Did 26Al and impact‐induced heating differentiate Mercury?
Did 26Al and impact‐induced heating differentiate Mercury?
复制标题
26Al 和冲击加热是否能够区分水银？
DOI：
10.1111/maps.12789
复制
发表时间：
2017
影响因子：
2.2
通讯作者：
S. Sahijpal
中科院分区：
文献类型：
--
作者：
G. K. Bhatia;S. Sahijpal
数值模型处理水星的行星尺度的分化与短寿命的核素，26铝，作为主要的热源沿着的碰撞引起的加热过程中的行星吸积。这两个热源被认为是导致火星分化的原因，火星是一颗大小与水星相当的行星。火星的年代记录和热模型表明，在太阳系形成的最初约100万年（Ma）期间，火星存在早期分化。我们的理论是，如果水星也在相同的时间尺度上吸积，这两个热源可能会区分行星。虽然与火星不同，水星的分化没有年代记录，但提出的机制值得研究。我们展示了不同的可行方案，为广泛的行星成分，可能产生的信使使命推断的水星的内部结构，与半径约2000公里的金属铁（Fe-Ni-FeS）的核心和硅酸盐地幔厚度约400公里。初始成分来源于形成于早期太阳系还原环境中的顽火辉石和CB（本库宾）顽火辉石。我们还考虑了不同的行星吸积方案，以了解它们对热处理的影响。我们的大多数模型都需要撞击引起的地幔剥离水星的撞击和运行机制与原行星后，它的分化，以产生适当大小的地幔。然而，如果我们将Fe-Ni-FeS含量增加到约71%（重量），则可以避免这种情况。最后，这里提出的模型可以用来理解类水星系外行星与金星和地球的行星胚胎的区别。
Numerical models dealing with the planetary scale differentiation of Mercury are presented with the short‐lived nuclide, 26Al, as the major heat source along with the impact‐induced heating during the accretion of planets. These two heat sources are considered to have caused differentiation of Mars, a planet with size comparable to Mercury. The chronological records and the thermal modeling of Mars indicate an early differentiation during the initial ~1 million years (Ma) of the formation of the solar system. We theorize that in case Mercury also accreted over an identical time scale, the two heat sources could have differentiated the planets. Although unlike Mars there is no chronological record of Mercury's differentiation, the proposed mechanism is worth investigation. We demonstrate distinct viable scenarios for a wide range of planetary compositions that could have produced the internal structure of Mercury as deduced by the MESSENGER mission, with a metallic iron (Fe‐Ni‐FeS) core of radius ~2000 km and a silicate mantle thickness of ~400 km. The initial compositions were derived from the enstatite and CB (Bencubbin) chondrites that were formed in the reducing environments of the early solar system. We have also considered distinct planetary accretion scenarios to understand their influence on thermal processing. The majority of our models would require impact‐induced mantle stripping of Mercury by hit and run mechanism with a protoplanet subsequent to its differentiation in order to produce the right size of mantle. However, this can be avoided if we increase the Fe‐Ni‐FeS contents to ~71% by weight. Finally, the models presented here can be used to understand the differentiation of Mercury‐like exoplanets and the planetary embryos of Venus and Earth.
DOI：
10.1002/jgre.20168
发表时间：
2013
期刊：
Journal of Geophysical Research: Planets
影响因子：
--
作者：
Tosi N;M. Grott;A.-C. Plesa;D. Breuer
通讯作者：
D. Breuer