Valles Marineris Region Research Articles

Origin of theater-headed valleys in the Valles Marineris region, Mars

This paper reports high-resolution observations of theater-headed valleys in the Valles Marineris region and proposes an integrated model of their formation and localization across the walls of the canyons of Valles Marineris. These theater-headed valleys have formed over a long period of time from Middle-Hesperian to Early-Amazonian. The valleys show several common features, namely, proximity to areas of high ejecta mobility on the Tharsis plateau; alignment along the major tectonic features such as wrinkle ridges, grabens, pit crater chains; association with fluvial channels and layered deposits on the plateau adjacent to the valley heads; and occurrences of mass wasting features at the valley mouths. Elevation profiles of the walls of Valles Marineris display ramp and cliff topography indicating mechanical stratification in the wall rocks. These observations reveal multiple controls over the formation and localization of theater-headed valleys in Valles Marineris. However, the major controls appear to be strong-over-weak stratigraphy in the canyon walls and the pre-existing zones of structural weakness in the Valles Marineris region. The source of water could likely be groundwater; however, snowmelt accumulated on the upper parts of the wallrock would additionally facilitate the process. Based on the above observations, we propose a sequence of events for the evolution of theater-headed valleys in the Valles Marineris region.

Craters in the vicinity of Valles Marineris region, Mars: Chronological implications to the graben and pits activities

Graben and pits are features closely associated with the Valles Marineris (VM) region on Mars. Earlier studies indicated that they are likely precursors for the VM trough formation, and thus they may assist in our understanding of how long the trough formation prevailed in the vicinity of VM. This study aims to understand how the graben and pit formation varied chronologically and spatially within a ~100 km vicinity of the VM region. We examined 1516 craters and found 48 craters that are superposed/cross-cut by graben, pits, and troughs or vice-versa with adequate ejecta or floor area for dating. Tithonium region graben and troughs cross-cut the craters around ~3.7 Ga. In the Ophir region, pits are formed on or post ~3.92 Ga at different elevations and have variable depths. Pital crater in the Ophir region interestingly hosts: 1) a broad catena ~14 km wide crosscutting its NE rim likely formed on or post to ~2.61 Ga, which inferred to be one-tenth to the adjoining Candor Chasma width of VM, 2) lobe like deposits associated with the catena emplaced over the Pital ejecta formed around ~1.14 Ga and 3) ~2 km wide pit superposed the lobe that reveals pit activity plausibly prolonged during Mid-Amazonian. Overall, our results likely point towards the contribution of graben and pits in the modification/development of peripheral areas of VM up to at least Mid-Amazonian. Thus, this study substantiated that the period and extent of graben and pit activities varied around the VM region.

Deep-seated gravitational slope deformation scaling on Mars and Earth: same fate for different initial conditions and structural evolutions

Abstract. Some of the most spectacular instances of deep-seated gravitational slope deformation (DSGSD) are found on Mars in the Valles Marineris region. They provide an excellent opportunity to study DSGSD phenomenology using a scaling approach. The topography of selected DSGSD scarps in Valles Marineris and in the Tatra Mountains is investigated after their likely similar postglacial origin is established. The deformed Martian ridges are larger than the deformed terrestrial ridges by 1 to 2 orders of magnitude with, however, a similar height-to-width ratio of ∼0.24. The measured horizontal spreading perpendicular to the ridges is proportionally 1.8 to 2.6 times larger for the Valles Marineris ridges than the Tatra Mountains and vertically 2.9 to 5.1 times larger, suggesting that starting from two different initial conditions, with steeper slopes in Valles Marineris, the final ridge geometry is now similar. Because DSGSD is expected to now be inactive in both regions, their comparison suggests that whatever the initial ridge morphology, DSGSD proceeds until a mature profile is attained. Fault displacements are therefore much larger on Mars. The large offsets imply reactivation of the DSGSD fault scarps in Valles Marineris, whereas single seismic events would be enough to generate DSGSD fault scarps in the Tatra Mountains. The required longer activity of the Martian faults may be correlated with a long succession of climate cycles generated by the unstable Martian obliquity.

