Constraints on the formation age of cometary material from the NASA Stardust mission.

We measured the 26Al-26Mg isotope systematics of a approximately 5-micrometer refractory particle, Coki, returned from comet 81P/Wild 2 in order to relate the time scales of formation of cometary inclusions to their meteoritic counterparts. The data show no evidence of radiogenic 26Mg and define an upper limit to the abundance of 26Al at the time of particle formation: 26Al/27Al < 1 x 10(-5). The absence of 26Al indicates that Coki formed >1.7 million years after the oldest solids in the solar system, calcium- and aluminum-rich inclusions (CAIs). The data suggest that high-temperature inner solar system material formed, was subsequently transferred to the Kuiper Belt, and was incorporated into comets several million years after CAI formation.

Properties of synthetic ferrihydrite as an amino acid adsorbent and a promoter of peptide bond formation.

Ferrihydrite, an iron oxide hydroxide, is found in all kinds of environments, from hydrothermal hot springs to extraterrestrial materials. It has been shown that this material is nanoporous, and because of its high surface area, it has outstanding adsorption properties and in some cases catalysis properties. In this work we studied the adsorption properties of ferrihydrite with respect to amino acids. Samples of pure ferrihydrite were synthesised and exposed to solutions of amino acids including both proteinaceous and non-proteinaceous species. These experiments revealed important characteristics of this mineral as both an adsorbent of amino acids and a promoter of peptide bond formation.

Corona chemistry in Titan.

The atmosphere of Titan is constantly bombarded by galactic cosmic rays and Saturnian magnetospheric electrons causing the formation of free electrons and primary ions, which are then stabilized by ion cluster formation and charging of aerosols. These charged particles accumulate in drops in cloud regions of the troposphere. Their abundance can substantially increase by friction, fragmentation or collisions during convective activity. Charge separation occurs with help of convection and gravitational settling leading to development of electric fields within the cloud and between the cloud and the ground. Neutralization of these charged particles leads to corona discharges which are characterized by low current densities. We have therefore, experimentally studied the corona discharge of a simulated Titan's atmosphere (10% methane and 2% argon in nitrogen) at 500 Torr and 298 K by GC-FTIR-MS techniques. The main products have been identified as hydrocarbons (ethane, ethyne, ethene, propane, propene+propyne, cyclopropane, butane, 2-methylpropane, 2-methylpropene, n-butane, 2-butene, 2,2-dimethylpropane, 2-methylbutane, 2-methylbutene, n-pentane, 2,2-dimethylbutane, 2-methylpentane, 3-methylpentane, n-hexane, 2,2-dimethylhexane, 2,2-dimethylpentane, 2,2,3-trimethylbutane, 2,3-dimethylpentane and n-heptane), nitriles (hydrogen cyanide, cyanogen, ethanenitrile, propanenitrile, 2-methylpropanenitrile and butanenitrile) and a highly branched hydrocarbon deposit. We present the trends of hydrocarbons and nitriles formation as a function of discharge time in an ample interval and have derived their initial yields of formation. The results clearly demonstrate that a complex organic chemistry can be initiated by corona processes in the lower atmosphere. Although photochemistry and charged particle chemistry occurring in the stratosphere can account for many of the observed hydrocarbon species in Titan, the predicted abundance of ethene is too low by a factor of 10 to 40. While some ethene will be produced by charged-particle chemistry, the production of ethene by corona processes and its subsequent diffusion into the stratosphere appears to be an adequate source. Because little UV penetrates to the lower atmosphere to destroy the molecules formed there, the corona-produced species may be long-lived and contribute significantly to the composition of the lower atmosphere and surface.