The SIMBIO-SYS (Spectrometer and Imaging for MPO BepiColombo Integrated Observatory SYStem) is a complex instrument suite part of the scientific payload of the Mercury Planetary Orbiter for the ...BepiColombo mission, the last of the cornerstone missions of the European Space Agency (ESA) Horizon + science program.
The SIMBIO-SYS instrument will provide all the science imaging capability of the BepiColombo MPO spacecraft. It consists of three channels: the STereo imaging Channel (STC), with a broad spectral band in the 400-950 nm range and medium spatial resolution (at best 58 m/px), that will provide Digital Terrain Model of the entire surface of the planet with an accuracy better than 80 m; the High Resolution Imaging Channel (HRIC), with broad spectral bands in the 400-900 nm range and high spatial resolution (at best 6 m/px), that will provide high-resolution images of about 20% of the surface, and the Visible and near-Infrared Hyperspectral Imaging channel (VIHI), with high spectral resolution (6 nm at finest) in the 400-2000 nm range and spatial resolution reaching 120 m/px, it will provide global coverage at 480 m/px with the spectral information, assuming the first orbit around Mercury with periherm at 480 km from the surface. SIMBIO-SYS will provide high-resolution images, the Digital Terrain Model of the entire surface, and the surface composition using a wide spectral range, as for instance detecting sulphides or material derived by sulphur and carbon oxidation, at resolutions and coverage higher than the MESSENGER mission with a full co-alignment of the three channels. All the data that will be acquired will allow to cover a wide range of scientific objectives, from the surface processes and cartography up to the internal structure, contributing to the libration experiment, and the surface-exosphere interaction. The global 3D and spectral mapping will allow to study the morphology and the composition of any surface feature. In this work, we describe the on-ground calibrations and the results obtained, providing an important overview of the instrument performances. The calibrations have been performed at channel and at system levels, utilizing specific setup in most of the cases realized for SIMBIO-SYS. In the case of the stereo camera (STC), it has been necessary to have a validation of the new stereo concept adopted, based on the push-frame. This work describes also the results of the Near-Earth Commissioning Phase performed few weeks after the Launch (20 October 2018). According to the calibration results and the first commissioning the three channels are working very well.
In this paper we present a crater age determination of several terrains associated with the Raditladi and Rachmaninoff basins. These basins were discovered during the first and third MESSENGER flybys ...of Mercury, respectively. One of the most interesting features of both basins is their relatively fresh appearance. The young age of both basins is confirmed by our analysis on the basis of age determination via crater chronology. The derived Rachmaninoff and Raditladi basin model ages are about 3.6
Ga and 1.1
Ga, respectively. Moreover, we also constrain the age of the smooth plains within the basins' floors. This analysis shows that Mercury had volcanic activity until recent time, possibly to about 1
Ga or less. We find that some of the crater size-frequency distributions investigated suggest the presence of a layered target. Therefore, within this work we address the importance of considering terrain parameters, as geo-mechanical properties and layering, into the process of age determination. We also comment on the likelihood of the availability of impactors able to form basins with the sizes of Rachmaninoff and Raditladi in relatively recent times.
► We constrain the formation age of Rachmaninoff and Raditladi basins on Mercury. ► We show the importance of taking into account the properties of the terrains for a reliable age determination. ► We provide age constraints for the recent episodes of volcanism.
Mass accretion rate on Earth is an important tool to discriminate the extraterrestrial nature of particles or isotopes found in different environments on the ground. In this context, the knowledge of ...the micrometeoroid flux arriving in our atmosphere is a key parameter and it needs to be calibrated. We provide a new calibration of the flux of submillimeter particles impacting the Earth in the mass range from 10 super(-9) to 10 super(-4) g, derived by computing a specific scaling law for impact craters on the Long Duration Exposure Facility (LDEF). We use the hydrocode iSALE to calculate the outcome of impacts on LDEF, adopting realistic impact velocities for dust particles derived from the numerical integration of their trajectories assuming either asteroidal or cometary origin. We estimate a particle mass accretion rate of (7.4 + or - 1.0) x 10 super(6) kg yr super(-1) if the Main Belt is assumed as the major source of dust, while it reduces to (4.2 + or - 0.5) x 10 super(6) kg yr super(-1) if cometary dust dominates. These values agree with the estimates provided by independent measurements made on ice core and ocean sediments and based on the abundance of some elements in the samples.
