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.     

Study of the Moon and comparative planetology: Problems and perspectives

On the base of the comparative planetologic study of the Moon and terrestrial planets two fundamental features of their history and structure have been established.Firstly, shell-like structure of the terrestrial planets could be understood only in the terms of the heterogeneous accretion theory. At the final stages of major terrestrial planet formation the leading role belonged to the planetosimals of carbonaceous chondritic composition. Secondly, there are two types of the crust on the planetary surface. Their formation are considered to be independent and differing in the geological time. The primary planetary crust of predominantly feldspathic composition is considered to form during the pregeologic period at the final stage of planetary formation due to the impact-explosive processes. The hydrosphere and atmosphere is thought to appear contemporaneously. The basaltic planetary crust is forming later due to the radioactive decay and superimposed on the primary feldspathic crust.     

Lunar apex–antapex cratering asymmetry as an impactor recorder in the Earth–Moon system

The degree of apex–antapex cratering asymmetry of a synchronously rotating satellite primarily depends on the mean encounter velocity of impactors with respect to the planetary system and the orbital velocity of the satellite. This means that we can estimate the mean encounter velocity of impactors by observing the apex–antapex cratering asymmetry, if the relationship between these is known. To apply this technique to the Moon, we attempt to derive the relationship between the mean encounter velocity of impactors and the degree of the lunar cratering asymmetry as a function of time, considering the temporal variation in the lunar orbital velocity during the last 4.0 Gyr. We used the cratering asymmetry of Zahnle et al. [Zahnle, K., Schenk, P., Sobieszczyk, S. et al. Differential cratering of synchronously rotating satellites by ecliptic comets. Icarus 153, 111–129, 2001] to obtain the relationship. Applying this relationship enables us to estimate the impactor’s velocity of the Earth–Moon system from an investigation of the spatial distribution of lunar craters. Furthermore, we re-evaluate the cratering asymmetry’s influence on lunar cratering chronology.     

月球和类地行星的化学成分的统计分析

本文对月球和类地行星的模型化学分析数据进行了多元统计分析, 结果表明月球成分更近似于火星和小行星, 与其它类地行星和地球则相差较大。因此, 月球可能形成于地球形成区域之外更靠近太阳系外部的地区。      

Cratering records of the satellites of Jupiter and Saturn

The surfaces of most of the satellites of Jupiter and Saturn show marks of large-meteoroid impacts produced over much of solar system history and partly stemming from the early post-accretional heavy bombardment. An analysis of the crater size distributions shows that (i) crater densities on the most ancient terrains are comparable to those found on the lunar highlands, (ii) crater size distributions differ somewhat from those in the inner solar system but exhibit striking similarities in shape, (iii) the crater size distributions on all terrain types from oldest to youngest are very similar, i. e. the underlying impactor size distribution does not seem to have changed over time, (iv) there is no obvious difference in crater densities between apex and antapex parts of the satellites, (v) the cratering record can better be explained by impacts from bodies in planetocentric orbits rather than by bodies in heliocentric orbits.     

A machine learning approach to crater detection from topographic data

Craters are distinctive features on the surfaces of most terrestrial planets. Craters reveal the relative ages of surface units and provide information on surface geology. Extracting craters is one of the fundamental tasks in planetary research. Although many automated crater detection algorithms have been developed to exact craters from image or topographic data, most of them are applicable only in particular regions, and only a few can be widely used, especially in complex surface settings. In this study, we present a machine learning approach to crater detection from topographic data. This approach includes two steps: detecting square regions which contain one crater with the use of a boosting algorithm and delineating the rims of the crater in each square region by local terrain analysis and circular Hough transform. A new variant of Haar-like features (scaled Haar-like features) is proposed and combined with traditional Haar-like features and local binary pattern features to enhance the performance of the classifier. Experimental results with the use of Mars topographic data demonstrate that the developed approach can significantly decrease the false positive detection rate while maintaining a relatively high true positive detection rate even in challenging sites.     

