Field reconnaissance geologic mapping of the Columbia Hills, Mars, based on Mars Exploration Rover Spirit and MRO HiRISE observations

Chemical, mineralogic, and lithologic ground truth was acquired for the first time on Mars in terrain units mapped using orbital Mars Reconnaissance Orbiter's High Resolution Imaging Science Experiment (MRO HiRISE) image data. Examination of several dozen outcrops shows that Mars is geologically complex at meter length scales, the record of its geologic history is well exposed, stratigraphic units may be identified and correlated across significant areas on the ground, and outcrops and geologic relationships between materials may be analyzed with techniques commonly employed in terrestrial field geology. Despite their burial during the course of Martian geologic time by widespread epiclastic materials, mobile fines, and fall deposits, the selective exhumation of deep and well-preserved geologic units has exposed undisturbed outcrops, stratigraphic sections, and structural information much as they are preserved and exposed on Earth. A rich geologic record awaits skilled future field investigators on Mars. The correlation of ground observations and orbital images enables construction of a corresponding geologic reconnaissance map. Most of the outcrops visited are interpreted to be pyroclastic, impactite, and epiclastic deposits overlying an unexposed substrate, probably related to a modified Gusev crater central peak. Fluids have altered chemistry and mineralogy of these protoliths in degrees that vary substantially within the same map unit. Examination of the rocks exposed above and below the major unconformity between the plains lavas and the Columbia Hills directly confirms the general conclusion from remote sensing in previous studies over past years that the early history of Mars was a time of more intense deposition and modification of the surface. Although the availability of fluids and the chemical and mineral activity declined from this early period, significant later volcanism and fluid convection enabled additional, if localized, chemical activity

Approximate and exact numerical integration of the gas dynamic equations

A highly accurate approximation and a rapidly convergent numerical procedure are developed for two dimensional steady supersonic flow over an airfoil. Examples are given for a symmetric airfoil over a range of Mach numbers. Several interesting features are found in the calculation of the tail shock and the flow behind the airfoil

Potential vorticity, angular momentum and inertial instabilities in the Martian atmospheric circulation from assimilated analyses of MGS/TES

Data based on re-analyses of the MGS/TES observations have been used to map distributions of potential vorticity and axial absolute angular momentum per unit mass. The data, discussed in more details in [1] and [2] stretches over nearly three Martian years and cover a wide range of atmospheric conditions. The spatial distribution and variation in time of angular momentum and potential vorticity are closely related to the zonal-mean circulation. Maps of potential vorticity distributions have been used to establish regions and times favourable for inertial instabilities. A narrow region near the equator which extends throughout the atmosphere is shown to be able to sustain inertial instabilities at different times of the year. The presence of inertial instabilities is predicted from the necessary (but not sufficient) condition for the occurrence of regions of atmosphere with PV of opposite sign to that of the planetary vorticity (PVanomalies). These regions are characterized as being favorable to mixing on small scales, while at larger scales there may be potential links to Rossby wave breaking (Knox et. al. 2005][3]. Analyses of the data indicates a hemispheric asymmetry where the northern hemisphere is more favorable to inertial instabilities particularly during NH winter. Barnes et. al. (1996)[4] used a global Martian circulation model to find that, during dusty solstice conditions, the Martian tropical and mid-latitude atmospheric circulation approximates to an angular-momentum conserving Hadley circulation, and is responsible for creating regions near the equator of low potential vorticity. Using the assimilated data we re-examine these results for a wider range of atmospheric states, including the period of the 2001 planet-encircling dust storm

Benchmark experiments with global climate models applicable to extra-solar gas giant planets in the shallow atmosphere approximation

The growing field of exoplanetary atmospheric modelling has seen little work on standardised benchmark tests for its models, limiting understanding of the dependence of results on specific models and conditions. With spatially resolved observations as yet difficult to obtain, such a test is invaluable. Although an intercomparison test for models of tidally locked gas giant planets has previously been suggested and carried out, the data provided were limited in terms of comparability. Here, the shallow PUMA model is subjected to such a test, and detailed statistics produced to facilitate comparison, with both time means and the associated standard deviations displayed, removing the time dependence and providing a measure of the variability. Model runs have been analysed to determine the variability between resolutions, and the effect of resolution on the energy spectra studied. Superrotation is a robust and reproducible feature at all resolutions

Thermal tides in an assimilation of three years of Thermal Emission Spectromenter data from Mars Global Surveyor

