NSF Young Investigator: Evolution of Planetary Atmospheres

小行星9457457 行星大气层的起源和演变将首先侧重于两个过程：彗星撞击和温室效应。 彗星和小行星与行星的碰撞最近被发现对太阳系的性质有重大影响。 这些撞击为月球的存在，天王星的倾斜和KT灭绝提供了最好的解释。 Zahnle等人（1992）的开创性工作表明彗星撞击解释了为什么泰坦有大气层而伽利略卫星没有的原因。 这个想法是，由于木星的质量更大，撞击速度在伽利略卫星上比在泰坦上更大，因此在侵蚀大气层方面更有效。 蒙特卡罗计算，解决问题的随机性将被用来调查这种影响更严格。这项技术还将用于研究火星保留挥发物的能力。 最终目标是确定行星碎石对行星大气层的影响，作为行星大小及其在太阳系中的作用。 这项研究将解决以下问题：对于一个给定的行星系统，人们可能期望在哪些天体上找到大气层？ 格里菲斯博士将在美国宇航局的红外望远镜设施从事补充工作，作为科学小组的一员，该小组将观察苏梅克-利维彗星与木星的碰撞。 这里的目的是，在某种程度上，调查如何将撞击能量分为化学能和动能到大气中。 动能的分配决定了彗星侵蚀行星大气层的效率。 金星表面的温度为7500 K，比地球高出近4000 K。 温室效应使金星大气层升温的巨大效率表明，如果温室气体存在，温暖的大气层将存在于距离太阳很远的地方。 这为太阳系的生态圈提出了一个有趣的可能性，即存在液态水的区域，这是生命的必要成分。 温室气体，如果存在于行星体上，可能会将生态圈扩展到离太阳很远的地方。 这种可能性将通过关注土卫六富含有机物的大气层来研究。 土卫六的大气层可能最初由氨（NH3紫外线辐射，一种强烈的温室气体）组成，随后被我们目前观察到的氮气（N2）分解。 在与Chris McKay，Kevin Zahnle和Jim Pollack（NASA艾姆斯研究中心）的合作中，泰坦的大气层足够温暖，过去有液态水的可能性将被调查。 这项工作将扩大到考虑太阳系中高度丰富的挥发物的温室效应（其中，受宇宙丰度的影响，很少）。 这个项目更大的目标是了解大气的热特性 as a function函数of their其composition组成. 这个奖项是为了表彰一位杰出的年轻教师在科学和工程。 该奖项将通过为研究和教育活动提供灵活的支持来提高教师的职业生涯。 鼓励与支持研究和教育的行业和机构合作。

9457457 Griffith The origin and evolution of planetary atmospheres will be investigated by focusing initially on two processes: cometary impacts and the greenhouse effect. Collisions of comets and asteroids with planets have recently been found to significantly shape the nature of the solar system. These impacts provide the best explanation for the existence of the moon, Uranus' tilt and the KT extinction. Pioneering work by Zahnle et al (1992) suggests that cometary impact explains the reason why Titan has an atmosphere and the Galilean satellites have none. The idea is that, because of Jupiter's greater mass, impact velocities are larger on the Galilean satellites than on Titan, and thus more efficient at eroding the atmospheres. Monte Carlo calculations that address the stochastic nature of the problem will be used to investigate this effect more rigorously. This technique will also be used to investigate the capability of Mars to retain volatiles. The ultimate goal is to determine the effect that planetary rubble has on a planetary atmosphere as a function of a planet's size and its context within a solar system. This research will address the following question: for a given planetary system, on which bodies might one expect to find an atmosphere? Dr. Griffith will pursue complementary work, at NASA's Infrared Telescope Facility, as a member of the science team that will observe comet Shoemaker-Levy's collision with Jupiter. The aim here is, in part, to investigate how the impact energy is partitioned into chemical energy and kinetic energy to the atmosphere. The partitioning into kinetic energy determines the efficiency with which comets erode planetary atmsopheres. The temperature at Venus' surface is 7500 K, almost 4000 K warmer than the Earth. The great efficiency with which the greenhouse effect warms Venus'atmosphere suggests that warm atmospheres would exist at large distances from the Sun, if greenhouse gases were present. This ra ises an interesting possibility for the ecosphere of the Solar System, that is, the region where liquid water exists, a necessary ingredient for life. Greenhouse gases, if present on a planetary body, may extend the ecosphere out to large distances from the Sun. This possibility will be investigated by focusing on Titan's organic-rich atmosphere. Titan's atmosphere may have originally consisted of ammonia (NH3 ultra violet radiation, a strong greenhouse gas) and subsequently been dissociated by solar on the nitrogen gas (N2) we presently observe. In collaboration with Chris McKay, Kevin Zahnle and Jim Pollack (NASA Ames Research Center), the possibility that Titan's atmosphere was warm enough to have had liquid water in the past will be investigated. This effort will be extended to consider the greenhouse efficiency of the highly abundant volatiles in the solar system (of which, governed by cosmic abundances, there are few). The larger aim of this project is to understand the thermal properties of atmospheres as a function of their composition. This award is to recognize an outstanding young faculty member in science and engineering. The award will enhance the career of the faculty member by providing flexible support for research and educational activities. Cooperation with industry and institutions that support research and education is encouraged.