Vreeland et al., 2000).
Spores of Bacillus subtilis survive the hostile environment of space for at least 6 years, provided they are shielded against the harmful solar UV radiation (Horneck et al., 1994). Mileikowsky et al. (2000) showed in a quantitative study that natural transfer of viable microbes from Mars to Earth or vice versa, via rocks greater than 1 m in size, is a highly probable process that could have occurred many times during the history of our Solar System. Organisms such as archaea, bacteria, fungi, lichen, algae, and protists (such as amoeba) can acquire the necessary resources for growth in the inner part of a rock, mineral, coral, animal shells, or in the pores between mineral grains of a rock (Joseph, 2022).
In the soft panspermia theory, instead of living forms, it is the amino acids, sugars, and the molecules required to form living-RNA that travel through space. Experiments consisting of the irradiation of interstellar ice analogs with stellar-like UV radiation have shown that indeed, the building blocks of the RNA can be produced in space. These laboratory results also agree with the measurements obtained from meteorites and the data gathered by the Rosetta mission from comet C67/Churyumov-Gerasimenko. The implications of this soft theory are enormous since, as a result, life forms in the Cosmos would be compatible at the molecular level.
Some suggest that life may have been purposely directed to Earth (Directed Panspermia or Intelligent Panspermia) by an intelligent species from another planet. Why not? All things are possible, no? I’m a limnologist but I also write science fiction. Of course, several works have already exploited this notion. Prometheus, the 2012 sequel to Alien, comes to mind. The extra-solar protomolecule of The Expanse is another.
Nina Munteanu is a Canadian ecologist / limnologist and novelist. She is co-editor of Europa SF and currently teaches writing courses at George Brown College and the University of Toronto. Visit www.ninamunteanu.ca for the latest on her books. Nina’s bilingual “La natura dell’acqua / The Way of Water” was published by Mincione Edizioni in Rome. Her non-fiction book “Water Is…” by Pixl Press (Vancouver) was selected by Margaret Atwood in the New York Times ‘Year in Reading’ and was chosen as the 2017 Summer Read by Water Canada. Her novel “A Diary in the Age of Water” was released by Inanna Publications (Toronto) in June 2020.
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The Meaning of Water 