Martian chaos terrains are fractured depressions consisting of block landforms that are often located in source areas of outflow channels. Numerous chaos and chaos-like features have been found on ...Mars; however, a global-scale classification has not been pursued. Here, we perform recognition and classification of Martian chaos using imagery machine learning. We developed neural network models to classify block landforms commonly found in chaos terrains—which are associated with outflow channels formed by water activity (referred to as Aromatum-Hydraotes-Oxia-like (or AHO) chaos blocks) or with geological features suggesting volcanic activity (Arsinoes-Pyrrhae-like (or AP) chaos blocks)—and also non-chaos surface features, based on >1400 surface images. Our models can recognize chaos and non-chaos features with 93.9% ± 0.3% test accuracy, and they can be used to classify both AHO and AP chaos blocks with >89 ± 4% test accuracy. By applying our models to ~3150 images of block landforms of chaos-like features, we identified 2 types of chaos terrain. These include hybrid chaos terrain, where AHO and AP chaos blocks co-exist in one basin, and AHO-dominant chaos terrain. Hybrid chaos terrains are predominantly found in the circum-Chryse outflow channels region. AHO-dominant chaos terrains are widely distributed across Aeolis, Cydonia, and Nepenthes Mensae along the dichotomy boundary. Their locations coincide with regions suggested to exhibit upwelling groundwater on Hesperian Mars.
To better understand the necessary triggers for the origin of the lunar boulder tracks, we report 650 tracks from the ~73 km in diameter Finsen crater. The tracks were identified on the crater wall ...and the central peak region of the Finsen crater, located within the South Pole ̶ Aitken basin on the lunar far side. In this manuscript, we assessed two main possibilities of triggers, 1) ground shakings by the recent meteorite impact, and 2) ground shaking from recent fault reactivation associated with the lobate scarps identified inside and in the vicinity of the Finsen crater. Our assessments revealed that the impact-induced seismicity could have generated the moonquake with the maximum moment magnitude (MW) 4.63. We also estimated that the moonquakes excited by the movements along the lobate scarps had an estimated cumulative (or maximum possible) moment magnitude (MW) up to 6.86 and 6.90, i.e., for the basaltic and noritic basement respectively. Considering the location of the Finsen crater positioned over the structural discontinuity along the boundary of the central and mid rings of the South Pole ̶ Aitken basin and higher moment magnitude generated from the fault movements, we propose that the region is potentially seismotectonically active, and reactivation of pre-existing faults possibly triggered/triggers the necessary ground motion for the boulders to initiate their movements. However, impact-induced ground shakings and deep-focused moonquakes also remain possibilities for triggers.
•Finsen crater records dynamic geological activity with 650 boulder tracks.•Lobate scarps generate higher Moment Magnitude (MW) than the impact craters.•Boulder tracks are observed around the vicinity of the lobate scarps.•Reactivation of normal faults in the ring boundary provided necessary triggers.•Part of South Pole ̶ Aitken basin is tectonically active.
One of the long-standing enigmas for lunar tectonic-thermal evolution is the spatiotemporal association of contractional wrinkle ridges and basaltic volcanism in a compressional regime. Here, we show ...that most of the 30 investigated volcanic (eruptive) centers are linked to contractional wrinkle ridges developed above preexisting basin basement-involved ring/rim normal faults. Based on the tectonic patterns associated with the basin formation and mass loading and considering that during the subsequent compression the stress was not purely isotropic, we hypothesize that tectonic inversion produced not only thrust faults but also reactivated structures with strike-slip and even extensional components, thus providing a valid mechanism for magma transport through fault planes during ridge faulting and folding of basaltic layers. Our findings suggest that lunar syn-tectonic mare emplacement along reactivated inherited faults provides important records of basin-scale structure-involved volcanism, which is more complex than previously considered.
Upwelling mantle plumes often instigate extensional stress within the continental crust of Earth. When stress exceeds crustal strength, extensional structures develop, reducing the effective stress ...and trigger magmatic processes at the crust–mantle boundary. However, such processes and their relationship to the formation of many surface structures remain poorly characterized on Mars. We identified a series of extensional structures in the southern highlands of Mars which collectively resemble continental rift zones on Earth. We further characterized these extensional structures and their surrounding region (area of ~1.8 M km2) by determining the surface mineralogy and bulk regional geochemistry of the terrain. In turn, this constrains their formation and yields a framework for their comparison with extensional structures on Earth. These terrains are notable for olivine and high-Ca pyroxene with a high abundance of potassium and calcium akin to alkali basalts. In the case of Mars, this Earth-like proto-plate tectonic scenario may be related to the plume-induced crustal stretching and considering their distribution and temporal relationship with the Hellas basin, we conclude that the plume is impact-induced. Overall, the findings of this work support the presence of mantle plume activity in the Noachian, as suggested by thermal evolution models of Mars.
