Meteorite organics in planetary environments ... - Science Direct

Planet. Space Sci.. Vol. 43. Nos. l/2, pp. 139-147, 1995

Pergamon

Elsevier Science Ltd Printed in Great Britain 0032-0633/95 $9.50 + 0.00 0032-0633(94)0020~3

Meteorite organics in planetary environments : hydrothermal release, surface activity, and microbial utilization Michael N. Mautner,’ Robert L. Leonard’ and David W. Deamer’ ‘Department of Soil Science, Lincoln University, Canterbury. New Zealand ‘Department of Chemistry, University of California, Santa Cruz, California,

U.S.A.

Received 27 July 1994 : revised I 1 October 1994; accepted 11 October 1994

Abs@ct. Up to 50% of the organics in the Murchison

meteorite, passibly inch@ing some of the polymer, is released .in high temperature and pressure aqueous environments, to 350°C ati 250 bar, that simulate submarine vtic, hydr&ermal or impact-induced unctions. Meteorite 0 * s of prebiotic signacame, su& as mmanoic ne, and pyrene survive the hydride conditions. The released material is sm4bze active with surface pressure8 up to 19.8 x 10q3 N m-l, and exhibits 8n extended surface ts a mixture of amphitension isotherm w&41 phik components. One caaaponent, nonanoic acid, is shown to farm vesicles. The materials extracted under mild conditions, at EWC, are n&rients for the humic acid bacterium Pseudomwas rn~~l~~~~~ and efficient nutrients for the oligotr~.@~ F~~~~e~~~rn oryzihabims, demonstrating the capaWity of microorganisms to metabolize extraterrestrial organics.

Introduction The infall of interplanetary dust particles (IDP), comets and carbonaceous meteorites (Anders, 1989 ; Chyba and Sagan, 1992) is a potentially significant source of prebiotic organic carbon on Earth (Oro et al., 1971; Delsemme, 1991), on early Mars (Nealson et al., 1992), and on icy moons and planets. An important example of such material is the Murchison meteorite, with about 2% organic carbon. Over 70% is present as insoluble kerogenlike polymer, which is also an important component of the more abundant IDP particles (Chyba and Sagan, 1992; Cronin and Chang, 1993 ; Hayatsu et al., 1977; Levy et al.. 1973; Studier et al., 1972). The soluble meteorite organics include C,-C,, carboxylic acids, polycyclic

Correspondence

to : M. N. Mautner

aromatics, hundreds of other aromatic and heterocyclic compounds, and up to 700 nmol g-’ amino acids (Oro et al., 1971 ; Kvenvolden et al., 1970, 1971 ; Yuen and Kvenvolden, 1973 ; Chang et al., 1983 ; Shimoyama et al., 1989; Cronin and Chang, 1993). Much of the IDPs and meteorites would fall into the early oceans and be subjected to conditions producing high temperatures and pressures, due to possible vulcanism in submarine eruptions and hydrothermal vents on the early Earth or other planets (Shock and McKinnon, 1993), and giant impacts (Maher and Stevenson, 1988; Sleep et al., 1989). The impacts of the carbonaceous meteorites themselves on water, ice or permafrost on early Earth and Mars or on icy planets, can also create short pulses of aqueous high temperature and pressure conditions. We shall examine whether such conditions can release complex organics efficiently. This is important since the high pressure can preserve complex molecular structures, and allow synthetic condensation reactions at high temperatures (Oro and Guidry, 1961 ; Siskin et al., 1990 ; Siskin and Katritzky, 1991 ; Shock and Hegelson, 1990; Shock, 1992a,b; Simoneit, 1992; Shock, 1993). Therefore, hydrothermal release would have been more likely to preserve and further process complex meteorite organics than dry pyrolysis on hot rocks. If effectively released, the organic components can be available for further chemical evolution in high temperature and high pressure aqueous environments, which were proposed to facilitate the appearance of the first microorganisms (Corliss et al., 1981). One possible prebiotic role is the formation of supramolecular assemblies necessary for cellular structures. We have observed that chemical extracts of the Murchison meteorite can form stable bilayers and vesicles (Deamer, 1985 ; Deamer and Pashley, 1989). In this work we shall examine whether the more natural hydrothermal extraction also yields surfaceactive materials and vesicle-forming components. Once microbial life is present, the meteorite organics may serve as early nutrients. Microbial response to extra-

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terrestrial organics is also of interest because similar materials on asteroids and other planetary bodies may serve as nutrients for microorganisms transported there by design or accident. Furthermore, microbial conversion to biomass may be useful to process asteroid materials as a proposed organic resource for space settlements (O’Neill, 1975 ; O’Leary, 1977). In these respects, we shall examine the response of two oligotrophic microorganisms to the hydrothermal meteorite extracts.

