Identifying the sources of colour and featural changes in Jupiter's atmosphere

巨大的行星云是我们太阳系行星所展示的最美丽和最复杂的现象之一。它们的空间分布揭示了力和能量交换机制（例如，大气层的垂直结构告诉我们云的组成和微观物理学;它们的颜色揭示了巨大行星大气中气溶胶的化学变化。虽然大多数云是白色，木星和土星的云是彩色的黄色和红色的各种色调，但这些颜色的性质，或“生色团”，尚未确定，仍然是一个持久的谜。在这个项目中，学生将分析现有的VLT/MUSE观测木星和土星的可见光/近红外光谱，并将其与现有的天王星和海王星的近红外VLT/SINFONI观测进行对比。他还将参与提出和减少未来的观测，并将获得望远镜观测和分析方面的经验。MUSE和SINFONI都是积分场单元光谱仪，观测到的光谱“立方体”将用复杂的多重散射辐射传输模型NEMESIS进行分析，NEMESIS是以前开发的太阳系行星观测模型。学生可以从一开始就获得真实的数据进行分析，并在项目期间获得更多数据，可能与朱诺号和卡西尼号分别在2016-17年对木星和土星的观测有关。这些数据将被分析，以寻找季节变化，并监测偶尔的云剧变事件，例如2010年土星上的大风暴，2012年木星上的NEB爆发以及2014年天王星上最近的云爆发，这是如此明亮，以至于业余天文学家都可以看到。此外，建立甚大望远镜/MUSE方案将为2016年7月抵达木星轨道的美国航天局/朱诺号使命提供宝贵的背景观测。该航天器将被放置在极地轨道上，在木星北极上方有一个低近心点。这项使命主要是通过绘制木星的引力场来确定木星的内部结构，但遥感相机也将在航天器飞越北极时观察木星的狭窄“条带”。解释这些观测结果需要我们知道观测到的“条带”与木星的整体外观和云结构有何关系。虽然简单的地面成像将能够将条带与更广泛的背景联系起来，但只有VLT/MUSE能够提供光谱成分，将朱诺号探测到的任何成分/发色团变化与广泛的木星大气联系起来。因此，VLT/MUSE将能够为Juno使命提供独特的“地面支持”，并将学生嵌入全球巨行星天文学家社区。

Giant planet clouds are amongst the most beautiful and complex phenomena displayed by the planets of our solar system. Their spatial distribution reveals the forces and energy exchange mechanisms (e.g., moist convection) shaping the banded appearance of the planetary weather layers; their vertical structure tells us about the composition and cloud microphysics; and their colour reveals the chemical alteration of aerosols in a giant planet atmosphere. While most clouds are white, the clouds of Jupiter and Saturn are coloured with various hues of yellow and red, but the nature of these colours, or 'chromophores,' has yet to be determined, and remains an enduring mystery. In this project, the student will analyse existing VLT/MUSE observations the visible/near-IR spectra of Jupiter and Saturn and contrast these with existing near-IR VLT/SINFONI observations of Uranus and Neptune. He will also participate in proposing and reducing future observations, and will gain experience in telescopic observations and analysis. Both MUSE and SINFONI are Integral Field Unit spectrometers and the observed spectral 'cubes' will be analysed with a sophisticated multiple-scattering radiative transfer model, NEMESIS, previously developed to model observations of solar system planets. The student has access to real data to analyse from the start, with further data being acquired during their project, possibly in association with observations of Jupiter and Saturn by Juno and Cassini, respectively, in 2016-17. These data will be analysed to look for seasonal changes and also monitor occasional cloud upheaval events, such as the great storm on Saturn in 2010, the NEB outbreak on Jupiter in 2012 and the recent cloud outbreak on Uranus in 2014, which was so bright that it was visible to amateur astronomers. In addition, establishing a VLT/MUSE programme will provide invaluable context observations for the NASA/Juno mission, which arrives in Jupiter orbit in July 2016. This spacecraft will be placed in a polar orbit, with a low periapsis over Jupiter's north pole. The mission is primarily designed to determine Jupiter's internal structure by mapping its gravitational field, but remote sensing cameras will also observe narrow 'strips' of Jupiter as the spacecraft flies over the north pole. Interpreting these observations requires that we know how the observed 'strips' relate to the overall appearance and cloud structure of Jupiter. While simple ground-based imaging will be able to relate the strips to the wider context, only VLT/MUSE will be able to provide the spectral component, relating any composition/chromophore changes detected by Juno with the wide Jovian atmosphere. Thus, VLT/MUSE will be able to provide unique 'ground-support' to the Juno mission, and embed the student within the global community of giant planet astronomers.