[show abstract][hide abstract] ABSTRACT: The Moon is key to understanding both Earth and our Solar System in terms of planetary processes and has been a witness of the Solar System history for more than 4.5 Ga. Building on earlier telescopic observations, our knowledge about the Moon was transformed by the wealth of information provided by Apollo and other space missions. These demonstrated the value of the Moon for understanding the fundamental processes that drive planetary formation and evolution. The Moon was understood as an inert body with its geology mainly restricted to impact and volcanism with associated tectonics, and a relative simple composition. Unlike Earth, an absence of plate tectonics has preserved a well-defined accretion and geological evolution record. However recent missions to the Moon show that this traditional view of the lunar surface is certainly an over simplification. For example, although it has long been suspected that ice might be preserved in cold traps at the lunar poles, recent results also indicate the formation and retention of OH− and H2O outside of polar regions. These volatiles are likely to be formed as a result of hydration processes operating at the lunar surface including the production of H2O and OH by solar wind protons interacting with oxygen-rich rock surfaces produced during micrometeorite impact on lunar soil particles. Moreover, on the basis of Lunar Prospector gamma-ray data, the lunar crust and underlying mantle has been found to be divided into distinct terranes that possess unique geochemical, geophysical, and geological characteristics. The concentration of heat producing elements on the nearside hemisphere of the Moon in the Procellarum KREEP Terrane has apparently led to the nearside being more volcanically active than the farside. Recent dating of basalts has shown that lunar volcanism was active for almost 3 Ga, starting at about 3.9–4.0 Ga and ceasing at ∼1.2 Ga. A recent re-processing of the seismic data supports the presence of a partially molten layer at the base of the mantle and shows not only the presence of a 330 km liquid core, but also a small solid inner core. Today, the Moon does not have a dynamo-generated magnetic field like that of the Earth. However, remnant magnetization of the lunar crust and the paleomagnetic record of some lunar samples suggest that magnetization was acquired, possibly from an intrinsic magnetic field caused by an early lunar core dynamo. In summary, the Moon is a complex differentiated planetary object and much remains to be explored and discovered, especially regarding the origin of the Moon, the history of the Earth–Moon system, and processes that have operated in the inner Solar System over the last 4.5 Ga. Returning to the Moon is therefore the critical next stepping-stone to further exploration and understanding of our planetary neighborhood.
Planetary and Space Science 12/2012; 74(1):15–41. · 2.11 Impact Factor
[show abstract][hide abstract] ABSTRACT: Astrometric measurements were obtained from frame images of the SRC on
Mars Express. Camera pointing was controlled and corrected with
background star observations, made just before and after the Deimos
(1 data file).
[show abstract][hide abstract] ABSTRACT: We will summarize 3.5 Martian years (Mars Years 27-30) of high-altitude
CO2 cloud data from MEx/OMEGA and selected results from Mex/HRSC. The
3-year dataset shows that the equatorial cloud activity is centered
around the northern summer solstice with a pause at the aphelion, and
that their appearance is limited in latitude and longitude.
HRSC-measured altitudes and cloud speeds provide a rare dataset for
comparison with GCMs. A comparison with the LMD Mars Global Climate
Model shows a good agreement between the model-predicted winds and those
observed by the HRSC. The LMD-MGCM predicts a strong diurnal variation
of temperature at the cloud observation altitudes due to the propagation
of the diurnal thermal tide. The coldest temperatures in the
near-equator cloud altitude range (60-85 km) are observed towards the
end of the afternoon, whereas the warmest temperatures are found in the
early morning hours. Most of the observed clouds are cirrus-type,
filamented clouds, but some OMEGA-observed clouds exhibit round, clumpy
structures that have been suggested to be of convective origin. We asses
the plausibility of the hypothesis of mesospheric convection in light of
observations and theoretical Convective Available Potential Energy
calculations. Estimates of convective potential and vertical velocities
based on observed cloud properties suggest that the convective clouds
could most likely be clusters of smaller scale convective updrafts.
SPICAM stellar occultations have revealed large supersaturations at high
altitudes: to attain the estimated values of CAPE and vertical velocity,
most probably only moderate deviations from saturation are required.
Based on nucleation modeling, such deviations may imply cloud formation
via heterogeneous nucleation onto small condensation nuclei.
