1. Introduction

Water on the moon of an endogenic origin supports the reality of lunar volcanism as does the analysis of terrestrial analogs. Together with the discovery of methane, ammonia and methanol in water fo und in the shadowed polar crater Cabeus, lunar protolife becomes a more viable concept. We define protolife as the assemblage of volcanic compounds via lipids, catalysts and templates through organic entities capable of self-replication and progression. Probably Earth and the moon both differentiated at about the same time. However, lunar protolife possibly began earlier than on Earth (or Mars) because lunar volcanism may have been more intense and widespread because of greater tidal and lesser gravity effects (Green, 1965). The moon would also harbor large permanently shadowed polar cold traps for fumarolic fluids as a source of water and components for protolife. We minimize the concept of cometary impact as a source of water and other fluids because of the likelihood that these components would be volatilized on impact. Also, we do not speculate on an alien liquid medium such as silane being critical in the formation of lunar or terrestrial protolife.

Finally, this paper has as its prime directive the goal of establishing a reasonable model for the origin of lunar protolife. We exclude the premise of panspermia because we see a logical endogenic evolutionary path from fumarolic and hot spring products to self- replicating DNA. This path recognizes (1) the availability of hydrothermal clays that could act as templates for hosting amphiphilic organic molecules, (2) the reality of inorganic processes such as Fischer-Tropsch reactions in creating lipids and (3) critical trace elements such as tungsten which would serve as a catalyst. Of even more significance, we see fumarolic emanations providing soluble polyphosphates as a component of the helixes of RNA and DNA.

Of course, it is possible to admit of tangents to the scenario presented such as the possibility of microbial life on the moon by panspermia earlier than protolife. However, pre-existing microbial life would likely not survive the harsh environments of the lunar Hadean time period. Also, there is no verified evidence in the NASA lunar sample archives or elsewhere of microbial life. We do not elect to consider any hypothetical reaction of earlier life forms originating by panspermia with later lunar protolife. The problem with panspermia is that it not only removes the origin of life elsewhere but fails to detail how this life originated. Our paper attempts to provide data to remedy both of the shortcomings of the panspermia approach. The concept of lunar protolife is based on what the author considers to be sound geological and geochemical principles. Lunar protolife is evolutionary. Should protolife on the moon possibly evolve into Archaea, biomarkers should be sought in volcanic shadow zones on the moon. We do not believe, nor is there evidence, that Hadean microbial life existed under any circumstances. We certainly do not believe microbial life existed prior to protolife on the moon. The concept of Hadean life forms is a tangent not considered in this paper.

2. Lunar Water as Related to the Origin of the Moon

One model for the origin of the moon involves a Mars-sized asteroid impacting Earth in the pre- Hadean prior to the origin of protolife or life on Earth. Such an impact would effectively volatilize water out of the molten mass of the proto-moon making a subsequent volcanic source of water virtually impossible. An alternate theory for the origin of the moon (Galimov and Krivstov, 2005) eliminates an impact origin and instead argues for an asymmetrical dust binary that evolved into Earth and moon.

The positive aspect of the Galimov and Krivstov model is that it accounts for both the low iron content of the moon and the integrity of common isotopic ratios of chromium for Earth and moon. This model also documents volatilization of lunar rock-making elements (K, Na) but admits of possible partitioning of the cooler condensate surrounding the proto-earth and moon. This author takes some license with the original argument by Galimov and Krivstov assuming this residual condensate to be relatively volatile-rich to account for the volatiles in Earth and probably in the moon. The premise is strengthened by the fact that the moon is a differentiated body for which water is essential (O’Hara, 2000). In addition, spectral reflectance calibrated by Mossbauer resonance measurements strongly indicates that most Apollo 17 fire fountaining spherules have fugacities equivalent to terrestrial volcanic spherules. Fugacity is a measure of the oxygen content of magmas and is taken as an index of its water content. See figure 9 in Green (2009) and data by Saal et al (2008).