Experimental

Hydrothermal processing was performed in a screw-top autoclave machined from stainless steel, with a cavity volume of 4 ml. Interior samples of the Murchison meteorite were hand-ground in a ceramic or glass mortar. Before use, the autoclave and all glassware were exposed overnight to chromic acid-sulfuric acid solution to remove organic contaminants. In a typical experiment, 20-80 mg powder was placed in 2 ml distilled, de-ionized water, and deaerated with helium. Some powder samples were preextracted by grinding for 5 min in equal volumes of 2: 1 chloroform-methanol and 0.1 N sulfuric acid. The untreated or treated powder samples were dried at room temperature and analyzed with a Europa Scientific Tracermass Stable Isotope Analyzer mass spectrometer. For GCMS analysis of the extracted surface-active, low vaporpressure chemicals, the aqueous extracts were acidified with HCl, extracted into 24 ml chloroform and dried with a nitrogen stream. Note that this analysis addresses only the non-volatile components as the volatile components are presumably lost in this step. The dry samples were redissolved in 50 ~1 acetonitrile, of which 5 ~1 were injected into an HP 5890 series II GCMS apparatus, sometimes after derivatization with bis-trimethylsilyl trifluoroacetamide. Components were identified by matching against the Wiley Mass Spectral Library using HP1043B software. For surface tension measurements, hydrothermal extracts were obtained from 1.59 g interior Murchison sample that was ground for 10 min in an acid-cleaned ceramic mortar and pestle, added to 5 ml deionized water and processed hydrothermally at 350°C for 1 h. The relatively non-polar organics were extracted with 2 ml chloroform, of which 100 ~1 were spread onto a 10 x 50 cm Teflon Langmuir trough. For the microbial experiments, we prepared samples of 2040 mg powdered meteorite samples in 0.2-0.6 ml deionized water. Hydrothermal extraction was performed by mild (125°C 15 min) or more severe (2OO”C, 24 h) processing, both of which also sterilize the solution. For inoculation, 5 ml samples of the microorganisms grown in tryptic soy broth were centrifuged to isolate the microorganisms, and washed three times with 5 ml deionized water. Each washing and centrifuging cycle diluted the residual nutrient by at least a factor of 50, giving a total dilution of > 1.2 x 105.After further dilution by > 100 for inoculation, and final dilution of ~20 upon inoculation, the procedure reduces the concentration of residual nutrients in the cultures to < lo-’ g l-‘, much lower than the

M. N. Mautner et al. : Meteorite organics in planetary environments extracted organics in the meteorite extract culture media, which is about IO-’ g 1-l. The effect of residual nutrients was also compensated by comparing the meteorite extracts with deionized water blanks, inoculated in the same manner. The microbial solutions were finally diluted and counted on agar before inoculation. Inoculations with 10 ~1 of the final microbial suspension were performed to achieve 2000-3000 CFU (colony forming unit) mll’ in 0.2-0.6 ml cultures in the hydrothermally processed, sterilized meteorite extracts. The cultures were incubated in the dark under aerobic conditions in containers with air saturated with water vapor, to prevent the drying of the small cultures. Counting was performed on nutrient agar. The microbial experiments were replicated three times with reproducible results.

