Assessing the role of clay and salts on the origin of MARSIS basal bright reflections

Anomalously bright basal reflections detected by MARSIS at Ultimi Scopuli have been interpreted to indicate the presence of water-saturated materials or ponded liquid water at the base of the South Polar Layered Deposits (SPLD). Because conventional models assume basal temperatures (≤200 K) much lower than the melting point of water, this interpretation has been questioned and other explanations for the source of the bright basal reflections have been proposed, involving clay, hydrated salts, and saline ices. Combining previous published data, simulations, and new laboratory measurements, we demonstrate that the dielectric properties of these materials do not generate strong basal reflections at MARSIS frequencies and Martian temperatures. Plausible candidates remain perchlorates and chlorides brines that exhibit a strong dielectric response at much lower temperatures than other materials. This explanation might require that metastability could be maintained for a long period of time on a geological scale

In-lab characterization of HYPSOS, a novel stereo hyperspectral observing system: first results

HYPSOS (HYPerspectral Stereo Observing System, patented) is a novel remote sensing instrument able to extract the spectral information from the two channels of a pushbroom stereo camera; thus it simultaneously provides 4D information, spatial and spectral, of the observed features. HYPSOS has been designed to be a compact instrument, compatible with small satellite applications, to be suitable both for planetary exploration as well for terrestrial environmental monitoring. An instrument with such global capabilities, both in terms of scientific return and needed resources, is optimal for fully characterizing the observed surface of investigation. HYPSOS optical design couples a pair of folding mirrors to a modified three mirror anastigmat telescope for collecting the light beams from the optical paths of the two stereo channels; then, on the telescope focal plane, there is the entrance slit of an imaging spectrograph, which selects and disperses the light from the two stereo channels on a bidimensional detector. With this optical design, the two stereo channels share the large majority of the optical elements: this allowed to realize a very compact instrument, which needs much less resources than an equivalent system composed by a stereo camera and a spectrometer. To check HYPSOS actual performance, we realized an instrument prototype to be operated in a laboratory environment. The laboratory setup is representative of a possible flight configuration: the light diffused by a surface target is collimated on the HYPSOS channel entrance apertures, and the target is moved with respect to the instrument to reproduce the in- flight pushbroom acquisition mode. Here we describe HYPSOS and the ground support equipment used to characterize the instrument, and show the preliminary results of the instrument alignment activities

Volcanic Holocrystalline Bedrock and Hydrothermal Alteration: A Terrestrial Analogue for Mars

Clay minerals have been detected on Mars to outcrop mainly as alteration of ancient bedrock, and secondarily, as deposition from aqueous environments or interlayered with evaporitic deposits on Mars. In order to better constrain the alteration environments, we focused on the process to form clays from volcanic rocks and experimentally reproduced it at different temperature and pH. A fresh, holocrystalline alkali-basalt sample collected in the Mount Etna volcanic sequence has been used as analogue of the Martian unaltered bedrock. Previous works considered only volcanic glass or single mineral, but this may not reflect the full environmental conditions. Instead, we altered the bulk rock and analyzed the changes of primary minerals to constrain the minimum environmental parameters to form clays. We observed that under acidic aqueous solution (pH ~ 3.5–5.0) and moderate temperature (~150–175 °C), clinopyroxene and plagioclase are altered in smectite in just a few days, while higher temperature appear to favor oxides formation regardless of pH. Plagioclases can also be transformed in zeolite, commonly found in association with clays on Mars. This transformation may occur even at very shallow depth if a magmatic source is close or hydrothermalism is triggered by meteoritic impact

Reconstruction of the sand transport pathways and provenance in Moreux crater, Mars

Our research focuses on the detailed study of the aeolian deposits within Moreux crater using multi-resolution imaging and spectral data from the Mars Reconnaissance Orbiter. The morphometric analysis on the dune slip faces and wind streak orientations allowed us to reconstruct the sand transport pathways and the changes of the transport pattern. We used a new automatic procedure based on the Line Detection algorithm in PCI Geomatics' Geomatica software to characterize small scale aeolian structures as ripples within Moreux crater from HiRISE images. After validation on a previously studied area in Herschel crater, we apply this method to reconstruct the wind regime at high spatial resolution in Moreux and reconstruct the wind circulation forming the aeolian bedforms. Moreover, we used three pairs of CTX images to perform a multi-temporal analysis of the wind streaks. We mapped more than 500 features with data acquisition spanning over four Earth years and the observed wind streak changes may reflect present day atmospheric variations due to local winds. CRISM datasets show an olivine and clinopyroxene mixture characterizing most of the dunes within Moreux crater, while the dark dunes in the northern sector of the crater showed an enrichment in Mg-olivine. This composition is similar to that detected in the central peak bedrock suggesting that central peak erosion contributes to the formation of the northly dunes meanwhile recent northeast wind flows and Moreux topography influence the wind circulation and determine the formation of the sand transport pathways within the crater. These results are consistent with the hypothesis that aeolian sands are generally sourced locally on Mars

Coupling rare earth element analyses and high-resolution topography along fault scarps to investigate past earthquakes: A case study from the Southern Apennines (Italy)

The systematic study of faults that have released strong earthquakes in the past is a challenge for seismic hazard assessment. In carbonate landscapes, the use of rare earth element (REE) concentrations on slickensides may aid the reconstruction of fault slip history. We applied this methodology to the Caggiano normal fault (Southern Apennines, Italy), cropping out southeast of the Irpinia 1980 CE earthquake fault (Mw 6.9), which was responsible for both the 1561 CE and partly the 1857 CE Basilicata earthquakes (Mw 6.7 and 7.1). We integrated the REE analysis approach with a high- resolution topographic analysis along 98 serial topographic profiles to measure vertical separations attributable to faulting since the Last Glacial Maximum (LGM). The asymmetric scarp height profiles suggest fault- lateral propagation and along- strike variations in the fault evolution. Our results indicate the occurrence of 7 to 11 earthquakes with variable slip between ~40 cm and ~70 cm within post- LGM times. We estimated the magnitudes of the respective earthquakes, between 5.5 and 7.0, and most commonly between 6.3 and 6.5. The results suggest a recurrence time between 1.6 k.y. and 2.3 k.y. and a slip rate ranging between 0.6 mm/yr and 0.9 mm/yr. This approach may be useful for application to carbonate fault planes in similar tectonic contexts worldwide