arXiv subjects

P. Grèbol-Tomàs

Publications and source records attributed to P. Grèbol-Tomàs.

3 recordsLinked to original sources

arXiv2025

On the spatiotemporal coincidence of meteorites in recent fall search campaigns

The meteoritical community widely assumes that the probability of finding two meteorites from different falls laying in close proximity is negligible. However, recent studies have suggested that spatiotemporal coincidences may be critical when associating a meteorite with a witnessed fall. In this work, we estimate the number of accumulated meteorites--those resulting from past falls--that are present in landing regions of new falls, while accounting for the effects of terrestrial weathering. We present a simple, fast-computing model to estimate such probability, validated with a Monte Carlo approach based on dark flight computations from real meteorite-dropping fireball data. Considering meteorite masses higher than 10 g, our results indicate that in regions with minimal weathering, like Antarctica, the probability of encountering a previous meteorite within a new fall strewn field may be as high as 75%. In environments with higher weathering rates, like countryside or urban regions, this probability decreases to <1%. When considering the 30 g Lake Frome 006 meteorite coincidence case, the probability of recovering a non-related meteorite with an age of 3.2 kyr from a 0.7 km^2 search area is 6.9%. In the case of the 1 kg Ischgl meteorite, the probability of coincidence with another fresh meteorite of similar mass is 0.06% assuming a large strewn field of 210 km^2. Applied to the Almahata Sitta case, our model predicts a 11.3% of coincidence with a previous meteorite fall. Our results strongly suggest that isotopic dating is essential before associating any meteorite with a witnessed fall.

astro-ph.EP↗

arXiv2025

Mechanical softening and enhanced elasticity of lunar olivine probed via nanoindentation and high-pressure X-ray diffraction measurements

The mechanical properties of minerals in planetary materials are not only interesting from a fundamental point of view but also critical to the development of future space missions. Here we present nanoindentation experiments to evaluate the hardness and reduced elastic modulus of olivine, (Mg, Fe)2SiO4, in meteorite NWA 12008, a lunar basalt. Our experiments suggest that the olivine grains in this lunaite are softer and more elastic than their terrestrial counterparts. Also, we have performed synchrotron-based high-pressure X-ray diffraction (HP-XRD) measurements to probe the compressibility properties of this meteorite and, for comparison purposes, of three ordinary chondrites. The HP-XRD results suggest that the axial compressibility of the orthorhombic $b$ lattice parameter of olivine relative to terrestrial olivine is higher in NWA 12008 and also in the highly-shocked Chelyabinsk meteorite. The origin of the observed differences is discussed. A simple model combining the results of both our nanoindentation and HP-XRD measurements allows us to describe the contribution of macroscopic and chemical-bond related effects, both of which are necessary to reproduce the observed elastic modulus softening. Such joint analysis of the mechanical and elastic properties of meteorites and returned samples opens up a new avenue for characterizing these highly interesting materials.

astro-ph.EP↗

arXiv2023

Bridging the gap in the mass-size relation of compact galaxies with MaNGA

We present the analysis of the full MaNGA DR17 sample to characterize its population of compact galaxies. We focus on galaxies that fill the stellar mass (M$_{\star}$) gap between compact elliptical galaxies (cEs; $8 \lesssim \log \left(M_{\star} / M_{\odot} \right) \lesssim 10$) and compact massive galaxies (CMGs; $10 \lesssim \log \left(M_{\star} / M_{\odot} \right)$). We study their stellar populations and kinematics to reveal how their properties depend on stellar mass. We select compact galaxies in the MaNGA DR17 sample according to their effective radius ($R_e$) and stellar mass. 37 galaxies fulfill our selection criteria in the bridging region between cEs and CMGs. We derive their kinematics and stellar population parameters from the stacked spectra at 1~$R_e$ using a full spectral fitting routine. We then classify the selected compact galaxies in three main groups based on their stellar population properties. One of the groups shows characteristics compatible with relic galaxies, i.e. galaxies that have remained mostly unchanged since their early formation epoch ($z \sim 2$). Another group shows more extended and continuous star formation histories (SFHs). The third group shows a low star-forming rate at initial times, which increases at around $\sim4$ Gyr. We compare the derived properties of the selected galaxies with those of previously studied compact galaxies at different mass ranges. The selected galaxies successfully fill the mass gap between cEs and CMGs. Their properties are compatible with the assumption that the scaling relations of compact galaxies at different mass ranges are related, although galaxies in the first group are clear outliers in the fundamental plane, suggesting different formation mechanisms for this relic population.

astro-ph.GA↗