Following Hadean differentiation (4.0 – 4.6 billion years), lunar defluidization is assumed to take place. Defluidization is the release of fluids and lavas to the surface of a cosmic body at any rate and at any time. Volcanism is the skin effect of defluidization and is assumed to have been intense during the Hadean and early Archeozoic. Note that the ages of Precambrian events on Earth and moon are nearly the same corroborating the Galimov and Krivstov model.

Based on fumarolic vapor pressures and lunar shadow temperatures, accumulation of water and other ices were predicted to occur in shadow at the lunar poles and elsewhere on the moon (Green, 1960, 1978, 2009). During the October 9, 2009 LCROSS mission "significant" volumes of water have been found by impacting Cabeus at the south pole and by the Chandrayaan-1 mission away from the poles. The source of the water according to the principal investigators was cometary impact (LCROSS) and solar wind impingement (Chandrayaan-1). A problem with the cometary source of water according to this author is that the D/H ratios for cometary water are far greater than oceanic waters on earth and may be so for water found on the moon. A problem for the solar wind-generated water is that the mass spectrometric depth of analysis is only a few microns into the lunar soil.

3. The Volcanic Origin of Major Lunar Features

Volcanism, as we know it, requires water. Appendix 1 provides a list of morphological features of the moon which have been variously interpreted; volcanic for some and meteorite impact for others. The volcanic features are based on tidal and gravity factors (Green, 1965). See Table 1.

Table 1

Various authorities subscribing to the impact origin of lunar craters have pointed out the large size of many lunar craters and that their central or off-central mountains are always below the rims of the craters. However, the deeper nucleation of bubbles in lunar magmatic systems would result in enhanced subsidence of calderas with the later evolution of volcanoes on their floors with elevations lower than the caldera rims. Lunar examples are given for most of the entries in Appendix 1 with daggers denoting terrestrial analogs. Space does not permit elaboration of the lunar terrestrial analogs; most of the analogs have been published by the author. Categories of interpretations have been tabulated. One set of interpretations is wholly allotted to impact. However, tabulation of the scores suggest that most major lunar features are volcanic or volcano-tectonic. The overriding conclusion is that volcanism requires water and water has been found on the moon. The argument that water molecules of any origin saltate from the equator to the polar cold traps is specious because migration times from the lunar equator to the poles is far greater than photodissociation times (Hodges, 1992, Crovisier, 1989). This places a severe constraint on both volcanic and solar wind-produced water. One conclusion of this paper is that polar ice is caused by fumarolic activity within 80 kilometers of the poles.

Away from the poles, the upper few millimeters of solar wind-produced water would tend to evaporate in sunlight. Note that this solar wind-produced water is maximized at night and is near nil in sunlight. Large volumes of volcanic ices could accumulate in permanently shadowed zones away from the poles in overhangs in breached volcano interiors, in caldera floor fractures and in lava tubes. Lava tubes, in addition to providing shelter in lunar basing, would provide cold traps at skylight sites for freezing out fumarolic fluids. A skylight is a collapsed roof section of a lava tube roof. The lava tubes of the Marius Hills region were imaged by the Selene lunar orbiter and a skylight in one of the tubes was described in a January 2, 2010 press release. This author compared the Marius Hills lava tubes with a terrestrial analog—Butte Crater on the flanks of the Island Park caldera (Green, 1969).

4. Lunar Protolife

We assume an early Archean thermodynamically stable (non-reactive) anoxic atmosphere of primarily methane, ammonia, methanol and water concentrated in topographic lows. The assumption is based on terrestrial analog. Fumarolic fluids would include water; nitrogen; ammonia, carbon and sulfur-bearing gases; halogens and formaldehyde. In shadow at 40 K, the photolysis of methane and ammonia would be minimized. Although hydrogen and helium would be lost in shadow, carbon dioxide, critical in prebiotic reactions, would be increased along with Hadean sulfur and cyanogen-bearing gases. Almost all Hadean fumarolic fluids would freeze in shadow having such low vapor pressures at 40 K that these ices would persist for hundreds of millions to billions of years if over one centimeter thick. A plot of these vapor pressures is shown in Figure 1, with the exception of formic acid and ammonium thiocyanate, both of which are close to the vapor pressure of water.

