James William Rice

Catastrophic flood sediments in Chryse Basin, Mars, and Quincy Basin, Washington: Application of sandar facies model

Viking visible and thermal infrared observations and terrestrial catastrophic flood deposits provide clues to identify the outflow channel sediments that went into Chryse Basin on Mars. On Earth, sandar (outwash plains formed by coalescence of many jokulhlaup floods) are described in terms of three laterally adjacent facies: proximal, midfan, and distal. The Missoula Flood sediments deposited in Quincy Basin, Washington, comprise a miniature analog of Chryse Basin. The terminology and general characteristics of the sandar facies model are applied to Quincy Basin, although the depositional environment and clast sizes are somewhat different (higher-energy flood, larger clasts, subaqueous rather than subaerial deposition). For example, the Ephrata Fan (a deposit of boulders, cobbles, and pebbles) forms the midfan facies analog; a downfan sandy deposit (reworked into a dune field) comprises the distal facies analog. In Chryse Basin the midfan is defined by a heterogeneous rocky (0–25%), intermediate-albedo (0.21–0.26), intermediate thermal inertia (260–460 J m−2 s−0.5 K−1) surface, while the distal facies has a low albedo (0.14–0.16) and higher thermal inertia (340–700 J m−2 s−0.5 K−1). The Chryse midfan unit has rocks and windblown dust exposed at the surface. The sand of the distal facies in Chryse/Acidalia is reworked by the wind, as in Quincy Basin. The Viking 1 and Mars Pathfinder landing sites are located on the midfan unit. Observations that can be made at the Mars Pathfinder site might help in reevaluating whether or not Viking 1 landed on outflow channel sediments.

Sedimentary geomorphology of the Mars Pathfinder landing site

The first landing on Mars in over 20 years will take place July 4, 1997, near the mouth of the Ares Vallis outflow channel located in southeastern Chryse Planitia. Mars Pathfinder, unlike Viking 1, is expected to land on a surface that has a distinct and unambiguous fluvial signature. For safety reasons, the landing site was selected within a broad plains region beyond the mouth of Ares Vallis so as to avoid large topographic obstacles that could pose hazards to the landing. However, this plain is not without its interesting, and in some cases rather problematic, landforms. The 100 km by 200 km landing ellipse contains the following features: (1) primary impact craters, (2) clusters of small secondary craters, (3) streamlined islands, (4) longitudinal grooves, (5) “scabland” or “etched” terrain, (6) pancake-like shields and dike-like structures, (7) knobs or buttes, and (8) a previously undetected, subtle undulating or hummocky texture to the plains surface. The nature of these landforms has important bearing on how we will interpret what we see at the scale of the Pathfinder lander once the first images are transmitted to Earth. With the exception of the craters, all of the remaining features described within the Mars Pathfinder landing ellipse can be interpreted as forming as a result of catastrophic flooding from Ares and Tiu Valles into Chryse Planitia, either during the flood itself, or through secondary modification of thick flood deposits after the event.

Field reconnaissance geologic mapping of the Columbia Hills, Mars, based on Mars Exploration Rover Spirit and MRO HiRISE observations

Chemical, mineralogic, and lithologic ground truth was acquired for the first time on Mars in terrain units mapped using orbital Mars Reconnaissance Orbiters High Resolution Imaging Science Experiment (MRO HiRISE) image data. Examination of several dozen outcrops shows that Mars is geologically complex at meter length scales, the record of its geologic history is well exposed, stratigraphic units may be identified and correlated across significant areas on the ground, and outcrops and geologic relationships between materials may be analyzed with techniques commonly employed in terrestrial field geology. Despite their burial during the course of Martian geologic time by widespread epiclastic materials, mobile fines, and fall deposits, the selective exhumation of deep and well-preserved geologic units has exposed undisturbed outcrops, stratigraphic sections, and structural information much as they are preserved and exposed on Earth. A rich geologic record awaits skilled future field investigators on Mars. The correlation of ground observations and orbital images enables construction of a corresponding geologic reconnaissance map. Most of the outcrops visited are interpreted to be pyroclastic, impactite, and epiclastic deposits overlying an unexposed substrate, probably related to a modified Gusev crater central peak. Fluids have altered chemistry and mineralogy of these protoliths in degrees that vary substantially within the same map unit. Examination of the rocks exposed above and below the major unconformity between the plains lavas and the Columbia Hills directly confirms the general conclusion from remote sensing in previous studies over past years that the early history of Mars was a time of more intense deposition and modification of the surface. Although the availability of fluids and the chemical and mineral activity declined from this early period, significant later volcanism and fluid convection enabled additional, if localized, chemical activity.

