A Programme of Research in Planetary and Solar System Science - Understanding the Formation of Phosphorus and Nitrogen Compounds

磷(P)和氮(N)是生物分子的重要组成部分。这个综合方案包括两个项目；第一个是研究早期地球、火星和金星大气中的流星粒子释放的生物可用磷的产生机制，第二个项目是研究将原子氮结合到复杂的有机分子中，这些复杂的有机分子与泰坦大气(土星的一个卫星)中产生天体生物学有趣的化合物和气溶胶粒子有关。磷和内行星-大气中产生磷的主要途径是随着流星粒子在内行星的上层大气中燃烧而释放出来的。我们试图描述这一过程，并确定进入大气的磷的量。元素P一旦释放，就会开始被O、OH、O2和O3氧化。我们已经确定了这一氧化过程中的关键步骤，这些步骤可能导致磷化合物、磷酸盐和亚磷酸盐，它们在到达地球表面时具有明显不同的生物利用度。我们将结合我们的流星消融研究和大气模型中的动力学数据来确定磷酸盐和亚磷酸盐生产的相对效率，并估计P到行星表面的总通量。该项目与正在进行的火星大气研究相关联，例如MAVEN项目。氮气和土卫六是一个有趣的太阳体，像地球一样，它的大气主要是氮气和氮气，但土卫六被橙色雾霾包围，其中气溶胶粒子含有复杂的有机分子。这些粒子的确切成分和形成机制尚不清楚。在过去10年左右的时间里，卡西尼号任务一直在传回关于土卫六(和土星)的数据，这刺激了许多领域的研究。在土卫六的低层大气中，氮气通常是极不活跃的，然而，在土卫六大气的上层，吸收高能辐射和其他过程会产生氮原子。我们将描述这些原子物种与存在于土卫六大气中的碳氢化合物结合的关键反应。HCN分子处于这一化学过程的核心，然而这种物种的测量结果和模型之间的一致性很差。我们将使用我们的实验室数据(在泰坦高层大气的低温和低压下测量这些反应的速率)和大气模型来试图缩小测量和模型之间的差距，并评估N被合并到泰坦阴霾层的机制。

Phosphorus (P) and Nitrogen (N) are important components of biologically interesting molecules. This consolidated proposal contains two projects; firstly looking at mechanisms of generating bioavailable phosphorus released from meteoric particles in the atmospheres of early Earth, Mars and Venus and secondly examining the incorporation of atomic nitrogen into complex organic molecules relevant for the production of astrobiologically interesting compounds and aerosol particles in Titan's atmosphere (one of Saturn's moons).Phosphorus and the Inner Planets - The major route to the generation of atmospheric phosphorus is its release as meteoric particles burn up in the upper atmospheres of the inner planets. We seek to characterize this process and to determine the amount of P entering into the atmosphere. Once released elemental P will start to be oxidized by O, OH, O2 and O3. We have identified crucial steps in this oxidation process that can lead to phosphorus compounds, phosphates and phosphites, which have markedly different bioavailability on reaching the planet's surface. We will combine our meteor ablation studies and kinetic data within atmospheric models to determine the relative efficiency of phosphate and phosphite production and estimate the total flux of P to the planet surface. The project links to on-going studies of the Martian atmosphere such as the MAVEN project.Nitrogen and Titan - Titan is an interesting solar body, like Earth its atmosphere is predominantly nitrogen, N2, but Titan is surrounded by an orange haze comprised of aerosol particles containing complex organic molecules. The exact composition and mechanism of formation of these particles is unknown. For the last 10 years or so, the Cassini mission has been sending back data on Titan (and Saturn) which has stimulated research in a variety of areas.Nitrogen is generally extremely unreactive in Titan's lower atmosphere, however, in the upper reaches of Titan's atmosphere absorption of high energy radiation and other processes generate N atoms. We will characterize critical reactions in the incorporation of these atomic species into the hydrocarbons that exist in Titan's atmosphere. The HCN molecule lies at the heart of this chemistry, yet there is very poor agreement between measurements and models of this species. We will use our laboratory data (measurements of the rates of these reactions at the cold temperatures and low pressures of Titan's upper atmosphere) and atmospheric models to try and close the gap between measurements and models and to assess the mechanisms by which N is incorporated into Titan's haze layer.