5. Energy Sources

Thermal, shock and electrical energy sources are all viable stimulants for prebiotic reactions. Cavitation in fumarolic systems can be created by sudden rupturing of an impervious cap rock such as alunite, opal or clay which would induce subsurface boiling. Volcanic shock effects under reducing conditions are capable of creating amino acids and formaldehyde with the appropriate start materials. One such start material in an aqueous environment is CO₂ which can not only form formaldehyde but also formate and methanol (Martin et al, 2008, p. 810). Methanol was detected in the Cabeus vapor plume.

Electrical phenomena such as flow charging in volcanic vents or triboelectric phenomena can create potentials for the generation of prebiotic compounds. Of lunar significance, fumarolic ices can create potentials by charge separation on freezing (Mel’nikova, 1969). Pyritic biofilms also have a positive surface charge which would attract the negative ends of amphiphilic compounds.

Both electric discharge and Fischer-Tropsch catalysis in aqueous environments were probably contemporaneous in creating prebiotic building blocks including vital porphyrins (Lindsey et al, 2009) leading to the creation of RNA and DNA. Under hydrothermal conditions, both mechanisms create lipids (Simoneit and Rushti, 2002) of various types (including fatty acids, waxes, triglycerides and phospholipids) from hydrous solutions of formic and oxalic acids. Phospholipids are the principal components of cell membranes and are amphiphilic having hydrophobic tail groups and hydrophilic head groups forming a lipid bilayer. Phospholipids fold upon themselves to form pockets or micelles in water under turbulent conditions. Fumaroles almost invariably create turbulence. Protolife probably began within semi-permeable double membraned lipid vesicles which facilitated reactions by minimizing external dilution effects (Hanczyc et al, 2003). The degree to which the vesicles permit entrance or exit of compounds is a function of the length of their carbon chains (from 10 to 18).

Fumarolic compounds contain relatively high concentrations of both tungsten and water-soluble polyphosphates (Yamagata et al, 1991); the former acting as a critical metallo-enzyme and the latter creating oligomeric amino acids leading to adenosine triphosphate and pre-RNA molecules. Amino acids (with cyanide) can assemble into proteins as membrane components. Ribose can also be formed and possibly be stabilized by boron in fumarolic fluids. D-ribose, purines (a heterocyclic aromatic compound) and phosphates may have led to pre-RNA replicating polymers. These polymers, in turn, may have evolved into RNA to DNA possibly involving a bridging medium of methyl-RNA.

Montmorillonite and kaolinite as hydrothermal clays in fumaroles have been suggested as metabolic platforms for protolife including polymerization of peptides and oligonucleotides. The convers ion of troilite—the most common lunar sulfide—with hydrogen can produce positively charged pyrite with a thermodynamically viable negative free energy of -41.9 kj/mole (Wächterhäuser, 1988). Other simple combinations of troilite, hydrogen sulfide and carbon dioxide with negative free energies can produce methylthiols.

6. Enzymes

Enzymes undoubtedly played a critical role in the evolution of protolife. For example, the protoenzyme histidyl- histidine may have been important during wet-dry cycles in fumaroles in promoting peptide bond catalysis. Regarding tungsten, on earth fumaroles can have up to a millionfold enrichment in this element over that of tungsten in seawater. Tungsten with sulfur and other fumarolic consituents form tungsto-enzymes which were critical for the formation of Archeae on earth (Kletzin and Adams 1996). Tungsto-enzyme activation of amino acids as thioesters could have facilitated attachment of amino acids to the RNA molecule.

