First in-situ analysis of dust devil tracks on Earth and their comparison with tracks on Mars

In this study we report about the first in-situ analysis of terrestrial dust devil tracks (DDTs) observed in the Turpan depression desert in northwestern China. Passages of active dust devils remove a thin layer of fine grained material (< ∼63 μm), cleaning the upper surface of coarse sands (0.5–1 mm). This erosional process changes the photometric properties of the upper surface causing the albedo differences within the track to the surroundings. Measurements imply that a removal of an equivalent layer thickness of ∼2 μm is sufficient to form the dark dust devil tracks. Our terrestrial results are in agreement with the mechanism proposed by Greeley et al. (2005) for the formation of DDTs on Mars

3D Morphometries of Eskers on Mars, and Comparisons to Eskers in Finland

International audienceIntroduction: We present new, high-resolution measurements of the 3D morphometries of eskers associated with debris-covered glaciers in the Phlegra Mon-tes [1] and NW Tempe Terra [2] regions of Mars' northern mid-latitudes. We compare them with the ancient south polar 'Dorsa Argentea' eskers on Mars [3], and first large database (n > 20,000) of 3D morphome-tries of terrestrial eskers, from SW Finland [4]. Eskers are ridges of glaciofluvial sediment deposited by meltwater flowing through tunnels within or beneath glaciers. They are vital tools for reconstructing the dynamics, extent, and environmental drivers of wet-based glaciation on Earth and Mars. For example, reconstructions of Mars' climate conditions at the Noa-chian-Hesperian transition [e.g., 5] have relied heavily upon insights from the Dorsa Argentea eskers [e.g., 3], which record basal melting of a large south polar ice sheet ~3.5 Ga. Morphometric studies of candidate eskers on Mars are vital both for testing hypotheses of their origins as eskers [e.g., 3], and for informing insights into the magnitude and dynamics of meltwater flows that formed them [e.g., 5-6]. Previously, such work has been limited by a lack of large-scale surveys of the 3D morphometries of eskers on Earth, to which the martian landforms can be compared. A new database comprising >20 000 measurements of 3D esker morphometries from SW Finland provides new opportunities for such-comparisons, which we exploit in this study [4]. Methods: We used 1-2 m/pixel digital elevation models generated from High Resolution Imaging Science Experiment (HiRISE) images to measure esker heights (H) and widths (W) from cross-sectional tran-sects spaced at 10 and 20 m intervals along the Phlegra Montes and NW Tempe Terra eskers, respectively (fol-lowing [3]). We calculated average slopes across cross-sectional transects (θ) as: tan −1 (H/0.5W). We classified transects into sharp-, multi-, and round-crested morphologies according to the scheme of [6]. The NW Tempe Terra esker comprises two 'stacked' esker ridges (see [7], this conference) which we treat separately in the present study. Storrar and Jones [4] obtained similar H, W, and θ measurements at 10 m intervals along ~70 km of Qua-ternary-aged eskers in SW Finland, using 2 m/pixel elevation data from airborne LiDAR

Multi-Phase Sedment-Discharge Dynamics of Subglacial Drainage Recorded by a Glacier-Linked Esker in NW Tempe Terra, Mars

International audienceIntroduction: Our recent discoveries of eskers associated with 110-150 Myr old debris-covered glaciers in Phlegra Montes [1] and NW Tempe Terra [2], Mars, indicate that localised wet-based glaciation has occurred in at least two locations during the late Amazonian , despite cold climate conditions. Eskers are sedi-mentary ridges deposited by meltwater flowing through drainage tunnels within or beneath glaciers. In this study, we use new 3D measurements of the NW Tempe Terra esker (46.17 °N, 83.06 °W) to develop a conceptual model for the sediment-discharge dynamics of the esker-forming drainage episode(s). Methods: Following [3], we used a 2 m/pixel digital elevation model derived from High Resolution Imaging Science Experiment (HiRISE) images to measure ridge height (H) and width (W) every ~20 m along the esker. We exclude ridge portions obscured by the parent glacier (Fig 1), as well as transitions between morphological zones. Results: A scatterplot of the raw height and width measurements (Fig 2A) has multiple limbs which correspond to subzones of the esker with common morphological characteristics (Fig 1)

Limitations to recording larger mammalian predators in savannah using camera traps and spoor

