Publications

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1994
Bada, JL, Bigham C, Miller SL.  1994.  Impact Melting of Frozen Oceans on the Early Earth - Implications for the Origin of Life. Proceedings of the National Academy of Sciences of the United States of America. 91:1248-1250.   10.1073/pnas.91.4.1248   AbstractWebsite

Without sufficient greenhouse gases in the atmosphere, the early Earth would have become a permanently frozen planet because the young Sun was less luminous than it is today. Several resolutions to this faint young Sun-frozen Earth paradox have been proposed, with an atmosphere rich in CO2 being the one generally favored. However, these models assume that there were no mechanisms for melting a once frozen ocean. Here we show that bolide impacts between about 3.6 and 4.0 billion years ago could have episodically melted an ice-covered early ocean. Thaw-freeze cycles associated with bolide impacts could have been important for the initiation of abiotic reactions that gave rise to the first living organisms.

1996
Becker, L, Poreda RJ, Bada JL.  1996.  Extraterrestrial helium trapped in fullerenes in the sudbury impact structure. Science. 272:249-252.   10.1126/science.272.5259.249   AbstractWebsite

Fullerenes (C-60 and C-70) in the Sudbury impact structure contain trapped helium with a He-3/He-4 ratio of 5.5 x 10(-4) to 5.9 x 10(-4). The He-3/He-4 ratio exceeds the accepted solar wind value by 20 to 30 percent and is higher by an order of magnitude than the maximum reported mantle value, Terrestrial nuclear reactions or cosmic-ray bombardment are not sufficient to generate such a high ratio. The He-3/He-4 ratios in the Sudbury fullerenes are similar to those found in meteorites and in some interplanetary dust particles. The implication is that the helium within the C-60 molecules at Sudbury is of extraterrestrial origin.

1998
Brinton, KLF, Engrand C, Glavin DP, Bada JL, Maurette M.  1998.  A search for extraterrestrial amino acids in carbonaceous Antarctic micrometeorites. Origins of Life and Evolution of Biospheres. 28:413-424.   10.1023/a:1006548905523   AbstractWebsite

Antarctic micrometeorites (AMMs) in the 100-400 mu m size range are the dominant mass fraction of extraterrestrial material accreted by the Earth today. A high performance Liquid chromatography (HPLC) based technique exploited at the limits of sensitivity has been used to search for the extraterrestrial amino acids alpha-aminoisobutyric acid (AIB) and isovaline in AMMs. Five samples, each containing about 30 to 35 grains, were analyzed. All the samples possess a terrestrial amino acid component, indicated by the excess of the L-enantiomers of common protein amino acids. In only one sample (A91) was AIB found to be present at a level significantly above the background blanks. The concentration of AIB (similar to 280 ppm), and the AIB/isovaline ratio (greater than or equal to 10), in this sample are both much higher than in CM chondrites. The apparently large variation in the AIB concentrations of the samples suggests that AIB may be concentrated in rare subset of micrometeorites. Because the AIB/isovaline ratio in sample A91 is much larger than in CM chondrites, the synthesis of amino acids in the micrometeorite parent bodies might have involved a different process requiring an HCN-rich environment, such as that found in comets. If the present day characteristics of the meteorite acid micrometeorite fluxes can be extrapolated back in time, then the flux of large carbonaceous micrometeorites could have contributed to the inventory of prebiotic molecules on the early Earth.