Recent seismicity in Valles Marineris, Mars: Insights from young faults, landslides, boulder falls and possible mud volcanoes

Current seismicity of Mars is poorly known. Geodynamic models and analysis of surface faults indicate that Mars could be seismically active globally, particularly within the Tharsis region. However, published geologic constraints on such activity are sparse. In this study, we use geomorphologic observations and crater size–frequency age determinations gleaned from high-resolution orbiter data to demonstrate that the Valles Marineris region is recently seismo-tectonically active. The chasmata shows evidence of reactivated dip-slip faults that cross-cut the chasmata walls and floors and indicates up to 1–2 km total vertical displacement along the trough bounding faults. More than 16000 boulder fall occurrences with pristine trails are observed throughout the chasmata wall with an average slope of 25 degrees. The boulder falls are interpreted to have been triggered by recent seismic shaking from the shallow marsquakes occurring along the chasmata faults, possibly in the last thousands of years. Synthetic ground motion models indicate several MW 4–6 marsquakes at shallow depths (∼1–6 km) are required to produce these canyon-wide boulder falls. In addition, the presence of many young landslides (22–790 Ma) proximal to the reactivated trough bounding faults and formation of thousands of possible mud volcanic cones throughout the chasmata floor all suggest marsquake-triggered shaking in the past tens to hundreds of million years, corresponding to Late to Middle Amazonian Epochs. We estimate formation of 20 m to 1.3 km diameter fresh impact craters around the chasmata had negligible contribution to the recent seismicity. Therefore, Valles Marineris tectonism is an important source of marsquakes that may be readily detectable by the upcoming InSight seismometers.

Analysing some martian atmospheric characteristics associated with a dust storm over the Lunae Planum region during October 2014

This study analyses the vertical aerosol distribution and associated atmospheric characteristics during a dust storm event in early Martian southern summer. The analysis is based on the observations of the Mars Colour Camera (MCC) onboard the Indian Mars Orbiter Mission during October 11 and October 20, 2014. A local-scale dust storm is found within the north-eastern portion of the Lunae Planum region on October 11, 2014, which is observed to be relatively larger during October 20. The dust storm disappeared in the next image taken over the same region during October 28, 2014, leaving a thick haze over Lunae Planum and the Valles Marineris region. It is observed from the Mars Daily Global Maps of the Mars Color Imager (MARCI) on board the Mars Reconnaissance Orbiter (MRO) that the dust storm was generated in the Acidalia region, moved south and came over Lunae Planum and Tempe Terra. Later on, this northern hemispheric storm sequence crossed the equator and merged with a Hellas sequence over Noachis Terra. An increase in vertically integrated dust opacity derived from the observations of Mars Climate Sounder on board MRO was seen over a large latitudinal extent i.e., 60° S to 60° N. Analysis of dust and water ice opacity and temperature profile is carried out before, during and after the dust storm period as observed by MCC and MARCI images. Dust opacity is found to have increased drastically up to 20 km altitude. An increase of dustiness at the HATDM (High Altitude Tropical Dust Maximum) layer is seen, but with a temporal delay of 2° LS after the dust storm disappearance. The study implicates the variation of convective boundary layer growth in the tenuous Martian atmosphere during the dust storm scenario for this temporal delay in dust lifting. The dust lifting is found to be exclusively responsible for the increase in heating rate at this layer, not cloud radiative heating caused by water ice clouds.

SWIR Albedo Mapping of Mars Using Mars Orbiter Mission Data

Global apparent short wave infrared (SWIR) (1.64-1.66 μm) albedo mapping results from data acquired by Methane Sensor for Mars (MSM) onboard Indian Mars Orbiter Mission from October 2014 to February 2015, are presented. Global analysis of low and high albedo patterns is discussed using MSM apparent SWIR albedo map. The occurrence frequency of MSM apparent SWIR albedo shows a clear bimodal behaviour and is in good agreement with OMEGA NIR albedo distribution. Based on MSM apparent SWIR albedo values, three classes (high, intermediate and low albedo values) are defined, which show a clear elevation dependency. Variation of weekly average apparent albedo during the study period over Syrtis Major, Daedalia Planum and Valles Marineris region, respectively, is presented.

