Recognition of Sedimentary Rock Occurrences in Satellite and Aerial Images of Other Worlds—Insights from Mars

Sedimentary rocks provide records of past surface and subsurface processes and environments. The first step in the study of the sedimentary rock record of another world is to learn to recognize their occurrences in images from instruments aboard orbiting, flyby, or aerial platforms. For two decades, Mars has been known to have sedimentary rocks; however, planet-wide identification is incomplete. Global coverage at 0.25–6 m/pixel, and observations from the Curiosity rover in Gale crater, expand the ability to recognize Martian sedimentary rocks. No longer limited to cases that are light-toned, lightly cratered, and stratified—or mimic original depositional setting (e.g., lithified deltas)—Martian sedimentary rocks include dark-toned examples, as well as rocks that are erosion-resistant enough to retain small craters as well as do lava flows. Breakdown of conglomerates, breccias, and even some mudstones, can produce a pebbly regolith that imparts a “smooth” appearance in satellite and aerial images. Context is important; sedimentary rocks remain challenging to distinguish from primary igneous rocks in some cases. Detection of ultramafic, mafic, or andesitic compositions do not dictate that a rock is igneous, and clast genesis should be considered separately from the depositional record. Mars likely has much more sedimentary rock than previously recognized.

Terraforming: synthetic biology's final frontier

Synthetic biology, the design and synthesis of synthetic biological systems from DNA to whole cells, has provided us with the ultimate tools for space exploration and colonisation. Herein, we explore some of the most significant advances and future prospects in the field of synthetic biology, in the context of astrobiology and terraforming.

Navigation Results from Desert Field Tests of the Rocky 7 Mars Rover Prototype

Upcoming missions to the surface of Mars will use mobile robots to traverse long distances from the landing site. To prepare for these missions, the prototype rover, Rocky 7, has been tested in desert field trials conducted with a team of planetary scientists. While several new capabilities have been demonstrated, foremost among these was sun-sensor-based traversal of natural terrain totaling a distance of 1 km. This paper describes navigation results obtained in the field tests, where cross-track error was only 6% of the distance traveled. Comparison with previous results of other planetary rover systems shows this to be a significant improvement. Methods for further improvement are also discussed.

Traction Control of Wheeled Robotic Vehicles in Rough Terrain with Application to Planetary Rovers

Mobile robots are being developed for high-risk missions in rough terrain situations, such as planetary exploration. Here, a rough-terrain control methodology is presented that exploits the actuator redundancy found in multiwheeled mobile robot systems to improve ground traction and reduce power consumption. The algorithm optimizes individual wheel torque based on multiple optimization criteria, which are a function of the local terrain profile. A key element of the method is to be able to include estimates of wheel-terrain contact angles and soil characteristics. A method using an extended Kalman filter is presented for estimating these angles using simple on-board sensors. Simulation and experimental results for a micro-rover traversing challenging terrain demonstrate the effectiveness of the algorithm.

Martian fluvial conglomerates at Gale crater

Observations by the Mars Science Laboratory Mast Camera (Mastcam) in Gale crater reveal isolated outcrops of cemented pebbles (2 to 40 millimeters in diameter) and sand grains with textures typical of fluvial sedimentary conglomerates. Rounded pebbles in the conglomerates indicate substantial fluvial abrasion. ChemCam emission spectra at one outcrop show a predominantly feldspathic composition, consistent with minimal aqueous alteration of sediments. Sediment was mobilized in ancient water flows that likely exceeded the threshold conditions (depth 0.03 to 0.9 meter, average velocity 0.20 to 0.75 meter per second) required to transport the pebbles. Climate conditions at the time sediment was transported must have differed substantially from the cold, hyper-arid modern environment to permit aqueous flows across several kilometers.

Human-vision-based selection of image processing algorithms for planetary exploration

Independent and automatic image processing is a fundamental objective of the computer vision community. Understanding the role of the eye movement scan path in human vision is an important step toward the achievement of this objective. This top-down model of higher human vision is a new approach to bottom-up image processing algorithms and provides an important new metric and tool in computer vision. We have demonstrated that a small and manageable collection of image processing algorithms, experimentally selected and then combined together can serve in a task such as predicting human eye fixations identifying geological features. Thus, automatic picture analysis based upon human vision could be an essential element in planetary exploration.

Magnetite biomineralization and ancient life on Mars

Certain chemical and mineral features of the Martian meteorite ALH84001 were reported in 1996 to be probable evidence of ancient life on Mars. In spite of new observations and interpretations, the question of ancient life on Mars remains unresolved. Putative biogenic, nanometer magnetite has now become a leading focus in the debate.