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An extremely high-altitude plume seen at Mars' morning terminator

机译：在火星早间终结者身上看到的极高的羽流

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The Martian limb (that is, the observed 'edge' of the planet) represents a unique window into the complex atmospheric phenomena occurring there. Clouds of ice crystals (CO_2 ice or H_2Oice) have been observed numerous times by spacecraft and ground-based telescopes, showing that clouds are typically layered and always confined below an altitude of 100 kilometres; suspended dust has also been detected at altitudes up to 60 kilometres during major dust storms. Highly concentrated and localized patches of auroral emission controlled by magnetic field anomalies in the crust have been observed at an altitude of 130 kilometres. Here we report the occurrence in March and April 2012 of two bright, extremely high-altitude plumes at the Martian terminator (the day-night boundary) at 200 to 250 kilometres or more above the surface, and thus well into the ionosphere and the exosphere. They were spotted at a longitude of about 195° west, a latitude of about -45° (at Terra Cimmeria), extended about 500 to 1,000 kilometres in both the north-south and east-west directions, and lasted for about 10 days. The features exhibited day-to-day variability, and were seen at the morning terminator but not at the evening limb, which indicates rapid evolution in less than 10 hours and a cyclic behaviour. We used photometric measurements to explore two possible scenarios and investigate their nature. For particles reflecting solar radiation, clouds of CO_2-ice or H_2O-ice particles with an effective radius of 0.1 micrometres are favoured over dust. Alternatively, the plume could arise from auroral emission, of a brightness more than 1,000 times that of the Earth's aurora, over a region with a strong magnetic anomaly where aurorae have previously been detected. Importantly, both explanations defy our current understanding of Mars' upper atmosphere.
机译：火星肢体（即观察到的行星“边缘”）代表了一个独特的窗口，可以看到那里发生的复杂大气现象。航天器和地面望远镜已多次观测到冰晶云（CO_2冰或H_2Oice），这表明云层通常是分层的并且总是局限在100公里以下。在重大沙尘暴期间，还可以在高达60公里的高度检测到悬浮粉尘。在海拔130公里的高空，观测到了由地壳中的磁场异常控制的极光发射的高度集中和局部的斑块。在这里，我们报告了在2012年3月和2012年4月，在火星终结者（白天边界）上，在距地面200至250公里或更远处出现了两个明亮的极高羽流，并因此进入电离层和系外层。它们在西经大约195度，北纬-45度（在Terra Cimmeria）处被发现，在南北和东西方向都延伸了约500至1,000公里，并持续了约10天。这些特征表现出日常的可变性，并且在早晨终结者处观察到，但在傍晚肢体却没有观察到，这表明在不到10小时的时间内迅速进化并且具有周期性行为。我们使用光度测量来探索两种可能的情况并研究其性质。对于反射太阳辐射的粒子，有效半径为0.1微米的CO_2-ice或H_2O-ice粒子云优于灰尘。或者，在先前已检测到极光的强磁异常区域，极光可能来自极光发射，其亮度是地球极光的1000倍以上。重要的是，这两种解释都违背了我们目前对火星高层大气的理解。

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  • 来源
    《Nature》 |2015年第7540期|525-528|共4页
  • 作者

    A. Sanchez-Lavega; A. Garcia Munoz; E. Garcia-Melendo; S. Perez-Hoyos; J. M. Gomez-Forrellad; C. Pellier; M. Delcroix; M. A. Lopez-Valverde; F. Gonzalez-Galindo; W. Jaeschke; D. Parker; J. Phillips; D. Peach;

  • 作者单位

    Departamento de Fisica Aplicada I, EST Ingenieria, Universidad del Pais Vasco, Alameda Urquijo s, 48013 Bilbao, Spain, Unidad Asociada Grupo Ciencias Planetarias UPV/EHU-IAA(CSIC), Alameda Urquijo s, 48013 Bilbao, Spain;

    European Space Agency, ESTEC, 2201 AZ Noordwijk, The Netherlands;

    Departamento de Fisica Aplicada I, EST Ingenieria, Universidad del Pais Vasco, Alameda Urquijo s, 48013 Bilbao, Spain, Fundacio Observatori Esteve Duran, Montseny 46, 08553 Seva(Barcelona), Spain;

    Departamento de Fisica Aplicada I, EST Ingenieria, Universidad del Pais Vasco, Alameda Urquijo s, 48013 Bilbao, Spain, Unidad Asociada Grupo Ciencias Planetarias UPV/EHU-IAA(CSIC), Alameda Urquijo s, 48013 Bilbao, Spain;

    Fundacio Observatori Esteve Duran, Montseny 46, 08553 Seva(Barcelona), Spain;

    Commission des Surfaces planetaires, Societe Astronomique de France, 3, rue Beethoven, 75016 Parts, France;

    Commission des Surfaces planetaires, Societe Astronomique de France, 3, rue Beethoven, 75016 Parts, France;

    Unidad Asociada Grupo Ciencias Planetarias UPV/EHU-IAA(CSIC), Alameda Urquijo s, 48013 Bilbao, Spain, Instituto de Astrofisica de Andalucia, CSIG, Glorieta de la Astronomia, 3, 18008 Granada, Spain;

    Unidad Asociada Grupo Ciencias Planetarias UPV/EHU-IAA(CSIC), Alameda Urquijo s, 48013 Bilbao, Spain, Instituto de Astrofisica de Andalucia, CSIG, Glorieta de la Astronomia, 3, 18008 Granada, Spain;

    Associatiom of Lunar and Planetary Obeservers, 200 Lawerence Drive, West Chester, Pennsylvania 19380, USA;

    Association of Lunar and Planetary Observers, 12911 Lerida Street, Coral Gables, Florida 33156, USA;

    Associatiom of Lunar and Planetary Obeservers, 570 Long Point Road STE 230, Mount Pleasant, South Carilina 29464, USA;

    British Astronomical Association, Burlington House, Piccadilly, London W1J 0DU, UK;

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