Martian outflow channels: How did their source aquifers form, and why did they drain so rapidly?

Catastrophic floods generated ~3.2 Ga by rapid groundwater evacuation scoured the Solar System’s most voluminous channels, the southern circum-Chryse outflow channels. Based on Viking Orbiter data analysis, it was hypothesized that these outflows emanated from a global Hesperian cryosphere-confined aquifer that was infused by south polar meltwater infiltration into the planet’s upper crust. In this model, the outflow channels formed along zones of superlithostatic pressure generated by pronounced elevation differences around the Highland-Lowland Dichotomy Boundary. However, the restricted geographic location of the channels indicates that these conditions were not uniform Boundary. Furthermore, some outflow channel sources are too high to have been fed by south polar basal melting. Using more recent mission data, we argue that during the Late Noachian fluvial and glacial sediments were deposited into a clastic wedge within a paleo-basin located in the southern circum-Chryse region, which was then completely submerged under a primordial northern plains ocean. Subsequent Late Hesperian outflow channels were sourced from within these geologic materials and formed by gigantic groundwater outbursts driven by an elevated hydraulic head from the Valles Marineris region. Thus, our findings link the formation of the southern circum-Chryse outflow channels to ancient marine, glacial, and fluvial erosion and sedimentation.

Fill and spill of giant lakes in the eastern Valles Marineris region of Mars

Research Article| June 01, 2013 Fill and spill of giant lakes in the eastern Valles Marineris region of Mars Nicholas H. Warner; Nicholas H. Warner * 1Department of Earth Science and Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK *Current address: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, California 91109, USA; E-mail: Nicholas.H.Warner@jpl.nasa.gov. Search for other works by this author on: GSW Google Scholar Mariam Sowe; Mariam Sowe 2Institute of Geological Sciences, Planetary Sciences and Remote Sensing, Freie Universitaet Berlin, Malteserstrasse 74-100, D-12249 Berlin, Germany Search for other works by this author on: GSW Google Scholar Sanjeev Gupta; Sanjeev Gupta 1Department of Earth Science and Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK Search for other works by this author on: GSW Google Scholar Alexander Dumke; Alexander Dumke 2Institute of Geological Sciences, Planetary Sciences and Remote Sensing, Freie Universitaet Berlin, Malteserstrasse 74-100, D-12249 Berlin, Germany Search for other works by this author on: GSW Google Scholar Kate Goddard Kate Goddard 1Department of Earth Science and Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK Search for other works by this author on: GSW Google Scholar Author and Article Information Nicholas H. Warner * 1Department of Earth Science and Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK Mariam Sowe 2Institute of Geological Sciences, Planetary Sciences and Remote Sensing, Freie Universitaet Berlin, Malteserstrasse 74-100, D-12249 Berlin, Germany Sanjeev Gupta 1Department of Earth Science and Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK Alexander Dumke 2Institute of Geological Sciences, Planetary Sciences and Remote Sensing, Freie Universitaet Berlin, Malteserstrasse 74-100, D-12249 Berlin, Germany Kate Goddard 1Department of Earth Science and Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK *Current address: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, California 91109, USA; E-mail: Nicholas.H.Warner@jpl.nasa.gov. Publisher: Geological Society of America Received: 25 Oct 2012 Revision Received: 14 Jan 2013 Accepted: 17 Jan 2013 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2013 Geological Society of America Geology (2013) 41 (6): 675–678. https://doi.org/10.1130/G34172.1 Article history Received: 25 Oct 2012 Revision Received: 14 Jan 2013 Accepted: 17 Jan 2013 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Nicholas H. Warner, Mariam Sowe, Sanjeev Gupta, Alexander Dumke, Kate Goddard; Fill and spill of giant lakes in the eastern Valles Marineris region of Mars. Geology 2013;; 41 (6): 675–678. doi: https://doi.org/10.1130/G34172.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The existence of Hesperian age (3.7–3.4 Ga) surface water bodies on Mars is a contentious issue, often conflicting with favored climate models. Extensive lakes are proposed to have filled parts of Valles Marineris during this period, yet evidence for their presence and temporal continuity is poorly constrained. Here we report geomorphic and chronologic evidence for the initiation and demise of a voluminous lake system within the basins of eastern Valles Marineris. We find that independent, kilometer-deep lakes were present here well after the wetter, global climate optimum that characterized the previous Noachian epoch (4.1–3.7 Ga). Relative and impact crater chronologies of flood channels emerging from lake basins indicate relatively late lake spillover in the Early Amazonian (ca. 3.0 Ga). Drawdown of the lake and cessation of interbasin sedimentation may be recorded by a similar Early Amazonian (ca. 3.1 Ga) crater retention age on the surface of Capri Mensa, a 4-km-tall, sulfate-bearing interior layered deposit. The topography data demonstrate that incision of the bedrock barriers between the basins during spillover was driven by a dramatic local base-level difference between the lake surface and downstream basin floors. We postulate that the lake spillover process created an integrated drainage routing system between a voluminous equatorial water supply and the northern plains basin. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Comparison of PFS and TES observations of temperature and water vapor in the martian atmosphere

