Gaetano Di Achille

The Orientale Basin, centered at ~19°S, ~93°W, is one of the most characteristic features on the surface of the Moon. Constituted by three concentric rings, the largest of which is between 930 and 950 km in diameter, this multi-ring basin is one of the youngest large impact basins on the Moon (Orientale is estimated to date back ~3.81 Ga) and one of the best-preserved large basins in the entire Solar System. Inside, its central depression hosts a relatively thin infilling of dark, smooth material interpreted as a mare basalt, whilst outside the outermost ring an ejecta blanket drapes the surrounding topography sometimes reaching over 1,400 km from the center of the basin. Throughout the years, the importance of the Orientale Basin has led to the creation of several geological maps at various scales, none of which, however, a scale greater than 1:200,000. Additionally, these maps never try to put together the two main methodological approaches adopted internationally up to this point at global scale for the Moon. Our work tries to bridge this gap by presenting a new medium-to-large-scale (1:118,000) geological map of both the inner and outer facies which makes use of a combination between a traditional planetary geological scheme and a more morphometric criterion.The map was created with the latest long-time stable release of QGIS (vrs. 3.40) mainly using the 59 m/px resolution Lunar Orbiter Laser Altimeter (LOLA)-Kaguya Shaded Relief and the 59 m/px resolution LOLA-Kaguya DEM. These two datasets, only covering latitudes within ±60° were utilized to distinguish the different units and subunits based off their general morphology, textures, and locations, but also to identify the structures. The 100 m/px resolution, grayscale mosaic of the Lunar Reconnaissance Orbiter Wide Angle Camera (LROC-WAC) and the 118 m/px LOLA elevation model were additionally used to make up for the missing portion of the LOLA-Kaguya datasets. The Clementine UVVIS colored mosaic (200 m/px) and the mineral abundance (wt% of Ol, Cpx, Opx, Pl, FeO) Kaguya mosaics also allowed to add a layer of information regarding differences in composition of apparently visually uniform features and terrains.We managed to identify over 20 between units and sub-units that we grouped based on the terrain or morphological feature they are related to (e.g. crater, mare, …), and over 10 classes of structures. Our final product represents the highest resolution map available for the Orientale Basin and when compared with already existing medium-scale maps, appears to depict with more detail and accuracy its complexity. Additionally, we made use of a color vision deficiency-friendly color scheme to make the map more accessible also to that part of the population having limited sensitivity to colors.

The knowledge of Mercury's crater record has significantly evolved during the last decade thanks to the MESSENGER mission, which enabled the implementation of updated global crater catalogs by allowing the identification of a wealth of previously unknown impact structures. Particularly, recent re-examination of MESSENGER data led to the identification of tens of previously unreported large (D>150 km) impact basins. These large basins have not yet been studied in detail despite their significant geological and geophysical importance. Here, we present geological, topographical, structural, compositional, and geophysical investigations of one (maybe the largest) of these basins. The basin has not yet an International Astronomical Union (IAU) name but it has been reported as b56 or Lennon-Picasso basin in the published literature. The basin has an approximate diameter of more than 1500 kilometers and is centered at about 15S, 50E, located north-westward of Rembrandt basin. However, the most external structures associated to this basin extend fairly more than 1500-km form its center, suggesting a diameter closer if not higher than 2000 km, thus equivalent if not bigger than Caloris basin, known as the largest Mercury’s basin. Geology, tectonics, and composition of this basin have been investigated by using photointerpretation and remote sensing techniques applied to all the available data. Visible imagery from MDIS camera has been integrated with Digital Elevation Models (DEM), spectral data (color mosaics and data from MASCS), and gravity data from the Radio Science (RS) experiment onboard of MESSENGER into Geographic Information System (GIS) environment. DEM and slope maps highlight the annular terraced floor of the basin, suggesting that this may have formed as a peak ring or multiring structure. The basin is defined by several major lineaments (up to thousands of km long) consisting of a series of tectonic structures encompassing a broadly circular topographic low corresponding to the internal floor of the basin. This central region shows a gravity anomaly and a low crustal thickness with respect to the surrounding areas. The impact triggered volcanic activity since the floor presents the typical characteristics of other volcanic infilled Mercury’s basins: a smoother texture and lower albedo with respect to the surroundings regions, radial faults, wrinkle ridges and concentric circular lobate scarps, and spectral signatures from MASCS data. Most importantly, our results show that the tectonics associated to this basin, along as that of many other recently discovered large basins, might have had a regional and global significance, which has been so far overlooked. Indeed, these impact-related structures have been so far included in current estimates of Mercury’s contraction, most likely leading to its overestimation. After presenting the above mentioned lines of evidence we will discuss the implications of the tectonics of Mercury’s large basins for the planet global tectonics and contraction estimates.

Several missions to Venus have recently been selected for launch, opening a new era for the exploration of the planet. A key question these missions seek to address is whether Venus is geologically active today. Detecting active volcanism on Venus would contribute to a better understanding of volcanic and atmospheric processes on Earth. The Analogs for VENus' GEologically Recent Surfaces (AVENGERS) initiative provides a comparative framework for the identification and analysis of terrestrial analog sites relevant to recent and possibly ongoing volcanic activity on Venus. Although this review focuses on terrestrial analogs for Venus exploration, the AVENGERS initiative also includes investigations that use Venus and Earth as analogs to better understand the evolution of terrestrial exoplanets. In addition, the AVENGERS initiative facilitates international collaboration by connecting Venus mission teams with the broader planetary and exoplanetary science communities. This review describes the scientific context of AVENGERS, details the selection criteria for terrestrial analog sites, and summarizes a set of suitable locations. Methodological approaches in analog studies that support the interpretation of Venus observations are also discussed.

