As a result, it would have been difficult for early Mars to have maintained a dense CO2 TPCA-1 molecular weight atmosphere prior to 4.1 billion years ago (Tian et al. 2008c). Inclusion of a parameterized nonthermal escape process at the exobase level consumes more energy and leads to a dramatically different upper atmosphere structure. The overall escape rate of the dominant gases at the exobase level is conserved, regardless of whether nonthermal loss processes were efficient (Tian and Kasting 2008). We will speculate about what the Mars calculations imply about early Earth’s atmosphere. Chyba, C., C. Sagan (1992)
Endogenous production, exogenous delivery and impact shock synthesis of organic molecules:
an inventory for the origins of life. Nature 355, 125–132. Kasting, J.F. (1993) buy RO4929097 Earth’s early atmosphere. Science 259, 920–926. Martins, Z. et al. (2008) Extraterrestrial nucleobases in the Murchison meteorite. Earth and Planetary Science Letters 270, 130–136. Miller, S.L. (1957) A production of amino acids under possible primitive Erath conditions. Science 117, 528–529. Tian, F., O.B. Toon, A.A. Pavlov, H. De Sterck (2005) A hydrogen-rich early Earth atmosphere. Science, 308, 1014–1017. C188-9 Tian, F., J.F. Kasting, H. Liu, R.G. Roble (2008a) Hydrodynamic planetary thermosphere model. I: the response of the Earth’s thermosphere to extreme solar EUV conditions and the significance of adiabatic cooling, JGR-planets 113, E05008 doi:10.1029/2007JE002946. Tian, F., S.C. Solomon, L. Qian, J. Lei, R.G. Roble (2008b) Hydrodynamic planetary thermosphere model. II: coupling of an electron transport/energy deposition model. JGR-planets, in press Tian, F., J.F. Kasting, S.C. Solomon (2008c) Fast thermal escape of carbon and oxygen from
a dense, CO2-ruch early Martian atmosphere. Science, under review. Tian, F. and J.F. Kasting (2008) Invariance of the total atmosphere escape rate from the atmosphere of early Mars. GRL, in preparation. Walker, J.C.G. (1977) Evolution of the atmosphere. Macmillan, New York. E-mail: feng.[email protected]edu Prebiotic Syntheses A Prebiotic Surface-Catalysed Formation of Alkyl Imines Nigel Aylward School of Physical Adenosine and Chemical Sciences Queensland University of Technology George St., Brisbane, Queensland 4000 AUSTRALIA Alkynes such as ethyne form weak charge-transfer, η 1 -alkenyl (vinyl) complexes (Collman et al., 1987) with surface catalysts such as Mg.porphin in which the alkenyl group has a net positive charge, and the conjugated porphin has a negative charge. The enthalpy change for the complex formation is small (−0.002 h). This neutral complex is polarised and undergoes a nucleophilic addition reaction with ammonia at the carbene carbon to form Mg.2-amino ethenyl (vinyl).porphin with a small enthalpy change (0.016 h).