The interval from L s = 330° in Mars Year (MY) 26 until L s = 84° in MY 27 has been used to compare and validate measurements from the Mars Global Surveyor Thermal Emission Spectrometer (TES) and the Mars Express Planetary Fourier Spectrometer (PFS). We studied differences between atmospheric temperatures observed by the two instruments. The best agreement between atmospheric temperatures was found at 50 Pa between 40°S and 40°N latitude, where differences were within ±5 K. For other atmospheric levels, differences as large as ∼25 K were observed between the two instruments at some locations. The largest temperature differences occurred mainly over the Hellas Planitia, Argyre Planitia, Tharsis and Valles Marineris regions. On this basis we report on the variability of the martian atmosphere during the 5.5 martian years of Mars climatology obtained by combining the two data sets from TES and PFS. Atmospheric temperatures at 50 Pa responded to the global-scale dust storms of MY 25 and in MY 28 raising temperatures from ∼220 K to ∼250 K during the daytime. An atmospheric temperature of ∼140 K at 50 Pa was observed poleward of 70°N during northern winter and poleward of 60°S during southern winter each year in both the PFS and TES results. Water vapor observed by the two spectrometers showed consistent seasonal and latitudinal variations.

Physicochemical properties of concentrated Martian surface waters

[1] Understanding the processes controlling chemical sedimentation is an important step in deciphering paleoclimatic conditions from the rock records preserved on both Earth and Mars. Clear evidence for subaqueous sedimentation at Meridiani Planum, widespread saline mineral deposits in the Valles Marineris region, and the possible role of saline waters in forming recent geomorphologic features all underscore the need to understand the physical properties of highly concentrated solutions on Mars in addition to, and as a function of, their distinct chemistry. Using thermodynamic models predicting saline mineral solubility, we generate likely brine compositions ranging from bicarbonate-dominated to sulfate-dominated and predict their saline mineralogy. For each brine composition, we then estimate a number of thermal, transport, and colligative properties using established models that have been developed for highly concentrated multicomponent electrolyte solutions. The available experimental data and theoretical models that allow estimation of these physicochemical properties encompass, for the most part, much of the anticipated variation in chemistry for likely Martian brines. These estimates allow significant progress in building a detailed analysis of physical sedimentation at the ancient Martian surface and allow more accurate predictions of thermal behavior and the diffusive transport of matter through chemically distinct solutions under comparatively nonstandard conditions.

