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The microscopic examination of the apollo-11 and -12 sample and the quest for life forms
© 1971 by Academic Press, Inc.
s. ULTRASTRUCTURERESEARCH35, 403-410 (1971)
403
The Microscopic Examination of the Apollo-11 and -12 Sample and the Quest for Life Forms DELBERT E. PHILPOTT AND CHARLES TURNBILL
Ames Research Center, NASA, Moffett Field, California, 94035 Received February 9, 1970 Examination of loose sediment and breccia (compacted sediment) returned from Apollo 11 and 12 has been accomplished by light, electron, and scanning electron microscopy. Glassy spheres 0.05 ~ to 1 mm in diameter appeared in a heterogeneous distribution. Their shape and structure is consistent with the theory of cooling during free flight. In the laboratory, spheres were produced from the lunar soil itself by heating with the electron beam in the vacuum of the electron microscope. The loose sediment seems the least likely place to discover any preexisting forms of life due to the hostile conditions of soil turnover, vacuum, temperature, and radiation present on the moon. The breccia might provide some protection; however, no organized forms were observed here either. Acid treatment produced a whitish insoluble portion partly explained by surface etching. Removal of radiation darkening is also possible, and it may be that some of the color of the moon is due to radiation effects. Etching with acid failed to reveal any life forms which we could recognize. Probably Pickering (7) was the most optimistic about finding life on the moon. After years of observations he concluded that the dull red and brown color changes in craters such as Grimaldi were due to huge swarms of insects. He also attributed other color changes to the spread and recession of plants. Over the years, although many color changes have been reported, none of the changes has had a really satisfactory explanation. Now not very many scientists hold much hope (1, 2) for life existing on the moon. Actually many of the conditions on the moon are what we use here on earth for sterilization: for example, extreme heat, radiation, X-rays, and ultraviolet light. In addition, the solar radiation, solar flares, and cosmic particles, along with the lack of water, add to the problems of any life developing on the surface of the moon. About the only favorable condition for the development of life is the lower gravity, which would require much less energy for movement. Therefore, life on the surface of the moon seems highly improbable. However, some areas must exist on the moon where these hostile conditions are moderated. If the moon cooled during some period
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PHILI?OTT AND TURNBILL
in its past history and contracted, caves should have formed. Here, or deep within the soil, conditions for both the development and preservation of life may be better. This latter problem, that of preservation, is of course extremely important. Even if some manifestation of life developed during more conducive times, it must be adequately preserved if we are to find it. Due to the hostile conditions of the surface, preservation would be more likely in caves, beneath the surface or in rocks. MATERIALS AND METHODS Two samples from Apollo 11 (a 2-g fraction of lunar soil sample 10 086.3 and a 0.7 g sample of breccia) and one sample from Apollo 12 (a 1-g soil sample ARC 12 023.07 containing a breccia chip) were studied and photographed using a Zeiss and Leitz light microscope and a Philips 300 electron microscope. The surface features of the sample were studied using an Advanced Materials Research scanning electron microscope. Gold and carbon were used to coat soil particles to prevent charging in the scanning electron microscope. Petrographic sections were prepared by embedding soil in epoxy on light microscope slides and grinding the surface. Electron diffraction and the X-ray probe aided sample analysis. A portion was also hydrolyzed for 1 hour with 1N HC1 under reflux and then centrifuged at 2 700 rpm and another portion was placed in 2% HF overnight. The remaining lunar material was studied using the scanning electron microscope. Glassy spheres were heated up to 800°C, and fines from the soil were melted using the beam of the electron microscope. Sorting was aided by the electrostatic charge on the particles, especially the glassy spheres, which caused them to jump up to a metal or wooden probe. Bacteria and Myeoplasma laidlawii were placed in 2 % HF for 24 hours as a control to test structural survival. RESULTS AND DISCUSSION Initial observations on the loose sediment showed sharp angular fragments and glassy spheres (Figs. 1 and 2). These lunar spheres ranged in size from 0.05 # to 1 ram. Their distribution was quite heterogeneous, a characteristic of the entire sample. Since fractured glass was also present and might represent shattered fragments of larger spheres, maximum sphere size was difficult to determine. The melted portion varied from spherical to cylindrical (Fig. 3) and included portions where the fines were embedded in the spheres (Fig. 4). Heterogeneous sphere interiors were common, varying from hollow to crystalline as evidenced by their effect on polarized light, but no liquid inclusions were seen in any of the spheres. The spheres and other glassy material generally had a number of pores on their surfaces (Fig. 5). The embedding media and the refractive index of the glassy spheres gave rise to pseudo-walls or membranes around their edge, thus producing an optical artifact in the light microscope. The rest of the fine material consisted of irregular shapes with sharp edges which resembled fractured faces. The crystallinity of these particles is easily established by observation in polarized light and by using electron diffraction.