Remote estimation of the structure of the surface layer of Mercury

Results of the optical observations of Mercury and the Moon confirm the close similarity of photometric properties of the bodies. Undoubtedly, the surface of Mercury, which is subjected to the same processes, is covered by a mantle of shattered rocks – the regolith. The structure of the reflecting layer determines the photometric and polarization characteristics of the surface of a planetary body. Despite the general similarity of the integral optical properties of the surfaces of Mercury and the Moon, specific characteristics of the media of these celestial bodies manifest themselves as identifiable differences in the details of the measured parameters: Mercury’s regolith is smoother than of the Moon, probably contains a greater fines fraction, and has greater maturity.     

The South Pole-Aitken basin region,Moon: GIS-based geologic investigation using Kaguya elemental information

Using Geographic Information Systems (GIS), we performed comparative analysis among stratigraphic information and the Kaguya (SELENE) GRS data of the ∼2500-km-diameter South Pole-Aitken (SPA) basin and its surroundings. Results indicate that the surface rock materials (including ancient crater materials, mare basalts, and possible SPA impact melt) are average to slightly elevated in K and Th with respect to the rest of the Moon. Also, this study demonstrates that K and Th have not significantly changed since the formation of SPA. The elemental signatures of the impact basin of Fe, Ti, Si, O through time include evidence for resurfacing by ejecta materials and late-stage volcanism. The oldest surfaces of SPA are found to be oxygen-depleted during the heavy bombardment period relative to later stages of geologic development, followed by both an increase in silicon and oxygen, possibly due to ejecta sourced from outside of SPA, and subsequent modification due to mare basaltic volcanism, which increased iron and titanium within SPA. The influence of the distinct geologic history of SPA and surroundings on the mineralogic and elemental abundances is evident as shown in our investigation.     

Indications and counterindications for applying different versions of closed ecosystems for space and terrestrial problems of life support.

Different versions of manned closed ecosystems (CES) based on photosynthesis of unicellular and/or higher plants and chemosynthesis or bacteria are considered. Different versions of CES have been compared for applying them on Earth, Moon, Mars and Venus orbital stations, for Mars missions and planetary stations as well as to provide high-quality life in extreme conditions on the Earth. In microgravity [correction of mycrogravity] we recommend CES with unicellular organisms based on photosynthesis or chemosynthesis (depending of the availability of the light or electric energy). For the planetary stations with Moon gravity and higher CES with higher plants are recommended. Improvement of indoor air quality by CES biotechnology is considered.     

Synergetic use of SAR and Thermal Infrared data to study the physical properties of the lunar surface

The surface layer of the Moon preserves vital evidences of lunar impact and cratering processes due to the absence of any Aeolian and fluvial erosion processes acting on it. By examining these evidences, which are recorded throughout the evolutionary history of the Moon, several basic aspects of lunar science can be understood, and this has direct relevance to the surfaces of other airless bodies within the solar system. In this study, rock abundance data obtained from Thermal Infrared (TIR) observations and radar Circular Polarization Ratio (CPR) data sets obtained from polarimetric SAR observations were correlated at some sample sites on the lunar surface. Preliminary results yielded qualitative and quantitative estimates for surface rock abundances. Except at distal ejecta deposits of young, bright craters a general correlation was observed between the two datasets. Mixed results were observed from the impact melt flows where the situation is complex due to the possible subsurface-volume and volume-subsurface interactions of the radar waves. But the flow features were clearly separated from the interior and ejecta regions of their parent craters in terms of CPR and rock abundances. The extent and distributions of pyroclastic deposits and dark haloed regions could not be distinctly identified at the resolution of datasets utilized. Near Gerasimovich D crater, the Diviner Radiometer has provided the first TIR observations of a newly discovered impact melt flow which was not visible in the optical imagery. This facilitated the first ever quantitative comparisons of the radar CPR and rock abundance values near such a region. Also, significant differences in spatial patterns between the radar and rock concentration data sets were observed, owing to the differences in the sensitivity of the two observations.     

