Mars finished forming while the solar nebula was still present, and acquired its primordial atmosphere from this reservoir. The absence of a detectable cometary xenon signature in the present-day Martian atmosphere suggests that the capture of solar nebular gas was significant enough to dilute later cometary contributions. By quantifying the mass of cometary material efficiently retained on Mars, we place a lower bound on the mass of the primordial Martian atmosphere. To test the robustness of our conclusions, we use cometary bombardment data from two independent studies conducted within a solar system evolutionary model consistent with its current structure. Our calculations show that, even under the most conservative scenario, the minimal mass of the primordial martian atmospheres would yield a surface pressure of no less than 2.9 bar. Such a massive nebular envelope is consistent with recent models in which atmospheric capture is strongly enhanced by the presence of heavier species on Mars - due to outgassing or redox buffering with a magma ocean.

The Laser Interferometer Lunar Antenna (LILA), a concept for measuring sub-Hz gravitational waves on the Moon, would use laser strainmeters to obtain extremely sensitive strain measurements from 1 mHz to 1 Hz. With proposed strain sensitivities, LILA would also be able to measure the normal modes of the Moon from 1-10 mHz at high signal-to-noise ratio. Such measurements would enable significant advances in our understanding of both the spherically symmetric and even 3D deep internal structure of the Moon. Strainmeter measurements may even be able to detect the translational mode of the solid inner core of the Moon at frequencies below 0.1 mHz. Inertial seismometers, on the other hand, are unlikely to reach the performance of $\sim10^{-16}$ m/s$^2$/$\sqrt{\mathrm{Hz}}$ required to reliably detect normal modes below 5-10 mHz, even with optimistic assumptions on future projected performance.

To date, the most widespread scenario is that the Earth originated without water and was brought to the planet mainly due to impacts by wet asteroids coming from further out in space. However, many uncertainties remain regarding the exact processes that supply water to inner terrestrial planets. This article explores a new mechanism that would allow water to be efficiently transported to planets without impacts. We propose that primordial asteroids were icy and that when the ice sublimated, it formed a gaseous disk that could then reach planets and deliver water. We have developed a new model that follows the sublimation of asteroids and evolves the subsequent gas disk using a viscous diffusion code. We can then quantify the amount of water that can be accreted onto each planet in a self-consistent manner. We find that this new disk-delivery mechanism can explain the water content on Earth as well as on other planets. Our model shows most of the water being delivered between 20 and 30 Myr after the birth of the Sun. Our scenario implies the presence of a gaseous water disk with substantial mass for 100s Myr, which could be one of the key tracers of this mechanism. We show that such a watery disk could be detected in young exo-asteroid belts with ALMA. We propose that viscous water transport is inevitable and more generic than the impact scenario. We also suggest it is a universal process that may also occur in extrasolar systems. The conditions required for this scenario to unfold are indeed expected to be present in most planetary systems: an opaque proto-planetary disk that is initially cold enough for ice to form in the exo-asteroid belt region, followed by a natural outward-moving snow line that allows this initial ice to sublimate after the dissipation of the primordial disk, creating a viscous secondary gas disk and leading to the accretion of water onto the exoplanets.

Single massive satellites are of great observational interest, as they can produce prominent and potentially detectable signatures. For terrestrial planets and super-Earths, giant impacts in the late stages of formation may generate dense self-gravitating disks - favourable environments for the formation of such satellites. Motivated by this, we explore satellite formation in dense solid-particle disks through three-dimensional N-body simulations, focusing on the effects of disk mass and the surface density exponent. Our results reveal significant variability in the masses and configurations of satellites formed under identical disk parameters, highlighting the stochastic nature of the process. Higher disk masses and flatter surface density profiles favour the formation of more massive satellites. Disks with masses above 0.03 planetary masses typically yield a single dominant satellite, while those between 0.003 and 0.03 tend to form two-satellite systems. On average, the mass of the largest satellite scales linearly with the initial disk mass, in agreement with analytical predictions. We estimate that a disk with a minimal mass of 0.03 planetary masses around a 1.6 Earth-mass planet orbiting a Sun-like star could form an Earth-Moon-like system detectable by telescopes with a photometric precision of 10 parts per million - a level achievable by the James Webb Space Telescope.

