Clarification of sources of material returned by Luna 24 spacecraft based on analysis of new images of the landing site taken by lunar reconnaissance orbiter   总被引：1，自引：0，他引：1  

A. T. Basilevsky  B. A. Ivanov  A. V. Ivanov  J. W. Head 《Geochemistry International》2013,51(6):456-472

We describe the results of the geologic analysis of high-resolution (0.5 m/px) LROC NAC images of the landing site of the Luna 24 spacecraft, which landed in the southeastern part of Mare Crisium, drilled a borehole to the depth of ～2 m and recovered a core, which was then delivered to the Earth. LROC NAC images show that the spacecraft landed on the rim of the 65-m crater Lev. Image analysis was aided by calculations of the expected thickness of ejecta from crater Lev found to be 0.5–1 m. Using these calculations and the results of photogeologic analysis, we reconsidered the characteristics of the Luna 24 core material. This led to an understanding of the geologic position of different parts of the Luna 24 core and allowed us to distinguish in the core the intervals dominated by: 1—effects of arrival of ejecta from the 6.5-km crater Fahrenheit (Zone IV), 2—gradual reworking of the local regolith by small impacts (Zones II and III), and 3—emplacement of ejecta of Lev crater, which is a secondary of the distant 22-km crater Giordano Bruno (Zone I). This understanding allowed us to propose that some additional new analyses of the Luna 24 material be undertaken, with emphasis on the study of Zone IV and Zone I. Additional analysis of zone IV could search for and identify material of ejecta from the crater Fahrenheit and their comparisons with local materials, while new analysis of Zone I could study the material derived from the deepest parts of the local regolith and search for material of the impactor (ejecta from the very young Giordano Bruno crater on the lunar farside) that formed Lev crater.  相似文献   

The selection and characterization of the <Emphasis Type="Italic">Phobos-Soil</Emphasis> landing sites     

A. T. Basilevsky  T. V. Shingareva 《Solar System Research》2010,44(1):38-43

This paper shortly describes the selection technique for the landing sites of the Phobos-Soil spacecraft, the characteristics of the Phobos relief, the history of choosing the potential landing sites in the process of working on the project, and the suggestions to shift the landing sites to the region recently imaged by the Mars Express spacecraft with a high spatial resolution under favorable illumination conditions.  相似文献   

The Destruction of Small Lunar Craters     

Basilevsky  A. T.  Michael  G. G.  Krasilnikov  S. S.  Kozlova  N. A. 《Solar System Research》2020,54(5):361-371

Solar System Research - The paper discusses three types of processes of destruction of small lunar craters: (1) destruction by overlapping craters; (2) destruction due to filling with ejecta from...  相似文献   

Lineaments on the Surface of the Consolidated Material of the Comet 67P/Churyumov−Gerasimenko Nucleus     

A. T. Basilevsky  Yu. V. Skorov  S. F. Hviid  S. S. Krasilnikov  U. Mall  H. U. Keller 《Solar System Research》2018,52(6):505-517

Morphologic analysis of the fragments (500 × 500 pixels) of images of comet 67P/Churyumov? Gerasimenko obtained with the OSIRIS camera for 18 regions, where the consolidated material is exposed on the surface, has been carried out. In terms of resolution, the images form a series from 0.04 to 1.29 m/pixel; consequently, the areas covered by these fragments vary from 400 to ~400000 m². In all of the regions, lineaments resembling tension fractures—several dozens of structures per region—are seen; and their number scarcely changes when passing from high-resolution images to lower-resolution ones. It is clear that relatively small lineaments cease to be reliably distinguished when the image resolution worsens, but the largest and well-defined ones remain observable, while the number of larger lineaments grows proportionally to the survey area increasing. Undoubtedly, this is an observational effect, which was demonstrated by examples with an artificially worsened resolution. However, on the other hand, this means that the tension fractures of the consolidated nucleus material represent a hierarchic population of smaller (meters long) to larger (decameters and longer) features. The lineaments seen in the analyzed fragments of images were counted, their lengths were measured, and the spacings (the mean distances between lineaments) and, from them, the depths of penetration of fractures into the nucleus material were estimated. It has been shown that the mean length of lineaments within each studied region depends on its area (which here correlates with the image resolution) and the depths of fracture penetration into the nucleus body depends on the mean length of lineaments. Both dependences are close to a power law. In the images of four regions covering the areas from 100000 to 400000 m² with a resolution of 0.66?1.29 m/pixel, the structures that look like layering or sheet jointing are seen in addition to fracture lineaments. The tension fractures are apparently formed due to seasonal and diurnal variations of the temperature, while the nature of the formation of the layer-like structures is not yet fully understood.  相似文献   

