The Role of Temperature-Driven Chemical Reactions in the Evolution of Solar System Ices

太阳系外许多冰冷的卫星表面和地下温度都很低。航天器对木星的卫星木卫二和土星的卫星土卫二的测量都测量了它们表面的各种分子种类。首席研究员和他的同事们最近的工作表明，这些分子物种在低温（~ 80k）下发生反应，完全在这些较低的卫星表面温度范围内。利用这笔资金，研究人员将研究温度驱动的不同化学成分的冰的反应在太阳系内冰物体的演化中所起的作用。他们将使用北亚利桑那大学新设计的超高真空实验室。冰样本将在类似太阳系中发现冰的条件下产生，然后以不同的速率加热研究。该项目通过促进我们对太阳系外冰质物体化学演化的理解来支持美国国家科学基金会的使命。PI将包括研究生和本科生参与这项研究，对当地一所小学进行演讲，并在Flagstaff科学节上进行科学演讲。含有氧化剂（臭氧和过氧化氢）和各种含硫、碳和氮化合物的冰样品将在与太阳系冰相关的条件下制备，并用红外光谱进行表征。然后，样品将以不同的速率加热，同时用红外光谱、质谱和微天平重量法进行监测。这种技术的结合使新产品得以识别，并对现有产品的销毁进行监测。以不同的速率加热样品可以计算反应的活化能。最后，这些混合物中的浓度会有所不同，这将有助于阐明这些不同化学系统中活跃的反应途径。这项新工作的结果将对我们的太阳系如何随着时间的推移而演变产生强烈的影响，并可能改变建模者和理论家对非辐射分解过程在太阳系冰和其他物体（如彗星或星际冰）的化学演化中所起作用的看法。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Many of the icy satellites in the outer Solar System have low surface and subsurface temperatures. Spacecraft measurements at both Jupiter's satellite Europa and Saturn's satellite Enceladus measured various molecular species on their surfaces. Recent work by the Principal Investigator and his colleagues have shown that these molecular species react at low temperatures (~80 K), well within the range of these lower satellite surface temperatures. Using this grant, the investigators will study the role that temperature-driven reactions of ices of different chemical compositions play in the evolution of icy objects within the Solar System. They will use the newly-designed ultra-high vacuum laboratory at Northern Arizona University. Ice samples will be created under conditions similar to those where Solar System ices are found, and then studied as they are heated at various rates. This project supports the mission of the NSF by promoting our understanding of the chemical evolution of icy objects in the outer Solar System. The PI will include graduate and undergraduate students in this research, speak to a local elementary school, as well as give science presentations at the Flagstaff Festival of Science.Ice samples containing oxidants (ozone and hydrogen peroxide) and various sulfur-, carbon-, and nitrogen-containing compounds will be prepared under conditions relevant to Solar System ices and characterized with infrared spectroscopy. Then, the samples will be warmed at various rates, while being monitored with infrared spectroscopy, mass spectrometry and microbalance gravimetry. This combination of techniques allows new products to be identified and the destruction of existing ones to be monitored. Heating the sample at different rates allows for the calculation of the activation energies for the reaction. Finally, the concentration will be varied in these mixtures, which will help to elucidate the reactions pathways that are active in these different chemical systems. The results of this new work will have strong implications on how our Solar System may evolve over time and could change how modelers and theorists view the role that non-radiolytic processes play in the chemical evolution of not only solar system ices but also other objects, such as comets or interstellar ices.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.