In response to ESA Voyage 2050 announcement of opportunity, we propose an ambitious L-class mission to explore one of the most exciting bodies in the Solar System, Saturn largest moon Titan. Titan, a "world with two oceans", is an organic-rich body with interior-surface-atmosphere interactions that are comparable in complexity to the Earth. Titan is also one of the few places in the Solar System with habitability potential. Titan remarkable nature was only partly revealed by the Cassini-Huygens mission and still holds mysteries requiring a complete exploration using a variety of vehicles and instruments. The proposed mission concept POSEIDON (Titan POlar Scout/orbitEr and In situ lake lander DrONe explorer) would perform joint orbital and in situ investigations of Titan. It is designed to build on and exceed the scope and scientific/technological accomplishments of Cassini-Huygens, exploring Titan in ways that were not previously possible, in particular through full close-up and in situ coverage over long periods of time. In the proposed mission architecture, POSEIDON consists of two major elements: a spacecraft with a large set of instruments that would orbit Titan, preferably in a low-eccentricity polar orbit, and a suite of in situ investigation components, i.e. a lake lander, a "heavy" drone (possibly amphibious) and/or a fleet of mini-drones, dedicated to the exploration of the polar regions. The ideal arrival time at Titan would be slightly before the next northern Spring equinox (2039), as equinoxes are the most active periods to monitor still largely unknown atmospheric and surface seasonal changes. The exploration of Titan northern latitudes with an orbiter and in situ element(s) would be highly complementary with the upcoming NASA New Frontiers Dragonfly mission that will provide in situ exploration of Titan equatorial regions in the mid-2030s.

We invert for motions at the surface of Earth's core under spatial and temporal constraints that depart from the mathematical smoothings usually employed to ensure spectral convergence of the flow solutions. Our spatial constraints are derived from geodynamo simulations. The model is advected in time using stochastic differential equations coherent with the occurrence of geomagnetic jerks. Together with a Kalman filter, these spatial and temporal constraints enable the estimation of core flows as a function of length and time-scales. From synthetic experiments, we find it crucial to account for subgrid errors to obtain an unbiased reconstruction. This is achieved through an augmented state approach. We show that a significant contribution from diffusion to the geomagnetic secular variation should be considered even on short periods, because diffusion is dynamically related to the rapidly changing flow below the core surface. Our method, applied to geophysical observations over the period 1950-2015, gives access to reasonable solutions in terms of misfit to the data. We highlight an important signature of diffusion in the Eastern equatorial area, where the eccentric westward gyre reaches low latitudes, in relation with important up/down-wellings. Our results also confirm that the dipole decay, observed over the past decades, is primarily driven by advection processes. Our method allows us to provide probability densities for forecasts of the core flow and the secular variation.

Digital surface model generation using traditional multi-view stereo matching (MVS) performs poorly over non-Lambertian surfaces, with asynchronous acquisitions, or at discontinuities. Neural radiance fields (NeRF) offer a new paradigm for reconstructing surface geometries using continuous volumetric representation. NeRF is self-supervised, does not require ground truth geometry for training, and provides an elegant way to include in its representation physical parameters about the scene, thus potentially remedying the challenging scenarios where MVS fails. However, NeRF and its variants require many views to produce convincing scene's geometries which in earth observation satellite imaging is rare. In this paper we present SparseSat-NeRF (SpS-NeRF) - an extension of Sat-NeRF adapted to sparse satellite views. SpS-NeRF employs dense depth supervision guided by crosscorrelation similarity metric provided by traditional semi-global MVS matching. We demonstrate the effectiveness of our approach on stereo and tri-stereo Pleiades 1B/WorldView-3 images, and compare against NeRF and Sat-NeRF. The code is available at this https URL

The origin of Mercury still remains poorly understood compared to the other rocky planets of the Solar System. One of the most relevant constraints that any formation model has to fulfill refers to its internal structure, with a predominant iron core covered by a thin silicate layer. This led to the idea that it could be the product of a mantle stripping caused by a giant impact. Previous studies in this line focused on binary collisions involving bodies of very different masses. However, such collisions are actually rare in N-body simulations of terrestrial planet formation, whereas collisions involving similar mass bodies appear to be more frequent. Here, we perform smooth particle hydrodynamics simulations to investigate the conditions under which collisions of similar mass bodies are able to form a Mercury-like planet. Our results show that such collisions can fulfill the necessary constraints in terms of mass (0.055 $M_\oplus$) and composition (30/70 silicate-to-iron mass ratio) within less than 5%, as long as the impact angles and velocities are properly adjusted according to well established scaling laws.