Modeling the collapse of Hebes Chasma, Valles Marineris, Mars

Research Article| July 01, 2011 Modeling the collapse of Hebes Chasma, Valles Marineris, Mars M.P.A. Jackson; M.P.A. Jackson † 1Bureau of Economic Geology, Jackson School of Geosciences, University of Texas, Austin, Texas 78713, USA †E-mail: martin.jackson@beg.utexas.edu. Search for other works by this author on: GSW Google Scholar J.B. Adams; J.B. Adams 2Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195, USA Search for other works by this author on: GSW Google Scholar T.P. Dooley; T.P. Dooley 1Bureau of Economic Geology, Jackson School of Geosciences, University of Texas, Austin, Texas 78713, USA Search for other works by this author on: GSW Google Scholar A.R. Gillespie; A.R. Gillespie 2Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195, USA Search for other works by this author on: GSW Google Scholar D.R. Montgomery D.R. Montgomery 2Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2011) 123 (7-8): 1596–1627. https://doi.org/10.1130/B30307.1 Article history received: 30 Mar 2010 rev-recd: 23 Jun 2010 accepted: 28 Jul 2010 first online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation M.P.A. Jackson, J.B. Adams, T.P. Dooley, A.R. Gillespie, D.R. Montgomery; Modeling the collapse of Hebes Chasma, Valles Marineris, Mars. GSA Bulletin 2011;; 123 (7-8): 1596–1627. doi: https://doi.org/10.1130/B30307.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Physical modeling and detailed mapping of Hebes Chasma provide new insights into the crustal composition and origin of the Valles Marineris region of equatorial Mars. Hebes Chasma is a 315-km-long and 8-km-deep closed depression containing distinctive landforms that include diapirs and extensive allochthonous flows that end in pits. A central puzzle of Hebes Chasma is how and where 105 km3 of missing material disappeared. Our physical models tested the hypothesis that the chasma formed by collapse and removal of material from below. Gravity-driven collapse in the models reproduced all the chasma's main landforms as subsidence evolved from early sagging of the upper surface, to inward collapse and removal of material, to emergence of diapirs and low-gradient flows. The models and geologic evidence suggest that Hebes Mensa arched upward diapirically and raised deep stratigraphy almost level with the chasma rim. If the chasma indeed collapsed by subsurface drainage as occurred in the models, the upper 8–10 km of deposits at Hebes must have been solid to depths of ∼5 km but viscous at greater depths. The materials removed could not have consisted mainly of basalt flows; instead, they probably were a mixture of hydrated and nonhydrated salts, water ice, liquid water, and insoluble (likely basaltic) particles. The proportions of these constituents are unknown but constrained because the material drained from the subsiding chasma and apparently contributed to the outburst floods released down neighboring Echus Chasma and Kasei Valles. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Evidence for subaqueously resedimented sulphate evaporites on Mars

This article documents the clastic nature of sulphate evaporite beds in the Tithonium Chasma located in the Valles Marineris region of Mars. These beds form a stratified succession characterised by very thick interbedded channel-fill breccia bodies. We infer that the bouldery channel-fills were deposited by voluminous mass-flow processes occurring in a relatively deep subaqueous environment. The redeposition of the coarse-grained evaporite would have responded to phases of high denudation rates in rapidly uplifting hinterlands. Tectonic activity also caused the diapiric uprise and exhumation of evaporite diapirs within the Valles Marineris chasmata, where the apparently young and well development karstic landforms probably formed during the late Amazonian age. These new data strongly suggest the deposition of both primary and resedimented evaporites in a marginal basin area, which effectively restricted ocean access through the proposed “proto-Valles Marineris Strait”. The associated ocean may be the “Ocean Borealis” of Late Noachian–Early Hesperian age.

New insight on genetic links between outflows and chasmata on Valles Marineris plateau, Mars

Within the Valles Marineris region on Mars, a huge system of interconnected valleys interpreted as flood channels reveals the presence of braided channels and strong incisions into the bedrock. We focus our study on Ganges Chasma, where two examples of outflow channels lie on the Valles Marineris plateau and take source in depressions. These channels may represent good examples for studying the relationship between the formation of Chasmata and outflow channels. No mass deposition is observed at the mouth of both channels, indicating that outflows were active before the opening of Ganges Chasma. In addition, possible sapping valleys were formed at the mouth in both cases. Residual aquifer could have been responsible for a late hydrogeological activity in this region after the opening and the widening of Ganges Chasma. From these observations and our flux calculations, we conclude that overpressure due to dyke ascent could have initiated outflows on Valles Marineris plateau, which is consistent with previous studies. Our results suggest that these mechanisms played a role in the opening and the widening of the Chasmata around 3 Gy to 3.5 Gy.

