Magnetic crust of Mars

Abstract

[1] The strong magnetic anomalies of Mars require highly magnetic sources in the crust. The bottom of the potentially magnetic layer is constrained by the Curie temperature of its magnetic carriers, and the top of the layer is constrained by the thickness of the uppermost crust that has been demagnetized by the impacts. This paper presents a systematic study of the thermal evolution of the Martian crust and the effects of eight major physical parameters on the thickness of the potentially magnetic layer in the crust. It is shown that the initial upper mantle temperature, the mantle viscosity, and the total radioactive content of Mars are the major parameters that have substantial effects on the thermal state of the crust in the first 1 Gyr of the planet's history. The magnetic source bodies that have been magnetized by the core field during the first 500 Myr are located in the upper about 100-90, 90-80, or 55-45 km of the crust if hematite, magnetite, or pyrrhotite is the major magnetic carrier of the source bodies, respectively. The shock pressures induced in the crust by impacts can demagnetize the uppermost part of the crust. It is demonstrated in this paper that impacts that create craters of diameters larger than $200 km are capable of demagnetizing the entire crust, and those that create craters of diameters less than $50 km can demagnetize the upper 10-20 km of the crust. Detailed studies of the secondary thermal remanent magnetization acquired by deeper parts of the crust, in the absence of the core field but in the presence of the magnetic field of the upper crust, suggest that the secondary magnetization has minor effects on the observed magnetic anomalies of Mars.

Prospects for cosmological collider physics

“…II we review the cosmological collider bispectrum results obtained in Refs. [7,20]. We then discuss overlap with well-known shapes in the literature.…”

“…In particular, Arkani-Hamed and Maldacena derived a general result [7] showing that the entire particle spectrum, including the mass and spin, is reflected in the scaling behavior of various soft limits of primordial nonGaussianities. Moreover, the spin of particles coupled to the inflaton can be geometrically disentangled with 3D surveys, by studying the trispectrum [13,[21][22][23].…”

“…[1]. This setup has been considered by a number of authors [2][3][4][5][6][7][8][9][10][11][13][14][15] and we briefly review their results, with an emphasis on the characteristics relevant for observation.…”

“…For heavier fields in the spectrum, however, the power becomes a complex number, which results in oscillatory signals in the bispectrum, with the "clock signal" being the oscillatory component of this bispectrum. Additionally, nonzero spins generate an additional dependence on the angle between the two modes, creating an incredibly rich phenomenology [7,29].…”

“…These fluctuations are most appreciable when the masses of the fields are of the same order as the Hubble scale H of the inflationary background or less. For this reason, this class of models is called Quasi-single-field (QSF) inflation models [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Fields with these masses may already be present in the spectrum of a UV-completed unification theory, such as the KK spectrum and stringy states in string theory [7]; they may arise from fields that are originally light, but their mass gets uplifted by loop corrections in the inflationary background [16,17] or by coupling to the background curvature.…”