Arcadia Planitia, a region in the northern midlatitudes of Mars, displays an uncommonly high abundance of simple craters with a concentric morphology, which is indicative of layering beneath the ...surface. Radar measurements suggest that the near surface layers could be made of excess water ice. In this study, we select two of these impact structures of similar size (Dc ~ 500 m), model their formation through iSALE shock physics code, and investigate the dependence of the final crater morphology on the material model parameters (cohesion and friction coefficient). Our parameter study shows that the intact and damaged cohesions of the nonporous ice play a fundamental role to obtain a good fit between our models and the topographic profiles taken from the digital terrain models in terms of crater diameter, crater wall inclination, and depth and size of the upper terrace. The central pit shape is instead controlled by the damaged friction coefficient of the basaltic crust, but it is mainly affected by projectile density and speed. Our results confirm that two layers of relatively pure water ice, each with different rheology and porosity, can explain the unique double‐terraced morphology of impact craters in Arcadia Planitia. The low values of cohesion we find for the ice might point to snowfall as emplacement mechanism in the region. The different thicknesses of the ice layers in the two crater areas seem to suggest variations in ice deposition and/or evolution history across Arcadia Planitia.
Plain Language Summary
Impact craters are described by a bowl‐shaped morphology at smaller sizes. Any departure from such a shape provides insight into subsurface target properties, including changes in density, strength, water content, porosity, and composition. In particular, the presence of steps (or “terraces”) along the walls of simple craters provides a straightforward example of complexity within the planetary crusts, and indicates an abrupt transition from upper, weaker layers to deeper, stronger material. Using numerical modeling, we studied two examples of terraced craters in Arcadia Planitia, Mars, to derive information about the rheological properties of the upper Martian crust. This analysis supports radar remote sensing measurements and suggests shallow ice‐rich layers in Martian midlatitudes terrains could plausibly cause the terraces observed in these craters. The distribution and properties of water ice are important for understanding Mars' climatic history, as well as the availability of in‐situ resources for future human exploration.
Key Points
We performed numerical modeling to investigate the formation of simple craters with a concentric morphology on Mars
The central pit dimensions are controlled both by the target material (damaged friction coefficient) and by the impactor (size and density)
Our modeling shows water ice over basement bedrock can create wall terraces in simple craters
The surface of (21) Lutetia is highly complex with significant interactions between ancient and more recent structures. This work attempts to summarize the surface geomorphology observed using the ...high resolution images from OSIRIS, the imaging system onboard the European Space Agency's Rosetta spacecraft. A wide range of surface morphologies are seen including heavily cratered terrain, extensive sets of lineaments, young impact craters, and a ridge, the height of which is more than 1/5th of the mean radius of the body. Very young and very old terrains (as inferred from crater densities) are seen in close proximity. The longest continuous lineament is over 80km long. The lineaments show regional-dependent organization and structure. Several categories of lineament can be described. Lineaments radial to impact craters as seen on other asteroidal bodies are mostly absent. Although the lineaments may be of seismic origin (and possibly the result of several impact-induced events), impacts producing recent large craters place constraints on seismic phenomena. In particular, stronger attenuation of shocks than seen on other asteroidal bodies seems to be required. Inhomogeneous energy transport, possibly matching observed inhomogeneous ejecta deposition may offer explanations for some of the observed phenomena. Some impact craters show unusual forms, which are probably the result of impact into a surface with relief comparable to the resultant crater diameter and/or oblique impact. There is evidence that re-surfacing through landslides has occurred at several places on the object.
► Description of geomorphology of asteroid (21) Lutetia from Rosetta/OSIRIS data. ► Extensive sets of lineaments with implications for impact-induced seismic activity. ► Wide range of surface ages and surface phenomena with highly complex interactions.
The flyby of the Main Belt asteroid Lutetia by the Rosetta spacecraft allows the camera OSIRIS to obtain very good images of about half of the body at the maximum resolution of 60m per pixel. From ...the images and radio-science experiment, a density of about (3.4±0.3)g/cm3 has been inferred for the asteroid.
Many impact craters have been observed on the surface of Lutetia and the largest, named Massilia, has a diameter of about 55km. Relative to the size of Lutetia (the longest axis is approximately 126km) the crater represents one of the dominating features on its surface. Whether or not the impact that formed Massilia affected the entire asteroid can be only evaluated via numerical modeling, with hydrocodes, of the impact process. The results of a suite of iSALE simulations are compared with the crater profile derived from the Digital Terrain Model of the observed surface. The best match to the DTM of the crater with hydrocode simulations has allowed to determine a value of 7.5km for the impactor diameter, which suggests a primordial origin of Lutetia due to the low probability of such an impact event.
A second interesting impact structure has been identified nearby Massilia within the North Pole Crater Cluster. The crater has a diameter of 24km and it lies over a larger crater of the North Pole Crater Cluster. This is strongly suggestive of a very young structure on Lutetia. The numerical simulations of this feature constrain the impactor to be 3.8km in diameter, assuming the same material properties for target and impactor as in the model of the formation of Massilia.
