Searching for Biosignatures in Exoplanetary Impact Ejecta
Searching for Biosignatures in Exoplanetary Impact Ejecta
复制标题
寻找系外行星撞击喷射物中的生物特征
DOI：
10.1089/ast.2015.1437
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发表时间：
2017
期刊：
影响因子：
4.2
通讯作者：
Olofsson Goran
中科院分区：
文献类型：
--
作者：
Cataldi Gianni;Brandeker Alexis;Thebault Philippe;Singer Kelsi;Ahmed Engy;de Vries Bernard L.;Neubeck Anna;Olofsson Goran
随着岩石系外行星数量的稳步增加，它们的表征和寻找系外行星生物圈正成为天体生物学中日益紧迫的问题。迄今为止，大多数努力都集中在系外行星大气的研究上。相反，我们的目标是调查描述系外行星的可能性（在可居住性，地质学，生命存在等方面）。通过研究撞击事件中从地表喷射出的物质。对于一些影响的情况下，我们估计逃逸的质量，并评估其随后的碰撞演化在拱星轨道，假设太阳一样的主机星星。我们计算的分数光度的尘埃作为一个函数的时间后的影响事件，并研究其可探测性与当前和未来的仪器。我们认为，限制dustcomposition的可能性，提供有关地质或生物圈的存在的信息。作为例子，我们调查是否可以检测到方解石，二氧化硅，或喷出的微生物。对于一个直径为20公里的撞击物，我们发现逃逸的尘埃质量与黄道尘埃大致相当，这取决于系外行星的大小。碰撞演化的最佳模型是考虑两个独立的尘埃种群，一个是由未熔化的喷出物组成的种群，其演化时间尺度为数百万年，另一个是由熔化或蒸汽凝结而成的尘埃种群，其演化时间尺度要短得多。虽然尘埃的存在可以用现有的望远镜推断出来，但研究其成分需要先进的仪器。对生物物质的直接探测是极具挑战性的。尽管存在相当大的困难（小的尘埃团、诸如外生尘埃的噪声等），研究从系外行星表面喷出的尘埃物质可能成为未来大气研究的一个有趣补充。关键词：生物特征-系外行星-撞击-行星际尘埃-遥感。天体生物学17，721-746。
With the number of confirmed rocky exoplanets increasing steadily, their characterization and the search for exoplanetary biospheres are becoming increasingly urgent issues in astrobiology. To date, most efforts have concentrated on the study of exoplanetary atmospheres. Instead, we aim to investigate the possibility of characterizing an exoplanet (in terms of habitability, geology, presence of life, etc.) by studying material ejected from the surface during an impact event. For a number of impact scenarios, we estimate the escaping mass and assess its subsequent collisional evolution in a circumstellar orbit, assuming a Sun-like host star. We calculate the fractional luminosity of the dust as a function of time after the impact event and study its detectability with current and future instrumentation. We consider the possibility to constrain the dustcomposition,giving information on the geology or the presence of a biosphere. As examples, we investigate whether calcite, silica, or ejected microorganisms could be detected. For a 20 km diameter impactor, we find that the dust mass escaping the exoplanet is roughly comparable to the zodiacal dust, depending on the exoplanet's size. The collisional evolution is best modeled by considering two independent dust populations, aspalledpopulation consisting of nonmelted ejecta evolving on timescales of millions of years, and dustrecondensedfrom melt or vapor evolving on much shorter timescales. While the presence of dust can potentially be inferred with current telescopes, studying its composition requires advanced instrumentation not yet available. The direct detection of biological matter turns out to be extremely challenging. Despite considerable difficulties (small dust masses, noise such as exozodiacal dust, etc.), studying dusty material ejected from an exoplanetary surface might become an interesting complement to atmospheric studies in the future. Key Words: Biosignatures—Exoplanets—Impacts—Interplanetary dust—Remote sensing. Astrobiology 17, 721–746.