Paradoxes in Science:
Should Fullerenes Still Be Around if
They Formed Many Millions of Years Ago?
| Author: John Woodmorappe Subject: Chemistry/Biochemistry Date: |
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Most of the elements that exist in nature are reactive, at least to some extent. For this reason, they usually do not occur in a free state. Carbon, however, is an element that exists in both a free and a combined state in nature. For a long time, the only two natural states of elemental carbon known were graphite and diamond. About ten years ago it was discovered, however, that another state of pure carbon existed (Baggott 1994). Many tens of carbon atoms per molecule, usually 60 or 70, could form a structure roughly spherical in shape (see Figure 1).
The bonds between the carbon atoms called to mind the famous architectural designs of R. Buckminster Fuller. Fuller was an inventor and architect who, among other things, built the first geodesic dome. The bonding of the carbon atoms in the newly-discovered form of elemental carbon closely resembled the shape of Fuller’s geodesic dome. Thus, these molecules were dubbed fullerenes, and have the chemical notation C60 or C70. (They are also known in scientific slang as “buckyballs,” after Fuller’s middle name Buckminster.)
Fullerenes form under conditions of extreme temperature and pressures (Becker et. al. 1994). For some years after their discovery, scientists believed fullerenes did not occur naturally on earth. It turns out that fullerenes are readily destroyed by ultraviolet (UV) light, as well as ozone (O3). Thus, in 1991, the chemist Roger Taylor and his colleagues published a letter in Nature arguing that “the reason for the failure hitherto to observe naturally occurring C60 on Earth now becomes clear,” namely, fullerenes just don’t last very long under earth conditions (Taylor et al. 1991).
Guess what? Fullerenes were discovered shortly thereafter in supposedly ancient rocks of Russia, specifically, in carbon-rich shungite (a curious metamorphic rock) of Precambrian age (Buseck et al. 1992). They were then discovered in much older formations, putatively of 1.85 billion years age (Becker et. al. 1994), as well as at the Cretaceous-Tertiary boundary (Heymann et al. 1994).
Interestingly, however, fullerenes still appear to be unstable little beasts, chemically speaking. “Fullerenes stored in ambient air,” write Rice University chemists Chibante and Heymann, “even when shielded against UV and visible radiation [light], are destroyed by O3 [ozone] in the air” (Chibante and Heymann 1993, p. 1881). Becker et al. (1994, p. 644) also observe that fullerenes are relatively fragile structures:
Fullerenes degrade quickly at fairly low temperatures when exposed to air . . . Perhaps the fullerenes in the Onaping rocks [1.85 billion years old] were protected from oxidation by the surrounding sulfide-silicate matrix in which they are contained, allowing fullerenes to survive to present.
We might consider another explanation, however. Perhaps the fullerenes still exist in earth’s rocks because those rocks are very much younger than is generally held. We find fullerenes, in other words, because not enough time has elapsed for them to degrade.
If the earth were really billions of years old, it is doubtful that any of these unstable molecules would have persisted to the present. At the very least, the persistence of these easily-decomposed fullerenes in “ancient” rock may be more consistent with a time scale of thousands of years rather than billions of years. Creationist chemists might consider investigating the stability of fullerenes under a variety of geochemical conditions. Some surprises may be in store from these little balls of carbon.
REFERENCES
Baggott, Jim. Perfect Symmetry: The Accidental Discovery of Buckminsterfullerene (Oxford: Oxford University Press, 1994). [Baggott observes that “the tendency for the closed-cage carbon molecules to burn, degrade, or become entrapped prevents the detection of naturally occurring fullerenes. Imagine the surprise, then, when it was announced in July 1992 that C60 and C70 had been found in samples of shungite, a coal-like rock from Shunga, a Russian town some 200 miles northeast of St. Petersburg. . . . How these fullerenes found their way into what are probably Precambrian rocks (making them 600 million years old) remains a complete mystery. It is possible that the molecules survived whatever process was responsible for their production hundreds of millions of years ago and were deposited and buried along with the carbonaceous material that was eventually to form into rock. To survive this long, they would have had to have been completely screened from light and air” (pp. 254-55).]
Becker, L., Bada, J. L., Winans, R. E., Hunt, J., Bunch, T. E., and B. M. French. “Fullerenes in the 1.85-billion-year-old Sudbury Impact Structure.” Science, 265 (1994): 642-644.
Buseck, P.R., Tsipursky, S.J. and R. Hettich. “Fullerenes from the Geological Environment.” Science, 257 (1992): 215-217.
Chibante, L. and D. Heymann. “On the geochemistry of fullerenes: Stability of C60 in ambient air and the role of ozone. Geochimica et Cosmochimica Acta, 57 (1993): 1879-1881.
Heymann, D., Chibante, L., Brooks, R., Wolbach, W., and R. Smalley. 1994. “Fullerenes in the Cretaceous-Tertiary Boundary Layer.” Science, 265 (1994): 645-47.
Taylor, R., Parsons, J.P., Avent, A.G., Rannard, S.P., Dennis, J.T., Hare, J.P., Kroto, H.W., and D.R. Walton. “Degradation of C60 by light.” Nature, 351 (1991): 271.
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