Unmixing of Laboratory IR Spectral Reflectance Measurements of Smooth Plains Analogs

The unmixing model used in this study has previ- ously been used for spectral unmixing of NASA RELAB data and lunar analog materials. In the framework of MERTIS it is applied to laborator mineral mixtures, including glasses and varying grain sizes [12-14]. These mixtures are prepared and analyzed at the IRIS (Infrared and Raman for Interplanetary Spectros- copy) laboratory of the Institut für Planetologie at the Westfälische Wilhelms-Universität Münster. Here we investigate a wide range of natural minerals, rock samples including impact rocks and meteorites, syn- thetic analogs, and glasses [3,7]. The results of these in- vestigations contribute to the generation of a mid-IR re- flectance database in the MERTIS-relevant wavelength range from 7-14 μm. This database enables the qualita- tive, but also quantitative interpretation of MERTIS spectra

Pointing and spectral assignment design and control for MERTIS

The development of MERTIS, a miniaturized thermal infrared imaging spectrometer onboard of ESA's cornerstone mission BepiColombo to Mercury has been completed. Qualification of the design is followed by the calibration of the instrument showing up first results of the technology used. Based on subsequent viewing of different targets including on-board calibration sources the push-broom instrument will use a 2-dimensional bolometer detector to provide spatial and spectral information. Here repetition accuracy of pointing and spectral assignment is supported by the design of instrument components under the restriction of limited resources. Additionally a concept of verification after launch and cruise phase of the mission was developed. The article describes how this has been implemented and what the results under environment testing are

Origin of lunar sinuous rilles:modeling effects of gravity, surface slope, and lava composition on erosion rates during the formation of Rima Prinz

Lunar sinuous rilles have long been interpreted as features that formed as the result of surficial lava flow, though the precise mechanism responsible for channel formation (constructed versus eroded origins) is still debated. In assessing the origin of Rima Prinz, a channel interpreted to have formed by erosion, two erosion regimes, mechanical and thermal, are considered. Measurements of channel dimensions are used as inputs to analytical models to constrain the origin of Rima Prinz, including lava compositions, mechanical and thermal erosion rates, eruption durations, and lava volumes required to form the feature. Key results indicate that Rima Prinz and other large sinuous rilles could have formed as the result of thermal erosion under the weak gravity and low slope conditions characteristic of these lunar features. Further analysis indicates that lava composition has significant effects on channel formation. Model results of four considered lava compositions show that komatiite-like lava will erode a similarly composed substrate most efficiently whereas a high-Ti basalt will erode a similarly composed substrate least efficiently; ocean island basalt and low-Ti basalt erode similarly composed substrates at intermediate rates. Results indicate that Rima Prinz may have formed over 0.4–2.2 Earth years, depositing 50–250 km3 of lava over a plausible deposit area of 2450 km2. Resulting deposit thicknesses suggest that the lava that incised Rima Prinz was most likely similar in composition to a terrestrial komatiite, ocean island basalt, or lunar low-Ti basalt. Further constraints on sinuous rille formation will serve as a window into the nature of volcanic activity of the Moon's past

Replication Data for: Studying the Global Spatial Randomness of Impact Craters on Mercury, Venus, and the Moon With Geodesic Neighborhood Relationship

• We improve approaches to quantify the spatial randomness of impact craters by applying geodesic methods • We apply these methods to analyze the global spatial randomness of impact crater populations on Mercury, Venus, and the Moon • We use the results to investigate known crater population variations and surface evolution scenarios on Mercury, Venus, and the Moon This is Version 2, Version 1 is stored in Mendeley, http://dx.doi.org/10.17632/mn2b542k5r.

Replication Data for: Studying the Global Spatial Randomness of Impact Craters on Mercury, Venus, and the Moon With Geodesic Neighborhood Relationship

• We improve approaches to quantify the spatial randomness of impact craters by applying geodesic methods • We apply these methods to analyze the global spatial randomness of impact crater populations on Mercury, Venus, and the Moon • We use the results to investigate known crater population variations and surface evolution scenarios on Mercury, Venus, and the Moon This is Version 2, Version 1 is stored in Mendeley, http://dx.doi.org/10.17632/mn2b542k5r.

Replication Data for: Studying the Global Spatial Randomness of Impact Craters on Mercury, Venus, and the Moon With Geodesic Neighborhood Relationship

• We improve approaches to quantify the spatial randomness of impact craters by applying geodesic methods • We apply these methods to analyze the global spatial randomness of impact crater populations on Mercury, Venus, and the Moon • We use the results to investigate known crater population variations and surface evolution scenarios on Mercury, Venus, and the Moon This is Version 2, Version 1 is stored in Mendeley, http://dx.doi.org/10.17632/mn2b542k5r.

