Mathematics – Logic
Scientific paper
Apr 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010ttt..work...83r&link_type=abstract
Through Time; A Workshop On Titan's Past, Present and Future, NASA Goddard Space Flight Center, April 6th - 8th, 2010. Edited b
Mathematics
Logic
Scientific paper
A laboratory study on the chemical transformation of Titan's aerosol analogues placed under putative surface conditions of the satellite was performed. The surface of Titan was one of the targets of the Cassini-Huygens mission and of several of the Cassini orbiter instruments, especially ISS, VIMS and Radar. The first images revealed an interesting solid surface with features that suggest aeolian, tectonic, fluvial processes and even an impact structure[1]. Since then, more detailed descriptions of dunes, channels, lakes, impact craters and cryovolcanic structures have been documented[2]. The existence of an internal liquid water ocean, containing a few percent ammonia has been proposed[2, 3]. It has also been proposed that ammonia-water mixtures can erupt from the putative subsurface ocean leading to cryovolcanism[4]. The Cassini Titan Radar Mapper obtained Synthetic Aperture Radar (SAR) images during 2004 and 2005 that revealed a highly complex geology occurring at Titan's surface[5], among which cryovolcanic features play a central role. The composition of the cryomagma is mainly proposed to be a mixture of water ice and ammonia[6, 7, 8], although ammonia has not been directly detected on Titan, but suggested by recent Cassini-VIMS observations[9]. In order to understand the role that ammonia may play on the chemical transformation of atmospheric aerosols once they reach the surface, we designed the following protocol: laboratory analogues of Titan's aerosols were synthesized from a N2:CH4 (98:2) mixture irradiated under a continuous flow regime of 845 sccm inside which, a cold plasma of 180 W was established. The synthesized analogues were recovered and partitioned in several 10.0 mg samples that were placed in 4.0 mL-volume of aqueous ammonia solutions (25.00, 12.50, 6.25 and 3.125%) at different temperatures (298, 277, 253 and 93 K) for 10 weeks. After a derivatization process performed to the aerosols' refractory phase with N-methyl-N-(tert-butyldimethylsilyl)-trifluoroacetamide in dimethylformamide, the products were identified and quantified by a GC-MS system. We found derived residues related to amino acids as well as urea, as shown by their mass spectra and chromatographic patterns. There seems to be a constant presence of alanine and glycine, no matter the ammonia concentrations to which the analogues were exposed. Our results have important astrobiological implications to Titan's environment particularly if the existence of the suggested subsurface water-ammonia liquids is validated. Titan is a place where organic compounds are produced and where liquid water might be present. Therefore, this kind of studies helps to better understand the geological processes of Titan's surface and its relationship with the active organic chemistry occurring in its atmosphere.
Brassé C.
Buch Anders
Coll Patrice
Poch O.
Ramirez Sandra I.
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