Light‐toned strata and inverted channels adjacent to Juventae and Ganges chasmata, Mars

Light‐toned layered deposits on the plains adjacent to Juventae and Ganges Chasmata have been identified and analyzed with several instruments onboard the Mars Reconnaissance Orbiter, including HiRISE, CTX, and CRISM. Beds exhibit variations in brightness, color, polygonal fracturing, and erosional properties that are not seen in light‐toned layered deposits within the chasmata. At both Juventae and Ganges, the light‐toned layered deposits along the plains have associated features we interpret as fluvial, including sinuous ridges (inverted channels) that exhibit light‐toned layering and an extensive valley system for the Ganges deposit. The strong correlation between the inverted channels and light‐toned layered deposits suggests an association with fluvial‐lacustrine processes, although pyroclastic and eolian activity may also be involved in their emplacement. The identification of potential fluvial‐lacustrine layered deposits and associated valley networks suggests surface water flow in the Valles Marineris region that occurred for sustained periods during the Hesperian (3.7–3.0 Gyr).

A glimpse of martian plumbing

Numerous long, wall-like ridges can be observed in the Valles Marineris region of Mars. They probably represent fault zones cemented by water-deposited minerals and are indicative of ancient groundwater flow.

Ancient groundwater flow in the Valles Marineris on Mars inferred from fault trace ridges

Long linear ridges in the Valles Marineris region of Mars most likely represent fault zones that have been cemented by water-deposited minerals. This implies that water in the Martian crust could have traversed long distances via faults and fractures.

Ages of rampart craters in equatorial regions on Mars: Implications for the past and present distribution of ground ice

Abstract— We are testing the idea of Squyres et al. (1992) that rampart craters on Mars may have formed over a significant time period and therefore the onset diameter (minimum diameter of a rampart crater) only reflects the ground ice depth at a given time. We measured crater size frequencies on the layered ejecta of rampart craters in three equatorial regions to derive absolute model ages and to constrain the regional volatile history. Nearly all rampart craters in the Xanthe Terra region are ˜3.8 Gyr old. This corresponds to the Noachian fluvial activity that region. Rampart crater formation declines in the Hesperian, whereas onset diameters (minimum diameter) increase. No new rampart craters formed after the end of the Hesperian (˜3 Gyr). This indicates a lowering of the ground ice table with time in the Xanthe Terra region. Most rampart craters in the Valles Marineris region are around 3.6 Gyr old. Only one large, probably Amazonian‐aged (˜2.5 Gyr), rampart crater exists. These ages indicate a volatile‐rich period in the Early Hesperian and a lowering of the ground ice table with time in the Valles Marineris study region. Rampart craters in southern Chryse Planitia, which are partly eroded by fluvial activity, show ages around 3.9 Gyr. Rampart craters superposed on channels have ages between ˜1.5 and ˜0.6 Gyr. The onset diameter (3 km at ˜1.5 Gyr) in this region may indicate a relatively shallow ground ice table. Loss of volatiles due to diffusion and sublimation might have lowered the ground ice table even in the southern Chryse Planitia region afterwards. In general, our study implies a formation of the smallest rampart craters within and/or shortly after periods of fluvial activity and a subsequent lowering of the ground ice table indicated by increasing onset diameter to the present. These results question the method to derive present equatorial ground ice depths from the onset diameter of rampart craters without information about their formation time.

A spatially continuous magnetization model for Mars

Using a three‐component magnetic field data set at over 100,000 satellite points previously compiled for spherical harmonic analysis, we have produced a continuously varying magnetization model for Mars. The magnetized layer was assumed to be 40 km thick, an average value based on previous studies of the topography and gravity field. The severe nonuniqueness in magnetization modeling is addressed by seeking the model with minimum root‐mean‐square (RMS) magnetization for a given fit to the data, with the trade‐off between RMS magnetization and fit controlled by a damping parameter. Our preferred model has magnetization amplitudes up to 20 A/m. It is expressed as a linear combination of the Green's functions relating each observation to magnetization at the point of interest within the crust, leading to a linear system of equations of dimension the number of data points. Although this is impractically large for direct solution, most of the matrix elements relating data to model parameters are negligibly small. We therefore apply methods applicable to sparse systems, allowing us to preserve the resolution of the original data set. Thus we produce more detailed models than any previously published, although they share many similarities. We find that tectonism in the Valles Marineris region has a magnetic signature, and we show that volcanism south of the dichotomy boundary has both a magnetic and gravity signature. The method can also be used to downward continue magnetic data, and a comparison with other leveling techniques at Mars' surface is favorable.

