[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: In this paper we study satellites in Phobos's quasiorbits. We estimated
the lifetime of quasi-satellites under the influence of various
perturbing forces. We also study Phobos observing conditions and
possible surface mapping strategies.
[show abstract][hide abstract] ABSTRACT: HRSC images from Mars Express Phobos flybys are used to study the
photometric character of the surface of the Martian satellite. This
investigation involves measuring of surface reflectance and illumination
angles for estimates of a phase curve, and fitting of theoretic
photometric functions. As results we obtain information on multispectral
and physical properties of the Phobos surface as well as photometrically
corrected geomorphological and albedo maps.
[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 present a new set of astrometric data for Deimos, obtained by the SRC
camera on Mars Express. New techniques have been developed involving the
Deimos shape model to improve accuracy of our measurements. The
observations are in agreement with current Martian satellite orbit
models within a few km.
[show abstract][hide abstract] ABSTRACT: We have presented a dataset of 3 Martian Years of observations of high-altitude CO2 clouds with OMEGA and HRSC on Mars Express and com-pared these observations to other published work. The clouds seem to have a quite regular seasonal behavior, even though we cannot draw definitive conclusions on interannual variability in the lack of full observational coverage. Extensions of existing datasets as well as analyses of new ones will help in filling the gaps and improving our knowledge on the cloud properties. The cloud observation dataset provides a rare source of information on mesos-pheric variables, such as temperature and winds, and can be used to constrain Global Climate Models.
Fourth International Workshop on the Mars Atmosphere: Modelling and Observations. 02/2011;
[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: Images obtained by the High Resolution Stereo Camera (HRSC) during recent Phobos flybys were used to study the proposed new landing site area of the Russian Phobos-Grunt mission, scheduled for launch in 2011 . From the stereo images (resolution of up to 4.4 m/pixel), a digital terrain model (DTM) with a lateral resolution of 100 m per pixel and a relative point accuracy of ±15 m, was determined. Images and DTM were registered to the established Phobos control point network . A map of the landing site area was produced enabling mission planers and scientists to extract accurate body-fixed coordinates of features in the Phobos Grunt landing site area.
The first Moscow Solar System Symposium (1M-S3); 09/2010
[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: 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: This study presents the latest results on the mesospheric CO2 clouds in the martian atmosphere based on observations by OMEGA and HRSC onboard Mars Express. We have mapped the mesospheric CO2 clouds during nearly three martian years of OMEGA data yielding a cloud dataset of ∼60 occurrences. The global mapping shows that the equatorial clouds are mainly observed in a distinct longitudinal corridor, at seasons Ls = 0–60° and again at and after Ls = 90°. A recent observation shows that the equatorial CO2 cloud season may start as early as at Ls = 330°. Three cases of mesospheric midlatitude autumn clouds have been observed. Two cloud shadow observations enabled the mapping of the cloud optical depth (τ = 0.01–0.6 with median values of 0.13–0.2 at λ = 1 μm) and the effective radii (mainly 1–3 μm with median values of 2.0–2.3 μm) of the cloud crystals. The HRSC dataset of 28 high-altitude cloud observations shows that the observed clouds reside mainly in the altitude range ∼60–85 km and their east–west speeds range from 15 to 107 m/s. Two clouds at southern midlatitudes were observed at an altitude range of 53–62 km. The speed of one of these southern midlatitude clouds was measured, and it exhibited west–east oriented speeds between 5 and 42 m/s. The seasonal and geographical distribution as well as the observed altitudes are mostly in line with previous work. The LMD Mars Global Climate Model shows that at the cloud altitude range (65–85 km) the temperatures exhibit significant daily variability (caused by the thermal tides) with the coldest temperatures towards the end of the afternoon. The GCM predicts the coldest temperatures of this altitude range and the season Ls = 0–30° in the longitudinal corridor where most of the cloud observations have been made. However, the model does not predict supersaturation, but the GCM-predicted winds are in fair agreement with the HRSC-measured cloud speeds. The clouds exhibit variable morphologies, but mainly cirrus-type, filamented clouds are observed (nearly all HRSC observations and most of OMEGA observations). In ∼15% of OMEGA observations, clumpy, round cloud structures are observed, but very few clouds in the HRSC dataset show similar morphology. These observations of clumpy, cumuliform-type clouds raise questions on the possibility of mesospheric convection on Mars, and we discuss this hypothesis based on Convective Available Potential Energy calculations.