It has been proposed that ~3.4 billion years ago an ocean fed by enormous catastrophic floods covered most of the Martian northern lowlands. However, a persistent problem with this hypothesis is the ...lack of definitive paleoshoreline features. Here, based on geomorphic and thermal image mapping in the circum-Chryse and northwestern Arabia Terra regions of the northern plains, in combination with numerical analyses, we show evidence for two enormous tsunami events possibly triggered by bolide impacts, resulting in craters ~30 km in diameter and occurring perhaps a few million years apart. The tsunamis produced widespread littoral landforms, including run-up water-ice-rich and bouldery lobes, which extended tens to hundreds of kilometers over gently sloping plains and boundary cratered highlands, as well as backwash channels where wave retreat occurred on highland-boundary surfaces. The ice-rich lobes formed in association with the younger tsunami, showing that their emplacement took place following a transition into a colder global climatic regime that occurred after the older tsunami event. We conclude that, on early Mars, tsunamis played a major role in generating and resurfacing coastal terrains.
Southern highlands of Mars have experienced regional to global scale deformations in the history of its evolution. Deformational structures originated from impact-induced stresses and later viscous ...relaxation of the impact basin to cooling related global contraction. Here in this study, we investigated an Early Hesperian (Eo-Archean / Paleo-Archean equivalent to the Earth) aged lobate scarp i.e., surface signature of thrust fault, possibly originated because of global contraction. We used ‘offset crater perimeter’ measurement technique using high-resolution data (both image and DTM) to execute most precise estimation of fault plane slope and length–displacement relationship. The derived range of fault plane slope is much narrower (21°–29°) than the previously cited 20° to 35° range. Displacement–length ratio (4.51 × 10−3) is also unique and lower than the previously evaluated values of lobate scarps from other region (mainly from dichotomy boundary) of Mars. The newly derived results from the morphometric analysis are due the differential stress pattern and the distinct basement rock rheology. Our results highlight the need for more high-resolution estimation of lobate scarps from several regions with the methodology employed in this study to better understand the global Martian early tectonic scenario.
•Morphometric analysis of a Hesperian aged compressional structure.•Precise estimation of fault plane slope using new technique.•Derived length-displacement relation using high-resolution data.•Derived data could impact on further stress/strain estimation.
The high-temperature (33–98 °C), highly acidic (pH 2.44–2.94) Goshogake mud volcano field in Akita Prefecture, northern Japan, is a mud volcano system associated with the Quaternary andesitic ...composite volcano Akita Yakeyama. The mud volcano features observed in Goshogake include salsa ponds, gryphons, and mud pots. This is a rare example of mud volcano systems linked with magmatic volcanism with the full range of landforms observed primarily in low-temperature mud volcanism in sedimentary settings. The Goshogake mud volcano field is probably not a simple hydrothermal system related to a magmatic volcano. Instead, it appears to be a hybrid system: sedimentary volcanism linked with deep mud sources and strongly influenced by its surrounding magmatic volcanism. The identified mineral species in the sampled mud include quartz group, hydrous silica, muscovite, kaolinite, pyrite, and sulfur. The presence of high-temperature silica polymorphs (tridymite and cristobalite) and/or microcrystalline opals (opal-C, opal-CT), and an amorphous form of silica (opal-A) in the mineralogy indicates that the mud volcano system likely involves conditions and processes such as high temperature, hydrothermal circulation, dehydration reaction at certain depths underneath the Goshogake mud volcano field. Although the source of the mud is not clearly determined, possible options include 1) hydrothermal alteration products of host rocks and sediments, 2) fine-grained sedimentary layer(s) at depth, or 3) a combination of 1) and 2). In-situ measurement of emitted gases from vents detected methane, which is possibly linked with the organic-rich sedimentary layer(s) aside from being a product of thermodynamic equilibrium with CO2 under the subsurface pressure-temperature conditions. The increases in δD and δ18O of water in Goshogake mud volcanoes with respect to the values of current meteoric water indicates that the water was derived not only from meteoric water, and deviation of the values may be explained by processes such as evaporation and mixing of other waters from deeper sources. Regarding the driving mechanisms at the Goshogake mud volcanoes, buoyancy of muddy sediment, high fluid pressure under overpressured or under-compacted conditions due to rapid sedimentation, together with the presence of a gas phase in the sediment, could be key factors. Although the Goshogake mud volcano field currently maintains a low-level activity resulting in only minor morphological changes of the mud volcano landforms, enhanced activities have been documented in the last half century. The historical records are inconclusive about the relationship between earthquakes and activity in the Goshogake mud volcano field.