LUNAR SAMPLE EXAMINATION
405
FIG. 1. Scanning electron microscope picture of the loose lunar soil. x 80. FIo. 2. Vertical illumination light microscope photograph of a petrographic section of lunar soil. The vesicles which are common to much of the glass can be seen in the elongated glassy sphere in the center of the photograph, x 180. FIG. 3. Scanning electron micrograph of a cylindrical glassy bead. x 2 300. F ~ . 4. Scanning electron micrograph showing soil particles embedded in one area of the glassy sphere, x 1 100.
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PHILPOTT AND TURNBILL
FIG. 5. Scanning electron micrograph showing a portion of a glassy melt with pores, x 560. FI~. 6. Vertical illumination light micrograph. The curving "V" shaped central figure is a light amber glass with dark brown lines and vesicles in it. x 180. Fro. 7. Stereo pair taken on the scanning microscope of a glassy sphere showing surface bombardment. x 2 300.
LUNAR SAMPLE EXAMINATION
407
Fro. 8. Transmission micrograph of Mycoplasma laidlawii after being in 2 % H F for 24 hours. No visible changes have occurred, x 12 000. FI~. 9. Scanning electron micrograph of the acid-insoluble fraction. Surface etching from the HC1 treatment is noticeable, and fracturing which is common to the sample can be seen. x 230. FIG. 10. Vertical illumination light micrograph of a sphere after petrographic sectioning (grinding) showing the darkening at its periphery, x 180.
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PHILPOTT AND TURNBILL
Glassy spheres were produced from the jagged fines by concentrating the electron beam in the vacuum of the electron microscope on the individual particles. Each particle was observed by electron diffraction during heating. The diffraction pattern disappeared instantaneously at the moment the particle melted and then no further change occurred. The lunar spheres also lack an electron diffraction pattern in the Philips 300. The theory of melting and then cooling in free flight is compatible with the present observations. Crystalline inclusions, quick zoning (Fig. 6), and holes from possible degassing would all be expected from fast cooling. The glassy material also contains many vesicles. Opening one of these vesicles under water allowed the water to enter and no gas appeared to be present. Apparently heating in the vacuum of the moon vaporized some of the particle which then recondensed upon cooling leaving hollow vesicles. This is reminiscent of methacrylate polymerization where excess heat during polymerization produces bubbles in the plastic. The presence of spheres with fines embedded on one face suggests that these spheres impacted the fines before their interior cooled. For example, melted ejecta from meteoric impact would send material for different distances and some of it could be expected to impact on the ground or even in free flight before complete cooling. Weathering, as we know it, is not present because there is no wind or water to cause erosion. However changes are taking place on the moon due to meteoritic impact, fracturing and solar wind effects. Figure 7 shows a sphere which has received extensive micrometeoritic bombardment. This particle received grazing hits cutting groves in its surface and more direct hits which splashed melted ejecta out of the holes. Since the initial investigation of our small Apollo 11 sample did not reveal these pits, some of the particles are either relatively new or were protected from bombardment. Many of the particles were electrostatically charged. This facilitated hand separation of different phases since all but the larger particles would jump to a metal or wooden probe. The charge was often strong enough to prove disadvantageous for metal shadowing since the charge deflected the oncoming