7. Biofilms

Biofilms, consisting of colloidal iron sulfide films on bubbles, would provide both a positively charged energy source and a platform to which polar organic molecules could attach and received energy. Such films are used in present-day flotation operations to separate ore minerals. Colloidal iron sulfide as FeS2 may increase the production of carbon dioxide by the oxidation of methane. These sulfides as biofilms can also activate amino acids to peptides even after long storage and frigid conditions. There are many stimuli for the origin of lunar protolife in Hadean and later fumaroles (Table 2). From the vent outwards we see: (1) environmental changes and zonation over distances of meters (eH, pH, freeze/thaw, fluctuating clay environments including homoionic montmorillonite), (2) possible proflavin (PAH) for nucleotide assembly into RNA (3) flash evaporation and (4) lower surface pressures. Lower surface pressures would greatly reduce the boiling points of fumarolic fluids and produce larger bubbles extending the vapor phase range of lunar protolife compounds enhancing reactivity. Reactivity would also be increased by convection and fluidization in fumarolic vents. One of the more interesting stimuli for Precambrian lunar protolife is fumarolic spatter and wet/dry cycles (Green, 2009).

Table 2

8. Evidence of Lunar Microbes

With the discovery of water and associated fumarolic-hot spring products in lunar shadow, the author’s cautious comment of possible fossil lunar extremophiles (Green, 2001) is strengthened. The trajectory of lunar protolife is logically directed toward the creation of life. A remarkable adaption and persistence of life exists from bacteria in gasoline tanks to the high temperature, high pressure darkness environment of black smokers to the cold of Antarctic ice. However, many of the claims for lunar life forms require review. A camera returned from the moon (as a component of Surveyor 3) after three years of exposure to radiation and the lunar weather supposedly contained a living organism, Streptococcus mitis, a mesophilic alpha-haemolytic bacterium. This bacillus is alien to the harsh conditions of and following the Hadean and is found in mucous membranes of humans. The bacterium was dormant, and found within the camera in a layer of foam between two circuit boards (Mitchell & Ellis, 1971). Contamination was ruled out by Mitchell and Ellis, the two NASA investigators who made the discovery. Since a droplet of saliva contains an average of 750 million organisms, if there was contamination due to a cough or sneeze, or an instrument laid down on a contaminated bench, a multitude of related and unrelated bacteria, and a "representation of the entire microbial population would be expected," rather than a single species and a single organism (Mitchell & Ellis, 1971). The source of this microbe, is therefore, unknown.

Zhmur and Gerasimenko (1999) have reported the presence of bacteria in Luna 20 return samples originating in hydrothermal environments. According to these investigators, the reported "fossils" about 1 to 2 micrometers in diameter, resemble Sulfolobus, Siderococcus and Phormidium frigidum. Dr. Rhawn Joseph (unpublished, personal communication) showed the photo of "Phormidium frigidum" to five internationally recognized experts in Cambrian and Pre-Cambrian evolutionary biology, without telling them the source, and four of the five identified it as a "microfossil" possibly of an unknown micro-organism. On the other hand, the latter "fossil" also closely resembles micrometeorite impact craterlets in lunar volcanic glass spherules.

Of more significance is the possibility that the globules of the claimed Sulfolobus and Siderococcus are non-biogenic proteinoid microspheres. Freezing of fumarolic fluids can produce such microspheres from ammonium cyanide and ammonium thiocyanate which are both possible in Hadean fumarolic fluids. The se spheres span the size range of the globules imaged by Zhmur and Gerasimenko. Proteinoid microspheres are motile, may coalesce, exhibit swellability, vary in shape, can be stained, simulate osmosis and form buds. They bear striking similarity to cocci forms of hyperthermophilic extremophiles of ancient Archeae and those today at Yellowstone National Park hot springs.

If verified, the Soviet claims for coccoidal bacteria, may in fact indicate they originated in lunar hydrothermal vents as these authors claim.

