9.1 Life and (near-life) in the form of bacteria and viruses (together called microbes) pervades the universe in the interior of comets, meteorites and clouds of interstellar dust.

NASA researchers in collaboration with researchers from the Russian Academy of Sciences analyzed several carbonaceous chondrite meteorites (named Murchison, Mighei, Efremovka, Murray, Nagoya) at magnifications of 2000-20,000x. They found fossils of bacteria, nanobacteria (very small bacteria) and remnants of microbiological activity in deep interiors of severalmeteorites. "These forms were found in-situ in freshly broken, interior surfaces of the meteorite."[92] Some scientists argue that the microfossils found by NASA McKay et al. (1996) in the Mars meteorite are actually due to terrestrial contamination.[93] If earthly bacteria can penetrate to the interior of meteoritic rock, this coupled with the acknowledged existence of bacterial extremophiles (see page 32) means it is also possible that bacteria lived in the rock and when the rock hit Earth, some minuscule portion of the bacteria survived and exited the rock to colonized the planet. It is two sides of the same coin and those that argue for contamination are assuming terrestrial genesis, when it is also plausible to assume extraterrestrial genesis, perhaps on another Earth-like planet. If life could have started on Earth, then it also could have started somewhere else.

The absorption spectra of interstellar dust and comets provide evidence that these objects contain living microbes (bacteria and viruses. Different materials absorb different parts of the electromagnetic spectrum. For example, a green shirt absorbs all color wavelengths except green. A spectrometer is an instrument used for measuring what wavelengths of the spectrum are absorbed or emitted by an object. In astronomy, one method of observation is to image a distant object using a spectrometer while recording which wavelengths are absorbed. This yields an absorption profile. This profile is then checked against a database of absorption/emission profiles of thousands and elements and molecules. The database has previously been accumulated by researchers working under laboratory conditions. The researchers measure pure samples of known materials to determine their baseline emission/absorption profile. Allen and Wickramasinghe (1981), report that spectroscopic observations of a cloud of interstellar dust in front of GC IRS-7[94] yield an absorption profile not that of some minerals or elements, but closest to the bacteria Escherichia coli (E. coli) (from 2.9-3.6 µm.).[95] Figure 2 below is a re-evaluation of that finding adding 1989 data from other researchers.

Figure 2. The graph above most plainly demonstrates the methodology involved. Data points (dark points and open circles) of remotely observed infrared flux across a wavelength range are matched to a model of E.coli flux at the same wavelengths (the continuous line). The E.coli model is derived from laboratory data.[96]

Hoyle and Wickramasinghe (1988) reevaluate the 1981 findings in light of new observational data.[97] They add data from independent observations in 1989 and 1994. They find that the new data are also a very good match to the E. coli absorption spectrum. They generate a graph in which represents the absorption characteristics of the interstellar dust between stars IRS 6E and IRS 7 for 3.3-3.55 micrometer wavelengths. On this graph they superimpose a curve of the absorption characteristics of a mixture of E. coli and a virus called TMV (Tobacco Mosaic Virus). The curve of the bacteria-virus mixture absorption is a quite good match to the data points of the interstellar dust absorption.[98] Hoyle and Wickramasinghe conclude that, at a minimum, there is complex organic matter in the interstellar dust. But there is no known non-biological mechanism for how such complex organic matter could be created. So they conclude that there is biological activity that generates the complex organic matter and that in fact the organic matter whose absorption spectra we are seeing in the interstellar dust is bacteria closely related to E. coli and the Tobacco Mosaic virus.

Similar methods have demonstrated that the absorption spectrum of "galactic infrared source OH 26.5 + .6" matches that of dessicated (dried) cellulose (whose spectrum was measured under laboratory conditions.). This is contended to be a piece of evidence that biological processes are occurring or have occurred in outer space.[99]

Many researchers had thought that the spectrum of infrared radiation passing through the Trapezium nebula over the wavelengths 8-35 µm matched the spectrum that laboratory models predicted would be produced by silicon. Hoyle and Wickramasinghe find that the nebula spectrum more closely matched the spectrum that would be produced by diatoms- a water borne microorganism that incorporates silicon into various components of its structure.[100]

