Observing Mercury: from Galileo to the stereo camera on the BepiColombo mission

AbstractAfter having observed the planets from his house in Padova using his telescope, in January 1611 Galileo wrote to Giuliano de Medici that Venus is moving around the Sun as Mercury. Forty years ago, Giuseppe Colombo, professor of Celestial Mechanics in Padova, made a decisive step to clarify the rotational period of Mercury. Today, scientists and engineers of the Astronomical Observatory of Padova and of the University of Padova, reunited in the Center for Space Studies and Activities (CISAS) named after Giuseppe Colombo, are busy to realize a stereo camera (STC) that will be on board the European (ESA) and Japanese (JAXA) space mission BepiColombo, devoted to the observation and exploration of the innermost planet. This paper will describe the stereo camera, which is one of the channels of the SIMBIOSYS instrument, aiming to produce the global mapping of the surface with 3D images

Variations in the amount of water ice on Ceres' surface suggest a seasonal water cycle.

The dwarf planet Ceres is known to host a considerable amount of water in its interior, and areas of water ice were detected by the Dawn spacecraft on its surface. Moreover, sporadic water and hydroxyl emissions have been observed from space telescopes. We report the detection of water ice in a mid-latitude crater and its unexpected variation with time. The Dawn spectrometer data show a change of water ice signatures over a period of 6 months, which is well modeled as ~2-km2 increase of water ice. The observed increase, coupled with Ceres' orbital parameters, points to an ongoing process that seems correlated with solar flux. The reported variation on Ceres' surface indicates that this body is chemically and physically active at the present time

First mineralogical maps of 4 Vesta

Before Dawn arrived at 4 Vesta only very low spatial resolution (~50 km) albedo and color maps were available from HST data. Also ground-based color and spectroscopic data were utilized as a first attempt to map Vesta’s mineralogical diversity [1-4]. The VIR spectrometer [5] onboard Dawn has ac-quired hyperspectral data while the FC camera [6] ob-tained multi-color data of the Vestan surface at very high spatial resolutions, allowing us to map complex geologic, morphologic units and features. We here re-port about the results obtained from a preliminary global mineralogical map of Vesta, based on data from the Survey orbit. This map is part of an iterative map-ping effort; the map is refined with each improvement in resolution

SeaBIRD: A Flexible and Intuitive Planetary Datamining Infrastructure

Description of SeaBIRD (Searchable and Browsable Infrastructure for Repository of Data), a software and hardware infrastructure for multi-mission planetary datamining, with web-based GUI and API set for the integration in users' software

Ceres: ice stability and water emission

Recent observations of H2O vapor plumes in localized regions [1] suggest the presence of ice on surface and/or on sub-surface regions of asteroid Ceres. In the hypothesis of a cometary-like emission mechanism (as already suggested by [2]), we performed several simulations in order to establish what are the likely physical conditions (in particular ice depth and thermal conductivity of crust) to fit Herschel observations [1]

Nature, formation, and distribution of carbonates on Ceres

Different carbonates have been detected on Ceres, and their abundance and spatial distribution have been mapped using a visible and infrared mapping spectrometer (VIR), the Dawn imaging spectrometer. Carbonates are abundant and ubiquitous across the surface, but variations in the strength and position of infrared spectral absorptions indicate variations in the composition and amount of these minerals. Mg-Ca carbonates are detected all over the surface, but localized areas show Na carbonates, such as natrite (Na_2CO_3) and hydrated Na carbonates (for example, Na_2CO_3·H_2O). Their geological settings and accessory NH_4-bearing phases suggest the upwelling, excavation, and exposure of salts formed from Na-CO_3-NH_4-Cl brine solutions at multiple locations across the planet. The presence of the hydrated carbonates indicates that their formation/exposure on Ceres’ surface is geologically recent and dehydration to the anhydrous form (Na_2CO_3) is ongoing, implying a still-evolving body

