名义上无水的近地小行星上与空间相关的水合特征

IF 2.5 2区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS
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引用次数: 0

摘要

近地小行星(NEAs)是研究影响无空气天体表面过程的绝佳实验室。预计大多数近地小行星的表面不会含有 OH/H2O ,因为它们主要是 S 复合天体,来自霜冻线内部的主带,其表面温度足以去除这些挥发物。然而,在太阳系内部其他看似干燥的天体上,如月球和灶神星,以及最近在近地天体(433)厄洛斯、(1036)甘尼米德和(3122)佛罗伦萨上,都发现了典型的表明OH/H2O的3μm特征。这些天体上的 OH/H2O 最可能的来源包括碳质软玉撞击或与太阳风植入的质子相互作用。我们将对厄洛斯和甘尼米德的新观测结果与之前发表的观测结果进行了比较,并对佛罗伦萨进行了旋转分辨光谱研究,从而研究了近地天体上波段深度和形状变化的原因。讨论的所有光谱都是由美国宇航局 IRTF 上的 SpeX 使用 LXD_short(1.67-4.2 μm)模式收集的,用于描述 3-μm 区域的特征。一些观测还使用棱镜(0.7-2.52 μm)模式来确定小行星的光谱类型并研究硅酸盐成分的相关性。这三颗小行星都具有外源的 OH/H2O,其光谱在波段深度或形状上显示出潜在的空间相关变化。厄洛斯的波段在两极比在较低的次观测纬度略宽,这可能是由于它的高倾角确保了每个极区在其轨道的大部分时间都朝向太阳。Ganymed的水合带深度与副太阳经度和I带中心的趋势表明,一个碳质或彗星撞击器在相对经度0°左右撞击了地表,挖掘出一个相对富含镁和橄榄石的层。佛罗伦萨的总氢浓度在整个表面保持稳定,即使随着小行星的旋转,OH 与 H2O 的比率也会发生变化。这三个例子表明,其他天体上的非原生 OH/H2O 很可能也与空间有关,而与输送机制无关。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Spatially dependent hydration features on nominally anhydrous near-earth asteroids

Near-Earth Asteroids (NEAs) are excellent laboratories for processes that affect the surfaces of airless bodies. Most NEAs were not expected to contain OH/H2O on their surfaces because they are primarily S-complex objects and sourced from the inner Main Belt, which is interior of the frost line, and their surface temperatures are high enough to remove these volatiles. However, a 3-μm feature typically indicative of OH/H2O was identified on other seemingly dry bodies in the inner Solar System, such as the Moon and Vesta, and more recently on the NEAs (433) Eros, (1036) Ganymed, and (3122) Florence. The most likely sources for OH/H2O on these bodies include carbonaceous chondrite impacts or interactions with protons implanted by solar wind. We investigated the causes of band depth and shape variations on NEAs by comparing new observations of Eros and Ganymed to those previously published and conducting a rotationally-resolved spectral study on Florence. All spectra discussed were collected by SpeX on NASA's IRTF using the LXD_short (1.67–4.2 μm) mode to characterize the 3-μm region. Some observations also used the prism (0.7–2.52 μm) mode to characterize asteroid spectral type and investigate silicate composition dependencies. All three asteroids possess exogenously sourced OH/H2O and have spectra that show potential spatially correlated variations in band depth or shape. Eros' band is slightly wider at the poles than at lower sub-observer latitudes, possibly due to its high obliquity, which ensures that each polar region is oriented toward the Sun over a significant part of its orbit. Ganymed's trends in hydration band depth with sub-solar longitude and band I center suggest a carbonaceous or cometary impactor that struck the surface around 0° relative longitude, excavating a relatively magnesium- and olivine-enriched layer. Florence's total hydrogen concentration remains stable across the surface even as the OH-to-H2O ratio changes as the asteroid rotates. These three examples suggest that non-native OH/H2O on other bodies will likely also be spatially dependent, regardless of delivery mechanism.

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来源期刊
Icarus
Icarus 地学天文-天文与天体物理
CiteScore
6.30
自引率
18.80%
发文量
356
审稿时长
2-4 weeks
期刊介绍: Icarus is devoted to the publication of original contributions in the field of Solar System studies. Manuscripts reporting the results of new research - observational, experimental, or theoretical - concerning the astronomy, geology, meteorology, physics, chemistry, biology, and other scientific aspects of our Solar System or extrasolar systems are welcome. The journal generally does not publish papers devoted exclusively to the Sun, the Earth, celestial mechanics, meteoritics, or astrophysics. Icarus does not publish papers that provide "improved" versions of Bode''s law, or other numerical relations, without a sound physical basis. Icarus does not publish meeting announcements or general notices. Reviews, historical papers, and manuscripts describing spacecraft instrumentation may be considered, but only with prior approval of the editor. An entire issue of the journal is occasionally devoted to a single subject, usually arising from a conference on the same topic. The language of publication is English. American or British usage is accepted, but not a mixture of these.
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