metal, and particles free of metal could be observed after the shadowing process. This was particularly true for the spheres which seemed to hold a stronger charge than the material having sharp edges. The X-ray probe was used to search for calcium as one method to locate microfossils. Strong peaks were found for calcium in conjunction with silicon, iron, and titanium. The calcium, however, could not be attributed to microfossils. Another method used in the search for microfossils consisted of etching lunar particles in 2 % HF and scanning their surface for organized elements. Figure 8 shows Mycoplasma laidlaw&which was also treated with 2 % HF for 24 hours. The appearance of these cells remains unchanged by the HF treatment, thus suggesting survival of structural
LUNAR SAMPLE EXAMINATION
409
organic material if it existed in the lunar soil. Our sample was devoid of any evidence of organic material. Emphasis was placed on the search for preexisting life within the limits of our knowledge of life forms. The loose sediment received extensive investigation without revealing any recognizable forms outside of several fibers resembling lens tissue fibers (6). However, the loose sediment would be the least likely place for survival of such evidence because of the continual cycle of very high and very low temperatures, continuous high vacuum, and gardening of the soil by meteorites. The breccia would provide some protection from the hostile elements if material survived until it could be incorporated. Our investigation of the breccia samples has not been rewarding in this respect. Rock or a deeper core sample would offer better protection for anything that might have been incorporated. Thus the material most extensively studied for connections to life, the loose sediment, seems the most hostile to its preservation. We also aided the chemists (3) by following several of their steps for extraction of organic material with microscopy. The acid (1 N HC1) insoluble portion was whitish in appearance. Observation by light and scanning electron microscopy (Fig. 9) provided at least a partial explanation. The HC1 treatment etched the surface of many particles much as glass is etched. "Frosted glass" thus appears to be at least part of the answer. Another possibility would be removal of the darker outer layers which are visible in the petrographic sections. Many of the sections revealed spheres whose centers were lighter in color (Fig. 10). Since color changes have been attributed to possible life forms on the moon (7) any color or color changes could be significant for explaining this phenomenon. Another possibility for the lightening effect of the acid would be removal of some of the possible radiation darkening from the surface of the particles. It is well known that glass darkens in response to a wide range of radiation. Some windows on Beacon street in Boston are highly prized for their radiation-induced discoloration. Manganese is considered responsible in this case, but glasses containing iron and other elements also darken. The glassy spheres in our sample have a general composition of 35-45 % SiO~, 10-15 % A1203, 10-25 % FeO, 10-15 % MgO, 5-10% TiO2, 10% CaO, 0.2-0.5 % Cr~O~, and 0.1% MnO plus other elements in small quantities (5). Since it might be possible to relieve radiation darkening by heating some of the soil was heated. Preliminary attempts have not been too successful, but some lightening does seem to occur. It appears possible that some of the color of the moon is a result of the extensive radiation hitting it (4), and any interplay of new surface exposure or heating, radiation, and solar wind could conceivably bring about color changes. Since we have not seen any evidence for life in our sample, one must look elsewhere for color explanations.