Evidence for precipitation on Mars from dendritic valleys in the Valles Marineris area.

Dendritic valleys on the plateau and canyons of the Valles Marineris region were identified from Thermal Emission Imaging System (THEMIS) images taken by Mars Odyssey. The geomorphic characteristics of these valleys, especially their high degree of branching, favor formation by atmospheric precipitation. The presence of inner channels and the maturity of the branched networks indicate sustained fluid flows over geologically long periods of time. These fluvial landforms occur within the Late Hesperian units (about 2.9 to 3.4 billion years old), when Mars was thought to have been cold. Our results suggest a period of warmer conditions conducive to hydrological activity.

Hydrogeologic processes of large-scale tectonomagmatic complexes in Mongolia–southern Siberia and on Mars

Research Article| April 01, 2004 Hydrogeologic processes of large-scale tectonomagmatic complexes in Mongolia–southern Siberia and on Mars Goro Komatsu; Goro Komatsu 1International Research School of Planetary Sciences, Università d'Annunzio, Viale Pindaro 42, 65127 Pescara, Italy Search for other works by this author on: GSW Google Scholar James M. Dohm; James M. Dohm 2Department of Hydrology and Water Resources, University of Arizona, Tucson, Arizona 85721, USA Search for other works by this author on: GSW Google Scholar Trent M. Hare Trent M. Hare 3U.S. Geological Survey, Flagstaff, Arizona 86001, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Goro Komatsu 1International Research School of Planetary Sciences, Università d'Annunzio, Viale Pindaro 42, 65127 Pescara, Italy James M. Dohm 2Department of Hydrology and Water Resources, University of Arizona, Tucson, Arizona 85721, USA Trent M. Hare 3U.S. Geological Survey, Flagstaff, Arizona 86001, USA Publisher: Geological Society of America Received: 25 Sep 2003 Revision Received: 30 Dec 2003 Accepted: 31 Dec 2003 First Online: 02 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2004) 32 (4): 325–328. https://doi.org/10.1130/G20237.2 Article history Received: 25 Sep 2003 Revision Received: 30 Dec 2003 Accepted: 31 Dec 2003 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Goro Komatsu, James M. Dohm, Trent M. Hare; Hydrogeologic processes of large-scale tectonomagmatic complexes in Mongolia–southern Siberia and on Mars. Geology 2004;; 32 (4): 325–328. doi: https://doi.org/10.1130/G20237.2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Large-scale tectonomagmatic complexes are common on Earth and Mars. Many of these complexes are created or at least influenced by mantle processes, including a wide array of plume types ranging from superplumes to mantle plumes. Among the most prominent complexes, the Mongolian plateau on Earth and the Tharsis bulge on Mars share remarkable similarities in terms of large domal uplifted areas, great rift canyon systems, and widespread volcanism on their surfaces. Water has also played an important role in the development of the two complexes. In general, atmospheric and surface water play a bigger role in the development of the present-day Mongolian plateau than for the Tharsis bulge, as evidenced by highly developed drainages and thick accumulation of sediments in the basins of the Baikal rift system. On the Tharsis bulge, however, water appears to have remained as ground ice except during periods of elevated magmatic activity. Glacial and periglacial processes are well documented for the Mongolian plateau and are also reported for parts of the Tharsis bulge. Ice-magma interactions, which are represented by the formation of subice volcanoes in parts of the Mongolian plateau region, have been reported for the Valles Marineris region of Mars. The complexes are also characterized by cataclysmic floods, but their triggering mechanism may differ: mainly ice-dam failures for the Mongolian plateau and outburst of groundwater for the Tharsis bulge, probably by magma-ice interactions, although ice-dam failures within the Valles Marineris region cannot be ruled out as a possible contributor. Comparative studies of the Mongolian plateau and Tharsis bulge provide excellent opportunities for understanding surface manifestations of plume-driven processes on terrestrial planets and how they interact with hydro-cryospheres. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.