Results and discussion 1. Hydrothermal release und processing

To test the possible undersea release of meteorite organics, we used hydrothermal processing at 121°C 2.1 bar; 200°C 15.5 bar; 300°C 85.9 bar; and 350°C 165.3 bar, where the pressures are the equilibrium vapor pressures in the autoclave. These conditions are equivalent to the temperature and pressure of boiling water at ocean depths of 21, 158, 876 and 1686 m, correspondingly. In some experiments for testing the survival of organics we used 38O”C, above the critical temperature of pure water. Note that water conditions such as oxygen and hydrogen fugacity and ionic strength may affect the chemistry (Shock, 1992a,b). Since free oxygen was not likely present on the early Earth, we removed the air from the solutions by bubbling with helium. Since the composition of the early oceans is unknown, we used pure water, but effects of pH and ionic strength on the release and survival of the organics would be of interest. The present results are shown in Table 1. We observe that hydrothermal processing leads to increasing release with increasing temperature. At 35O”C, as much as 51% of the total organic carbon is released. This may include some polymer components, as solvent extract alone removes only 23% of the carbon. Extending the processing time from 24 to 96 h does not release further carbon, consistent with dry pyrolysis which is completed in about 10 min (Levy er al.. 1973). In fact, we observe in Table 1 that at 200 and 350°C both dry and hydrothermal processing release similar amounts of organic carbon. If the similarity extends to 550°C where 94% of the carbon is released, aqueous release at such temperatures may also be almost complete. Such high temperatures may be present under vulcanic or impact conditions, although not in hydrothermal vents that go only to about 4OO’C (Von Damm, 1990). Table 1 also shows that nitrogen release and decreasing 6 ‘*N (%D) enrichment proceed in parallel with carbon release. The latter is consistent with previous isotopic studies which suggest that the extractable and polymeric material have different origins (Becker and Epstein. 1982; Robert and Epstein, 1982).

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Table 1. Total C and N content, percent in Murchison meteorite samples” Extraction

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environments

T(“C)

Untreated Hydrothermal Hydrothermal Dry pyrolysis Hydrothermal Hydrothermal Dry pyrolysis

121 200 200 300 350 350

Solvent extraction Solvent + hydrothermal Dry pyrolysis

20 350 550

of C and N removed,

and 15N enrichment

%Ch

%Nh

AC’

AN’

S(15N)”

I .86 1.68

0.10 0.09 0.08 0.08 0.07 0.07 0.07

10 28 26 30 51 54

10 30 20 30 30 30

51.4 53.9 34.0 42.7 20.7 18.4 23.5

18 3 3 7 ; 7 3

0.08 0.06 0.01

20 42 94

20 40 90

44.7 Il.5 12.0

l;, 4 7

1.36

I .41 1.31 0.89 0.87

1.49 I .07 0.12

I?”

’ Error estimates, from standard deviation in 2-6 replicates %C. k 0.2 ; %N. t-0.02; 6(“N) (%o), + 10. All hydrothermal treatments and pyrolysis for 24 h, except for the 121°C treatment for 15 min. A 96 h hydrothermal treatment at 350 ‘C showed similar results to the 24 h treatments. ‘Percent of total weight. ’ Percent of total C or N removed. “6(“N) (%0) = 1000 x A((“N) -A(15N) (reference))/A(“N) (reference)), where A( “N) is atom percent 15N in the sample and A(“N) (reference) is atom percent ‘“N in a standard terrestrial sample. ‘Number of measurements.

In addition to total carbon measurement, we also performed GCMS analysis of some of the involatile organics of the hydrothermal extracts. The analysis was aimed at major involatile. potentially membrane-forming or photochemically active components (see below). Several GCMS analyses were performed with or without TMS derivatization. The results showed naphthalene, methylnaphthalene, dimethylnaphthalene, vinylindene, phenethylanthracene or ethylphenanthrene, anthrene, fluoranthene and/or pyrene, methylpyrene, elemental sulfur, and octanoic acid and nonanoic acids as TMS derivatives. The latter is of special interest in relation to the surface-active and membrane-forming properties as discussed below. The meteoritic sulfur appeared to be converted to H,S under aqueous autoclave conditions above 3OO”C, and this was observed also with pure elemental sulfur in water. In order to participate in prebiotic synthesis, meteorite organics must survive the release conditions, similar to the hydrothermal survival of a variety of complex organics (Siskin et al., 1990 ; Siskin and Katritzky, 1991 ; Shock, 1992a,b, 1993). We therefore subjected several minor but prebiotically important components to our hydrothermal release conditions. These included nonanoic acid as a membrane-forming component, as well as glycine, and pyrene that can create proton gradients as a potential prebiotic energy source (Deamer, 1992). All of the compounds were used in 0.01 M solutions or suspensions. After exposure to various temperatures for 1 h, we observed the following percent survival. Nonanoic acid: 25”C, 100% : 2OO”C, 75% ; 3OO”C, 73%; 38O”C, 63%. In a separate experiment at 0.1 M concentration and GCMS analysis with octanoic acid internal standard, at least 10% survived at 300°C after 24 h. Glycine : 25”C, 100% ; 2OO’.C,85%. At 300 and 38O’C