•The Goshogake mud volcano field in Japan is an acidic, high-temperature system.•This active field exhibits a wide range of mud volcano morphology.•The mineralogy indicates high temperature, hydrothermal circulation, dehydration.•The mud originates by alteration, from deep sedimentary layer(s), and/or both.•This field appears to be a hybrid system of sedimentary and magmatic volcanism.
Abstract
Carbonaceous asteroids, including Ryugu and Bennu, which have been explored by the Hayabusa2 and OSIRIS-REx missions, were probably important carriers of volatiles to the inner Solar System. ...However, Ryugu has experienced significant volatile loss, possibly from hypervelocity impact heating. Here we present impact experiments at speeds comparable to those expected in the main asteroid belt (3.7 km s
−1
and 5.8 km s
−1
) and with analogue target materials. We find that loss of volatiles from the target material due to impacts is not sufficient to account for the observed volatile depletion of Ryugu. We propose that mutual collisions in the main asteroid belt are unlikely to be solely responsible for the loss of volatiles from Ryugu or its parent body. Instead, we suggest that additional processes, for example associated with the diversity in mechanisms and timing of their formation, are necessary to account for the variable volatile contents of carbonaceous asteroids.
•Small edifice features up a few km in diameter widely occur in Chryse Planitia, Mars.•Their overall diverse morphology is consistent with the mud volcano origin.•Their detailed characteristics may ...require conditions unique to martian environment.•Our CRISM analysis has detected nanophase ferric minerals and hydrated minerals.•Mud volcanism may have been promoted by rapid sedimentation in Chryse Planitia.
Small edifice features that are less than a few kilometers in diameter and up to a few hundred meters in height are widely distributed in Chryse Planitia on Mars. They exhibit a broad range of morphological properties that are here classified as Type 1 (steep-sided cones typically with a summit crater), Type 2 (nearly flat features with single or multiple central/summit craters or cones) and Type 3 (nearly circular features in plan view, characterized by steep sides and a broadly flat summit area). Their origins have not been determined with certainty, but our study utilizing the High Resolution Imaging Science Experiment (HiRISE) images supports the interpretation of mud volcanism, based on the observed morphological characteristics of these small edifices and comparisons with terrestrial analogs. Additionally, hydrated minerals detected on these edifice features in data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), further support the mud volcano hypothesis. Injection features such as clastic mega-pipes and sand blow features may coexist with the mud volcanoes. Alternative mechanisms such as magmatic volcanism are not excluded, but they have less support from our remote sensing observations. Further confirmation or rejection of the mud volcano hypothesis will require in-situ investigation by landers or rovers.
In 1976, NASA's Viking 1 Lander (V1L) was the first spacecraft to operate successfully on the Martian surface. The V1L landed near the terminus of an enormous catastrophic flood channel, Maja Valles. ...However, instead of the expected megaflood record, its cameras imaged a boulder-strewn surface of elusive origin. We identified a 110-km-diameter impact crater (Pohl) ~ 900 km northeast of the landing site, stratigraphically positioned (a) above catastrophic flood-eroded surfaces formed ~ 3.4 Ga during a period of northern plains oceanic inundation and (b) below the younger of two previously hypothesized megatsunami deposits. These stratigraphic relationships suggest that a marine impact likely formed the crater. Our simulated impact-generated megatsunami run-ups closely match the mapped older megatsunami deposit's margins and predict fronts reaching the V1L site. The site's location along a highland-facing lobe aligned to erosional grooves supports a megatsunami origin. Our mapping also shows that Pohl's knobby rim regionally represents a broader history of megatsunami modification involving circum-oceanic glaciation and sedimentary extrusions extending beyond the recorded megatsunami emplacement in Chryse Planitia. Our findings allow that rocks and soil salts at the landing site are of marine origin, inviting the scientific reconsideration of information gathered from the first in-situ measurements on Mars.
PDF
