The ratio of 40 Ar/ 36 Ar trapped within lunar grains, commonly known as the lunar antiquity indicator, is an important semi -empirical method for dating the time at which lunar samples were exposed to the solar wind. The behavior of the antiquity indicator is governed by the relative implantation fluxes of solar wind -derived 36 Ar ions and indigenously sourced lunar exospheric 40 Ar ions. Previous explanations for the behavior of the antiquity indicator have assumed constancy in both the solar wind ion precipitation and exospheric ion recycling fluxes; however, the presence of a lunar paleomagnetosphere likely invalidates these assumptions. Furthermore, most astrophysical models of stellar evolution suggest that the solar wind flux should have been significantly higher in the past, which would also affect the behavior of the antiquity indicator. Here, we use numerical simulations to explore the behavior of solar wind 36 Ar ions and lunar exospheric 40 Ar ions in the presence of lunar paleomagnetic fields of varying strengths. We find that paleomagnetic fields suppress the solar wind 36 Ar flux by up to an order -of -magnitude while slightly enhancing the recycling flux of lunar exospheric 40 Ar ions. We also find that at an epoch of similar to 2 Gya, the suppression of solar wind 36 Ar access to the lunar surface by a lunar paleomagnetosphere is - somewhat fortuitously - nearly equally balanced by the expected increase in the upstream solar wind flux. These counterbalancing effects suggest that the lunar paleomagnetosphere played a critical role in preserving the correlation between the antiquity indicator and the radioactive decay profile of indigenous lunar 40 K. Thus, a key implication of these findings is that the accuracy of the 40 Ar/ 36 Ar indicator for any lunar sample may be strongly influenced by the poorly constrained history of the lunar magnetic field.

In this article, we propose a method using T(0,1) guided waves combined with coil coding technique to detect defects in buried liquid-filled pipes implemented by an electromagnetic acoustic transducer (EMAT). Due to its non-dispersive properties and the fact that there is no energy loss in nonviscoelastic fluids, the T(0,1) mode is selected for pipe defects detection. The electromagnetic device that generates the circumferential magnetic field is optimized to excite the pure T(0,1) mode. To realize energy enhancement and defect location identification, the electromagnetic acoustic coil is spatially encoded by 11-bit Barker code and the receiver coil is multiplexed consisting of a spatial coded coil and a unit coil. The defect detection is accomplished through time-of-flight (TOF) time-frequency analysis, and the defect location identification is achieved by digital signal processing methods (cross correlation and convolution). The feasibility of this method is verified by the finite element (FE) model and experimental analysis, indicating the defect locating error in a liquid-filled pipes is less than 1%. Overall, the proposed method achieves a high-precision flaw detection and location identification.

Solar wind ion sputtering is one of several non-negligible loss mechanisms for water ice in permanently shadowed regions (PSRs) near the lunar poles. Previous estimates of the solar wind ion flux within south polar PSRs have considered only the ambient solar wind flow and effects of topography. Here, improved maps of crustal magnetic fields in the lunar polar regions are constructed, confirming that more anomalies are present near the south pole than near the north pole. These anomalies have moderate amplitudes, occur over at least two permanently shadowed craters, and correlate approximately with the exposed water ice distribution. Because of the low angle of solar wind incidence near the poles, these anomalies are likely effective in reducing the ion flux, and any resulting water ice loss rate. These anomalies may therefore explain why more water ice is found near the south pole than near the north pole.

The Earth-like planets and moons in our solar system have iron-rich cores, silicate mantles, and a basaltic crust. Differentiated icy moons can have a core and a mantle and an outer water-ice layer. Indirect evidence for several icy moons suggests that this ice is underlain by or includes a water-rich ocean. Similar processes are at work in the interiors of these planets and moons, including heat transport by conduction and convection, melting and volcanism, and magnetic field generation. There are significant differences in detail, though, in both bulk chemical compositions and relative volume of metal, rock and ice reservoirs. For example, the Moon has a small core [similar to 0.2 planetary radii (R-P)], whereas Mercury's is large (similar to 0.8 R-P). Planetary heat engines can operate in somewhat different ways affecting the evolution of the planetary bodies. Mercury and Ganymede have a present-day magnetic field while the core dynamo ceased to operate billions of years ago in the Moon and Mars. Planets and moons differ in tectonic style, from plate-tectonics on Earth to bodies having a stagnant outer lid and possibly solid-state convection underneath, with implications for their magmatic and atmosphere evolution. Knowledge about their deep interiors has improved considerably thanks to a multitude of planetary space missions but, in comparison with Earth, the data base is still limited. We describe methods (including experimental approaches and numerical modeling) and data (e.g., gravity field, rotational state, seismic signals, magnetic field, heat flux, and chemical compositions) used from missions and ground-based observations to explore the deep interiors, their dynamics and evolution and describe as examples Mercury, Venus, Moon, Mars, Ganymede and Enceladus.