We analyze radio tracking data obtained during 1311 orbits of the MESSENGER spacecraft in the period March 2011 to April 2014. A least-squares minimization of the residuals between observed and computed values of two-way range and Doppler allows us to solve for a model describing Mercury's gravity, tidal response, and spin state. We use a spherical harmonic representation of the gravity field to degree and order 40 and report error bars corresponding to 10 times the formal uncertainties of the fit. Our estimate of the product of Mercury's mass and the gravitational constant, $GM = (22031.87404 \pm 9 \times 10^{-4})$ km$^{3}$s$^{-2}$, is in excellent agreement with published results. Our solution for the geophysically important second-degree coefficients ($\bar{C}_{2,0} = -2.25100 \times 10^{-5} \pm 1.3 \times 10^{-9}$, $\bar{C}_{2,2} = 1.24973 \times 10^{-5} \pm 1.2 \times 10^{-9}$) confirms previous estimates to better than 0.4\% and, therefore, inferences about Mercury's moment of inertia and interior structure. Our estimate of the tidal Love number $k_2 = 0.464 \pm 0.023$ indicates that Mercury's mantle may be hotter and weaker than previously thought. Our spin state solution suggests that gravity-based estimates of Mercury's spin axis orientation are marginally consistent with previous measurements of the orientation of the crust.
At Mercury, several processes can release ions and neutrals out of the planet's surface. Here we present enhancements of dayside planetary ions in the solar wind entry layer during flux transfer event (FTE) "showers" near Mercury's northern magnetospheric cusp. The FTE showers correspond to the intervals of intense magnetopause reconnection of Mercury's magnetosphere, which form a solar wind entry layer equatorward of the magnetospheric cusps. In this entry layer, solar wind ions are accelerated and move downward (i.e. planetward) toward the cusps, which sputter upward-moving planetary ions wi…
This review summarizes the research of Mercury's magnetosphere in the Post-MESSENGER era and compares its dynamics to those in other planetary magnetospheres, especially to those in Earth's magnetosphere. This review starts by introducing the planet Mercury, including its interplanetary environment, magnetosphere, exosphere, and conducting core. The frequent and intense magnetic reconnection on the dayside magnetopause, which is represented by the flux transfer event "shower", is reviewed on how they depend on magnetosheath plasma beta and magnetic shear angle across the magnetopause, followin…
The large-scale magnetic structure of interplanetary coronal mass ejections (ICMEs) has been shown to cause decreases in the galactic cosmic ray (GCR) flux measured in situ by spacecraft, known as Forbush decreases (Fds). We use measurements of the GCR count rate obtained by MESSENGER during its orbital phase around Mercury to identify such Fds related to the passage of ICMEs and characterize their structure. Of the 42 ICMEs with corresponding high-quality GCR data, 79% are associated with a Fd. Thus a total of 33 ICME-related Fds were identified, 24 of which (73%) have a two-step structure. W…
Mercury and frame-dragging in light of the MESSENGER flybys: conflict with general relativity, poor knowledge of the physical properties of the Sun, data reduction artifact, or still insufficient observations?
广义相对论利用日震学中太阳的角动量S = 190 x 10^39 kg m^2 s^-1，预测水星近日点经度的兰斯-瑟林岁差为-2.0毫角秒/世纪（在天体赤道参考系中计算）。在4-σ水平上，它与标准牛顿/爱因斯坦岁差的0.4 +/- 0.6毫角秒/世纪修正值不一致，只要后者完全归因于标架拖曳。补充岁差是最近用INPOP 10a星历表与一个长行星数据记录（1914-2010年）进行全球拟合确定的，其中包括2008-2009年从信使号航天器收集的3个数据点。INPOP 10a模型根本不包括太阳重力磁场，因此它的特征可能在数据简化过程中被部分删除。另一方面，Lense-Thirring进动可能在一定程度上被竞争进动所抵消，这些竞争进动是由太阳四极质量矩和PPN参数β进入Schwarzschild类1 PN进动的小错误建模引起的，两者都是在INPOP 10a中建模的。相反，水星本身的扁率对其近日点的影响可以忽略不计。最大的单个小行星和小行星环的错误模型行为也是如此。未来对目前正在进行的信使号任务的更多观测结果的分析将进一步阐明这一问题，如果得到证实，可能会挑战我们目前对目前公认的引力定律和/或太阳物理特性的看法。
Mercury Craters Named after Tajik-Persian Poets: Planetary Nomenclature as a Form of Preserving Cultural Heritage
Institute of Astrophysics, National Academy of Sciences of Tajikistan（塔吉克斯坦国家科学院天体物理研究所）；S. U. Umarov Physical-Technical Institute, National Academy of Sciences of Tajikistan（塔吉克斯坦国家科学院S.U.乌马尔诺夫物理技术研究所）
In a study to provide ground truth data for mid infrared observations of the surface of Mercury with the MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer) instrument onboard the ESA/JAXA BepiColombo mission, we have studied 17 synthetic glasses. These samples have the chemical compositions of characteristic Hermean surface areas based on MESSENGER data. The samples have been characterized using optical microscopy, EMPA and Raman spectroscopy. Mid infrared spectra have been obtained from polished thin sections using Micro FTIR, and of powdered size fractions of bulk material (0-25, …
As an end-member of terrestrial planet formation, Mercury holds unique clues about the original distribution of elements in the earliest stages of solar system development and how planets and exoplanets form and evolve in close proximity to their host stars. This Mercury Lander mission concept enables in situ surface measurements that address several fundamental science questions raised by MESSENGER's pioneering exploration of Mercury. Such measurements are needed to understand Mercury's unique mineralogy and geochemistry; to characterize the proportionally massive core's structure; to measure…
We establish the feasibility of measuring the neutron lifetime via an alternative, space-based class of methods, which use neutrons generated by galactic cosmic ray spallation of planets' surfaces and atmospheres. Free neutrons decay via the weak interaction with a mean lifetime of around 880 s. This lifetime constrains the unitarity of the CKM matrix and is a key parameter for studies of Big-Bang nucleosynthesis. However, current laboratory measurements, using two independent approaches, differ by over 4$σ$. Using data acquired in 2007 and 2008 during flybys of Venus and Mercury by NASA's MES…