[show abstract][hide abstract] ABSTRACT: We have investigated 12 prominent regions on Mars in detail with respect to their geologic evolution through time on the basis of detailed geologic mapping exercises and determining age relationships through crater counting techniques using imagery. New data in combination with previously obtained data have been analyzed by way of a refined method of cratering age extraction that also gives fine details of periods of resurfacing. We have found that there has been volcanic and fluvial/glacial geologic activity on the Martian surface at all times from > 4 Ga ago until today. This activity shows episodic pulses in intensity of both volcanic and fluvial/glacial processes at ~ 3.8–3.3 Ga, 2.0–1.8 Ga, 1.6 to 1.2 Ga, ~ 800 to 300 m.y., ~ 200 m.y., and ~ 100 m.y., and a possible weaker phase around ~ 2.5–2.2 Ga ago. In between these episodes, there was relative quiescence of volcanic and/or fluvial/glacial activity. The episodes we find on the Martian surface in the crater frequency analyses of HRSC, MOC and THEMIS data coincide with some age groups of the Martian meteorites (~ 1.3 Ga, ~ 600–300 m.y., ~ 170 m.y.). It appears that the surface activity expressions and their episodicity are related to the interior evolution of the planet when convection in the asymptotic stationary state changes from the so-called stagnant-lid regime to an episodic behavior. Similarities in episodic behavior are found for the other terrestrial planets: Venus, the Earth's moon, and the Earth itself suggesting a common general relationship in the evolutionary tracks.
Earth and Planetary Science Letters 06/2010; · 4.35 Impact Factor
[show abstract][hide abstract] ABSTRACT: The Exomars Panoramic Camera System is an imaging suite of three camera heads to be mounted on the ExoMars
rover‘s mast, with the boresight 1.8 m above ground. As late as the ExoMars Pasteur Payload Design Review
(PDR) in 2009, the PanCam consists of two identical wide angle cameras (WAC) with fixed focal length lenses,
and a high resolution camera (HRC) with an automatic focus mechanism, placed adjacent to the right WAC. The
WAC stereo pair provides binocular vision for stereoscopic studies as well as 12 filter positions (per camera) for
stereoscopic colour imaging and scientific multispectral studies. The stereo baseline of the pair is 500 mm. The
twoWAC have 22 mm focal length, f/10 lenses that illuminate detectors with 1024 � 1024 pixels.WAC lenses are
fixed, with an optimal focus set to 4 m, and a focus ranging from 1.2 m (corresponding to the nearest view of the
calibration target on the rover deck) to infinity. The HRC is able to focus between 0.9 m (distance to a drill core
on the rover‘s sample tray) and infinity. The instantaneous field of views of WAC and HRC are 580 μrad/pixel and
83 μrad/pixel, respectively. The corresponding resolution (in mm/pixel) at a distance of 2 m are 1.2 (WAC) and
0.17 (HRC), at 100 m distance it is 58 (WAC) and 8.3 (HRC). WAC and HRC will be geometrically co-aligned.
The main scientific goal of PanCam is the geologic characterisation of the environment in which the rover is
operating, providing the context for investigations carried out by the other instruments of the Pasteur payload.
PanCam data will serve as a bridge between orbital data (high-resolution images from HRSC, CTX, and HiRISE,
and spectrometer data from OMEGA and CRISM) and the data acquired in situ on the Martian surface. The
position of HRC on top of the rover‘s mast enables the detailed panoramic inspection of surface features over
the full horizontal range of 360° even at large distances, an important prerequisite to identify the scientifically
most promising targets and to plan the rover‘s traverse. Key to success of PanCam is the provision of data that
allow the determination of rock lithology, either of boulders on the surface or of outcrops. This task requires high
spatial resolution as well as colour capabilities. The stereo images provide complementary information on the
three-dimensional properties (i.e. the shape) of rocks. As an example, the degree of rounding of rocks as a result
of fluvial transport can reveal the erosional history of the investigated particles, with possible implications on the
chronology and intensity of rock-water interaction. The identification of lithology and geological history of rocks
will strongly benefit from the co-aligned views of WAC (colour, stereo) and HRC (high spatial resolution), which
will ensure that 3D and multispectral information is available together with fine-scale textural information for each
scene. Stereo information is also of utmost importance for the determination of outcrop geometry (e.g., strike and
dip of layered sequences), which helps to understand the emplacement history of sedimentary and volcanic rocks
(e.g., cross-bedding, unconformities, etc.). PanCam will further reveal physical soil properties such as cohesion
by imaging sites where the soil is disturbed by the rover‘s wheels and the drill. Another essential task of PanCam
is the imaging of samples (from the drill) before ingestion into the rover for further analysis by other instruments.