MERTIS - MErcury Radiometer and Thermal Infrared Spectrometer- a novel thermal imaging spectrometer for the exploration of Mercury

The MERTIS instrument is a state of the art imaging spectrometer in the TIR range onboard ESA’s Bepi Colombo mission to the planet Mercury. MERTIS has four science goals: the study of Mercury’s surface composition, identification of rock-forming minerals, mapping of the surface mineralogy, and the study of surface temperature variations and of the thermal inertia. The instrument is designed to achieve a signal-to-noise-ratio above 100 in the 7-14 µm range with a spectral channel width of 90 nm and a nominal spatial ground resolution of 500 m within the complex thermal and radiation environment of Mercury

A Dedicated Small Lunar Exploration Orbiter and a Mobile Surface Element

The Moon is an integral part of the Earth-Moon system, it is a witness to more than 4.5 b. y. of solar system history, and it is the only planetary body except Earth for which we have samples from known locations. The Moon is thus a key object to understand our Solar System. The Moon is our closest companion and can easily be reached from Earth at any time, even with a relatively modest financial budget. Consequently, the Moon was the first logical step in the exploration of our solar system before we pursued more distant targets such as Mars and beyond. The vast amount of knowledge gained from the Apollo and other lunar missions of the late 1960's and early 1970's demonstrates how valuable the Moon is for the understanding of our planetary system (e.g. [1], [2]). Even today, the Moon remains an extremely interesting target scientifically and technologically. New data have helped to address some of our questions about the Earth-Moon system, but many remain and new questions arose. In particular, the discovery of water at the lunar poles, and water and hydroxyl bearing surface materials and volatiles, as well as the discovery of young volcanism have changed our view of the Moon. Therefore, returning to the Moon is the critical stepping-stone to further exploring our immediate planetary neighborhood. Here, we present scientific and technological arguments for a Small Lunar Explorations Orbiter (S-LEO) dedicated to investigate so far unsolved questions and processes. Numerous space-faring nations have realized and identified the unique opportunities related to lunar exploration and have planned missions to the Moon within the next few years. Among these missions, S-LEO will be unique, because of its unprecedented spatial and spectral resolutions. S-LEO will significantly improve our understanding of the lunar environment in terms of composition, surface ages, mineralogy, physical properties, and volatile and regolith processes. S-LEO will carry an entire suite of innovative, complementary technologies, including high-resolution camera systems, several spectrometers that cover previously unexplored parts of the electromagnetic spectrum over a broad range of wavelengths, and a communication system to interact with landed equipment on the farside. The Small Lunar Explorations Orbiter concept is technologically challenging but feasible, and will gather unique, integrated, interdisciplinary data sets that are of high scientific interest and will provide an unprecedented new context for all other international lunar missions. The most visible mission goal of S-LEO will be the identification and mapping of lunar volatiles and investigating their origin and evolution with high spatial as well as spectral resolution. Therefore, in addition to mapping the geological context in the sub-meter range, a screening of the electromagnetic spectrum within a very broad range will be performed. In particular, spectral mapping in the ultraviolet and mid-infrared will provide insight into mineralogical and thermal properties so far unexplored in these wavelength ranges. The determination of the dust distribution in the lunar orbit will provide information about processes between the lunar surface and exosphere supported by direct observations of lunar flashes. Measuring of the radiation environment will finally complete the exosphere investigations. Combined observations based on simultaneous instrument adjustment and correlated data processing will provide an integrated geological, geochemical and geophysical database that enables: • the exploration and utilization of the Moon in the 21st century; • the solution of fundamental problems of planetology concerning the origin and evolution of terrestrial bodies; • understanding the uniqueness of the Earth-Moon System and its formation and evolution; • the absolute calibration of the impact chronology for the dating of solar system processes; • deciphering the lunar regolith as record for space environmental conditions; • mapping lunar resources. S-LEO is featuring a set of unique scientific capabilities w.r.t. other planned missions including: (1) dedicated observation of volatiles (mainly H2O and OH), their formation and evolution in direct context with the geological and mineralogical surface with high spectral and spatial resolution (< 1m/px); (2) besides the VIS-NIR spectral range so far uncovered wavelengths in the ultraviolet (0.2 – 0.4 µm) and mid-infrared (7 - 14 µm) will be mapped to provide mineralogical context for volatile processes (e.g. sources of oxygen); (3) detection of rock-forming elements by means of x-ray fluorescence in the spectral range of .5-10 keV in order to constrain the composition of key elements of lunar surface materials; (4) monitoring of dust and radiation in the lunar environment and its interaction with the surface; and (5) monitoring of present-day meteoroitic impacts. In 2009 ESA commissioned a Mobile Payload Element (MPE) to assist the ESA Lunar Lander mission. The MPE, currently under study in Germany, is designed to be a small, autonomous, innovative vehicle of roughly 10 12 kg for scouting the environment in the vicinity of the lunar landing site. The novel capability of the MPE will be to acquire samples of lunar soil in an area of >100m around the lander and to bring them back to the spacecraft for analysis by on-board instruments. This will enable access to soils that are less contaminated by the descent propulsion system plumes to increase the chances of detection of any indigenous lunar volatiles. The MPE shall acquire samples of regolith with landing-induced contamination being below the detection limit of the associated volatile-seeking instruments. Subsurface regolith sampling is preferable to understand the concentration of volatiles as a function of depth. Additional benefits for the overall science accomplished by a Lunar Lander mission could be obtained if the MPE were to conduct ‘field geology’ type observations and measurements along its traverses, such as geochemical and mineralogical in situ investigations with dedicated instruments on rocks, boulders and regolith. This would dramatically expand the effective area studied by the ESA Lunar Lander mission. Based on technology trades the baseline concept for the MPE system is composed by a 4-wheel active chassis with wheels, a power supply with fixed solar generators plus a secondary battery, a thermal system with active heating and passive insulation, a sensor package for autonomous operations and a VHF/UHF communication system between MPE and the Lander. One unique scientific aspect of the MPE could be the in situ study of rocks, boulders and lithic (rock) fragments which otherwise would only be amenable to measurements using any instrument heads mounted on the lander robotic arm (provided any rocks were within reach of the arm). To fulfill the science objectives, the MPE will be equipped with a stereo camera, the PLUTO mole subsurface regolith sampling system (as flown on Beagle 2) as well as a close-up imager. This instrument package allows acquisition of regolith samples from both illuminated and locally shaded terrain, sampling from the subsurface and from underneath large boulders and documentation of the samples acquired by close-up imaging of the sample site, ideally before and after sample acquisition. A suite of terrain temperature sensors is implicitly included to provide context for the samples acquired from permanently shadowed locations or below the surface, but also to contribute to landing site general science. As an option for the in-situ characterization of the sample material with respect to mineralogy and possibly volatile content, spectrometer experiments or a color capability of the camera could be added. Further, a laboratory environment is currently being established at Freie Universität Berlin in order to allow sample-based geochemical measurements of key rock-forming elements in the soft X-Ray domain (.5-10 keV). The laboratory is used for the hardware development of X-Ray spectrometer experiments to be employed on lunar orbiter and on lunar lander missions. References: [1] H. Hiesinger, J.W. Head, New Views of Lunar Geoscience: An Introduction and Overview, In: Ne Views of the Moon (B.L. Jolliff et al. eds.) Rev. Min. Geochem., 60, 1-81 (2006). [2] R. Jaumann, The Moon, In: Encyclopedia of Astrobiology, M. Gargaud et al. (eds.), Vol. 2, Springer, 280-282 (2011)