Preliminary temperature maps of dwarf planet Ceres as derived by Dawn/VIR

The NASA Dawn mission [1] spacecraft was captured by the dwarf planet Ceres on March 6, 2015. During the Approach phase in the months preceding capture, the remote sensing instruments on the spacecraft acquired data with increasing spatial resolution. Analogous to the observation campaign planned at protoplanet Vesta during 2011-12, Dawn at Ceres proceeds in a series of orbits, carried out at increasingly lower altitudes over the mean surface, with a consequent increase of the spatial resolution. The Visible InfraRed (VIR) mapping spectrometer onboard Dawn [2] operates in the overall spectral range 0.25-5.1 μm, with the main goal of inferring the surface composition of the target in its uppermost layer, as thick as several tens of microns [3]. Taking advantage of the wavelength range longward of 3 μm, it is possible to use VIR as a thermal mapper, i.e. as a tool to derive thermal images and spatially-resolved temperature maps. To do this, the VIR team uses a Bayesian approach to nonlinear inversion [4] that was extensively applied to the Vesta dataset, as well as to Rosetta/VIRTIS data of small bodies [e.g., 5,6]. In the case of Vesta, this capability allowed us to build both global thermal maps for each orbit phase (spatial resolution) as well as for different local solar times [7], and to investigate the thermal behavior of specific regions of interest seen at the local scale [4]. Such investigations fall well within the broad science goals that Dawn/VIR should address at Ceres. In February 2015, still with a coarse spatial resolution (~11.4 km/px), VIR was able to obtain temperature images of Ceres that revealed the existence of differences in the thermal behavior of two bright spots seen at broad regional scale (Figs. 1, 2). At that time it was too early to say if this was the result of a real difference in the physical structure of the material and/or in its composition, because low resolution has the effect of averaging together very different areas. In this work, we focus on VIR data acquired just after capture and in the first science orbit, namely the Rotation Characterization 3 (RC3) and Survey phases, yielding VIR spatial resolution of 3.4 km/px and 1.1 km/px, respectively. We derive global/broadly regional temperature maps as well as highlight thermal anomalies that may be observed at those spatial scales. These data allow a preliminary determination of thermal properties of Ceres: in fact, thermophysical models that simulate the diurnal temperature variation for a given surface point, returning unknown quantities such as thermal conductivity and ultimately thermal inertia, may be appropriately constrained by these measurements

Homogeneous spectral units on Ceres as inferred from Dawn/VIR

The dwarf planet Ceres, the largest object in the main asteroid belt, is being closely investigated by the NASA Dawn mission since the beginning of 2015. The Visible InfraRed (VIR) mapping spectrometer onboard Dawn has obtained hyperspectral images of Ceres, with spatial resolution increasing with decreasing distance from the surface. Using its overall spectral range from 0.25 to 5.1 μm, VIR will ultimately enable a comprehensive mapping of Ceres' mineralogy and surface temperature. Prior to Dawn, Ceres was extensively observed with the Hubble Space Telescope (HST), which resulted in low-resolution (30 km/px) albedo and color maps in the UV-VIS spectral domain. During the approach phase VIR acquired data with a spatial resolution of ~11 km/px, and confirmed the regional color trends identified by HST earlier. In the subsequent Survey mission phase hyperspectral coverage of Ceres was obtained at ~1.3 km/px, while in the High Altitude Mapping Orbit (HAMO) the nominal spatial resolution will be ~0.4 km/px. Unlike Vesta, which was investigated by Dawn in 2011-2012, the spectrum of Ceres does not display prominent absorption bands in the VIS-near IR range. Ground-based observations of Ceres highlighted a decrease in reflectance shortward of 0.4 μm and the existence of a broad absorption feature in the 3-μm region, associated with hydrated minerals. VIR data are key to unveiling the surface composition of Ceres at different spatial scales, providing answers to several unsolved questions. Compositionally homogeneous surface units, emerging in the VIS-IR spectral range sampled by VIR, are presented here for the first time. These units and their degree of similarity in terms of spectral parameters might provide insight on the surface processes that led to the composition observed nowadays. <P /