PanCam can be tilted vertically and will also study the atmosphere (e.g., dust loading, opacity, clouds) and aeolian
processes related to surface-atmosphere interactions, such as dust devils.
[show abstract][hide abstract] ABSTRACT: Phobos flyby images obtained by the High Resolution Stereo Camera (HRSC) and the Super Resolution Channel (SRC) onboard the Mars Express spacecraft were used to produce a global Digital Terrain Model and orthoimage mosaics. We derived a set of Phobos topographic image maps, which are combined into an atlas that consists of four quadrangles on three map sheets at the scale of 1: 50,000. The lateral geometric accuracy of these maps of ± 20 m is more than four times better than that of past products. They are based on a shape model with 0.52° × 0.52° grid spacing and show significantly more detail in comparison to previous data products.
Earth and Planetary Science Letters 01/2010; · 4.35 Impact Factor
[show abstract][hide abstract] ABSTRACT: A new independent control point network for Phobos was computed from image
data obtained by the SRC (Super Resolution Channel) on board the European
Mars Express Mission. The network solution includes 3D coordinates of 665
surface control points and was used to observe the forced libration amplitude
of Phobos. Based on the network control points a spherical harmonic function
model to degree and order 17 was derived, from which volume, bulk density and
moments of inertia were computed. The modeled forced libration amplitude
agrees to our observation within the error bands, indicating a homogeneous
mass distribution for Phobos. To bring both values into exact agreement with
the observations, different mass distribution models were applied. It appears
that the amplitude is relatively insensitive to a simple two-layer density model.
[show abstract][hide abstract] ABSTRACT: In this study we have used observations by MEx/OMEGA and MEx/HRSC to analyse equatorial CO2 cloud occurrences as well as some properties of the clouds (altitude, particle size, opacity). We will present the results acquired so far using the two datasets.
[show abstract][hide abstract] ABSTRACT: Astrometric measurements were obtained from frame images of the SRC on Mars Express. Camera pointing was controlled and corrected with background star observations, made just before and after the Phobos encounter. (1 data file).
[show abstract][hide abstract] ABSTRACT: The Mars Express spacecraft carries the pushbroom scanner high-resolution stereo camera (HRSC) and its added imaging subsystem super resolution channel (SRC). The SRC is equipped with its own optical system and a 1024×1024 framing sensor. SRC produces snapshots with 2.3 m ground pixel size from the nominal spacecraft pericenter height of 250 km, which are typically embedded in the central part of the large HRSC scenes. The salient features of the SRC are its light-weight optics, a reliable CCD detector, and high-speed read-out electronics. The quality and effective visibility of details in the SRC images unfortunately falls short of what has been expected. In cases where thermal balance cannot be reached, artifacts, such as blurring and “ghost features” are observed in the images. In addition, images show large numbers of blemish pixels and are plagued by electronic noise. As a consequence, we have developed various image improving algorithms, which are discussed in this paper. While results are encouraging, further studies of image restoration by dedicated processing appear worthwhile. The SRC has obtained more than 6940 images at the time of writing (1 September 2007), which often show fascinating details in surface morphology. SRC images are highly useful for a variety of applications in planetary geology, for studies of the Mars atmosphere, and for astrometric observations of the Martian satellites. This paper will give a full account of the design philosophy, technical concept, calibration, operation, integration with HRSC, and performance, as well as science accomplishments of the SRC.
