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Martian magmatism within recent several hundreds of millions years is still controversial. Central Elysium Planitia (CEP) is suspected as a site of the latest magmatism on Mars, but hot debates have been caused as for the origin o...
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Martian magmatism within recent several hundreds of millions years is still controversial. Central Elysium Planitia (CEP) is suspected as a site of the latest magmatism on Mars, but hot debates have been caused as for the origin of this flat plain. Cones in CEP are expected to be a key to resolve this controversy. In previous works, there are 2 models proposed for the origin of CEP cones: volcanic rootless cone (e.g. Jaeger et al., 2007) and periglacial pingo (e.g. Burr et al., 2002; Page et al., 2009). In this study, we described detail morphology, distribution and size of CEP cones by using high-resolution images and topographic data. CEP cones are classified into 3 morphological types: Single Cone (SC), Double Cone (DC), and Lotus Fruit Cone (LC). DC has an inner cone in the summit crater of the outer cone, and LC has several inner cones in the summit crater of the outer cone. Several cones have moat structure around the edifice with peripheral rise. DCs and LCs are located in very flat areas of Athabasca Valles in the vicinity of Cerberus Fossae, while SCs distribute in the entire region of CEP. We compared CEP cones with terrestrial rootless cones and pingos in aerial photos. In Lake Myvatn, Iceland, there. exist rootless cones which resemble DCs and LCs in CEP. Based on the similarities with terrestrial analogies, we concluded that the most feasible origin of CEP cones is rootless cones. (C) 2015 Elsevier Ltd. All rights reserved.
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The nature of large hills in the Martian equatorial regions like Zephyria Planum and the southern part of Elysium Planitia has not been studied, despite the fact that they have characteristic similar shapes and sharply contrast wi...
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The nature of large hills in the Martian equatorial regions like Zephyria Planum and the southern part of Elysium Planitia has not been studied, despite the fact that they have characteristic similar shapes and sharply contrast with the surrounding lava plains. The paper develops the previously proposed view on the permafrost injection nature of these formations. Morphological analysis of satellite imagery in the visible and infrared ranges of large cone-shaped and dome-shaped hills in the equatorial parts of Zephyria Planum and the southern part of Elysium Planitia gives grounds to interpret these structures as large hydrolaccoliths. Analysis of the terrain and signs of ongoing geological processes using satellite images of various years and modern views on the permafrost and subpermafrost waters of the planet confirms this interpretation. The origin of these structures is associated with temperature changes and phase transitions in the permafrost layer. It is assumed that their structure does not fundamentally differ from the terrestrial analogues like pingo, or bulgunnyakh: the core contains ice-containing permafrost and massive ice, from the surface they are covered with regolith. The differences are the significantly large dimensions of these features and the assumed hydraulic connection with the brine subpermafrost hydrosphere. Morphological signs of modern activity of some of the large hydrolaccoliths are observed, which indicates a hydraulic connection with the underlying supply reservoirs. Large hydrolaccoliths are of interest as significant reserves of water surrounded by a waterless landscape and as places to search for traces of life in ice substrates and feeding brines. Considering their significant resource and scientific potential, the equatorial areas, where the described and similar features occurred, are promising as places for the first crewed missions and setting up human settlements.
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Analysis of erosional valleys, geologic materials and features, and topography through time in the Thaumasia region of Mars using co-registered digital spatial data sets reveals significant associations that relate to valley origi...
