title: Hydrogen cyanide production due to mid-size impacts in a redox-neutral N2-rich atmosphere.
abstract: Cyanide compounds are amongst the most important molecules of the origin of life. Here, we demonstrate the importance of mid-size (0.1-1 km in diameter) hence frequent meteoritic impacts to the cyanide inventory on the early Earth. Subsequent aerodynamic ablation and chemical reactions with the ambient atmosphere after oblique impacts were investigated by both impact and laser experiments. A polycarbonate projectile and graphite were used as laboratory analogs of meteoritic organic matter. Spectroscopic observations of impact-generated ablation vapors show that laser irradiation to graphite within an N2-rich gas can produce a thermodynamic environment similar to that produced by oblique impacts. Thus, laser ablation was used to investigate the final chemical products after this aerodynamic process. We found that a significant fraction (>0.1 mol%) of the vaporized carbon is converted to HCN and cyanide condensates, even when the ambient gas contains as much as a few hundred mbar of CO2. As such, the column density of cyanides after carbon-rich meteoritic impacts with diameters of 600 m would reach ~10 mol/m(2) over ~10(2) km(2) under early Earth conditions. Such a temporally and spatially concentrated supply of cyanides may have played an important role in the origin of life.
authors.affiliation: Planetary Exploration Research Center, Chiba Institute of Technology, 2-17-1, Tsudanuma, Narashino, Chiba, 275-0016, Japan. kosuke.kurosawa@perc.it-chiba.ac.jp
authors.forename: Kosuke
authors.initials: K
authors.lastname: Kurosawa
authors.forename: Seiji
authors.initials: S
authors.lastname: Sugita
authors.forename: Ko
authors.initials: K
authors.lastname: Ishibashi
authors.forename: Sunao
authors.initials: S
authors.lastname: Hasegawa
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Sekine
authors.forename: Nanako O
authors.initials: NO
authors.lastname: Ogawa
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Kadono
authors.forename: Sohsuke
authors.initials: S
authors.lastname: Ohno
authors.forename: Naohiko
authors.initials: N
authors.lastname: Ohkouchi
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Nagaoka
authors.forename: Takafumi
authors.initials: T
authors.lastname: Matsui
mesh_terms: D001272:Atmosphere / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry; D018534:Earth, Planet; D019418:Evolution, Chemical; D006856:Hydrogen Cyanide / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007834:Lasers; D019110:Meteoroids; D009584:Nitrogen / Q000737:chemistry; D010084:Oxidation-Reduction
chemical_list: D006856:Hydrogen Cyanide; D002244:Carbon; D009584:Nitrogen