However, these vents, as fumaroles or hot springs, would have to be in shadow and protected from lunar temperature and radiation extremes. It would be desirable to analyze the Luna 20 globules with an ion microprobe analysis system. Regarding the 1999 Soviet publication, proponents of panspermia as well as those of impact mechanisms appear to minimize the hydrothermal origin claimed for these "fossils." This author is tempted to suggest the possibility that lunar, early Precambrian fossil extremophiles may have had an aborted evolution from protolife forms. What is needed is unequivocal proof of fossil lunar extremophiles by the identification of biomarkers and organic features using muramic acid (C₉H₁₇NO₇) and 3-hydroxy fatty acids (Fox, 2002) or high carbon 12 concentrations (Nemchin et al 2008) either in situ or in sealed return samples from shadowed zones from the moon. Finally, the claim by Sears and Kral (1998) that a lunar meteorite had "microfossils" is irrelevant because the authors concluded the features were abiotic and the result of terrestrial contamination.

9. Protolife Transfer to the Earth

We have no evidence as to whether Earth or the moon first created protolife although we favor the moon. Certainly there were enhancing conditions for lunar protolife such as greater tides, lower lunar gravity and surface pressures. If we grant an earlier formation of lunar protolife, could transfer of organics to Earth be achieved by volcanic explosions? Figure 2 shows dynamic lift curves as a function of initial velocity and ejection angle.

Using maximum initial volcanic blast velocities (on earth) of 600 meters per second, Figure 2 shows that it is impossible to achieve lunar escape velocities. A maximum lunar range of 210 kilometers at about 45 degrees ejection angle is shown. For fumarolic spatter, the range of ejecta might be only 600 meters. On the other hand, a meteorite impact at some 15 kilometers per second could generate particulate ejecta velocities in excess of 1700 meters per second and achieve lunar escape velocities especially at low ejection angles. However, the impact must target very small lunar areas with protolife compounds under unknown thicknesses of dust. High angle eternally-shadowed slopes may have a thin dust cover. Moreover, lunar hydrothermal sites would likely be soft and friable (if not silicified) and would be finely comminuted by impacting meteorites. We conjecture that most of the ejected organicrich debris would probably be vaporized if not captured in the nearby Lagrangian points. We are not optimistic about any organic material blasted from the moon reaching favorable host environments on Earth during the early Precambrian.

10. Conclusions

The author interprets the abundance of water, methane, ammonia and methanol in Cabeus to be evidence of endogenic or volcanic water. If so, the discovery reinforces the author’s contention that most major lunar surface features are volcanic or volcano-tectonic including the rayed craters and circular basins such as Imbrium, Crisium, Orientale and Aitkin. Small lunar features must include millions of meteorite craters, maars and subsidiary forms. Omitting the obvious survival and resource benefits of easily extractable water is the creation of protolife which depends on a hydrous environment such as is found in fumaroles and hot springs. Volcanism with its associated fluids, including water, is conceptually reinforced by observation of large scale water emissions from Enceladus imaged by Cassini in July 2005 (Porco, 2009) and sulfur and lava flows on Io imaged by Voyager 1 in March 1979. Of greater significance is the discovery of over 400 exoplanets. If defluidization is a generally operative cosmic process, then protolife or life may exist on our distant celestial planetary neighbors.

The discovery of water in Cabeus was a remarkable achievement, but it represents an undesirable, if not deplorable, lunar exploration philosophy. Impact methods to obtain geological data can result in a loss of critical details. Possibly destroyed in Cabeus were priceless clathrate structures, frost features, fumarole morphologies, zoning chemistries and mineralogies and details of possible ice layering in unknown thicknesses of impact and pyroclastic dust. We strongly recommend that both altitude remote sensing (exemplified in the current December 28, 2009 NASA LRO mission) and passive surface remote sensors (such as cavity-enhanced absorption spectroscopy) should replace impact exploration. A candidate active remote sensor is a geologist with a hammer and camera.