Modifications of Martian ice-saturated regolith due to meteoroid impact

The possibility of water ice in the Martian subsurface regolith continues to present an intriguing enigma. We submit that any exo-martian source of energy, i.e. meteorite, asteroid or cometary impact, must disturb the equilibrium within the regolith surrounding an impact site. We farther propose impactors with the size range of 100 m and larger with velocities of 10 km s⁻¹ are effective in causing significant temperature increases in the regolith and subsequent ice melting. We present our studies of the crater formation within Martian surface layers that presumably are a solid mixture of regolith and water ice. Mass ratio of rocks to ice, as well as the thermal gradient in the crust, are the parameters. We have completed numerical simulations of a cratering event by means of two-dimensional, axialsymmetric hydrocodes involving a free particles' method in order to provide a simulation of an impact cratering. A fraction of subsurface ice melts and the crater partially forms from mud-like material. Comparison of a calculated crater and observed Martian crater is presented. The simplified analytical estimates concerning melting of ground ice in the regolith surrounding a Martian impact crater are presented.     

Laboratory investigations of the survivability of bacteria in hypervelocity impacts.

It is now well established that material naturally moves around the Solar System, even from planetary surface to planetary surface. Accordingly, the idea that life is distributed throughout space and did not necessarily originate on the Earth but migrated here from elsewhere (Panspermia) is increasingly deemed worthy of consideration. If life arrived at the Earth from space, its relative speed will typically be of order many km s-1, and the resulting collision with the Earth and its atmosphere will be in the hypervelocity regime. A mechanism for the bacteria to survive such an impact is required. Therefore a programme of hypervelocity impacts in the laboratory at (4.5 +/- 0.6) km s-1 was carried out using bacteria (Rhodococcus) laden projectiles. After impacts on a variety of target materials (rock, glass and metal) attempts were made to culture Rhodococcus from the surface of the resulting craters and also from the target material ejected during crater formation. Control shots with clean projectiles yielded no evidence for Rhodococcus growth from any crater surface or ejecta. When projectiles doped with Rhodococcus were used no impact crater surface yielded colonies of Rhodococcus. However, for four shots of bacteria into rock (two on chalk and two on granite) the ejecta was afterwards found to give colonies of Rhodococcus. This was not true for shots onto glass. In addition, shots into aerogel (density 96 kg m-3) were also carried out (two with clean projectiles and two with projectiles with Rhodococcus). This crudely simulated aero-capture in a planetary atmosphere. No evidence for Rhodococcus growth was found from the projectiles captured in the aerogel from any of the four shots.     

Limits of photosynthesis in extrasolar planetary systems for earth-like planets.

We present a general modeling scheme for investigating the possibility of photosynthesis-based life on extrasolar planets. The scheme focuses on the identification of the habitable zone in main-sequence-star planetary systems with planets of Earth mass and size. Our definition of habitability is based on the long-term possibility of photosynthetic biomass production as a function of mean planetary surface temperature and atmospheric CO2-content. All the astrophysical, climatological, biogeochemical, and geodynamic key processes involved in the generation of photosynthesis-driven life conditions are taken into account. Implicitly, a co-genetic origin of the central star and the orbiting planet is assumed. The numerical solution of an advanced geodynamic model yields realistic look-up diagrams for determining the limits of photosynthesis in extrasolar planetary systems, assuming minimum CO2 levels set by the demand of C4 photosynthesis.     

Radioactivity of the Moon and planets

In this report the main results of the study of radioactivity of the solar sistem bodies are considered. The radioactivity of the Moon and planets was measured by means of vehicles in situ. The radioactivity of the lunar samples, brought to the Earth was studied with laboratory equipment.     

Planetary protection policy overview and application to future missions.

The 1967 treaty on the peaceful uses of outer space reflected both concerns associated with the unknown nature of the space environment and the desire of the world scientific community to preserve the pristine nature of celestial objects until such times as they could be studied in an effective manner. Since 1967, NASA has issued policy directives that have adopted the guidelines of COSPAR for protecting the planets from contamination by Earth organisms and for protecting the Earth from the unknown. This paper presents the current status of planetary protection (quarantine) policy within NASA, and a prospectus on how planetary protection and back contamination issues might be addressed in relation to future missions envisioned for development by NASA either independently, or in cooperation with the space agencies of other nations.     