the glycine disappeared entirely from a TLC plate, and was replaced by a more polar ninhydrin-positive spot. Pyrene : 100% survival at all the temperatures. Meteorite or IDP powder in water flash-heated by undersea volcanism or impacts, or in contact with jets exiting hydrothermal vents, will be heated for periods much shorter than the 1 h exposure time used here, allowing for better quenching and increased survival of the released organics. Material in the hydrothermal systems will be exposed for longer times.

2. Surface uctiuitx and membrane_forming propertirs In order to self-assemble into supramolecular structures such as bilayer membranes (Deamer, 1985; Deamer and Pashley, 1989) the released material must contain amphiphiles, and their presence can be tested by measuring the surface activity. We followed the surface pressure changes of a solution of water and powdered sample from the interior of the meteorite, using the Wilhelmy plate method, as shown in Fig. 1. The sequence started with a pH 2 aqueous solution where carboxylate groups are protonated. Addition of meteorite powder at room temperature released little surface-active material, with the surface pressure changing to 0.6 x lo--’ N rn- ‘. However, brief heating to 100°C raised the surface pressure substantially, to 8.4 x 10e3 N m-l, indicating the release of amphiphiles. Titrating the suspension to pH 11 had little effect, which shows that surface activity is maintained over a wide pH range including that likely under any natural conditions. A brief second heating to 100°C caused a further rise of the surface pressure to 10.8 x 10-j N m-‘. When the surface was cleaned for a few seconds by water vacuum suction, the surface pressure dropped to 2.4 x lO-3 N m-‘. but then rose spontaneously to

M. N. Mautner

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Clean surface pHII

-

I

-

t Heat

Add powder c

-1

t

PHI

Heat

L

Time (min)

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(Yuen and Kvenvolden, 1973; Shimoyama et al., 1989). A mixture of amphiphiles in the meteorite is also suggested by the stability of vesicles formed from solvent extracts of the meteorite (Deamer, 1985 ; Deamer and Pashley, 1989). as membranes from pure amphiphiles of the size found in the meteorite are relatively fragile and cannot maintain concentration gradients for more than a few seconds. The abundance of carboxylic acids in meteorites decreases with increasing chain length. On the other hand, the formation of bilayers and vesicles requires a minimal chain length. Specifically, we observed previously that decanoic acid forms vesicles but that octanoic acid cannot (Gebicki and Hicks, 1973; Hargreaves and Deamer, 1978). In the analysis of the extract we found the acid intermediate between these, i.e. nonanoic acid, to be present. In fact, this was the longest chain acid that we could identify by GCMS analysis. In the present experiments we found that it can indeed form vesicles, at high concentrations of 0.1 M and neutral pH ranges, as shown in Fig. 3. Interestingly, therefore, the longest chain acid observed in the hydrothermal extract happens to be just long enough to be able to form vesicles.

Surface pressure - Murchison powder

‘Ok-

et al. : Meteorite

0

Fig. 1. Surface pressure changes in a sample of powderized meteorite in deionized water upon heating and pH changes

3. Microbial 7.8 x 10e3 N m-’ as additional surface-active material came to the interface. After more severe processing of the sample at 350°C for 1 h, a higher concentration of amphiphiles was suggested by a surface pressure of 19.8 x lo-’ N m-l. The surface-active material produced a highly expanded surface pressure isotherm as shown in Fig. 2, in contrast to the sharp surface pressure transitions characteristic of pure amphiphiles. This suggests that the released materials contain a complex mixture of various amphiphiles, possibly including branched-chain carboxylic acids up to CIZ

0

I

I

I

50

100

150

I

200

250

Surface area (cm*)

