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We study the secular behaviour of a test particle orbiting a dominant central body and perturbed by a Miyamoto–Nagai (MN) disc. We derive a quadrupole-level secular Hamiltonian of this system, which involves a dimensionless parameter η that is used to characterize the flattening of MN disc. (The smaller η, the flatter disc; and η = 0 gives the infinitely thin Kuzmin disc.) We find that, in the quadrupole approximation, the perturbation of the MN disc can give rise to the von Zeipel–Lidov–Kozai (ZLK)-like dynamics and depending on the value of η the dynamics has two different manifestations: (i) when η < 1/3, the test particle’s behaviour is similar to that described in the classical ZLK problem. In particular, as η increases from 0 to 1/3, the critical inclination for the large eccentricity oscillations decreases from $26{_{.}^{\circ}}56$ to 0°, ; (ii) when η > 1/3, the orbital evolution of the test particle and the phase-space morphology are opposite to the classical ZLK case. This leads to a striking result that the test particle cannot remain on a near-coplanar orbit if its eccentricity is sufficiently large. However, as η increases further the ZLK-like dynamics would be gradually suppressed by the spherical term in the Hamiltonian. We also survey the global secular dynamics numerically in which the quadrupole approximation is no longer valid.

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International audience; A new method of determining the thickness of mare basalts on the Moon is introduced that is made possible by high-resolution gravity data acquired from NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission. Using a localized multitaper spherical-harmonic analysis, an effective density spectrum is calculated that provides an estimate of the average crustal density as a function of spherical harmonic degree. By comparing the observed effective density spectrum with one generated from a theoretical model, the thickness of mare basalts can be constrained. We assume that the grain density of the basalts is known from remote sensing data and petrologic considerations, we assign a constant porosity to the basalts, and we let both the thickness of the basalts and the density of the underlying crust vary. Using this method, the total thickness of basalts was estimated on the nearside hemisphere, yielding an average of 0.74 km with 1 upper and lower bounds of 1.62 km and 100 m, respectively. The region of Marius Hills, which is a long-lived volcanic complex, is found to have the thickest basalts, with an average of 2.86 km and 1 limits of 3.65 and 1.02 km, respectively. The crust beneath the Mare Imbrium basalts is found to have an atypically high density of about 3000 kg m −3 that we interpret as representing a mafic, unfractured, impact melt sheet.

[1] Size-segregated budgets of soil dust aerosols in Asia for spring 2001 during ACE-Asia were investigated using the NARCM model [Gong et al., 2003b]. Simulated mass size distributions of dust deposition showed a similar size distribution to the dust emission fluxes over the source regions and a decreased peak corresponding to a 1–3 μm diameter range over downwind regions. The simulations suggest that dry deposition was a dominant dust removal process near the source areas and the removal of dust particles by precipitation was the major process over the trans-Pacific transport pathway, where wet deposition exceeded dry deposition by up to a factor of 10. The Asian dust deposition from the atmosphere to the North Pacific Ocean was correlated not only with precipitation over the North Pacific but also with the dust transport patterns. Variations of monthly Asian dust outflow were identified with the latitudinal center of transport at 38°N in March, 42°N in April, and 47°N in May. The monthly trans-Pacific transport patterns of Asian dust in spring were characterized. The transport axis extended around 30°N and 40°N from the east Asian subcontinent to the North Pacific in March. A zonal transport pathway around 40°N was well developed in April over the North Pacific and reached North America. However, the transport in May was separated into two pathways: an eastward zonal path over the North Pacific and a meridional path from the source regions to the northeast Asian continent. On the basis of the averaged dust budgets during spring 2001, it was found that the major sources of Asian dust were located in the desert regions in China and Mongolia with an estimated dust emission of 21.5 tons km−2, and the regions from the Loess Plateau to the North Pacific were sinks of soil dust aerosols with the Loess Plateau as the main sink for Asian dust.