Episodes of floods in Mangala Valles,Mars, from the analysis of HRSC,MOC and THEMIS images     

Alexander T. Basilevsky  Gerhard Neukum  Stephanie C. Werner  Alexander Dumke  Stephan van Gasselt  Thomas Kneissl  Wilhelm Zuschneid  Daniela Rommel  Lorenz Wendt  Mary Chapman  James W. Head  Ronald Greeley 《Planetary and Space Science》2009,57(8-9):917-943

The Mangala Valles is a 900-km long outflow channel system in the highlands adjacent to the south-eastern flank of the Tharsis bulge. This work was intended to answer the following two questions unresolved in previous studies: (1) Was there only one source of water (Mangala Fossa at the valley head which is one of the Medusae Fossae troughs or graben) or were other sources also involved in the valley-carving water supply, and (2) Was there only one episode of flooding (maybe with phases) or were there several episodes significantly separated in time. The geologic analysis of HRSC image 0286 and mapping supported by analysis of MOC and THEMIS images show that Mangala Valles was carved by water released from several sources. The major source was Mangala Fossa, which probably formed in response to magmatic dike intrusion. The graben cracked the cryosphere and permitted the release of groundwater held under hydrostatic pressure. This major source was augmented by a few smaller-scale sources at localities in (1) two mapped heads of magmatic dikes, (2) heads of two clusters of sinuous channels, and (3) probably several large knob terrain locals. The analysis of results of crater counts at more than 60 localities showed that the first episode of formation of Mangala Valles occurred ～3.5 Ga ago and was followed by three more episodes, one occurred ～1 Ga ago, another one ～0.5 Ga ago, and the last one ～0.2 Ga ago. East of the mapped area there are extended and thick lava flows whose source may be the eastern continuation of the Mangala source graben. Crater counts in 10 localities on these lava flows correlate with those taken on the Mangala valley elements supporting the idea that the valley head graben was caused by dike intrusions. Our observations suggest that the waning stage of the latest flooding episode (～0.2 Ga ago) led to the formation at the valley head of meander-like features sharing some characteristics with meanders of terrestrial rivers. If this analogy is correct this could suggest a short episode of global warming in Late Amazonian time.  相似文献   

Height-to-diameter ratios of moon rocks from analysis of Lunokhod-1 and -2 and Apollo 11–17 panoramas and LROC NAC images     

N. E. Demidov  A. T. Basilevsky 《Solar System Research》2014,48(5):324-329

An analysis is performed of 91 panoramic photographs taken by Lunokhod-1 and -2, 17 panoramic images composed of photographs taken by Apollo 11–15 astronauts, and six LROC NAC photographs. The results are used to measure the height-to-visible-diameter (h/d) and height-to-maximum-diameter (h/D) ratios for lunar rocks at three highland and three mare sites on the Moon. The average h/d and h/D for the six sites are found to be indistinguishable at a significance level of 95%. Therefore, our estimates for the average h/d = 0.6 ± 0.03 and h/D = 0.54 ± 0.03 on the basis of 445 rocks are applicable for the entire Moon’s surface. Rounding off, an h/D ratio of ≈0.5 is suggested for engineering models of the lunar surface. The ratios between the long, medium, and short axes of the lunar rocks are found to be similar to those obtained in high-velocity impact experiments for different materials. It is concluded, therefore, that the degree of penetration of the studied lunar rocks into the regolith is negligible, and micrometeorite abrasion and other factors do not dominate in the evolution of the shape of lunar rocks.  相似文献   

Geology of the Venera and Vega Landing-Site Regions     

Abdrakhimov  A. M.  Basilevsky  A. T. 《Solar System Research》2002,36(2):136-159

Using Magellan radar images of the Venera and Vega landing-site regions, we carried out a photogeologic analysis and mapping of these regions, the soil composition of which was earlier analyzed by the spacecraft of these series. All these landing-site regions are shown to possess a similar set of geologic situations, which are typical of the planet as a whole, and a similar sequence of geologic evolution. Judging by the results of mapping, a geochemically advanced material analyzed at the Venera-8 landing site appears to be a complex of shield plains (Psh). Tholeiitic compositions obtained by Venera-9/10 and Vega-1/2 probably represent the unit of plains with wrinkle ridges (Pwr), which is most common on Venus. The material of tholeiitic composition analyzed by Venera-14 is likely to be the unit of relatively young lobate plains (Pl).  相似文献   

Onset Time and Duration of Corona Activity on Venus: Stratigraphy and History from Photogeologic Study of Stereo Images     