Recent models of solar system formation suggest that a dynamical instability among the giant planets happened within the first 100 Myr after disk dispersal, perhaps before the Moon-forming impact. As a direct consequence, a bombardment of volatile-rich impactors may have taken place on Earth before internal and atmospheric reservoirs were decoupled. However, such a timing has been interpreted to potentially be at odds with the disparate inventories of Xe isotopes in Earth's mantle compared to its atmosphere. This study aims to assess the dynamical effects of an Early Instability on the delivery of carbonaceous asteroids and comets to Earth, and address the implications for the Earth's volatile budget. We perform 20 high-resolution dynamical simulations of solar system formation from the time of gas disk dispersal, each starting with 1600 carbonaceous asteroids and 10000 comets, taking into account the dynamical perturbations from an early giant planet instability. Before the Moon-forming impact, the cumulative collision rate of comets with Earth is about 4 orders of magnitude lower than that of carbonaceous asteroids. After the Moon-forming impact, this ratio either decreases or increases, often by orders of magnitude, depending on the dynamics of individual simulations. An increase in the relative contribution of comets happens in 30\% of our simulations. In these cases, the delivery of noble gases from each source is comparable, given that the abundance of 132Xe is 3 orders of magnitude greater in comets than in carbonaceous chondrites. The increase in cometary flux relative to carbonaceous asteroids at late times may thus offer an explanation for the Xe signature dichotomy between the Earth's mantle and atmosphere.

The Laser Interferometer Lunar Antenna (LILA), a concept for measuring sub-Hz gravitational waves on the Moon, would use laser strainmeters to obtain extremely sensitive strain measurements from 1 mHz to 1 Hz. With proposed strain sensitivities, LILA would also be able to measure the normal modes of the Moon from 1-10 mHz at high signal-to-noise ratio. Such measurements would enable significant advances in our understanding of both the spherically symmetric and even 3D deep internal structure of the Moon. Strainmeter measurements may even be able to detect the translational mode of the solid inner core of the Moon at frequencies below 0.1 mHz. Inertial seismometers, on the other hand, are unlikely to reach the performance of $\sim10^{-16}$ m/s$^2$/$\sqrt{\mathrm{Hz}}$ required to reliably detect normal modes below 5-10 mHz, even with optimistic assumptions on future projected performance.

Cosmogenic isotopes provide the only quantitative proxy for analyzing the long-term solar variability over a centennial timescale. While essential progress has been achieved in both measurements and modeling of the cosmogenic proxy, uncertainties still remain in the determination of the geomagnetic dipole moment evolution. Here we improve the reconstruction of solar activity over the past nine millennia using a multi-proxy approach. We used records of the 14C and 10Be cosmogenic isotopes, current numerical models of the isotope production and transport in Earth's atmosphere, and available geomagnetic field reconstructions, including a new reconstruction relying on an updated archeo-/paleointensity database. The obtained series were analyzed using the singular spectrum analysis (SSA) method to study the millennial-scale trends. A new reconstruction of the geomagnetic dipole field moment, GMAG.9k, is built for the last nine millennia. New reconstructions of solar activity covering the last nine millennia, quantified in sunspot numbers, are presented and analyzed. A conservative list of grand minima and maxima is provided. The primary components of the reconstructed solar activity, as determined using the SSA method, are different for the series based on 14C and 10Be. These primary components can only be ascribed to long-term changes in the terrestrial system and not to the Sun. They have been removed from the reconstructed series. In contrast, the secondary SSA components of the reconstructed solar activity are found to be dominated by a common ~2400-yr quasi-periodicity, the so-called Hallstatt cycle, in both the 14C and 10Be based series. This Hallstatt cycle thus appears to be related to solar activity. Finally, we show that the grand minima and maxima occurred intermittently over the studied period, with clustering near highs and lows of the Hallstatt cycle, respectively.

Tsunamis can trigger internal gravity waves (IGWs) in the ionosphere, perturbing the Total Electron Content (TEC) - referred to as Traveling Ionospheric Disturbances (TIDs) that are detectable through the Global Navigation Satellite System (GNSS). The GNSS are constellations of satellites providing signals from Earth orbit - Europe's Galileo, the United States' Global Positioning System (GPS), Russia's Global'naya Navigatsionnaya Sputnikovaya Sistema (GLONASS) and China's BeiDou. The real-time detection of TIDs provides an approach for tsunami detection, enhancing early warning systems by providing open-ocean coverage in geographic areas not serviceable by buoy-based warning systems. Large volumes of the GNSS data is leveraged by deep learning, which effectively handles complex non-linear relationships across thousands of data streams. We describe a framework leveraging slant total electron content (sTEC) from the VARION (Variometric Approach for Real-Time Ionosphere Observation) algorithm by Gramian Angular Difference Fields (from Computer Vision) and Convolutional Neural Networks (CNNs) to detect TIDs in near-real-time. Historical data from the 2010 Maule, 2011 Tohoku and the 2012 Haida-Gwaii earthquakes and tsunamis are used in model training, and the later-occurring 2015 Illapel earthquake and tsunami in Chile for out-of-sample model validation. Using the experimental framework described in the paper, we achieved a 91.7% F1 score. Source code is available at: this https URL Our work represents a new frontier in detecting tsunami-driven IGWs in open-ocean, dramatically improving the potential for natural hazards detection for coastal communities.