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Analysis of erosional valleys, geologic materials and features, and topography through time in the Thaumasia region of Mars using co-registered digital spatial data sets reveals significant associations that relate to valley origin. Valleys tend to originate (1) on Noachian to Early Hesperian (stages I and 2) large volcanoes, (2) within 50-100 km of stages 1 and 2 rift systems, and (3) within 100 km of Noachian (stage 1) impact craters >50 km in diameter. These geologic preferences explain observations of higher valley-source densities (VSDs) in areas of higher elevations and regional slopes (>1 degrees) because the volcanoes, rifts, and craters form high, steep topography or occur in terrain of high relief. Other stage 1 and stage 2 high, steep terrains, however, do not show high VSDs. The tendency for valleys to concentrate near geologic features and the overall low drainage densities in Thaumasia compared to terrestrial surfaces rule out widespread precipitation as a major factor in valley formation (as is proposed in warm, wet climate scenarios) except perhaps during the Early Noachian, for which much of the geologic record has been obliterated. Instead, volcanoes and rifts may indicate the presence of shallow crustal intrusions that could lead to local hydrothermal circulation, melting of ground ice and snow, and groundwater sapping. However, impact-crater melt would provide a heat source at the surface that might drive away water, forming valleys in the process. Post-stage I craters mostly have low nearby VSDs, which, for valleys incised in older rocks, suggests burial by ejecta and, for younger valleys, may indicate desiccation of near-surface water and deepening of the cryosphere. Later Hesperian and Amazonian (stages 3 and 4) valleys originate within 100-200 fun of three young, large impact craters and near rifts systems at Warrego Valles and the southern part of Coprates rise. These valleys likely developed when the cryosphere was a couple kilometers or more thick, inhibiting valley development by hydrothermal circulation, However, eruption of,groundwater may have occurred from impact-induced fracturing and lateral and perhaps minor upward transport of water due to seismic pumping. The two smaller craters formed along the plateau margin where the highest potential hydraulic head would occur in aquifers beneath the plateau. In the case of the larger crater (Lowell, 200 km in diameter), potential aquifers would likely be at depths of kilometers below the cryosphere; Seismic energy generated by the Lowell impactor would have been much greater, pumping both groundwater and perhaps fluidized slurry to the surface from beneath the cryosphere to form the young valleys and flow deposit. Along the margin of Thaumasia, tectonic pressurization of groundwater also may have contributed to valley formation. Dissection of rim materials of the Argyre impact may relate to tectonic activity and the unconsolidated state of basin ejecta. [References: 39]
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The rate of occurrence of High Frequency (HF) marsquakes, as recorded by InSight at Homestead Hollow, Elysium Planitia, increased after about L-S= 33 degrees, and ceased almost completely by L-S= 187 degrees, following an apparent...
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The rate of occurrence of High Frequency (HF) marsquakes, as recorded by InSight at Homestead Hollow, Elysium Planitia, increased after about L-S= 33 degrees, and ceased almost completely by L-S= 187 degrees, following an apparently seasonal variation with a peak rate near aphelion. We define seismic rate models based on the declination of the Sun, annual solar tides, and the annual CO2 cycle as measured by atmospheric pressure. Evaluation of Akaike weights and evidence ratios shows that the declination of the Sun is the most likely, and the CO2 cycle the least likely driver of this seismic activity, although the discrimination is weak, and the occurrence of a few events in August 2020 is in favor for a triggering by CO2 ice load. We also show that no periodicity related to Phobos' orbit is present in the HF event sequence. Event rate forecasts are presented to allow further discrimination of candidate mechanisms from future observations. (C) 2021 The Author(s). Published by Elsevier B.V.
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Northern Arabia Terra, Mars is characterized by a complex landscape that includes fretted terrain, fretted channels, completely closed canyons, shallow troughs, and fracture-bounded depressions. The importance of ground ice in the...
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Northern Arabia Terra, Mars is characterized by a complex landscape that includes fretted terrain, fretted channels, completely closed canyons, shallow troughs, and fracture-bounded depressions. The importance of ground ice in the initiation and development of these features, and of large impact structures in controlling channel courses, has long been recognized. The development of the fretted channel systems, including the integration of closed canyons, craters, and surface depressions into throughgoing channels, has previously been attributed primarily to mass-wasting processes. The two channel systems in southern Ismenius Lacus quadrangle, Mamers Valles and Ismeniae Fossae, incorporate craters of probable impact origin, but both also include irregular crater-like features and scalloped channel reaches that have characteristics not consistent with an impact origin. Some of these are, by analogy with morphologically similar features on Earth and elsewhere an Mars, reasonably interpreted as of volcanic origin. The detailed morphologies of a few diagnostic features associated with Ismeniae Fossae suggest a hydrovolcanic origin, an inference supported by the probable presence of abundant ground ice or groundwater at the time of their formation. The evidence described here for hydrovolcanism supports the inference that, in addition to mass-wasting processes, explosive excavation, intrusion-driven sublimation, subsurface erosion, and erosion by running water may have played important roles in channel formation and evolution as well. All of these processes are consistent with magma interacting with groundwater or ground ice. [References: 60]
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The presence of rocks in the ejecta of craters at the InSight landing site in southwestern Elysium Planitia indicates a strong, rock-producing unit at depth. A finer regolith above is inferred by the lack of rocks in the ejecta of...