[show abstract][hide abstract] ABSTRACT: One of the unique features of the Martian climate is the existence of
CO2 ice clouds formed from the main atmospheric constituent. These
clouds were thought to form only in the polar night, where the CO2
condenses on the winter pole. Recently, Mars Express has observed
several occurrences of high-altitude CO2 clouds mainly in the equatorial
areas. We use observations by OMEGA (Bibring et al., 2004) and HRSC
(Jaumann et al., 2007) to analyse these high-altitude CO2 cloud
occurrences. As shown by Montmessin et al. (2007), the spectral
signature of CO2 clouds seen in OMEGA spectra exhibits one or two
distinct peaks that appear inside a strong CO2 gas absorption band
centered at 4.3 microns. We have mapped this spectral signature with a
3-sigma detection method. The mapping of the clouds in three Martian
years of OMEGA data have provided a cloud dataset of about 60
occurrences. These observations provide information on the spatial and
seasonal distribution of CO2 cloud formation at the equatorial region
and information on variations of cloud particle size, related to the
variations in the spectral signature of the clouds. The clouds exhibit
variable morphology from clearly convective type, round structures
(about 15% of all cases), to more filamented, cirrus type clouds. We
have also analysed some properties of the clouds (altitude, particle
size, opacity) using two shadow observations by OMEGA. We will present
the results acquired so far using the datasets of the two instruments.
OMEGA shows that the clouds exhibit interannual variations, but in
general the clouds are concentrated on specific spatial and seasonal
bins, mainly around the equator and around Ls=45 and Ls=135, before and
after the northern summer solstice. Most high-altitude clouds are
observed in a longitudinally limited area, between 150 W and 30 E.
During the first year of observations the cloud shadow was also observed
on two orbits. The analysis of the cloud observations have revealed that
the clouds are thick with near-infrared opacities (at 1 micron) between
0.2--0.7, they are at around 80 km altitude in the atmosphere and the
mean particle effective radius is mainly 1-2microns, although
submicronic particles are also observed. HRSC images have also been
analysed and the presence of these high-altitude clouds in them has been
confirmed. The HRSC observes through a set of colour filters, which
allows for the determination of the cloud altitude through
photogrammetry analysis and westward wind speeds at cloud altitude
through relative cloud movement between images taken through two filters
at different times. HRSC observations provide also a higher spatial
resolution, as well as a wider image, providing more context for mapping
the cloud morphology. Preliminary analysis of the HRSC orbits have
revealed CO2 cloud altitudes ranging from 59 km to 83 km, each with an
altitude accuracy of +/- 1-2 km and cloud (wind) speeds of 15-107 m/s
(+/-15m/s). One cloud, observed far from the equator, shows a varying
altitude of 53-67 km in a latitude bin of 46-53 S. We will present the
datasets and cloud characteristics acquired so far in the analysis.
Bibring, J.-P., Soufflot,A., Berthe,M., Langevin, Y., Gondet, B.,
Drossart, P., Bouye, M., Combes, M., Puget, P., Semery, A., Bellucci,
G., Formisano, V., Moroz, V., Kottsov, V., the OMEGA Co-I team, Bonello,
G., Erard, S., Forni, O., Gendrin, A., Manaud, N., Poulet, F., Poulleau,
G., Encrenaz, T., Fouchet, T., Melchiorri, R., Altieri, F., Ignatiev,
N., Titov, D., Zasova, L., Coradini, A., Capacionni, F., Cerroni, P.,
Fonti, S., Mangold, N., Pinet, P., Schmitt, B., Sotin, C., Hauber, E.,
Hoffmann, H., Jaumann, R., Keller, U., Arvidson, R., Mustard, J. and
Forget, F.: OMEGA: Observatoire pour la minéralogie, l'eau, les
glaces et l'activité. ESA SP-1240: Mars Express: the scientific
payload, pp. 37-49, 2004. R. Jaumann, G. Neukum, T. Behnke, T. C.
Duxbury, J. Flohrer, S. V. Gasselt, B. Giese, K. Gwinner, E. Hauber, H.
Hoffmann, A. Hoffmeister, U. Köhler, K.-D. Matz, T. B. McCord, V.
Mertens, J. Oberst, R. Pischel, D. Reiss, E. Ress, T. Roatch, P. Saiger,
F. Scholten, G. Schwarz, K. Stephan and M. Wählisch: The high
resolution stereo camera (HRSC) experiment on Mars Express: Instrument
aspects and experiment conduct from interplanetary cruise through the
nominal mission. Planet. Space Sci., 55, pp. 928-952, 2007. Montmessin,
F., B. Gondet, J.-P. Bibring, Y. Langevin, P. Drossart, F. Forget and
T. Fouchet: Hyper-spectral imaging of convective CO2 ice clouds in the
equatorial mesosphere of Mars. J. Geophys. Res., 112, 2007.
[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: Aims. New astrometric measurements for Phobos are reported on the basis of 69 SRC (Super Resolution Channel) images obtained during 28 Mars Express Phobos flybys executed between 2004 and 2007.
Methods: The measurements have been made using a newly developed technique that involves positional measurements of surface control points and verification of camera pointing by background stars.
Results: The astrometric positions are in excellent agreement with currently available Phobos orbit models. However, we find remaining systematic offsets of 1.5-2.6 km such that Phobos is ahead of its predicted position along the track.
Conclusions: Our observations will be a basis for further improvements in the Phobos ephemeris. The methods that we have developed will be useful for the astrometric tracking of planetary or asteroidal targets and spacecraft optical navigation in future planetary missions.
Astronomy and Astrophysics 09/2008; · 5.08 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 Phobos encounter. (1 data file).