The distinctive set of Saturnian small satellites, Aegaeon, Methone, Anthe, and Pallene, constitutes an excellent laboratory to understand the evolution of systems immersed in co-orbital dusty rings/arcs, subjected to perturbations from larger satellites and non-gravitational forces. In this work, we carried out a comprehensive numerical exploration of the long-term evolution of Pallene and its ring. Through frequency map analysis, we characterised the current dynamical state around Pallene. A simple tidal evolution model serves to set a time frame for the current orbital configuration of the system. With detailed short and long-term N-body simulations we determine whether Pallene is currently in resonance with one or more of six of Saturn's major moons. We analysed a myriad of resonant arguments extracted from the direct and indirect parts of the disturbing function, finding that Pallene is not in mean motion resonance from the present up to 5~Myr into the future; nonetheless, some resonant arguments exhibit intervals of libration and circulation at different timescales and moon pairings. We studied the dynamical evolution of micrometric particles forming the ring, considering gravitational and non-gravitational forces. Non-gravitational forces are responsible for particles vertical excursions and outward migration. By estimating the satellite's mass production rate, we find that Pallene could be responsible for keeping its ring in steady-state only if it is mainly composed of large micrometre-sized particles. If mainly composed of particles with a few micrometres for which Pallene is the only source, the ring will spread out, both radially and vertically, until it finally disappears.

Fireballs are infrequently recorded by seismic sensors on the ground. If recorded, they are usually reported as one-off events. This study is the first seismic bulk analysis of the largest single fireball data set, observed by the Desert Fireball Network (DFN) in Australia in the period 2014-2019. The DFN typically observes fireballs from cm-m scale impactors. We identified 25 fireballs in seismic time series data recorded by the Australian National Seismograph Network (ANSN). This corresponds to 1.8% of surveyed fireballs, at the kinetic energy range of 10$^6$ to 10$^{10}$ J. The peaks observed in the seismic time series data were consistent with calculated arrival times of the direct airwave or ground-coupled Rayleigh wave caused by shock waves by the fireball in the atmosphere (either due to fragmentation or the passage of the Mach cone). Our work suggests that identification of fireball events in the seismic time series data depends both on physical properties of a fireball (such as fireball energy and entry angle in the atmosphere) and the sensitivity of a seismic instrument. This work suggests that fireballs are likely detectable within 200 km direct air distance between a fireball and seismic station, for sensors used in the ANSN. If each DFN observatory had been accompanied by a seismic sensor of similar sensitivity, 50% of surveyed fireballs could have been detected. These statistics justify the future consideration of expanding the DFN camera network into the seismic domain.

We present the first density model of Stromboli volcano (Aeolian Islands, Italy) obtained by simultaneously inverting land-based (543) and sea-surface (327) relative gravity data. Modern positioning technology, a 1 * 1 m digital elevation model, and a 15 * 15 m bathymetric model made it possible to obtain a detailed 3-D density model through an iteratively reweighted smoothness-constrained least-squares inversion that explained the land-based gravity data to 0.09 mGal and the sea-surface data to 5 mGal. Our inverse formulation avoids introducing any assumptions about density magnitudes. At 125 m depth from the land surface, the inferred mean density of the island is 2380 kg m-3, with corresponding 2.5 and 97.5 percentiles of 2200 and 2530 kg m-3. This density range covers the rock densities of new and previously published samples of Paleostromboli I, Vancori, Neostromboli and San Bartolo lava flows. High-density anomalies in the central and southern part of the island can be related to two main degassing faults crossing the island (N41 and N64) that are interpreted as preferential regions of dyke intrusions. In addition, two low-density anomalies are found in the northeastern part and in the summit area of the island. These anomalies seem to be geographically related with past paroxysmal explosive phreato-magmatic events that have played important roles in the evolution of Stromboli Island by forming the Scari caldera and the Neostromboli crater, respectively.

