A Martian origin for the Mars Trojan asteroids
A Martian origin for the Mars Trojan asteroids
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DOI：
10.1038/s41550-017-0179
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发表时间：
2017-07
期刊：
影响因子：
14.1
通讯作者：
D. Polishook;Seth Andrew Jacobson;A. Morbidelli;O. Aharonson
中科院分区：
文献类型：
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作者：
D. Polishook;Seth Andrew Jacobson;A. Morbidelli;O. Aharonson
已知的九颗火星特洛伊小行星中有七颗属于一个轨道星团，以其最大的成员（5261）尤里卡命名。尤里卡可能是整个星系团的前身，它至少在1光年前形成。有人认为热YORP（Yarkovsky-O 'Keefe-Radzievskii-Paddack）效应使尤里卡旋转起来，导致碎片通过旋转裂变机制喷射出来。尤里卡的光谱在1 μm附近有一个宽而深的吸收带，表明其成分富含橄榄石。在这里，我们展示的证据表明，特洛伊尤里卡集群的祖先可能起源于从火星地幔挖掘的撞击碎片。我们对两颗特洛伊星（（311999）2007 NS 2和（385250）2001 DH 47）进行了新的近红外观测，发现它们都具有类似于尤里卡的富橄榄石反射光谱。这些测量结果证实，该集团的祖先有一个无软骨成分。富含橄榄石的反射光谱在小行星中是罕见的，但在火星上最大的盆地周围可以看到。它们也与一些火星陨石（例如，Chassigny）和构成火星地幔的物质相一致。使用数值模拟，我们表明，火星特洛伊更有可能是从火星的撞击喷出物比捕获的富含橄榄石的小行星从主带运输。这一结果直接将特定的小行星与形成行星的碎片联系起来。
Seven of the nine known Mars Trojan asteroids belong to an orbital cluster,named after its largest member, (5261) Eureka. Eureka is probably the progenitor of the whole cluster, which formed at least 1 Gyr ago. It has been suggested that the thermal YORP (Yarkovsky–O'Keefe–Radzievskii–Paddack) effect spun up Eureka, resulting in fragments being ejected by the rotational-fission mechanism. Eureka’s spectrum exhibits a broad and deep absorption band around 1 μm, indicating an olivine-rich composition. Here we show evidence that the Trojan Eureka cluster progenitor could have originated as impact debris excavated from the Martian mantle. We present new near-infrared observations of two Trojans ((311999) 2007 NS2and (385250) 2001 DH47) and find that both exhibit an olivine-rich reflectance spectrum similar to Eureka’s. These measurements confirm that the progenitor of the cluster has an achondritic composition. Olivine-rich reflectance spectra are rare amongst asteroids but are seen around the largest basins on Mars. They are also consistent with some Martian meteorites (for example, Chassigny) and with the material comprising much of the Martian mantle,. Using numerical simulations, we show that the Mars Trojans are more likely to be impact ejecta from Mars than captured olivine-rich asteroids transported from the main belt. This result directly links specific asteroids to debris from the forming planets.