Fig. 2. Surface tension isotherm of hydrothermal meteorite extracts. When the surface area was reduced by a moving barrier, surface pressure first appeared at approximately 200 cm’, then increased with decreasing area as shown. When increased again to 200 cm2 and reduced to 20 cm2, the same isotherm was produced

utilization

In the presence of early microbial life, the released organics may have provided nutrients. An interesting observation was made in this respect (Stoker et a/., 1990) who showed that a large variety of microorganisms can survive on the synthetic mixture tholin which is formed in Miller-Urey type experiments. In the present experiments, we tested microbial response to actual extraterrestrial organics in the hydrothermal extracts. The possible nutrients in these extracts are at low total concentrations of 10-3-10-4 M, with individual compounds possibly below lOA M, suggesting that the microorganisms used should be oligotrophs, and also heterotrophs, as expected of early microorganisms. The material is extracted from meteorite organics similar to kerogens, which are related to humic substances, suggesting the use of soil microorganisms that utilize such materials. One of the microorganisms used was isolated from a sample of meteorite powder that was kept in deionized water for four months without intentional inoculation, which suggested that it is an oligotroph and uses meteorite organics, and therefore suitable as a test microorganism. This microorganism was identified as the common environmental microorganisms Fluuobacterium oryzihabitans.* We cultured this microorganism and used the culture to inoculate the meteorite extracts. We also tested a humic acid utilizing soil microorganism Pseudomonas rna~~o~hj~j~. Note that the conditions used to extract the meteorite organics at temperatures of 120°C or higher for at least 15 min also sterilized the samples, so that the only organisms present in the incubated samples were those introduced subsequently through deliberate inoculation.

*This identification is tentative. The quality of identification was acceptable but low. Further work may require a change in the name of this organism.

M. N. Mautner et al. : Meteorite organics in planetary environments

Fig. 3. Membrane formation by nonanoic acid. Nonanoic acid (100 mM) was titrated to pH I1 with I M NaOH, at which point a clear micellar solution was present. The solution was then titrated back to pH 6.9 by dropwise addition of 1 M HCl, and the turbid dispersion was examined by phase microscopy. Bar indicates 20 pm

143

144

M. N. Mautner

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Fig. 4. Transmission electron micrographs. bar shows 200 nm. (a) Flawbacterium ory5habitans on the background of meteorite powder. Bacteria grown on meteorite extract and powder which were processed at 121 ‘C, 1.5 min. (b) Flarobactrrium oryzihabitans grown on nutrient agar, for comparison

environments

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Flavobacterium 1E+O9

in planetary environments

145

Flavobacterium orzihabitans

orzihabitans 1E+09

No oarticles

r

125°C/15 min extr

I E+08 ci $ lE+07

water

kz ” lE+06

Deionized water

Acid washed sand + Di water

.4 IE+05 2 4 1E+04 ‘;6 ‘5 IE+03

With particles

,E+02ff

i

lE+Oll 0

2

4

6 8 10 12 14 Days after innoculation Pseudomonas

16

18

20

0

\- 2OOW24h extr ’ 2

I I I .! ’ 6 8 10 12 14 Days after innoculation

b; 4

maltophilia

I E+09

+ powder

Pseudomonas

I 16

I 18

1 20

maltophilia

lE+O9

No particles

With particles

1E+08

_ F

lE+08

2 :

lE+07

2 . lE+07

2 ”

lE+06

2 g

q

lE+06

/

’

Acid washed sand

.B IE+05 2 4 lE+04 1 ‘S lE+03

200°C/24 h extr

8 lE+02 m

powder-

lE+Ol

lE+Ol 0

2

4 Days

6

8

IO

12

after innoculation

0

2

I

I

I

I

I

4 6 8 Days after innoculation

10

12

Fig. 5. Microbial growth in meteorite extracts produced under the conditions shown. or in deionized (DI) water for reference, with or without particulates present as indicated. All samples incubated at 34 C in dark

