Development of a micro-balance system for dust and water vapour detection in the Mars atmosphere

Quartz crystal piezoelectric sensors are suitable for deposition analyses that need very high sensitivity. Due to the wide working ranges and high performances, micro-balances can measure the mass settling in average Mars conditions during a period of months before saturation is reached. This ensures a proper use for short and long term water and dust deposition monitoring. Micro-balances have been studied, calibrated and used for the GIADA (grain impact analyser and dust accumulator) experiment for the ESA-Rosetta space mission. Experience on micro-balance performance study by dust deposition has been acquired and water vapour deposition studies are in progress in a Martian atmosphere simulation chamber. Preliminary results show that micro-balances are capable to detect up to partial pressure values corresponding to parts per billion of the typical Martian atmosphere.     

Numerical simulations of the regional characteristics of dust transport on Mars

Using a Martian general circulation model (GCM), regions favorable for expansion of dust storms on Mars are identified. Dust transport simulations for the northern fall provide global maps of dust expansibility. These global maps show that dust injected from certain areas in the northern mid-latitudes tends to spread widely within a few days. The high expansibility of dust in such areas results from thermal tides, baroclinic waves, and quasi-stationary disturbances. Dust injected into the vast regions around Tharsis and the Sirenum–Aonia regions also tends to spread extensively. However, dust expansion around these two regions largely depends on the local time of dust injection. On the other hand, dust injected at high latitudes in either hemisphere does not spread extensively. Such global maps indicating regions favorable for dust storm expansion are a clue to understanding the expansion processes and climatology of great dust storms on Mars.     

Automated determination of the orientation of dust devil tracks in mars orbiter images

The paper presents and evaluates three methods for automatically estimating the main orientation of Martian dust devil tracks in MOC and HiRISE images. Inferring such information about dust devils from their tracks is important to better understand the near surface wind. The methods considered were based on gradient direction, directional openings and morphological granulometry. The accuracy of the methods was asserted by comparing the results to a set of directions estimated visually and assumed to be the ground truth. The higher accuracy was reached using directional openings. Besides, the directions inferred by this method were compared to those predicted by the GCM and the results agreed.     

Radar detection of subsurface features on Mars

The structure of the pulse radar signal reflected from continuously changing layered Martian crust is investigated theoretically. As a simple model of stratigraphy, we considered one layer with electrodynamics’ parameters increasing or decreasing exponentially upon a depth laying on monolith base and covered by homogeneous layer. This exponential changing of electromagnetic properties of the layer is assumed due to exponential changing of porosity (or saturation) in the bedrocks with pores filled by seawater. The conditions of subsurface features resolution are obtained. It is shown that the sign and value for gradient of the electromagnetic properties change can be resolved from the reflection peaks trend. These results are important for subsurface detection of liquid water on Mars by orbit-based radars.     

Observation of aphelion cloud belt over Martian tropics,its evolution,and associated dust distribution from MCS data