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The presence of rocks in the ejecta of craters at the InSight landing site in southwestern Elysium Planitia indicates a strong, rock-producing unit at depth. A finer regolith above is inferred by the lack of rocks in the ejecta of 10-m-scale craters. This regolith should be penetrable by the mole of the Heat Flow and Physical Properties Package (HP3). An analysis of the size-frequency distribution (SFD) of 7988 rocky ejecta craters (RECs) across four candidate landing ellipses reveals that all craters > 200 m in diameter and < 750 +/- 30 Ma in age have boulder-sized rocks in their ejecta. The frequency of RECs however decreases significantly below this diameter (D), represented by a roll-off in the SFD slope. At 30 m< D< 200 m, the slope of the cumulative SFD declines to near zero at D< 30 m. Surface modification, resolution limits, or human counting error cannot account for the magnitude of this roll-off. Rather, a significant population of < 200 m diameter fresh non-rocky ejecta craters (NRECs) here indicates the presence of a relatively fine-grained regolith that prevents smaller craters from excavating the strong rock-producing unit. Depth to excavation relationships and the REC size thresholds indicate the region is capped by a regolith that is almost everywhere 3 m thick but may be as thick as 12 to 18 m. The lower bound of the thickness range is independently confirmed by the depth to the inner crater in concentric or nested craters. The data indicate that 85% of the InSight landing region is covered by a regolith that is at least 3 m thick. The probability of encountering rockier material at depths > 3 m by the HP3 however increases significantly due to the increase in boulder-size rocks in the lower regolith column, near the interface of the bedrock.
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China's first Mars mission Tianwen-1 successfully touched down the surface of the southern Utopia Planitia on 15th May 2021. In this study we investigate the geological characteristics of the target landing site (Site 1) and a bac...
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China's first Mars mission Tianwen-1 successfully touched down the surface of the southern Utopia Planitia on 15th May 2021. In this study we investigate the geological characteristics of the target landing site (Site 1) and a backup landing site (Site 2) on Utopia Planitia for Tianwen-1 Mission. Site 1 is located in a topographic low and generally flat area to the southern Utopia basin, while Site 2 is located in the Utopia-Elysium transition zone. Several geological features indicative of the presence of a large reservoir of volatiles are identified and mapped in detail for both landing sites, including pitted cones, giant polygons, rampart and pancake craters. The volcanismrelated morphologies, e.g., lava flows, lahars, and dikes, are also mapped for Site 2. The compositional analysis reveals little exposures of hydrous materials due to dust cover and/or lacking of data coverage over the regions. Crater counting analysis showed that the Site 1 has an absolute model age of similar to 3.68 Ga and similar to 3.45 Ga when including and excluding ghost craters, respectively. The absolute model age of Site 2 is similar to 3.34 Ga. Finally, the evolutionary history of the Utopia Planitia is discussed, and the related scientific hypotheses to be tested for the in situ exploration are suggested. Our study provides a framework for the Tianwen-1 in situ exploration, which will impose important constraints on the nature and evolution history of the northern lowlands.
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Subsurface water processes are common for planetary bodies in the solar system and are highly probable for exoplanets (planets outside the solar system). For many solar system objects, the subsurface water exists as ice. For Earth...
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Subsurface water processes are common for planetary bodies in the solar system and are highly probable for exoplanets (planets outside the solar system). For many solar system objects, the subsurface water exists as ice. For Earth and Mars, subsurface saturated zones have occurred throughout their planetary histories. Earth is mostly clement with the recharge of most groundwater reservoirs from ample precipitation during transient ice-and hot-house conditions, as recorded through the geologic and fossilized records. On the other hand, Mars is mostly in an ice-house stage, which is interrupted by endogenic-driven activity. This activity catastrophically drives short-lived hydrological cycling and associated climatic perturbations. Regional aquifers in the Martian highlands that developed during past, more Earth-like conditions delivered water to the northern plains. Water was also cycled to the South Polar Region during changes in climate induced by endogenic activity and/or by changes in Mars' orbital parameters. Venus very likely had a warm hydrosphere for hundreds of millions of years, before the development of its current extremely hot atmosphere and surface. Subsequently, Venus lost its hydrosphere as solar luminosity increased and a run-away moist greenhouse took effect. Subsurface oceans of water or ammonia-water composition, induced by tidal forces and radiogenic heating, probably occur on the larger sate lites Europa, Ganymede, Callisto, Titan, and Triton. Tidal forces operating between some of the small bodies of the outer solar system could also promote the fusion of ice and the stability of inner liquid-water oceans.
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