Transmission electron micrographs of the Flavobacterium or~~zihabilans grown on meteorite extract and powder that was processed at 121°C 15 min, and on nutrient agar for comparison, are shown in Fig. 4. In a sample of 10 microorganisms, the Flavobacterium oryzihabitans grown on the meteorite extract had an average size of (0.95 fO.13) x (0.70f0.05) pm, and were more globular in appearance than the same bacteria grown on nutrient agar. which in a sample of 23 had an average size of (0.97 + 0.28) x (0.47 &-0.05) pm. The more globular shape in the dilute meteorite extract may provide a larger surface-volume ratio for more efficient nutrient uptake, and may also result in part from osmotic effects. The population growth curves with meteorite extracts, first in the absence of powder, are summarized in Fig. 5. Both bacteria show some growth in pure deionized H,O. showing that they are oligotrophs. However, with meteorite extract obtained under mild hydrothermal conditions of I2O’C at 15 min, the Flavobacterium oryzihabitans showed increased growth by up to three orders of magnitude. compared with the deionized water blank. The long-term steady-state populations. up to 84 days, were also larger by two orders of magnitude than in deionized water. An extract obtained under more severe release conditions of 200°C. 24 h, was similarly stimulating. The above experiments were performed in the soluble extract, in the absence of meteorite powder. Further experiments were done also with the meteorite powder

also present. The unprocessed. unextracted meteorite powder in deionized water stimulated more growth after 3-4 days of incubation than a blank of acid-washed sand in deionized water. Powder from which organics were pre-extracted with chloroform-methanol acted similarly. These observations suggest that some nutrient or inorganic micronutrient may be slowly released at 2O’C, or that the Flat>obacterium oryzihabitarts utilizes the insoluble material in the powder. In experiments where both the hydrothermal extract from 125°C. 15 min, and the powder remaining after this extraction were present, the powder had no significant effect compared with the extract alon However, in an analogous experiment with the extract and powder processed under more severe conditions at 2OO”C, 24 h. the powder was toxic. as was also powder from dry pyrolysis at 550’ C. 24 h. With Pseudomonas ntalrophilia, the extract from mild processing at I25 ‘C. I5 min, had a small nutrient effect. The solution obtained by the higher temperature extraction at 200’ C. 24 h, was even less stimulating. The presence of any form of meteorite powder was toxic to this bacterium. Preliminary experiments with a third microorganism, Pseudomonasfluorescens also showed enhanced growth in the meteorite extract, with growth rates intermediate between Flavobacterium orkihabitans and Pseudomonas maltophilia, and a toxic effect of the powder. The toxic effects of the powder may be due to chemical inhibition. However. Pseudomonas fh~orescens showed a

146 strong adhesion to the test-tube walls, suggesting that the toxic effects of the meteorite powder may be at least partially due to the trapping of the microorganisms on the large surface area of the finely ground meteorite powder. The amount of bacterial carbon may be compared with the amount of released meteorite carbon in the cultures. Based on an average volume of 3.7 x lo-l3 cm3 from transmission electron microscopy, assuming 10% carbon content, with a final steady-state density of live Fluuobacterium oryzihabitans of 1.4 x 10’ CFU ml- ’ in 0.2 ml culture, the total live microbial carbon content is 1 x 10e6 g, and in the Pseudomonas rn~lto~~i~~~ population of 3 x lo6 CFU ml-’ ml the live microbial carbon content is about 2 x lo-’ g. Both are less than the extracted organics from 20 mg powder in these solutions at 121“C. 15 min which yields 3.6 x 10e5 g carbon according to the results in Table 1. A large fraction of meteorite organics is unsubstituted or substituted carboxylic acids that are common in biological materials and may well be usable as microbial nutrients. Of special interest may be amino acids that constitute about 7 x lo-’ mol g-’ of the meteorite, about half of which are biological type compounds (Kvenvolden et ul., 1970 ; Cronin and Chang, 1993). With an average molecular weight of 100 comprising 60% carbon, the biological type amino acid content in a 20 mg sample contains 8 x lo-’ g carbon, which may be released only partially under mild extraction. From these results, the Fluvobacterium orjzihabitans utilizes 3% of the total released carbon, which is somewhat more than that accountable by the meteorite amino acids. Therefore, other released meteorite organics are apparently also utilized by Fhobacterium oryzihabitans. On the other hand, the carbon content of Pseudomonas multophiliu may be well accounted for by the released amino acids, although this microorganism may be also utilizing other released organics as well.