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PHILPOTT AND TURNBILL
REFERENCES 1. BARGHOORN, E. S., PHILPOTT, D. E., and TURNBILL, C., Apollo-ll Lunar Sci. Conf. Abstr. 11, (1970). 2. CLOUD,P., MARGOLIS,S. V., KRINSLEY,D., BARNES,V. E., MOORMAN,M., BAKER,J. M. and LICARI, F. R., ApoIlo-ll Lunar Sci. Conf. Abstr. 22 (1970). 3. GEHRKE, C. W., ZUMWALT,R. W., AUE, W. A., STALLING,D. L., DUFEIELD,A., PONNAMPERUMA,C. and KVENVOLDEN,K., Geochim. Cosmochim., submitted (1970). 4. HAPKE, B., Ann. N. Y. Acad. Sci. 123 (2), 711-721 (1965) 5. KVENVOLDEN,K. A. et al. (Ames Consortium), Geochim. Cosmochim., submitted (1970). 6. LSPET (Lunar Sample Preliminary Examination Team), Science 165, 1211-1227 (1969). 7. PICKERING,W. H., Publ. Astron. Soc. Pac. 17, 181 (1905). 8. SCHOPF,J. W., Apollo-ll Lunar Sci. Conf. Abstr. 130 (1970)
s. ULTRASTRUCTURERESEARCH35, 403-410 (1971)
403
The Microscopic Examination of the Apollo-11 and -12 Sample and the Quest for Life Forms DELBERT E. PHILPOTT AND CHARLES TURNBILL
Ames Research Center, NASA, Moffett Field, California, 94035 Received February 9, 1970 Examination of loose sediment and breccia (compacted sediment) returned from Apollo 11 and 12 has been accomplished by light, electron, and scanning electron microscopy. Glassy spheres 0.05 ~ to 1 mm in diameter appeared in a heterogeneous distribution. Their shape and structure is consistent with the theory of cooling during free flight. In the laboratory, spheres were produced from the lunar soil itself by heating with the electron beam in the vacuum of the electron microscope. The loose sediment seems the least likely place to discover any preexisting forms of life due to the hostile conditions of soil turnover, vacuum, temperature, and radiation present on the moon. The breccia might provide some protection; however, no organized forms were observed here either. Acid treatment produced a whitish insoluble portion partly explained by surface etching. Removal of radiation darkening is also possible, and it may be that some of the color of the moon is due to radiation effects. Etching with acid failed to reveal any life forms which we could recognize. Probably Pickering (7) was the most optimistic about finding life on the moon. After years of observations he concluded that the dull red and brown color changes in craters such as Grimaldi were due to huge swarms of insects. He also attributed other color changes to the spread and recession of plants. Over the years, although many color changes have been reported, none of the changes has had a really satisfactory explanation. Now not very many scientists hold much hope (1, 2) for life existing on the moon. Actually many of the conditions on the moon are what we use here on earth for sterilization: for example, extreme heat, radiation, X-rays, and ultraviolet light. In addition, the solar radiation, solar flares, and cosmic particles, along with the lack of water, add to the problems of any life developing on the surface of the moon. About the only favorable condition for the development of life is the lower gravity, which would require much less energy for movement. Therefore, life on the surface of the moon seems highly improbable. However, some areas must exist on the moon where these hostile conditions are moderated. If the moon cooled during some period
404
PHILI?OTT AND TURNBILL
in its past history and contracted, caves should have formed. Here, or deep within the soil, conditions for both the development and preservation of life may be better. This latter problem, that of preservation, is of course extremely important. Even if some manifestation of life developed during more conducive times, it must be adequately preserved if we are to find it. Due to the hostile conditions of the surface, preservation would be more likely in caves, beneath the surface or in rocks. MATERIALS AND METHODS Two samples from Apollo 11 (a 2-g fraction of lunar soil sample 10 086.3 and a 0.7 g sample of breccia) and one sample from Apollo 12 (a 1-g soil sample ARC 12 023.07 containing a breccia chip) were studied and photographed using a Zeiss and Leitz light microscope and a Philips 300 electron microscope. The surface features of the sample were studied using an Advanced Materials Research scanning electron microscope. Gold and carbon were used to coat soil particles to prevent charging in the scanning electron microscope. Petrographic sections were prepared by embedding soil in epoxy on light microscope slides and grinding the surface. Electron diffraction and the X-ray probe aided sample analysis. A portion was also hydrolyzed for 1 hour with 1N HC1 under reflux and then centrifuged at 2 700 rpm and another portion was placed in 2% HF overnight. The remaining lunar material was studied using the scanning electron microscope. Glassy spheres were heated up to 800°C, and fines from the soil were melted using the beam of the electron microscope. Sorting was aided by the electrostatic charge on the particles, especially the glassy spheres, which caused them to jump up to a metal or wooden probe. Bacteria and Myeoplasma laidlawii were placed in 2 % HF for 24 hours as a control to test structural survival. RESULTS AND DISCUSSION Initial observations on the loose sediment showed sharp angular fragments and glassy spheres (Figs. 1 and 2). These lunar spheres ranged in size from 0.05 # to 1 ram. Their distribution was quite heterogeneous, a characteristic of the entire sample. Since fractured glass was also present and might represent shattered fragments of larger spheres, maximum sphere size was difficult to determine. The melted portion varied from spherical to cylindrical (Fig. 3) and included portions where the fines were embedded in the spheres (Fig. 4). Heterogeneous sphere interiors were common, varying from hollow to crystalline as evidenced by their effect on polarized light, but no liquid inclusions were seen in any of the spheres. The spheres and other glassy material generally had a number of pores on their surfaces (Fig. 5). The embedding media and the refractive index of the glassy spheres gave rise to pseudo-walls or membranes around their edge, thus producing an optical artifact in the light microscope. The rest of the fine material consisted of irregular shapes with sharp edges which resembled fractured faces. The crystallinity of these particles is easily established by observation in polarized light and by using electron diffraction.