Synergies of Earth science and space exploration

A more flexible policy basis from which to manage our planet in the 21st century is desirable. As one contribution, we note that synergies between space exploration and the preservation of our habitat exist, and that protecting life on Earth requires similar concepts and information as investigations of life beyond the Earth, including the expansion of human presence in space. Instrumentation and data handling to observe both planetary objects and planet Earth are based on similar techniques. Moreover, while planetary surface operations are conducted under different conditions, the technology to probe the surface and subsurface of both the Earth and other planets requires similar tools, such as radar, seismometers, and drilling devices. The Earth observation community has developed some exemplary tools and has featured successful international cooperation in data handling and sharing that could be equally well applied to robotic planetary exploration. Here we propose a network involving both communities that will enable the interchange of scientific insights and the development of new policies and management strategies. Those tools can provide a vital forum through which the management of this planet can be assisted, and in which a new bridge between the Earth-centric and space-centric communities can be built.     

Simulation software for the spiral trajectory of our Moon

At 4.56 Ga, the accretion of the slowly rotating Solar Nebula led to the formation of Sun and its Planets in the plane of disc of accretion. Moon was formed by accretion from a circumterrestrial disk of debris generated by the glancing angle impact of the young Earth by a Mars size planetary embryo at about 4.5 Ga at a distance of 15,000 km. The Moon since then has migrated to the present position of 384,400 km from the center of the Earth. In course of this outward migration it has slowed down the spin rate of Earth and caused the lengthening of diurnal day length from 5 h initially to 24 h presently. The basic mechanics of Earth–Moon System has been worked out and theoretical determination of lengthening of day curve is carried out. This theoretical lengthening of day curve is compared with the observed lengthening of day curve based on paleobotanical evidences, ancient tidalites and Australian Banded Iron Formation. There is a remarkable correspondence between the two curves except for intermittent deviations due to geographical and geophysical factors. Based on the theoretical curve of lengthening of day, an empirical formula for the lunar orbital radius expansion is determined. Based on this empirical formula, simulation software is developed that gives the correct evolution of the semi-major axis (a) of our Moon for any time span from the inception to the time chosen under study. For mathematical simplicity the system is considered to be a two body rotating system throughout its evolutionary history of 4.5 Gyrs. This simulation draws the Moon’s spiral trajectory from its inception to any subsequent epoch. The terminal epoch is an input to the simulation software to arrive at the spiral trajectory of the Moon from the inception to the given epoch. The basic mechanics of Earth–Moon System and this simulation can be generalized to lay the foundation of simulation software for any Planet–Satellite pair or any Sun-Planet pair in our Solar System or Star-Planet pair in any Extra-Solar System. The basic dynamics has been found to be valid for Star–Planet pair also. So this Simulation Methodology can as well be applied to study the migratory evolution of Gas Giants also.     

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.     

From the interstellar clouds, through the inner to the outer solar system: a universally distributed complex organic chemistry. Preface.

High molecular weight organic compounds are involved in the chemistry and physics of many astrophysical and planetary objects. They are or should be present in interstellar dust, in comets and meteorites, in the Giant planets and Titan, in asteroids Triton and icy satellites. They represent a class of very complex organic material, part of which may have played a role in the origin of life on Earth. Thus they directly concern prebiotic chemistry and exobiology.     

A new approach based on crater detection and matching for visual navigation in planetary landing

This paper provides an approach of crater detection and matching to visual navigation in planetary landing missions. The approach aims to detect craters on the planetary surface and match them to a landmark database during the descent phase of a planetary landing mission. Firstly an image region pairing method is proposed to detect the crater by using an image region feature detector. Then a WTA-rule is adopted to match the detected crater to the crater in database. To further reduce the false matching rate, an efficient method for reducing false matches using parameters of crater in 3-D database is proposed. Real images of planetary terrain and a semi-physical planetary landing simulation platform are utilized to test the performance of the approach, simulation results show the proposed approach is able to match the required number of craters to the database for pin-point planetary landing with a low rate of false detection and false matching, which will lead to an improved planetary landing precision.