The present study uses five Martian years of observations from Mars Climate Sounder onboard Mars Reconnaissance Orbiter for investigating the Aphelion Cloud Belt (ACB) over the tropics. Analysis of zonal mean water ice column opacity suggests that the spatial extension of the ACB is mainly confined over the tropics and mid-latitudes (-20 – 40°N) during L_S ~ 45 – 135° (L_S = 0° signifies northern spring equinox). The ACB is seen primarily in the nighttime only due to the truncation of the daytime profile observations at significantly higher altitudes (at ~30 km). Zonal mean ice extinction profiles show ACB’s altitudinal range within ~10 – 40 km, and the existence of a thin cloud band in the absence of a thick ACB during aphelion season. Three phases of the ACB could be identified as the formation phase during L_S = 45 – 75° (phase 1), the peak phase during L_S = 76 – 105° (phase 2), and the decaying phase during L_S = 106 – 135° (phase 3). Observation of the cloud latitude belt shows a northward movement starting from phase 2, prominent over regions nearby Lunae Planum and Xanthe Terra. During this phase, the top level of thick clouds within the ACB decreases to ~20 km in the southern hemisphere, while it increases a little over the northern hemisphere (NH). The decreasing tendency continues in phase 3 over the entire region ?10 – 10°N, and the thick cloud base moves higher over the NH, though the vertical depth of it becomes narrower than phase 2. Temperature profiles do not show any noticeable influence on the northward evolution of the ACB. However, the study at a regional level indicates a possible association of upper tropospheric dustiness with the ACB’s evolution. The mechanism is evident in the correlation analysis mostly at an altitude range of ~18 – 35 km. The migrating semidiurnal tide (SMD) as a proxy of dust or water ice forcing, and the calculated upper tropospheric dust radiative heating, shows an apparent northward movement of their peak amplitude within the three phases of the ACB. This match between the spatiotemporal variations of the SMD and the water ice was not observed previously. However, the correlating behavior seems to be prominent in the areas nearby Lunae Planum and Xanthe Terra and the upper-tropospheric region of the atmosphere.     

Schumann resonance frequency and conductivity in the nighttime ionosphere of Mars: A source for lightning

We have solved the Maxwellian equations of electromagnetic waves which oscillate within the cavity formed in the lower ionosphere of Mars between 0 and 70?km. The electrical conductivity and Schumann Resonance (SR) frequencies are calculated in the lower ionosphere of Mars, in the presence of a major dust storm that occurred in Martian Year (MY) 25 at low latitude region (25°–35°S). It is found that the atmospheric conductivity reduced by one to two orders of magnitude in the presence of a dust storm. It represents a small dust layer at about 25–30?km altitudes where lightning can occur. We also found that the SR frequencies peak at?～18?km with values 19.9, 34.5 and 48.8?Hz for the modes l?=?1, 2 and 3, respectively, in the non-homogeneous medium. Our results indicate that practical or measurable values of SR are dependent on the altitudes.     

Detection of sub-kilometer craters in high resolution planetary images using shape and texture features

Counting craters is a paramount tool of planetary analysis because it provides relative dating of planetary surfaces. Dating surfaces with high spatial resolution requires counting a very large number of small, sub-kilometer size craters. Exhaustive manual surveys of such craters over extensive regions are impractical, sparking interest in designing crater detection algorithms (CDAs). As a part of our effort to design a CDA, which is robust and practical for planetary research analysis, we propose a crater detection approach that utilizes both shape and texture features to identify efficiently sub-kilometer craters in high resolution panchromatic images. First, a mathematical morphology-based shape analysis is used to identify regions in an image that may contain craters; only those regions - crater candidates - are the subject of further processing. Second, image texture features in combination with the boosting ensemble supervised learning algorithm are used to accurately classify previously identified candidates into craters and non-craters. The design of the proposed CDA is described and its performance is evaluated using a high resolution image of Mars for which sub-kilometer craters have been manually identified. The overall detection rate of the proposed CDA is 81%, the branching factor is 0.14, and the overall quality factor is 72%. This performance is a significant improvement over the previous CDA based exclusively on the shape features. The combination of performance level and computational efficiency offered by this CDA makes it attractive for practical application.     

Open framework for objective evaluation of crater detection algorithms with first test-field subsystem based on MOLA data