LUNAR SAMPLE EXAMINATION
405
FIG. 1. Scanning electron microscope picture of the loose lunar soil. x 80. FIo. 2. Vertical illumination light microscope photograph of a petrographic section of lunar soil. The vesicles which are common to much of the glass can be seen in the elongated glassy sphere in the center of the photograph, x 180. FIG. 3. Scanning electron micrograph of a cylindrical glassy bead. x 2 300. F ~ . 4. Scanning electron micrograph showing soil particles embedded in one area of the glassy sphere, x 1 100.
406
PHILPOTT AND TURNBILL
FIG. 5. Scanning electron micrograph showing a portion of a glassy melt with pores, x 560. FI~. 6. Vertical illumination light micrograph. The curving "V" shaped central figure is a light amber glass with dark brown lines and vesicles in it. x 180. Fro. 7. Stereo pair taken on the scanning microscope of a glassy sphere showing surface bombardment. x 2 300.
LUNAR SAMPLE EXAMINATION
407
Fro. 8. Transmission micrograph of Mycoplasma laidlawii after being in 2 % H F for 24 hours. No visible changes have occurred, x 12 000. FI~. 9. Scanning electron micrograph of the acid-insoluble fraction. Surface etching from the HC1 treatment is noticeable, and fracturing which is common to the sample can be seen. x 230. FIG. 10. Vertical illumination light micrograph of a sphere after petrographic sectioning (grinding) showing the darkening at its periphery, x 180.
408
PHILPOTT AND TURNBILL
Glassy spheres were produced from the jagged fines by concentrating the electron beam in the vacuum of the electron microscope on the individual particles. Each particle was observed by electron diffraction during heating. The diffraction pattern disappeared instantaneously at the moment the particle melted and then no further change occurred. The lunar spheres also lack an electron diffraction pattern in the Philips 300. The theory of melting and then cooling in free flight is compatible with the present observations. Crystalline inclusions, quick zoning (Fig. 6), and holes from possible degassing would all be expected from fast cooling. The glassy material also contains many vesicles. Opening one of these vesicles under water allowed the water to enter and no gas appeared to be present. Apparently heating in the vacuum of the moon vaporized some of the particle which then recondensed upon cooling leaving hollow vesicles. This is reminiscent of methacrylate polymerization where excess heat during polymerization produces bubbles in the plastic. The presence of spheres with fines embedded on one face suggests that these spheres impacted the fines before their interior cooled. For example, melted ejecta from meteoric impact would send material for different distances and some of it could be expected to impact on the ground or even in free flight before complete cooling. Weathering, as we know it, is not present because there is no wind or water to cause erosion. However changes are taking place on the moon due to meteoritic impact, fracturing and solar wind effects. Figure 7 shows a sphere which has received extensive micrometeoritic bombardment. This particle received grazing hits cutting groves in its surface and more direct hits which splashed melted ejecta out of the holes. Since the initial investigation of our small Apollo 11 sample did not reveal these pits, some of the particles are either relatively new or were protected from bombardment. Many of the particles were electrostatically charged. This facilitated hand separation of different phases since all but the larger particles would jump to a metal or wooden probe. The charge was often strong enough to prove disadvantageous for metal shadowing since the charge deflected the oncoming metal, and particles free of metal could be observed after the shadowing process. This was particularly true for the spheres which seemed to hold a stronger charge than the material having sharp edges. The X-ray probe was used to search for calcium as one method to locate microfossils. Strong peaks were found for calcium in conjunction with silicon, iron, and titanium. The calcium, however, could not be attributed to microfossils. Another method used in the search for microfossils consisted of etching lunar particles in 2 % HF and scanning their surface for organized elements. Figure 8 shows Mycoplasma laidlaw&which was also treated with 2 % HF for 24 hours. The appearance of these cells remains unchanged by the HF treatment, thus suggesting survival of structural