Volatile Analysis by Pyrolysis of Regolith for planetary resource exploration

The extraction and identification of volatile resources that could be utilized by humans including water, oxygen, noble gases, and hydrocarbons on the Moon, Mars, and small planetary bodies will be critical for future long-term human exploration of these objects. Vacuum pyrolysis at elevated temperatures has been shown to be an efficient way to release volatiles trapped inside solid samples. In order to maximize the extraction of volatiles, including oxygen and noble gases from the breakdown of minerals, a pyrolysis temperature of 1400°C or higher is required, which greatly exceeds the maximum temperatures of current state-of-the-art flight pyrolysis instruments. Here we report on the recent optimization and field testing results of a high temperature pyrolysis oven and sample manipulation system coupled to a mass spectrometer instrument called Volatile Analysis by Pyrolysis of Regolith (VAPoR). VAPoR is capable of heating solid samples under vacuum to temperatures above 1300°C and determining the composition of volatiles released as a function of temperature.

DIRTCam in the desert: The Silver Lake field test of the Robotic Arm Camera

The Robotic Arm Camera (RAC) is a panchromatic imager included as part of the Mars Volatiles and Climate Surveyor (MVACS) science experiment on Mars Polar Lander and on the Mars 2001 lander. It is designed to take both panoramic and microscopic images in order to gather data on the morphology and mineralogy of surface materials. In order to demonstrate these capabilities, a field test was conducted at Silver Lake playa in the Mojave Desert. The test consisted of going to a remote site unknown to the science team and providing that team with a data set of RAC panoramic, anaglyph, and microscopic images similar to what would be available during an actual landing. With only this information the science team attempted a determination of the position and the geology of the field test site. Using panoramic and anaglyph images provided by RAC, in conjunction with overflight images simulating data from a descent camera, the landing site for the field test was determined within 50 m of the actual site as lying near both a playa and an alluvial fan. Images of samples from the surface and within the trench revealed grain morphology, texture, and mineralogy indicating a soil dominated by quartz and feldspar, interspersed with a minor mafic component. Grain-size distribution was bimodal, with small, rounded to subrounded grains dominant at lower depths and larger, more angular grains more plentiful near the surface. This mineralogy is confirmed by the geology of the site and the data provided by the descent images and mid-IR measurements. RAC has demonstrated its ability to image the local geology and identify the major mineralogic components of an unknown site. These abilities will be crucial in understanding both the macroscopic and the microscopic geology of future Mars landing sites. This test also has demonstrated the crucial link between RAC data and complementary data sets such as context images and compositional data that can support the mineralogic observations made by RAC.

Scientists, educators prepare for Mars Pathfinder mission

Mars scientists, engineers, and 13 K-12 educators invaded eastern Washingtons Channeled Scabland for a week in September to explore terrain similar to the kind Mars Pathfinder will encounter when it touches down on the red planet on July 4, 1997. Through field trips and workshops, the scientists and engineers reached consensus on a number of issues about Mars history and shared their knowledge and enthusiasm with the public. The teachers, who came from Washington and Idaho, witnessed engineering, scientific investigation, and debate in action, and acquired a great deal of knowledge about Mars that they can bring back to their classrooms and communities. “We worked side by side with the scientists and engineers as they researched, experimented, problem-solved and debated different aspects of the Mars Pathfinder mission,” explained high school teacher John Gallagher.