Traditionally, spoor (tracks, pug marks) have been used as a cost effective tool to assess the presence of larger mammals. Automated camera traps are now increasingly utilized to monitor wildlife, primarily as the cost has greatly declined and statistical approaches to data analysis have improved. While camera traps have become ubiquitous, we have little understanding of their effectiveness when compared to traditional approaches using spoor in the field. Here, we a) test the success of camera traps in recording a range of carnivore species against spoor; b) ask if simple measures of spoor size taken by amateur volunteers is likely to allow individual identification of leopards and c) for a trained tracker, ask if this approach may allow individual leopards to be followed with confidence in savannah habitat. We found that camera traps significantly under-recorded mammalian top and meso-carnivores, with camera traps more likely under-record the presence of smaller carnivores (civet 64%; genet 46%, Meller’s mongoose 45%) than larger (jackal sp. 30%, brown hyena 22%), while leopard was more likely to be recorded by camera trap (all recorded by camera trap only). We found that amateur trackers could be beneficial in regards to collecting presence data; however the large variance in measurements of spoor taken in the field by volunteers suggests that this approach is unlikely to add further data. Nevertheless, the use of simple spoor measurements in the field by a trained field researcher increases their ability to reliably follow a leopard trail in difficult terrain. This allows researchers to glean further data on leopard behaviour and habitat utilisation without the need for complex analysis

The PanCam Instrument for the ExoMars Rover

The scientific objectives of the ExoMars rover are designed to answer several key questions in the search for life on Mars. In particular, the unique subsurface drill will address some of these, such as the possible existence and stability of subsurface organics. PanCam will establish the surface geological and morphological context for the mission, working in collaboration with other context instruments. Here, we describe the PanCam scientific objectives in geology, atmospheric science, and 3-D vision. We discuss the design of PanCam, which includes a stereo pair of Wide Angle Cameras (WACs), each of which has an 11-position filter wheel and a High Resolution Camera (HRC) for high-resolution investigations of rock texture at a distance. The cameras and electronics are housed in an optical bench that provides the mechanical interface to the rover mast and a planetary protection barrier. The electronic interface is via the PanCam Interface Unit (PIU), and power conditioning is via a DC-DC converter. PanCam also includes a calibration target mounted on the rover deck for radiometric calibration, fiducial markers for geometric calibration, and a rover inspection mirror.publishersversionPeer reviewe

Ancient alluvial plains at Oxia Planum, Mars

The geologic origin of the ancient, phyllosilicate-bearing bedrock at Oxia Planum, Mars, the ExoMars rover landing site, is unknown. The phyllosilicates record ancient aqueous processes, but the processes that formed the host bedrock remain elusive. Here, we use high-resolution orbital and topographic datasets from the HiRISE, CaSSIS and CTX instruments to investigate and characterize fluvial sinuous ridges (FSRs), found across the Oxia Planum region. The FSRs form segments up to 70 km long, are 20-600 m wide, and up to 9 m in height, with sub-horizontal layering common in ridge margins. Some FSRs comprise multi-story ridge systems; many are embedded within the phyllosilicate-bearing bedrock. We interpret the FSRs at Oxia Planum as deposits of ancient, episodically active, alluvial river systems (channel-belt and overbank deposits). Thus, at least some of the phyllosilicate-bearing bedrock was formed by ancient alluvial rivers, active across the wider region, though we do not exclude other processes from contributing to its formation as well. The presence of alluvial floodplains at Oxia Planum increases the chances of the ExoMars rover detecting signs of ancient life. Future exploration by the ExoMars rover can verify the alluvial interpretation and provides an opportunity to investigate some of the oldest river deposits in the Solar System

Water induced sediment levitation enhances downslope transport on Mars

On Mars, locally warm surface temperatures (~293 K) occur, leading to the possibility of (transient) liquid water on the surface. However, water exposed to the martian atmosphere will boil, and the sediment transport capacity of such unstable water is not well understood. Here, we present laboratory studies of a newly recognized transport mechanism: “levitation” of saturated sediment bodies on a cushion of vapor released by boiling. Sediment transport where this mechanism is active is about nine times greater than without this effect, reducing the amount of water required to transport comparable sediment volumes by nearly an order of magnitude. Our calculations show that the effect of levitation could persist up to ~48 times longer under reduced martian gravity. Sediment levitation must therefore be considered when evaluating the formation of recent and present-day martian mass wasting features, as much less water may be required to form such features than previously thought

Collapse of the world's largest herbivores

Large wild herbivores are crucial to ecosystems and human societies. We highlight the 74 largest terrestrial herbivore species on Earth (body mass ≥100 kg), the threats they face, their important and often overlooked ecosystem effects, and the conservation efforts needed to save them and their predators from extinction. Large herbivores are generally facing dramatic population declines and range contractions, such that ~60% are threatened with extinction. Nearly all threatened species are in developing countries, where major threats include hunting, land-use change, and resource depression by livestock. Loss of large herbivores can have cascading effects on other species including large carnivores, scavengers, mesoherbivores, small mammals, and ecological processes involving vegetation, hydrology, nutrient cycling, and fire regimes. The rate of large herbivore decline suggests that ever-larger swaths of the world will soon lack many of the vital ecological services these animals provide, resulting in enormous ecological and social costs