LUNAR SAMPLE EXAMINATION
409
organic material if it existed in the lunar soil. Our sample was devoid of any evidence of organic material. Emphasis was placed on the search for preexisting life within the limits of our knowledge of life forms. The loose sediment received extensive investigation without revealing any recognizable forms outside of several fibers resembling lens tissue fibers (6). However, the loose sediment would be the least likely place for survival of such evidence because of the continual cycle of very high and very low temperatures, continuous high vacuum, and gardening of the soil by meteorites. The breccia would provide some protection from the hostile elements if material survived until it could be incorporated. Our investigation of the breccia samples has not been rewarding in this respect. Rock or a deeper core sample would offer better protection for anything that might have been incorporated. Thus the material most extensively studied for connections to life, the loose sediment, seems the most hostile to its preservation. We also aided the chemists (3) by following several of their steps for extraction of organic material with microscopy. The acid (1 N HC1) insoluble portion was whitish in appearance. Observation by light and scanning electron microscopy (Fig. 9) provided at least a partial explanation. The HC1 treatment etched the surface of many particles much as glass is etched. "Frosted glass" thus appears to be at least part of the answer. Another possibility would be removal of the darker outer layers which are visible in the petrographic sections. Many of the sections revealed spheres whose centers were lighter in color (Fig. 10). Since color changes have been attributed to possible life forms on the moon (7) any color or color changes could be significant for explaining this phenomenon. Another possibility for the lightening effect of the acid would be removal of some of the possible radiation darkening from the surface of the particles. It is well known that glass darkens in response to a wide range of radiation. Some windows on Beacon street in Boston are highly prized for their radiation-induced discoloration. Manganese is considered responsible in this case, but glasses containing iron and other elements also darken. The glassy spheres in our sample have a general composition of 35-45 % SiO~, 10-15 % A1203, 10-25 % FeO, 10-15 % MgO, 5-10% TiO2, 10% CaO, 0.2-0.5 % Cr~O~, and 0.1% MnO plus other elements in small quantities (5). Since it might be possible to relieve radiation darkening by heating some of the soil was heated. Preliminary attempts have not been too successful, but some lightening does seem to occur. It appears possible that some of the color of the moon is a result of the extensive radiation hitting it (4), and any interplay of new surface exposure or heating, radiation, and solar wind could conceivably bring about color changes. Since we have not seen any evidence for life in our sample, one must look elsewhere for color explanations.
410
PHILPOTT AND TURNBILL
REFERENCES 1. BARGHOORN, E. S., PHILPOTT, D. E., and TURNBILL, C., Apollo-ll Lunar Sci. Conf. Abstr. 11, (1970). 2. CLOUD,P., MARGOLIS,S. V., KRINSLEY,D., BARNES,V. E., MOORMAN,M., BAKER,J. M. and LICARI, F. R., ApoIlo-ll Lunar Sci. Conf. Abstr. 22 (1970). 3. GEHRKE, C. W., ZUMWALT,R. W., AUE, W. A., STALLING,D. L., DUFEIELD,A., PONNAMPERUMA,C. and KVENVOLDEN,K., Geochim. Cosmochim., submitted (1970). 4. HAPKE, B., Ann. N. Y. Acad. Sci. 123 (2), 711-721 (1965) 5. KVENVOLDEN,K. A. et al. (Ames Consortium), Geochim. Cosmochim., submitted (1970). 6. LSPET (Lunar Sample Preliminary Examination Team), Science 165, 1211-1227 (1969). 7. PICKERING,W. H., Publ. Astron. Soc. Pac. 17, 181 (1905). 8. SCHOPF,J. W., Apollo-ll Lunar Sci. Conf. Abstr. 130 (1970)