arXiv subjects

F. Zambon

Publications and source records attributed to F. Zambon.

4 recordsLinked to original sources

arXiv2026

Analysis of Io's tidal response as a function of the properties of the partially molten layer

Io's internal heat is generated by Jupiter-driven tidal dissipation and Laplace resonance. This energy partially melts the mantle, but the melt fraction, depth, and spatial distribution of dissipation remain poorly constrained. Tidal deformation is linked to the mantle's physical state via a parametric approach accounting for melting onset depth and latent heat of fusion. Io is modeled as a three-layer body comprising a fluid core, a viscoelastic mantle, and an elastic lithosphere. The degree-2 potential Love number k2 is computed by solving spheroidal oscillation equations with an adapted California Planetary Geophysics Code (CPGC). Mantle properties (viscosity, shear modulus, Andrade parameter beta) are iteratively updated based on the local melt fraction, and mantle compressibility is explicitly incorporated. Results show a self-consistent shallow-mantle enhancement of tidal heating. Melt presence decreases effective viscosity and increases anelasticity, amplifying upper-mantle dissipation. Reproducing the observed real part of k2 in 1D models requires melt fractions below the rheologically critical threshold. Compressibility yields higher values for the real part of k2, reinforcing this upper bound. Mass flux analysis confirms melt percolation capacity exceeds thermodynamic production, implying efficient drainage. The reference Andrade parameter beta strongly influences the imaginary Love numbers (k2, h2, l2) and the predicted libration amplitude. These constraints support a heterogeneous mantle characterized by a magmatic sponge structure rather than a global magma ocean, establishing a quantitative framework linking Io's interior, partial melting, and tidal dissipation to Juno observations.

astro-ph.EP↗

arXiv2025

Synchronized Eruptions on Io: Evidence of Interconnected Subsurface Magma Reservoirs

On December 27, 2024, Juno's JIRAM infrared experiment observed an unprecedented volcanic event on Io's southern hemisphere, covering a vast region of ~ 65,000 square km, near 73{\deg}S, 140{\deg}E. The total power output is estimated between 140 and 260 TW, potentially the most intense ever recorded, surpassing the brightest eruption at Surt in 2001 (~80 TW). Within that region, only one hot spot was previously known (Pfd454). This feature was earlier estimated to cover an area of 300 square km with a total power output of 34 GW. JIRAM results show that the region produces a power output of 140-260 TW, over 1,000 times higher than earlier estimates. Three adjacent hot spots also exhibited dramatic power increases: P139, PV18, and an unnamed feature south of the main one that surged to ~1 TW, placing all of them among the top 10 most powerful hot spots observed on Io. A temperature analysis of the features supports a simultaneous onset of these brightenings and suggests a single eruptive event propagating beneath the surface across hundreds of kilometers, the first time this has been observed on Io. This implies a connection among the hotspots' magma reservoirs, while other nearby hotspots that have been known to be active in the recent past, such as Kurdalagon Patera, appear unaffected. The simultaneity supports models of massive, interconnected magma reservoirs. The global scale of this event involving multiple hotspots and covering several hundred thousand square km should be considered in the future models of the lithosphere and interior of Io.

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arXiv2023

JIRAM Observations of Volcanic Flux on Io: Distribution and Comparison to Tidal Heat Flow Models

Juno has allowed clear, high-resolution imaging of Io's polar volcanoes using the Jovian Infrared Auroral Mapper (JIRAM) instrument. We have used data from JIRAM's M-band (4.78 um) imager from eleven Juno orbits to construct a global map of volcanic flux. This map provides short-term insight into the spatial distribution of volcanoes and the ways in which high- and low-latitude volcanoes differ. Using spherical harmonic analysis, we quantitatively compare our volcanic flux map to the surface heat flow distribution expected from models of Io's tidal heat deposition (summarized in de Kleer et al. 2019). Our observations confirm previously detected systems of bright volcanoes at high latitudes. Our study finds that both poles are comparably active and that the observed flux distribution is inconsistent with an asthenospheric heating model, although the south pole is viewed too infrequently to establish reliable trends.

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arXiv2017

Spectrophotometric properties of dwarf planet Ceres from the VIR spectrometer on board the Dawn mission

We study the spectrophotometric properties of dwarf planet Ceres in the VIS-IR spectral range by means of hyper-spectral images acquired by the VIR imaging spectrometer on board the NASA Dawn mission. Disk-resolved observations with a phase angle within the $7^{\circ}<α<132^{\circ}$ interval were used to characterize Ceres' phase curve in the 0.465-4.05 $μ$m spectral range. Hapke's model was applied to perform the photometric correction of the dataset, allowing us to produce albedo and color maps of the surface. The $V$-band magnitude phase function of Ceres was fitted with both the classical linear model and H-G formalism. The single-scattering albedo and the asymmetry parameter at 0.55$μ$m are $w=0.14\pm0.02$ and $ξ=-0.11\pm0.08$, respectively (two-lobe Henyey-Greenstein phase function); the modeled geometric albedo is $0.094\pm0.007$; the roughness parameter is $\barθ=29^{\circ}\pm6^{\circ}$. Albedo maps indicate small variability on a global scale with an average reflectance of $0.034 \pm 0.003$. Isolated areas such as the Occator bright spots, Haulani, and Oxo show an albedo much higher than average. We measure a significant spectral phase reddening, and the average spectral slope of Ceres' surface after photometric correction is $1.1\%kÅ^{-1}$ and $0.85\%kÅ^{-1}$ at VIS and IR wavelengths, respectively. Broadband color indices are $V-R=0.38\pm0.01$ and $R-I=0.33\pm0.02$. H-G modeling of the $V$-band magnitude phase curve for $α<30^{\circ}$ gives $H=3.14\pm0.04$ and $G=0.10\pm0.04$, while the classical linear model provides $V(1,1,0^{\circ})=3.48\pm0.03$ and $β=0.036\pm0.002$. The comparison with spectrophotometric properties of other minor bodies indicates that Ceres has a less back-scattering phase function and a slightly higher albedo than comets and C-type objects. However, the latter represents the closest match in the usual asteroid taxonomy.

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