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Abstract:

Abstract. We present a novel method to retrieve daytime atmospheric dust and ash plume heights using a synergy of infrared hyper-spectral radiances and retrieved visible optical depths. The method is developed using data from the Atmospheric Infrared Sounder (AIRS) and Moderate Resolution Imaging Spectroradiometer (MODIS), both of which are on NASA's Aqua platform, and lends itself to also a χ2 height derivation based on the smallest bias between observations and calculations in the thermal infrared window. The retrieval methodology is validated against almost 30 months of dust centroid heights obtained from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIOP) data, and against ash plume heights obtained from the Advanced Along-Track Scanning Radiometer (AATSR) after the Puyehue Cordon Caulle volcanic eruption of June 2011. Comparisons are also made against Goddard Chemistry Aerosol Radiation and Transport (GOCART) climatological aerosol heights. In general there is good agreement between the heights from the CALIPSO data and the AIRS/MODIS retrieval, especially over the Atlantic and Mediterranean regions; over land one there are more noticeable differences. The AIRS/MODIS derived heights are within typically 25% of the CALIOP centroid heights.

Abstract:

The end of the late heavy bombardment era coincides with the emergence of life on the Earth 4 billion years ago. This coincidence suggests that the impacts of extraterrestrial bodies might have contributed to the formation of the first molecules involved in early living structures. We have simulated a high-energy synthesis of nucleic acid bases from formamide in the impact of an extraterrestrial body. The high-power laser system PALS was employed in simulation of impact plasma by inducing a laser dielectric breakdown in formamide. In hot and dense plasma, formamide decomposed producing reactive radicals. The radicals reacted with formamide and nucleic acid bases were produced. Formamide was pretreated with laser plasma in the presence of catalysts. The products were analyzed by FTIR spectrometry and GC-MS. Time-resolved emission spectra of formamide discharge plasma were measured. Kinetic models and formation pathways for nucleic acid bases were calculated. The results show that the nucleic acid bases can be synthesized in impact plasma involving CN and NH radicals and formamide.