Introduction. Thermal tides are particularly prominent in the Mars atmosphere with the result that temperature and wind fields have a strong dependence on local solar time (LT). Tides include westward propagating migrating (sun-synchronous) waves driven in response to solar heating and additional nonmigrating waves resulting from zonal variations in the thermotidal forcing. Zonal modulation of forcing can arise from longitudinal variations of the boundary (topography and surface thermal inertia) and radiatively active aerosols (dust and water ice clouds). Nonmigrating tides appear as diurnally varying upslope/ downslope circulations within the near-surface boundary layer that, like their migrating counterparts, are also able to propagate vertically to aerobraking altitudes in the lower thermosphere. The Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) has yielded atmospheric temperature profiles with unprecedented latitude and longitude coverage that has provided the basis for characterizing the seasonal evolution of tides and stationary waves [1]. However, the twice-daily observations (2 am and 2 pm LT) are insufficient to unambiguously resolve the sunsynchronous tides. Recently the technique of data assimilation has been sufficiently developed for Mars to yield a dynamically consistent set of thermal and dynamic fields suitable for detailed investigations of various aspects of the martian circulations system [2,3,4,5]. We will refer to this data set an the TES Reanalysis, which represents the current best estimate of the evolving state of the martian atmosphere during the MGS mission. The assimilated thermal and dynamical fields provide a means of assessing circulation variability and transport capability reflecting the variability of the actual Mars atmosphere

Super-rotating jets in a re-analysis of the martian atmosphere

Strong westerly, prograde jets have been identified in the martian atmosphere between about 10–20 km altitude throughout much of the year in a Mars Global Circulation Model (MGCM) study [2]. The development of data assimilation techniques for Mars [3, 5] now permits the analysis of super-rotation in less highly idealized cases using an atmospheric reanalysis, as would be done for the Earth. This paper reviews recent atmospheric reanalyses, in order to validate previous modeling results, to quantify jet amplitudes and to diagnose possible mechanisms supplying angular momentum to the jets. [2] Lewis, S. R., and Read, P. L.: Equatorial jets in the dusty martian atmosphere, J. Geophys. Res., Vol. 108 (E4), 5034, pp. 1–15, 2003. [3] Lewis, S. R., Read, P. L., Conrath, B. J., Pearl, J. C., and Smith, M. D.: Assimilation of Thermal Emission Spectrometer atmospheric data during the Mars Global Surveyor aerobraking period, Icarus, Vol. 192 (2), pp. 327–347, 2007. [5] Montabone, L., Lewis, S. R., Read, P. L., Hinson, D. P., Validation of Martian meteorological data assimilation for MGS/TES using radio occultation measurements, Icarus Vol. 185 (1), pp. 113–132, 2006

USSR Space Life Sciences Digest

Research in exobiology, life sciences technology, space biology, and space medicine and physiology, primarily using data gathered on the Salyut 6 orbital space station, is reported. Methods for predicting, diagnosing, and preventing the effects of weightlessness are discussed. Psychological factors are discussed. The effects of space flight on plants and animals are reported. Bioinstrumentation advances are noted

Assessing atmospheric predictability on Mars using numerical weather prediction and data assimilation

Introduction: Studies of the time series of surface measurements of wind, pressure and temperature at the two Viking landers by Barnes [1], [2] revealed that baroclinic transient travelling waves on Mars occur mostly during northern hemisphere autumn, winter and early spring, and typically take the form of highly coherent patterns with planetary wavenumbers 1-3 that can persist for intervals of up to 30-60 sols before changing erratically. Such behaviour is almost unknown on Earth, where individual baroclinic weather systems typically persist for no longer than 5-10 days and seldom remain coherent around entire latitude circles. This occurrence of planetary-scale coherent baroclinic wave-like weather systems on Mars led to suggestions [3] that Mars' atmospheric circulation operates in a quite different dynamical regime to that of the Earth, one that tends to favour regular, symmetrical baroclinic wave activity in a manner reminiscent of the regular wave regimes found in laboratory fluid dynamics experiments on sloping convection in a rotating, thermally-driven fluid annulus (e.g. [4], [5]). In its extreme form, this hypothetical comparison would suggest the possibility of a fully non-chaotic atmospheric circulation on Mars, though subsequent modelling work [6] indicated that perturbations due to the thermal tide would lead to chaotic transitions back and forth between different intransitive wave states. This form of (relatively low-dimensional) chaotic modeflipping appeared to be consistent with the Viking observations of Mars, suggesting nevertheless that the intrinsic predictability of Mars' mid-latitude meteorology was qualitatively and quantitatively quite different from that of the Earth

Midwinter suppression of baroclinic storm activity on Mars: observations and models

We present results from assimilated analyses of observations from the Mars Global Surveyor Thermal Emission Spectrometer showing evidence for a regular suppression of baroclinic circumpolar storm activity in both hemispheres of Mars around winter solstice. General circulation model simulations are then used to elucidate the structure and possible causes of this suppression, for which the local ‘Eady growth rate’ appears to be a good predictor