Wickramasinghe et al[101] conducted Earth-based spectroscopy of the coma of Halley's Comet during the 1986 flyby.[102] Over a specific range of infrared wavelengths (3-4 µm), the emissions characteristics of the comet coma are very close to the emissions characteristics of E. coli bacteria that have been heated to 320 degrees K. This is probably a reasonable temperature approximation of the temperature conditions in the coma. The Earth based observations were conducted on March 31. The European comet intercept probe Giotto measured the temperature of the outer nucleus sometime in the month of March, returning a temperature of 330 degrees K.[103] Any material in outer space is also subject to intense radiation. To better approximate the conditions in the coma, the authors subjected a sample of E. coli to a radiation dose of 1.5 megarads and then heated the sample to 320 degrees K. The infrared emissions characteristics of this irradiated sample were even closer to that of Halley's comet. The authors conclude this empirical finding is evidence that some of what is expelled from a comet is bacteria from its interior.

Based on the empirical findings, Hoyle and Wickramasinghe argue that primitive life forms extant in outer space would be frozen by the cold and dried by the absence of moisture in outer space. If this hypothesis is accurate, could the microbes survive? Is the bacteria floating outer space dead? They contend that based on what we know about the extreme survivability of terrestrial bacteria, the bacteria in outer space could be alive or dormant.[104]

Clarke et al. (1999) explain that the major obstacles to survivability of bacteria in small bodies in outer space are three: intense radiation, intense cold and absolute absence of water.[105] They note that, given the hardihood of some species of Earth bacteria, it is conceivable that some species could survive any one or even two of these factors, but the combination of all three would be insurmountable. Given the intensity of radiation, bacteria would have to be several meters below the surface of any object in order to have enough shielding to survive. Asteroids and moons of different planets may contain life at appropriate depths below the surface. The authors conclude that comets would be the most likely place where life would be found, presumably bacteria in spore form. The bacteria could be several meters under the crust of the comet, encased in ice. The factor of radiation would be absent, and since the bacteria would be encased in ice, moisture would be locked into the spores. For their part, Hoyle and Wickramasinghe suggest that bacteria could survive in the interior of an interstellar dust cloud. These bacteria would be shielded from radiation by outer part of the cloud.[106]

When Clarke et al. speak of the hardihood of bacteria, they are referring to evidence of extremophile microbes onEarth. It is worth examining some of these findings in order to understand how life could possibly survive in outer space if protected within a comet. It is well documented that there are bacteria which live in boiling water (hot springs), bacteria that eat sulfur, bacteria that live deep below the Earth in high heat and pressure and eat rocks, and organisms that live in the deep ocean around ocean vents. Vents are openings in the sea floor from which heat and various chemicals seep out from the interior of the planet. These organisms survive in almost total darkness, under great water pressure, using heat and various chemicals as their energy sources.[107] Overmann et al. (1992) found bacteria in seawater that can photo-synthesize at .0005% of the light intensity at the sea surface.[108]

One specific extremophile is Deinococcus radiodurans. This bacteria was first discovered in 1956 by a researcher working on preserving food by irradiating it. Meat that had been irradiated spoiled anyway, and the culprit turned out to be D. radiodurans. Since its discovery, it has been shown to survive radiation of up to 1.5 million rads (1500 times the dose needed to kill a human) and if frozen, it can survive up to 3 million rads. It can also survive extended periods without water (dessication).[109] Radiation in space is up to 18 million rads.[110]

When adverse conditions develop, many bacteria protect themselves by becoming dormant. "Such dormant forms are called endospores in Bacillus and Clostridium, cysts in Azotobacter, and heterocysts in some cyanobacteria. ... Endospores have no metabolic activity and exhibit extreme resistance to the lethal effects of heat, desiccation, freezing, chemicals, and radiation."[111]

Recent discoveries about the longevity of bacterial spores make more plausible the scenario that dormant bacteria could survive for eons inside small bodies in outer space. Vreeland et al. successfully cultured bacterial spores from a 250-million-year-old salt deposit in New Mexico.[112]