M. N. Mautner et al. : Meteorite organ& in planetary environments that are similar to carbonaceous chondrites could be converted directly to biomass by microbial processing, as organic resources for lunar and space-based settlements (O’Neill, 1975). We are studying other microorganisms, and methods of adaptation to meteorite organics, in this respect. The observed microbial growth on extraterrestrial organics is also pertinent to planetary quarantine (Nealson et cd., 1992). panspermia (Arrhenius, 1908; Crick and Orgel, 1973). and to the possible implantation of microbial life on nearby young solar systems (Meot-Ner

(Mautner) and Matloff, 1979). Ackno~lrdgenzents. We thank Dr R. R. Sherlock for helpful discussions and for making facilities available. Dr E. White and Dr P. Ellerbe for GCMS analyses, Dr G. Paltridge of the Canterbury Health Laboratories for the microbial analyses. and William Ong for technical assistance. Supported by NASA Grant NAGW- I 119.

References Anders, E., Pre-biotic

organic matter from comets and asteroids. Nuture 342,255-258, 1989. Arrhenius, S., Veldarnas Ultveckling, Stockholm, 1908, cited by A. I. Oparin in Genesis and Evolutionary Development of Lifh. Academic Press, New York, 1957.

Becker, R. and Epstein, S., Carbon hydrogen and nitrogen isotopes in solvent-extractable organic matter from carbonaceous chondrites. Geochirn. Cosmochim. Acta 46, 97103, 1982.

Chang, S., Des Marais, D., Mack, R., Miller, S. L. and Strathearn, G. E., Prebiotic organic synthesis and the origin of Life. in The Earth’s Earliest Biosphere (edited by J. W. Schopf). ~;~p.y-92. Princeton University Press, Princeton, New Jersey,

Chyha, C. and Sagan, C., Endogenous production, exogenous delivery and impact-shock synthesis of organic molecules : an inventory for the origins of Life. Nuture 335, 125-I 32, 1992.

Corliss, J. B., Baross, J. A. and Hoffman, S. E., An hypothesis Conclusions

The present results show that complex meteorite organics are released efficiently by high-temperature, high-pressure aqueous undersea or impact conditions. The high-pressure release conditions preserve the complex materials, some of which are surface active and can form membranes and vesicles. The released materials become available for prebiotic processes in the hydrothermal environments where early life may have arisen (Corliss et al., 1981 ; Simoneit, 1992). These observations support the conjecture that extraterrestrial materials could have played a role in prebiotic processes (Chyba and Sagan, 1992). The results also show that extraterrestrial organics can serve as microbial nutrients. In this respect, we are examining the response of more primitive thermophiles and archaebacteria under simulated early planetary anaerobic conditions. Microbial response to IDP organics, if these become available, would be also of interest, as these materials were more abundant than meteorite organics on the early Earth (Chyba and Sagan, 1992). The microbial results suggest that asteroid materials

concerning the relationship between submarine hot springs and the origin of Life on Earth. Oceanol. Actu. Proc. 26th Int. Geol. Congress, pp. 59-69, 1981. Crick, F. H. and Orgel, L. E., Directed panspermia, Icurus 19, 341,1973. Cronin, J. R. and Chang, S., Organic matter in meteorites: molecular and isotopic analyses of the Murchison meteorite, in The Chemistry oflife’s Origins (edited by J. M. Greenberg et al.), pp. 209-258. 1993. Deamer, D. W., Boundary structures are formed by organic components of the Murchison carbonaceous chondrite. Nature 317, 792-794. 1985. Deamer, D. W., Polycyclic aromatic hydrocarbons : primitive pigment systems in the prebiotic environment. Adv. Space Res. 12, 183-189, 1992. Deamer, D. W. and Pashley, R. M., Amphiphilic components of the Murchison carbonaceous chondrite : surface properties and membrane formation. Orig. Life and Evol. Biosphere 90, 21-28, 1989. Delsemme, A. H., Cornets in the Post-Halley Era (edited by R. L. Newburn, M. Negbauer and J. Rahe), pp. 377-428. Kluwer, Dordrecht, 199 I. Gehicki, J. M. and Hicks, M., Ufasomes are stable particles surrounded by unsaturated fatty acid membranes. Nature

243,232-234,

1973.

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in planetary

environments

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