► Hydrocode iSALE simulations of the largest crater on the asteroid Lutetia. ► iSALE simulations of one component of the North Polar Crater Cluster having the diameter of 24km. ► The largest crater of 55km has been simulated with an impactor of 7.5km and the 24km with an impactor of 3.8km. ► The hydrocode fit the two craters diameter/depth without assuming a crust. ► A pre-fracturated layer could have been created in the largest crater generation.
Inflation is an emplacement process of lava flows, where a thin visco-elastic layer, produced at an early stage, is later inflated by an underlying fluid core. The core remains hot and fluid for ...extended period of time due to the thermal-shield effect of the surface visco-elastic crust. Plentiful and widespread morphological fingerprints of inflation like tumuli and lava rises are found on the Payen volcanic complex (Argentina), where pahoehoe lava flows extend over the relatively flat surface of the Pampean foreland and reach at least 180
km in length.
The morphology of the Argentinean Payen flows were compared with lava flows on Daedalia Planum (Mars), using Thermal Emission Imaging System (THEMIS), Mars Orbiter Laser Altimeter (MOLA), Mars Orbiter Camera (MOC), Mars Reconnaissance Orbiter (MRO)/High-Resolution Imaging Science Experiment (HiRISE). THEMIS images were used to map the main geological units of Daedalia Planum and determine their stratigraphic relationships. MOLA data were used to investigate the topographic surface over which the flows propagated and assess the thickness of lava flows. Finally, MOC and MRO/HIRISE images were used to identify inflations fingerprints and assess the cratering age of the Daedalia Planum’ s youngest flow unit which were found to predate the caldera formation on top of the Arsia Mons. The identification of similar inflation features between the Daedalia Planum and the Payen lava fields suggests that moderate and long lasting effusion rates coupled with very efficient spreading processes could have cyclically occurred in the Arsia Mons volcano during its eruptive history. Consequently the effusion rates and rheological proprieties of Daedalia lava flows, which do not take into account the inflation process, can be overestimated. These findings raise some doubts about the effusion rates and lava rheological properties calculated on Martian flows and recommends that these should be used with caution if applied on flows not checked with high-resolution images and potentially affected by inflation. Further HiRISE data acquisition will permit additional analysis of the flow surfaces and will allow more accurate estimates of effusion rates and rheological properties of the lava flows on Mars particularly if this data is acquired under a favourable illumination.
Skylights are openings on subsurface voids as lava tubes and caves. Recently deep hole structures, possibly skylights, were discovered on lunar photo images by the JAXA SELenological and ENgineering ...Explorer (SELENE)-Kaguya mission, and successively confirmed by the NASA Lunar Reconnaissance Orbiter (LRO) mission. Vertical hole structures and possibly underlying subsurface voids have high potential as resources for scientific study, and future unmanned and manned activities on the Moon. One mechanism proposed for their formation is impact cratering. The collapse of craters is due to the back spallation phenomena on the rear surface of the lava tube roofs. Previous analysis in this topic was based on small-scales laboratory experiments. These have pointed out that (i) the target thickness-to-crater diameter ratio is 0.7, and (ii) the projectile diameter-to-target thickness ratio is 0.16, at the ballistic limit once extrapolated to planetary conditions.
We investigate the impact process that might trigger the formation of lunar skylight candidates by numerically simulate the craters associated to the observed hole structures. The Marius Hills hole (MHh, located in a 26m thick target) was formed by a 4m projectile, which originated an impact crater of 40.0±1.6m in diameter. The Mare Tranquillitatis hole (MTh, located in a 47m thick target) was formed by a 7.2m projectile, which originated an impact crater of 75.6±3.0m in diameter. The target thickness-to-crater diameter ratio is 0.65 and 0.62, respectively for MHh and MTh. These values are smaller than the laboratory experiment ballistic limit ratio (0.7), supporting the hypothesis of collapse at the studied sites. The projectile diameter-to-target thickness ratio is 0.15 for both MHh and MTh, which is slightly smaller than we expected. The discrepancy could be due to the model assumption of vertical impact. We derived via modelling the ballistic limit for planetary scales and found that the target thickness-to-crater diameter ratio is 0.87.
We discuss the implications of the proposed scenario for skylight formation in terms of future robotic or human exploration of the Moon, as evaluated in COSPAR and ILEWG.
•We examine impact craters as triggering mechanism for skylight formation.•We carry out numerical modelling of impact craters to investigate our hypothesis.•We compare numerical modelling and recent laboratory experiment results.•We revise the ratio of the minimum lava tubes roof thickness vs. impact crater depth.•We explore the importance of lava tubes for future human lunar exploration.
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