Planetary and Space Science 03/2008; 56(2008-3-4):473-491. · 2.11 Impact Factor
[show abstract][hide abstract] ABSTRACT: During the Galileo mission, the near-infrared mapping spectrometer (NIMS) collected data of the icy satellite Ganymede between 0.7 and 5.2 μm. Spectra are mainly characterized by signatures of water ice as well as some signatures of non-ice components and trace constituents like CO2. The detailed analysis of the spectral parameters of specific absorptions in NIMS spectra, i.e. their wavelength position and band depth, depends strongly on the signal-to-noise ratio (SNR) over the specific wavelength range. A high SNR is essential for mapping the spectral properties of a planetary surface as well as for detecting new compounds in the NIMS spectra. We used a novel technique based on the principal component analysis (PCA) in order to improve the SNR and to retain the full spatial information of the NIMS cubes. This application made it possible to correct instrument artifacts and remove more random noise probably caused by the operation in the radiation-intense environment of the Jovian system without significantly affecting the relevant spectral information contained in each NIMS spectrum. This application results in higher quality spectral data, especially beyond of 3 μm where the signal (and thus the SNR) is often very low. The detection and characterization of several important spectral features at the long wavelengths can be improved, including the Fresnel reflection peak at 3.1 μm that can be used to characterize the crystallinity of water ice as well as weak absorptions due to CO2 and other trace compounds. This is essential to map their distribution across a planetary surface and to study the relationships of the chemical composition and the physical properties (e.g. origin of the rocky non-ice material, crystallization and amorphization of water ice, origin of CO2) on Ganymede to geological and morphological surface features and processes (e.g. impact cratering, tectonics).
Planetary and Space Science 01/2008; · 2.11 Impact Factor
[show abstract][hide abstract] ABSTRACT: The German initiative for the Lunar Exploration Orbiter (LEO) originated from the national conference ?Exploration of our Solar System?, held in Dresden in November 2006. Major result of this conference was that the Moon is of high interest for the scientific community for various reasons, it is affordable to perform an orbiting mission to Moon and it insures technological and scientific progress necessary to assist further exploration activities of our Solar System. Based on scientific proposals elaborated by 50 German scientists in January 2007, a preliminary payload of 12 instruments was defined. Further analysis were initated by DLR in the frame of two industry contracts, to perform a phase-zero mission definition. The Moon, our next neighbour in the Solar System is the first choice to learn, how to work and live without the chance of immediate support from earth and to get prepared for further and farther exploration missions. We have to improve our scientific knowledge base with respect to the Moon applying modern and state of the art research tools and methods. LEO is planed to be launched in 2012 and shall orbit the Moon for about four years in a low altitude orbit.
LEAG Workshop on Enabling Exploration: The Lunar Outpost and Beyond,; 10/2007
[show abstract][hide abstract] ABSTRACT: Martian valley networks have been cited as the best evidence that Mars maintained flow of liquid water across its surface. Although internal structures associated with a fluvial origin within valleys such as inner channels, terraces, slip-off and undercut slopes are extremely rare on Mars (Carr and Malin, 2000) such features can be identified in highresolution imagery (e.g. Malin and Edgett, 2001; Jaumann et al., 2005). However, besides internal features the source regions are an important indicator for the flow processes in Martian valleys because they define the drainage area and thus constrain the amount of available water for eroding the valley network. Furthermore, the morphology of the source regions and their topographic characteristics provide information about the origin of the water. On Mars valley networks are thought to have been formed by retreating erosion where the water is supplied from the sub-surface. However, the mechanisms that are responsible for the release of ground water are poorly understood. The three-dimensional highly resolved data of the High Resolution Stereo Camera (HRSC) on the Mars Express Mission (Jaumann et al., 2007) allow the detailed examination of valley network source regions.
38th Lunar and Planetary Science Conference; 03/2007
[show abstract][hide abstract] ABSTRACT: In this paper we report about a small region on the northern scarp of Olympus Mons showing an increase of the 3 μm hydration band in the OMEGA spectra, together with low superficial temperatures. Although water ice clouds can occurs on the flank of big martian volcanoes, radiative transfer modeling indicates that atmospheric water ice alone cannot justify the shape of the observed band. A fit of the 1.9–3 μm absorption features is obtained by hypothesizing that the study region consists of a mixture of dust and water ice covered by an optically thin (τ=0.08 at 3 μm) layer of dust. Thermal modeling also suggests that water ice in this region may be stable during most of the martian year due to the saturation of the atmosphere. If water ice is responsible for the observed spectral behavior, it might consist of a number of ice or snow patches possibly deposited in small depressions.