Exploration of Saturnalia Fossa and Associated Structures in Vesta’s Northern Hemisphere

Since its arrival at Vesta on July 16th 2011, NASA’s Dawn spacecraft has collected spectacular imaging, compositional and geophysical data. Dawn is scheduled to depart Vesta on August 26th and during this eventful year many unexpected discoveries have been made about this diverse asteroid. One such discovery is the Saturnalia Fossa trough in Vesta’s northern hemisphere. Saturnalia Fossa is the chief structure of at least 5 parallel troughs, many of which partly coalesce into one another at various locations. The sizeable Saturnalia Fossa dominates Vesta’s northern hemisphere and lends its name to the Saturnalia Ridge and Trough Terrain. Saturnalia Fossa has a maximum width of ~39 km, making it almost twice the width of the ~ 22 km wide Divalia Fossa equatorial trough. Currently Saturnalia Fossa (~366 km long) is shorter than Divalia Fossa (~465 km long) (Buczkowski et al., 2012, submitted to GRL). But, Saturnalia Fossa extends into the currently shadowed northern region and its length will increase as Dawn gains coverage in this enigmatic area. The northern troughs are covered in an obscuring layer of regolith, which makes identifying their specific form challenging. Comparative planetology, along with the analysis of Dawn data, helps to indicate whether the troughs are graben or another structure. The orientation of the troughs makes it likely that their formation is linked to that of the southern Veneneia basin (Buczkowski et al., 2011, AGU). There are many smaller structures, which include grooves, pit crater chains and small ridges that are preferentially oriented sub-parallel or sub-perpendicular to the troughs. This suggests that they have a related formation mechanism. An initial analysis of the distribution of the troughs and smaller structures indicates that they are oriented as if they were formed by large-scale shearing. This shear is possibly a result of the Veneneia-forming impact

Composition and structure of the shallow subsurface of Ceres revealed by crater morphology

Before NASA’s Dawn mission, the dwarf planet Ceres was widely believed to contain a substantial ice-rich layer below its rocky surface. The existence of such a layer has significant implications for Ceres’s formation, evolution, and astrobiological potential. Ceres is warmer than icy worlds in the outer Solar System and, if its shallow subsurface is ice-rich, large impact craters are expected to be erased by viscous flow on short geologic timescales. Here we use digital terrain models derived from Dawn Framing Camera images to show that most of Ceres’s largest craters are several kilometres deep, and are therefore inconsistent with the existence of an ice-rich subsurface. We further show from numerical simulations that the absence of viscous relaxation over billion-year timescales implies a subsurface viscosity that is at least one thousand times greater than that of pure water ice. We conclude that Ceres’s shallow subsurface is no more than 30% to 40% ice by volume, with a mixture of rock, salts and/or clathrates accounting for the other 60% to 70%. However, several anomalously shallow craters are consistent with limited viscous relaxation and may indicate spatial variations in subsurface ice content