Valley development on Hawaiian volcanoes

Work in progress on Hawaiian drainage evolution indicates an important potential for understanding drainage development on Mars. Similar to Mars, the Hawaiian valleys were initiated by surface runoff, subsequently enlarged by groundwater sapping, and eventually stabilized as aquifers were depleted. Quantitative geomorphic measurements were used to evaluate the following factors in Hawaiian drainage evolution: climate, stream processes, and time. In comparing regions of similar climate, drainage density shows a general increase with the age of the volcani island. With age and climate held constant, sapping dominated valleys, in contrast to runoff-dominated valleys, display the following: lower drainage densities, higher ratios of valley floor width to valley height, and more positive profile concavities. Studies of stream junction angles indicate increasing junction angles with time on the drier leeward sides of the major islands. The quantitative geomorphic studies and earlier field work yielded important insights for Martian geomorphology. The importance of ash mantling in controlling infiltration on Hawaii also seems to apply to Mars. The Hawaiian valley also have implications for the valley networks of Martian heavily cratered terrains

Fluvial valleys on Martian volcanoes

Channels and valleys were known on the Martian volcanoes since their discovery by the Mariner 9 mission. Their analysis has generally centered on interpretation of possible origins by fluvial, lava, or viscous flows. The possible fluvial dissection of Martian volcanoes has received scant attention in comparison to that afforded outflow, runoff, and fretted channels. Photointerpretative, mapping, and morphometric studies of three Martian volcanoes were initiated: Ceraunius Tholus, Hecate Tholus, and Alba Patera. Preliminary morphometric results indicate that, for these three volcanoes, valley junction angles increase with decreasing slope. Drainage densities are quite variable, apparently reflecting complex interactions in the landscape-forming factors described. Ages of the Martian volcanoes were recently reinterpreted. This refined dating provides a time sequence in which to evaluate the degradational forms. An anomaly has appeared from the initial study: fluvial valleys seem to be present on some Martian volcanoes, but not on others of the same age. Volcanic surfaces characterized only by high permeability lava flows may have persisted without fluvial dissection

Fluvial erosion on Mars: Implications for paleoclimatic change

Fluvial erosion on Mars has been nonuniform in both time and space. Viking orbiter images reveal a variety of different aged terrains exhibiting widely different degrees of erosion. Based on our terrestrial analog studies, rates of fluvial erosion associated with the formation of many of the valleys on Mars is probably on the order of hundreds of meters per million years, while rates of erosion associated with the formation of the outflow channels probably ranged from tens to hundreds of meters in several weeks to months. However, estimated rates of erosion of the Martian surface at the Viking Lander sites are extremely low, on the order of 1 micron/yr or less. At most this would result in a meter of material removed per million years, and it is unlikely that such an erosion rate would be able to produce the degree of geomorphic work required to form the fluvial features present elsewhere on the surface. In addition, single terrain units are not eroded uniformly by fluvial processes. Instead fluvial valleys, particularly in the cratered highlands, typically are situated in clusters surrounded by vast expanses of uneroded surfaces of the same apparent lithologic, structural, and hydrological setting. Clearly throughout its geologic history, Mars has experienced a nonuniformity in erosion rates. By estimating the amount of fluvial erosion on dissected terrains and by studying the spatial distribution of those locations which have experienced above normal erosion rates, it should be possible to place further constraints on Mars' paleoclimatic history

Remote Exploration: Understanding Martian Surface Processes

Earth and Mars share many similar physical features, including canyons, valleys, craters, volcanoes, ice, and gullies. My research focuses on two distinct projects. The first concentrates on the formation of gullies, which are channel networks generally formed on mid-latitude crater walls on Mars. Debated gully-forming processes include the melting of snowpacks, sublimation of accumulated carbon dioxide frost, melting of snow-rich dusty mantle material, and groundwater flows. Using High Resolution Imaging Science Experiment (HiRISE) images of gullies and working with Digital Elevation Models (DEMs) in ENVI, we are able to perform detailed studies of gully morphology, including volume calculations using slope, distance, and elevation. The second topic focuses on determining the mineral composition of Martian rocks. Using Raman spectroscopy, I am testing the mineral composition of igneous rocks and recording spectral peaks for key rock-forming minerals, such as olivine, plagioclase, potassium feldspar, quartz, and pyroxene. Raman spectroscopy is an inelastic light scattering technique that measures the change in energy of a photon. These samples and spectra will be used to help create an automated computer mineral identification algorithm that might be used on future Mars rover missions. Both projects contribute to scientific studies of remote exploration and understanding of the Martian surface