The presence of rings around a transiting planet can cause its radius to be overestimated and lead to an underestimation of its density if the mass is known. We employ a Bayesian framework to show that the anomalously low density ($\sim$0.09 g cm${^{-3}}$) of the transiting long-period planet HIP$\,$41378$\,f$ might be due to the presence of opaque circum-planetary rings. Given our adopted model priors and data from the K2 mission, we find the statistical evidence for the ringed planet scenario to be comparable to that of the planet-only scenario. The ringed planet solution suggests a larger planetary density of $\sim$1.23$\,$g$\,$cm$^{-3}$ similar to Uranus. The associated ring extends from 1.05 to 2.59 times the planetary radius and is inclined away from the sky-plane by $\sim$25$^\mathrm{o}$. Future high-precision transit observations of HIP$\,$41378$\,f$ would be necessary to confirm/dismiss the presence of planetary rings.

Imaging geological structures through cosmic muon radiography is a newly developed technique particularly interesting in volcanology. Here we show that muon radiography may be efficient to detect and characterize mass movements in shallow hydrothermal systems of low-energy active volcanoes like the La Soufri\`ere lava dome. We present an experiment conducted on this volcano during the Summer $2014$ and bring evidence that huge density changes occurred in three domains of the lava dome. Depending on their position and on the medium porosity the volumes of these domains vary from $1 \times 10^6 \; \mathrm{m}^3$to$7 \times 10^6 \; \mathrm{m}^3$. However, the mass changes remain quite constant, two of them being negative ($\Delta m \approx -0.6 \times 10^9 \; \mathrm{kg}$) and a third one being positive ($\Delta m \approx +2 \times 10^9 \; \mathrm{kg}$). We attribute the negative mass changes to the formation of steam in shallow hydrothermal reservoir previously partly filled with liquid water. This coincides with the apparition of new fumaroles on top of the volcano. The positive mass change is synchronized with the negative mass changes indicating that liquid water probably flowed from the two reservoirs invaded by steam toward the third reservoir.

For reasons of computational constraint, most global ocean circulation models used for Earth System Modeling still rely on parameterizations of sub-grid processes, and limitations in these parameterizations affect the modeled ocean circulation and impact on predictive skill. An increasingly popular approach is to leverage machine learning approaches for parameterizations, regressing for a map between the resolved state and missing feedbacks in a fluid system as a supervised learning task. However, the learning is often performed in an `offline' fashion, without involving the underlying fluid dynamical model during the training stage. Here, we explore the `online' approach that involves the fluid dynamical model during the training stage for the learning of baroclinic turbulence and its parameterization, with reference to ocean eddy parameterization. Two online approaches are considered: a full adjoint-based online approach, related to traditional adjoint optimization approaches that require a `differentiable' dynamical model, and an approximately online approach that approximates the adjoint calculation and does not require a differentiable dynamical model. The online approaches are found to be generally more skillful and numerically stable than offline approaches. Others details relating to online training, such as window size, machine learning model set up and designs of the loss functions are detailed to aid in further explorations of the online training methodology for Earth System Modeling.

The origins of Uranus and Neptune are not fully understood. Their inclined rotation axes -- obliquities -- suggest that they experienced giant impacts during their formation histories. Simulations modeling their accretion from giant impacts among ~5 Earth masses planetary embryos -- with roughly unity impactors' mass ratios -- have been able to broadly match their current masses, final mass ratio, and obliquity. However, due to angular momentum conservation, planets produced in these impacts tend to rotate too fast, compared to Uranus and Neptune. One potential solution for this problem consists of invoking instead collisions of objects with large mass ratios (e.g. a proto-Uranus with 13 Mearth and an embryo of 1 Mearth). Smooth-particle hydrodynamics simulations show that in this scenario final planets tend to have rotation periods more consistent with those of Uranus and Neptune. Here we performed a large suite of N-body numerical simulations modelling the formation of Uranus and Neptune to compare these different dynamical views. Our simulations start with a population of protoplanets and account for the effects of type-I migration, inclination and eccentricity tidal damping. Our results show that although scenarios allowing for large impactors' mass ratio favour slower rotating planets, the probability of occurring collisions in these specific simulations is significantly low. This is because gas tidal damping is relatively less efficient for low-mass embryos (<~1 Merath) and, consequently, such objects are mostly scattered by more massive objects (~13 Mearth) instead of colliding with them. Altogether, our results show that the probability of broadly matching the masses, mass ratio, and rotation periods of Uranus and Neptune in these two competing formation scenarios is broadly similar, within a factor of ~2, with overall probabilities of the order of ~0.1-1%.