Basilevsky  A. T.  Head  J. W. 《Earth, Moon, and Planets》1997,76(1-2):67-115

The details of stratigraphic units and structures making up six coronae and their regional surroundings on Venus were examined using full resolution Magellan images and stereoscopic coverage. Altimetry and stereoscopic coverage were essential in establishing the local stratigraphic relationships and the timing of corona-related topography. The degree of preservation of signatures of earlier corona-related activities and the scale of later corona-related activities vary significantly from corona to corona. We compared the geologic sequence in each corona to regional and global stratigraphic units, placing the coronae in the broader context of the geologic history of Venus. The results of this study were compared with earlier analyses bringing the total number of corona considered to about 15% of the total corona population. We found that corona started forming soon after tessera formation and largely spanned a significant part of the subsequent geologic history of Venus, over about 200–400 million years. Topographic annulae were initiated in early post-tessera time but were largely completely formed by the time of emplacement of regional plains with wrinkle ridges. Some coronae ceased activity by this time, while others continued until closer to the present, although showing evidence of waning activity. Coronae-associated volcanism dominated many coronae during this later stage. Convincing evidence of pre-regional plains corona- related volcanism was not found in the population examined here. We conclude that coronae formed in a two stage process; the first stage (tectonic phase) involved the annular warping of early extensive stratigraphic units of volcanic origin and the second (volcanic phase) involved coronae-related lava flow activity and local fracturing. For the vast majority of coronae, the first tectonic phase was largely complete prior to the emplacement of the regional plains (Pwr, plains with wrinkle ridges). The vast majority of corona-related volcanic activity (emplacement of Pl, lobate flows) occurred subsequent to the emplacement of regional plains. We found no evidence of coronae initiation in substantially later periods of the observed history of Venus. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Beta Regio, Venus: Evidence for uplift, rifting, and volcanism due to a mantle plume   总被引：1，自引：0，他引：1  

Alexander T. Basilevsky  James W. Head 《Icarus》2007,192(1):167-186

Geophysical data have led to the interpretation that Beta Regio, a 2000×25000 km wide topographic rise with associated rifting and volcanism, formed due to the rise of a hot mantle diapir interpreted to be caused by a mantle plume. We have tested this hypothesis through detailed geologic mapping of the V-17 quadrangle, which includes a significant part of the Beta Regio rise, and reconnaissance mapping of the remaining parts of this region. Our analysis documents signatures of an early stage of uplift in the formation of the Agrona Linea fracture belts before the emplacement of regional plains and their deformation by wrinkle ridging. We see evidence that the Theia rift-associated volcanism occurred during the first part of post-regional-plains time and cannot exclude that it continued into later time. We also see evidence that Devana Chasma rifting was active during the first and the second parts of post-regional-plains time. These data are consistent with uplift, rifting and volcanism associated with a mantle diapir. Geophysical modeling shows that diapiric upwelling may continue at the present time. Together these data suggest that the duration of mantle diapir activity was as long as several hundred million years. The regional plains north of Beta rise and the area east and west of it were little affected by the Beta-forming plume, but the broader area (at least 4000 km across), whose center-northern part includes Beta Regio, could have experienced earlier uplift as morphologically recorded in formation of tessera transitional terrain.  相似文献   

History of tectonic deformation in the interior plains of the Caloris basin,mercury     

A. T. Basilevsky  J. W. Head  C. I. Fassett  G. Michael 《Solar System Research》2011,45(6):471-497

Analysis of images from the Messenger MDIS narrow angle camera imply that at least part of the radial graben of the Pantheon Fossae structure, and probably the structure as a whole, predate the deformation that led to circumferential ridges on the Caloris interior plains. This follows from structural analysis and comparison with similar geological relationships on Venus and the Moon, where graben are known to both postdate and predate ridges. Observations suggest that the Pantheon Fossae radial graben (extension) formed first, pre-dating observed circumferential graben (also extension), with ridges (compression) formed in between. This scenario puts constraints on the models for the deformation of the Caloris basin and its vicinity. Our observations and analysis are consistent with Pantheon Fossae having formed in a similar manner to Venusian astra/novae, where radial dikes that propagate away from a magmatic center led to graben formation. Our results also have implications for the length of time between the emplacement of the basin volcanic fill and the onset of the compressional stresss regime that led to ridge-formation. If the Pantheon Fossae structure formed before the emplacement of ridges, as we suggest, this means that compressional stresses took some time to develop sufficiently to deform the volcanic plains. Since the Caloris interior plains had to have been already in place when Pantheon Fossae formed, and since these plains represented a significant load to the underlying lithosphere, it is striking that compression took some time to develop. These observations may provide new information about the rigidity of the basin-filling material and will help constrain models for the mechanisms and timing of events within and around the Caloris basin.  相似文献