Large topographic rises on Venus are regions thought to be formed in response to the presence of a mantle plume or mantle upwelling, equivalent to hot spots on Earth. In this work, we study the geology and evolution of one of these large topographic rises, Imdr Regio, based on geologic mapping and analysis of geophysical data of the area. Imdr Regio presents a complex structure with two very different areas: (a) an elevated southeast area that is dominated by volcanism associated with Idunn Mons, a large volcano that has been proposed as a site of recent or even active volcanism; (b) another elevated area in the northwest area that also has a large volcano (Arasy Mons), but that is dominated by volcanism and tectonic activity associated with the formation of the Olapa Chasma rift system. These two very differentiated topographically elevated areas also exhibit differences in their geology, volcanic and tectonic style, and geophysical characteristics, which leads us to suggest that more than the classic volcano‐dominated rise classification attributed to Imdr Regio the area could rather be considered as an intermediate or hybrid volcano‐rift dominated large topographic rise. The evaluation of the different genetic scenarios and its correspondence with the observed geology in the area suggests that the complex geology of Imdr Regio could be better explained if we consider models of hot spot evolution that involve the presence of several mantle plumes or secondary upwellings derived from a mantle plume emplaced at a deeper rheological boundary.

The recently selected NASA VERITAS and DAVINCI missions, the ESA EnVision, the Roscosmos Venera‐D will open a new era in the exploration of Venus. One of the key targets of the future orbiting and in situ investigations of Venus is the identification of volcanically active areas on the planet. The study of the areas characterized by recent or ongoing volcano‐tectonic activity can inform us on how volcanism and tectonism are currently evolving on Venus. Following this key target, Brossier et al. (2022, https://doi.org/10.1029/2022GL099765) extend the successful approach and methodology used by previous works to Ganis Chasma in Atla Regio. Here we comment on the main results published in Brossier et al. (2022, https://doi.org/10.1029/2022GL099765) and discuss the important implications of their work for the future orbiting and in situ investigation of Venus. Their results add further lines of evidence indicating possibly recent volcanism on Venus.

The recently selected NASA VERITAS and DAVINCI missions, the ESA EnVision, the Roscosmos Venera-D will open a new era in the exploration of Venus. One of the key targets of the future orbiting and in-situ investigations of Venus is the identification of volcanically active areas on the planet. The study of the areas characterized by recent or ongoing volcano-tectonic activity can inform us on how volcanism and tectonism are currently evolving on Venus. Following this key target, the manuscript by Brossier et al. (2022) (https://doi.org/10.1029/2022GL099765) extends the successful approach and methodology used by previous works to Ganis Chasma in Atla Regio. We comment here on the main results of the manuscript published by Brossier et al. (2022) (https://doi.org/10.1029/2022GL099765) and discuss the important implications of their work for the future orbiting and in-situ investigation of Venus. Their results add further lines of evidence indicating possibly recent volcanism on Venus.

Martian deltaic deposits are good indicators of water distribution and provide insight into the climate evolution of Mars [1]. A notable case is the fan deposit located in Jezero crater, currently being studied by the Perseverance rover. Hydrated silica-bearing deposits were identified in this area [2, 3, 4], and the overall stratigraphy and morphology point to an evolution passing through a progradation and a transgression phase, to an erosion episode [5]. All these evidences suggest that this deposit was formed by fluvio-deltaic activity in an ancient lake basin [6] during the late Noachian or early Hesperian epochs [7]. After its formation, the deposit likely suffered a complex and profound exhumation [8] which we will try to constrain through a mass balance analysis.Here, we present the first results of a project seeking to understand the depositional and post-depositional evolution of the Jezero delta, including the study of its hydrographic basin [9]. We will focus on a mass-balance survey, analyzing and comparing the volume of sediments that were eroded from the basin and deposited into the crater. We integrate HRSC, CTX and HiRISE data to create a regional DTM and orthophoto map covering the Jezero crater and its drainage basin. These datasets enable us to estimate the volume of sediments eroded from the drainage basin, as well as the present-day volume of the fan deposit. Finally, we will apply the mass balance model introduced by [10], aiming at evaluating putative sediment offshore loss and post-depositional fan erosion. This will allow to infer the initial volume of the deltaic deposit and test different lake water levels. [1] Di Achille, G. and Hynek, B. M. (2010). Nature Geoscience, Vol. 3 (7),459-463. [2] Pan, L., et al, (2021). Planet. Sci. J., 2(2), 65., [3] Horgan, B., et al, (2020). Icarus, 339. [4] Mangold, N., (2007). J. Geophys. Res. 112(8). [5] Goudge, T. A., et al. (2018). Icarus, 301 58–75. [6] Fassett, C. I., & Head, J. W. (2005). Geophys. Res. Let., 32(14), 1–5., [7] Mangold, N., et al, (2021). Science 10.1126, [8] Quantin-Nataf, C., et al (2021). 52nd LPSC, [9] Goudge, T. A., et al, (2015). J. Geophys. Res. Planets 120., [10] Vaz, D. A., et al, (2020). Earth Planet. Sci. Lett., Vol. 533.

The Mercury Orbiter Radio Science Experiment (MORE) of the ESA mission BepiColombo will provide an accurate estimation of Mercury’s gravity field and rotational state, improved tests of general relativity, and a novel deep space navigation system. The key experimental setup entails a highly stable, multi-frequency radio link in X and Ka band, enabling two-way range rate measurements of 3 micron/s at nearly all solar elongation angles. In addition, a high chip rate, pseudo-noise ranging system has already been tested at 1-2 cm accuracy. The tracking data will be used together with the measurements of the Italian Spring Accelerometer to provide a pseudo drag free environment for the data analysis. We summarize the existing literature published over the past years and report on the overall configuration of the experiment, its operations in cruise and at Mercury, and the expected scientific results.