Mars and Titan's atmosphere and interior

火星和土卫六（土星最大的卫星）是太阳系中最像地球的两个天体。这两颗行星都被认为是过去、现在或未来可能存在生物活动的地点。什么类型的生物可能存在以及它们是否存在是激烈的科学辩论和研究的主题。如果在另一个星球上发现了生命，它将对我们看待我们在宇宙中的位置的方式产生深远的影响，并成为有史以来最伟大的科学发现之一。要了解这些星球上可能存在的生命类型，以及我们如何寻找它们，需要对每个星球的环境有深入的了解。这就是我计划研究的重点——与美国宇航局和欧空局等世界主要机构合作。火星有稀薄的二氧化碳大气层，并且有许多与地球相同的表面特征——比如河谷（现在已经干涸）和沉积岩。最近的证据表明，火星在过去的温度更高，大气层更厚，与地球早期的大气层相似，更加适宜居住。美国宇航局火星探测车的新结果显示，火星表面长期存在液态水的证据。了解火星早期环境的关键是火星的内部结构，因为它决定了年轻火星表面的很多东西，包括保护大气层不受太阳辐射的影响，火山可能提供了大量的大气气体，内部对流/热流影响了火星表面的地质情况。目前对火星内部的了解非常有限，我们甚至不知道火星的核心有多大，是液体还是固体。探测火星内部的最好方法是地震学，就像我们在地球上做的那样。ExoMars任务包括一个地震仪，它将利用火星地震探测火星内部。我将对地震仪进行校准和测试，以确保数据能够得到正确的解释，同时利用从地球全球地震学发展而来的技术，开发火星内部的地震模型。了解火星过去环境的关键是了解现在的大气和气候变化。目前尚不清楚火星目前的气候是否稳定——每年火星的夏天，水蒸气都会从两极迁移，而且不知道它是否会返回。一个令人兴奋的可能性是，火星正在从一种气候状态转变为另一种气候状态。这个问题只能通过宇宙飞船和望远镜的观测来回答。美国宇航局的火星勘测轨道飞行器（MRO）是进入火星轨道的最新、最先进的航天器。我将使用MRO的数据来确定火星大气中的水和尘埃分布，并确定它们对气候的影响。土卫六是寒冷的外太阳系中类地行星的一个例子。土卫六的大气层很厚，有云和雨，就像地球一样，但土卫六是由甲烷而不是水构成的。最近的卡西尼号任务展示了许多迷人的表面特征，包括甲烷湖、山谷、火山和由小冰晶组成的沙丘。土卫六的大气层是苯等有机分子的滋生地。一些非常复杂的分子被认为存在于北极，在那里，它们被泰坦的阴影保护着，不受阳光的破坏。卡西尼号在2006-2007年间多次飞越极地，让我们第一次看到了这个令人兴奋的区域。在测量的红外光谱中存在的许多有机分子尚未被识别。有机分子的全球分布可以用来探测土卫六的大气运动，比如极地涡旋和行星范围内的循环细胞。土卫六的春分是在2009年，当时模型预测大气会发生广泛而迅速的变化——尤其是在冬季极点。从地球上永远看不到这个极点，卡西尼号提供了一个独特的机会来观察极地涡旋的破裂，这至少在30年内是不可能的。

Mars and Titan (Saturn's largest moon) are the two most Earth-like bodies in the solar system. Both planets have been suggested as possible locations for biological activity, either in the past, present, or future. What type of organisms might exist and whether they do exist is the topic of intense scientific debate and research. If life is found on another planet, it would have far reaching effects on the way we view our place in the universe and be one of the greatest scientific discoveries of all time. To understand the type of life that could occur on these bodies, and how we might look for it, requires in-depth knowledge of the environment of each planet. This is what I plan to focus my research on - in collaboration with major world-wide institutes such as NASA and ESA. Mars has a thin CO2 atmosphere and many surface features in common with Earth - e.g. river valleys (now dry) and sedimentary rocks. Recent evidence shows Mars was much more hospitable in the past with warmer temperatures and a thicker atmosphere, similar to Earth's early atmosphere. New results from NASA's Mars Exploration Rovers show evidence for prolonged existence of liquid water on the surface. Key to understanding this early environment is Mars' internal structure as this determined much about the surface of young Mars, including protection of the atmosphere from solar radiation, volcanoes which may have supplied much of the atmospheric gases, and interior convection/heat-flow which influenced surface geology. Knowledge of Mars' interior is currently very limited - we do not even know how big Mars' core is and whether it is liquid or solid. The best way to probe the interior is with seismology, as we do on Earth. The ExoMars mission includes a seismometer, which will use Marsquakes to probe the interior. I will calibrate and test the seismometer to ensure that the data can be interpreted properly, while simultaneously developing seismic models of Mars' interior using techniques modified from those developed for global seismology of Earth. Also key to understanding Mars' past environment is understanding the present atmosphere and climate change. It is not known if Mars' current climate is stable - water vapour migrates away from the poles each Martian summer and it is not known if it returns. One exciting possibility is that Mars is changing from one climate state to another. This question can only be answered with a combination of spacecraft and telescope observations. NASA's Mars Reconnaissance Orbiter (MRO) spacecraft is the latest and most advanced to enter orbit around Mars. I will use data from MRO to determine water and dust distribution in Mars' atmosphere and determine what effect these have on climate. Titan is an example of an Earth-like planet in the cold outer solar system. Titan has a thick atmosphere and has clouds and rain just like on Earth, but made of methane instead of water. The recent Cassini mission has shown many fascinating surface features including, methane lakes, valleys, volcanoes, and sand dunes made of tiny ice crystals. Titan's atmosphere is a breeding ground for organic molecules like benzene. Some very complicated molecules are expected to exist at the North pole, where they are protected from destruction by sun light by Titan's shadow. Cassini performed multiple flybys over the pole during 2006-2007, giving us our first ever view of this exciting region. Many of the organic molecules present in the measured infra-red spectra are yet to be identified. The global distribution of organic molecules can be used to probe Titan's atmospheric motions like the polar vortex and planet-wide circulation cells. Titan's spring equinox is in 2009 when models predict extensive and rapid changes in the atmosphere - especially at the winter pole. This pole is never visible from Earth and Cassini provides a unique opportunity to observe the polar vortex break-up, which will not be possible again for at least 30years.