By what conceivable scenario might bacteria have ended up in the interior of a comet? Hoyle and Wickramasinghe provide a scenario and others provide empirical support. They state that, when a comet is formed, the core of the comet is a radioactive material that emits heat for several hundred thousand years before the heat decreases to a non-significant level. The heat from the radioactive core maintains water around the core in liquid form. Comets are 80% water and 20% other materials. Perhaps 10% of these other materials are complex organic molecules.[113] So early in the life of a comet, we have a heat source, water and nutrients (the complex organic molecules). This is all that is thought to be needed to support primitive life. [114] "Microorganisms are extremely versatile, chemically. They can live on a very simple medium with little more than water, carbon and nitrogen sources, and some simple organic compounds for their energy. Most can synthesize their need for vitamins and amino acids."[115] As the heat from the core and the supply of nutrients diminishes, the primitive life goes into a dormant state. We already know that bacteria can be revived after 250 million years. One of the main points of the landmark Gold article is that, "The chemistry of life we now know need not be the one associated with its essential origin."[116] Hoyle and Wickramasinghe hypothesize that the earliest forms of primitive could be revived after billions of years.

When a comet travels through the inner solar system, dormant bacteria are released from the nucleus into the coma and tail of the comet, where some of it reaches the Earth surface in viable condition. Once vented from the tail of a comet, any microbes would be floating in space and subject to the extremes of temperature, the vacuum and the ionizing radiation discussed by Clarke et al. These factors would render even hardy spores non-viable relatively quickly. However, once a century or more, [117] the Earth passes through a recently formed comet tail, which yields an instantaneous input of perhaps 2,000 tons of dust into the stratosphere.[118] In such conditions, the microbes would not have to survive for long in outer space before entering the atmosphere.

9.1.1 Empirical Verification

Given Hoyle and Wickramasinghe's spectral findings suggestive of the existence of microbes in space, and the reasoning of other scientists that it might indeed be possible for microbial life in the interiors of small bodies in outer space, it remains to verify the remote observations and theoretical reasoning. Most proposals focus on comets. A number of missions are currently planned that will yield relevant empirical data.

The ideal situation for investigation of comets would be for researchers to be in physical possession of a supply of material from a comet nucleus so that they can conduct a virtually unlimited amount of tests as ideas occur to them. The idea is to land on the surface of a comet, drill into the comet and retrieve a core sample several meters long. Successful return of the sample to Earth would enable scientists to study cometary material with the extensive tools available in an Earth-based laboratory. Such study would determine whether microscopic life exists in comets, provided that terrestrial contamination could be ruled out. The technology involved in a sample return mission is difficult and the author knows of no such missions that are even in the planning stages.[119]

While we wait for a nucleus sample return mission, there are several missions to comets that are either launched or near launch.

Stardust: launched 1999 Fly into the tail of a comet, collect comet dust using a material called aerogel, return samples to Earth. If the aerogel comes back with bacteria on it, that would certainly indicate that comets do harbor life, provided terrestrial contamination can be ruled out. However, Clarke et al. (1999)[120] caution that this mission could be self-sterilizing because the comet dust will strike the aerogel at 6.1 km/sec, instantaneously converting kinetic energy to extreme heat.[121]

Contour: launch 2002

Close flyby (60 miles) of a comet nucleus. Perform spectrometry similar to Earth based work done on interstellar dust by Wickramasinghe et al. in order to determine constituents of the comet.

Deep Impact: launch 2004

Launch copper projectile at nucleus of comet. The impact will excavate a deep crater in the nucleus, revealing the deep interior of the comet. Use remote sensing instruments to look inside the crater and analyze the ejecta in order determine the make-up of the comet. Observations will be made from as close as 310 miles.

Rosetta: launch 2003 Prolonged close up observation (as close as 10 miles), land on the nucleus and conduct in-situ examination of the surface of the nucleus. However, Rosetta will not dig into the interior of the comet. As Clarke et al. concluded, the microbes, if there are any, would be found in the protected interior of the comet.

Even if it is proven that bacteria and/or viruses exist in the interior of comets (step 1), it would still remain to be proven (2) that these bacteria/viruses can enter the Earth's atmosphere and (3) that they can reach the surface of the Earth as viable life forms, and (4) that they are incorporated into the biosphere, or that they started the biosphere (genesis).