Launched onboard the BepiColombo Mercury Planetary Orbiter (MPO) in October 2018, the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) is on its way to planet Mercury. MERTIS consists of a push-broom IR-spectrometer (TIS) and a radiometer (TIR), which operate in the wavelength regions of 7-14 μm and 7-40 μm, respectively. This wavelength region is characterized by several diagnostic spectral signatures: the Christiansen feature (CF), Reststrahlen bands (RB), and the Transparency feature (TF), which will allow us to identify and map rock-forming silicates, sulfides as well as other minerals. Thus, the instrument is particularly well-suited to study the mineralogy and composition of the hermean surface at a spatial resolution of about 500 m globally and better than 500 m for approximately 5-10% of the surface. The instrument is fully functional onboard the BepiColombo spacecraft and exceeds all requirements (e.g., mass, power, performance). To prepare for the science phase at Mercury, the team developed an innovative operations plan to maximize the scientific output while at the same time saving spacecraft resources (e.g., data downlink). The upcoming fly-bys will be excellent opportunities to further test and adapt our software and operational procedures. In summary, the team is undertaking action at multiple levels, including performing a comprehensive suite of spectroscopic measurements in our laboratories on relevant analog materials, performing extensive spectral modeling, examining space weathering effects, and modeling the thermal behavior of the hermean surface.

The study of the fluvial systems present on the Martian surface is a key in the investigation of the paleoclimate of the planet: Various indications suggest that these features could have formed under climatic conditions very different from the present one. For this reason, it seems necessary to update the previous maps of Martian valleys using newer mosaics and data at higher resolution. In this work we present a detailed global map of Martian valleys classified according to their morphology. Our data set includes all the valleys longer than 20 km mapped within the QGIS (Quantum Geographic Information System) software. With respect to previous global maps, the coupling of topographic information with data of higher image quality allowed us a better mapping of these structures at a fine scale: New small valleys and more tributaries for several systems have been observed. We mapped valleys of various typologies for a global total length of 773,559 km. The mapped valley networks cover the 69% of this total length. Moreover, a rough estimation of the valleys' age spatial distribution was performed. We found that the 94% of the mapped valleys have a maximum age consistent with an origin in the Noachian period; the 4% have a Hesperian maximum age, while the remaining 2% have a maximum age consistent with an origin in the Amazonian period. Finally, we also estimated the total eroded volume of the mapped valley networks finding a value in the order of 3 × 1014 m3 in good agreement with what found in literature.

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BepiColombo has a larger and in many ways more capable suite of instruments relevant for determination of the topographic, physical, chemical and mineralogical properties of Mercury’s surface than the suite carried by NASA’s MESSENGER spacecraft. Moreover, BepiColombo’s data rate is substantially higher. This equips it to confirm, elaborate upon, and go beyond many of MESSENGER’s remarkable achievements. Furthermore, the geometry of BepiColombo’s orbital science campaign, beginning in 2026, will enable it to make uniformly resolved observations of both northern and southern hemispheres. This will offer more detailed and complete imaging and topographic mapping, element mapping with better sensitivity and improved spatial resolution, and totally new mineralogical mapping. We discuss MESSENGER data in the context of preparing for BepiColombo, and describe the contributions that we expect BepiColombo to make towards increased knowledge and understanding of Mercury’s surface and its composition. Much current work, including analysis of analogue materials, is directed towards better preparing ourselves to understand what BepiColombo might reveal. Some of MESSENGER’s more remarkable observations were obtained under unique or extreme conditions. BepiColombo should be able to confirm the validity of these observations and reveal the extent to which they are representative of the planet as a whole. It will also make new observations to clarify geological processes governing and reflecting crustal origin and evolution. We anticipate that the insights gained into Mercury’s geological history and its current space weathering environment will enable us to better understand the relationships of surface chemistry, morphologies and structures with the composition of crustal types, including the nature and mobility of volatile species. This will enable estimation of the composition of the mantle from which the crust was derived, and lead to tighter constraints on models for Mercury’s origin including the nature and original heliocentric distance of the material from which it formed.

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In situ information on the surface composition of Venus is based on measurements of a small number of landing sites. In the laboratory, we measured the emissivity of a range of igneous rocks at temperatures up to 480°C. We show that high-temperature laboratory spectra of basalts are consistent with the only existing multispectral data from the surface of Venus obtained by the photometers on the Venera 9 and 10 landers. We derive the FeO abundances for these landing sites of 12.2 and 9.5 weight %, respectively. From orbit, Venus’ surface is only observable on the nightside through small spectral windows near 1 μm where the CO2 atmosphere is largely transparent. The new laboratory data show that different rock types can be distinguished using only a small set of spectral bands. Therefore, future orbital spectral observations can provide a much-needed global composition map.

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