Ancient oceans and Martian paleohydrology

The global model of ocean formation on Mars is discussed. The studies of impact crater densities on certain Martian landforms show that late in Martian history there could have been coincident formation of: (1) glacial features in the Southern Hemisphere; (2) ponded water and related ice features in the northern plains; (3) fluvial runoff on Martian uplands; and (4) active ice-related mass-movement. This model of transient ocean formation ties these diverse observations together in a long-term cyclic scheme of global planetary operation

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

Tsunami waves extensively resurfaced the shorelines of an early Martian ocean

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

Surface Morphologies in a Mars-Analog Ca-Sulfate Salar, High Andes, Northern Chile

Salar de Pajonales, a Ca-sulfate salt flat in the Chilean High Andes, showcases the type of polyextreme environment recognized as one of the best terrestrial analogs for early Mars because of its aridity, high solar irradiance, salinity, and oxidation. The surface of the salar represents a natural climate-transition experiment where contemporary lagoons transition into infrequently inundated areas, salt crusts, and lastly dry exposed paleoterraces. These surface features represent different evolutionary stages in the transition from previously wetter climatic conditions to much drier conditions today. These same stages closely mirror the climate transition on Mars from a wetter early Noachian to the Noachian/Hesperian. Salar de Pajonales thus provides a unique window into what the last near-surface oases for microbial life on Mars could have been like in hypersaline environments as the climate changed and water disappeared from the surface. Here we open that climatological window by evaluating the narrative recorded in the salar surface morphology and microenvironments and extrapolating to similar paleosettings on Mars. Our observations suggest a strong inter-dependence between small and large scale features that we interpret to be controlled by extrabasinal changes in environmental conditions, such as precipitation-evaporation-balance changes and thermal cycles, and most importantly, by internal processes, such as hydration/dehydration, efflorescence/deliquescence, and recrystallization brought about by physical and chemical processes related to changes in groundwater recharge and volcanic processes. Surface structures and textures record a history of hydrological changes that impact the mineralogy and volume of Ca-sulfate layers comprising most of the salar surface. Similar surface features on Mars, interpreted as products of freeze-thaw cycles, could, instead, be products of water-driven, volume changes in salt deposits. On Mars, surface manifestations of such salt-related processes would point to potential water sources. Because hygroscopic salts have been invoked as sources of localized, transient water sufficient to support terrestrial life, such structures might be good targets for biosignature exploration on Mars

Magmatic intrusions and hydrothermal systems: Implications for the formation of Martian fluvial valleys.

This dissertation investigates the possible role of hydrothermally driven groundwater outflow in the formation of fluvial valleys on Mars. Although these landforms have often been cited as evidence for a past wanner climate and denser atmosphere, recent theoretical modeling precludes such climatic conditions on early Mars when most fluvial valleys formed. Because fluvial valleys continued to form throughout Mars' geological history and the most earth-like stream valleys on Mars formed well after the decline of the early putative earth-like climate, it may be unnecessary to invoke drastically different climatic conditions for the formation of the earliest stream valleys. The morphology of most Martian fluvial valleys indicates formation by ground-water sapping which is consistent with a subsurface origin. Additionally, many Martian fluvial valleys formed on volcanoes, impact craters, near fractures, or adjacent to terrains interpreted as igneous intrusions; all are possible locales of vigorous, geologically long-lived hydrothermal circulation. Comparison of Martian valley morphology to similar features on Earth constrains valley genesis scenarios. Volumes of measured Martian fluvial valleys range from 10¹⁰ to 10¹³ m³. Based on terrestrial analogs, total water volumes required to erode these valleys range from -10¹⁰ to 10¹⁵ m³. The clustered distribution of Martian valleys within a given terrain type, the sapping dominated morphology, and the general lack of associated runoff valleys all indicate the importance of localized ground-water outflow in the formation of these fluvial systems. An analytic model of a conductively cooling cylindrical intrusion is coupled with the U.S. Geological Survey's numerical ground-water computer code SUTRA to evaluate the magnitude of ground-water outflow expected from magmatically-driven hydrothermal systems on Mars. Results indicate that magmatic intrusions of several 10² km³ or larger can provide sufficient ground-water outflow over periods (several 10⁵ years) required to form Martian fluvial Valleys. Therefore, a vastly different climate on early Mars may not be necessary to explain the formation of the observed Valleys. Martian hydrothermal systems would have also produced long-lived sources of near-surface water; these localized regions may have provided oases for any microbial life that may have evolved on the planet