Crater Detection Algorithms (CDAs) applications range from estimation of lunar/planetary surface age to autonomous landing on planets and asteroids and advanced statistical analyses. A large amount of work on CDAs has already been published. However, problems arise when evaluation results of some new CDA have to be compared with already published evaluation results. The problem is that different authors use different test-fields, different Ground-Truth (GT) catalogues, and even different methodologies for evaluation of their CDAs. Re-implementation of already published CDAs or its evaluation environment is a time-consuming and unpractical solution to this problem. In addition, implementation details are often insufficiently described in publications. As a result, there is a need in research community to develop a framework for objective evaluation of CDAs. A scientific question is how CDAs should be evaluated so that the results are easily and reliably comparable. In attempt to solve this issue we first analyzed previously published work on CDAs. In this paper, we propose a framework for solution of the problem of objective CDA evaluation. The framework includes: (1) a definition of the measure for differences between craters; (2) test-field topography based on the 1/64° MOLA data; (3) the GT catalogue wherein each of 17,582 craters is aligned with MOLA data and confirmed with catalogues by N.G. Barlow et al. and J.F. Rodionova et al.; (4) selection of methodology for training and testing; and (5) a Free-response Receiver Operating Characteristics (F-ROC) curves as a way to measure CDA performance. The handling of possible improvements of the framework in the future is additionally addressed as a part of discussion of results. Possible extensions with additional test-field subsystems based on visual images, data sets for other planets, evaluation methodologies for CDAs developed for different purposes than cataloguing of craters, are proposed as well. The goal of the proposed framework is to contribute to the research community by establishing guidelines for objective evaluation of CDAs.     

Integrated method for crater detection from topography and optical images and the new PH9224GT catalogue of Phobos impact craters

In a large majority of lunar and planetary surface images, impact craters are the most abundant geological features. Therefore, it is not surprising that crater detection algorithms (CDAs) are one of the most studied subjects of image processing and analysis in lunar and planetary science. In this work we are proposing an Integrated CDA, consisting of: (1) utilization of DEM (digital elevation map)-based CDA; (2) utilization of an optical-based CDA; (3) re-projection of used datasets and crater coordinates from normal to rotated view and back; (4) correction of the brightness and contrast of a used optical image; and (5) tile generation for the optical-based CDA and an assembling of results with an elimination of multiple detections, in combination with a pyramid approach down to the resolution of the available DEM image; and (6) a final integration of the results of DEM-based and optical-based CDAs, including a removal of duplicates. The proposed CDA is applied to one specific asteroid-like body, the small Martian moon Phobos. The experimental evaluation of the proposed CDA is done by a manual verification of crater-candidates and a search for uncatalogued craters. The evaluation has shown that the proposed CDA was used successfully for cataloging Phobos craters. The major result of this paper is the PH9224GT – currently the most complete global catalogue of the 9224 Phobos craters. The possible applications of the new catalogue are: (1) age estimations for any selected location; and (2) comparison/evaluation of the different chronology and production functions for Phobos. This confirms the practical applicability of the new Integrated CDA – an additional result of this paper, which can be used in order to considerably extend the current crater catalogues.     

Hybrid method for crater detection based on topography reconstruction from optical images and the new LU78287GT catalogue of Lunar impact craters

Impact craters are ubiquitous and well-studied structures of high geological relevance on the surfaces of the Earth’s Moon, the terrestrial planets, the asteroids and the satellites of the outer planets. Therefore, it is not surprising that crater detection algorithms (CDAs) are one of the most studied subjects of image processing and analysis in lunar and planetary science. In this paper we are proposing a Hybrid CDA: a modified DEM (digital elevation map) reconstruction method used as a step in an existing CDA based on Hough transform. The new Hybrid CDA consists of: (1) reconstruction of topography from optical images using a shape from shading approach; (2) utilization of the DEM-based CDA; (3) correction of brightness and contrast of optical images used in order to be more suitable for evaluation of detections. An additional result of this work is a new method for evaluation of topography reconstruction algorithms, using a DEM-based CDA and an earlier approach for evaluation of CDAs. The new Hybrid CDA was tested using two Chandrayaan-1 Moon Mineralogy Mapper (M³) images and two excerpts of the Lunar Reconnaissance Orbiter (LRO) Wide Angle Camera (WAC) global optical image mosaic. As a result, the number of craters inside these four regions increased considerably from 1754 (as available in the previous LU60645GT catalogue) to 19 396 craters (as available in the resulting new LU78287GT catalogue). This confirmed the practical applicability of the new Hybrid CDA, which can be used in order to considerably extend current crater catalogues.