Microfossils and Stromatolites
Strong fossil evidence for ancient microscopic life is present in 3-Gyr-old rocks, less-certain fossil evidence exists in 3.5-Gyr-old rocks, and substantially more controversial isotopic evidence exists in 3.8-Gyr-old rocks. Carbonate deposits in 3-Gyr-old South African sedimentary rocks show well-preserved stromatolites that match well with similar, known biogenic structures seen in much younger rocks and even in modern aqueous sedimentary environments Beukes and Lowe, 1989 . Similar...
Interstellar Dust and the PQQEnigma for Catalysis
Looking more carefully into the chemical structure of primordial coenzymes there is an astonishing diversity in unity Duine, 1999 . A huge diversity of, mostly nucleophilic, reactions very important for peptide as well as for RNA synthesis, already on an early bacterial level, are catalyzed by substances of astonishing unity in chemical structure, namely of quinoic type. For instance, flavines related to flavones are quinoic, riboflavine and a lot of quinoproteins and even quinohemoproteins...
Hydrocode Simulations
We carried out numerical simulations of impact cratering events on various planetary surfaces, using both two-dimensional 2D and three-dimensional 3D hydrocodes. Earlier studies were carried out using the 2D Eulerian hydrocode CSQ , developed at Sandia National Laboratories Thompson, 1979 1985 . By assuming axial symmery, CSQ is used to model vertical impacts. However, it is well known that the most probable impact angle is 45 Gilbert, 1893 Shoemaker, 1962 . Modeling the impact process in its...
References
Alden, W.C. 1929 , Thomas Chrowder Chamberlin's contributions to glacial geology. Jour. Geo., 37, 293-319. Allen, C.S. 1973 , Astrophysical Quantities The Athlone Press, London . Alvarez, W. and Muller, R.A. 1984 , Evidence from crater ages for periodic impacts on Earth. Nature, 308, 718-720. Alvarez, L.W., Alvarez, W., Asaro, F., and Michel, H.V. 1980 , Extraterrestrial cause for the Cretaceous-Tertiary extinction, Science, 208, 1095-1108. Anders, E. 1989 , Pre-biotic organic matter from...
The Integrated Micrometeorite Flux The Lunar Cratering Estimates
We used the smooth, roughly exponential decay, of lunar cratering rates, K t , relatively to the present-day value Fig. 3.4 , given by Hartmann 1999 . This curve gives a monitoring of the dominant population of crater forming bodies with sizes gt 500 m existing in the interplanetary medium at any given time. Fig. 3.4. Variation with time of relative lunar cratering rates, K t . This curve represents the conjuncture of the late heavy bombardment, proposed by Hartmann. Such rates refer to the...
References Ixj
Alvarez, W. 1986 . Toward a theory of impact crises. Eos, 67, 649-658. Arndt, N.T., Nelson, D.R., Compston, W., Trendall, A.F. and Thorne, A.M. 1991 . The age of the Fortescue Group, Hamersley Basin, Western Australia, from ion microprobe zircon U-Pb results. Aust. J. Earth Sci., 38, 261-281. Barlow, N.G. 1990 . Estimating the terrestrial crater production rate during the late heavy bombardment period. Lunar Planet. Instit. Contr., 746, 4-7. Brasier M., Green O., Lindsay J. and Steele A. 2004 ....
Radioactive Heating
In the years since the work of Whipple and Stefanic 1966 , our picture of radioactive heating has changed in several ways. One of the most important is the realization that 26 Al, an extinct radionuclide, may have been an important heat source. In 1976, Lee et al. presented strong evidence that 26Al had been present in the early solar nebula. Afterwards 7-ray observations from the HEAO 3 and Solar Maximum Mission satellites detected 26Al dispersed throughout the galaxy Mahoney et al., 1982...
Rock Vapor
Panel a of Fig. 7.5 begins at this point. The rock vapor atmosphere radiates to space with an effective temperature of order 000 K. The saturation vapor pressure of rock is sensitive to temperature, and therefore the cloudtop temperature is relatively insensitive to details. The high radiating temperature demands rapid condensation and corresponding very strong updrafts. In addition to the updrafts associated with weather, there is a net updraft of w 0.4 Trad 2000 K 4 p 60 bars cm s below the...
Volcanism Nebular Gases and Comets
The two first processes are generally disregarded to day cf. Owens 1998 and Delsemme 1997 . In particular, Hawaiian volcanoes eject gases generated by the most primitive deep-seated magma originating from the undegassed part of the Earth's mantle. Their H2O N2 and CO2 N2 ratios Table 3.1, column 6 do not fit the corresponding ratios measured for the atmosphere column 4 . About the capture of nebular gases, the Ne N2 ratio predicted for the solar nebula is about 105 times higher than the...