Manual mapping of drumlins in synthetic landscapes to assess operator effectiveness

Mapped topographic features are important for understanding processes that sculpt the Earth's surface. This paper presents maps that are the primary product of an exercise that brought together 27 researchers with an interest in landform mapping wherein the efficacy and causes of variation in mapping were tested using novel synthetic DEMs containing drumlins. The variation between interpreters (e.g. mapping philosophy, experience) and across the study region (e.g. woodland prevalence) opens these factors up to assessment. A priori known answers in the synthetics increase the number and strength of conclusions that may be drawn with respect to a traditional comparative study. Initial results suggest that overall detection rates are relatively low (34–40%), but reliability of mapping is higher (72–86%). The maps form a reference dataset

Characterising the ocean frontier : a review of marine geomorphometry

Geomorphometry, the science that quantitatively describes terrains, has traditionally focused on the investigation of terrestrial landscapes. However, the dramatic increase in the availability of digital bathymetric data and the increasing ease by which geomorphometry can be investigated using Geographic Information Systems (GIS) has prompted interest in employing geomorphometric techniques to investigate the marine environment. Over the last decade, a suite of geomorphometric techniques have been applied (e.g. terrain attributes, feature extraction, automated classification) to investigate the characterisation of seabed terrain from the coastal zone to the deep sea. Geomorphometric techniques are, however, not as varied, nor as extensively applied, in marine as they are in terrestrial environments. This is at least partly due to difficulties associated with capturing, classifying, and validating terrain characteristics underwater. There is nevertheless much common ground between terrestrial and marine geomorphology applications and it is important that, in developing the science and application of marine geomorphometry, we build on the lessons learned from terrestrial studies. We note, however, that not all terrestrial solutions can be adopted by marine geomorphometric studies since the dynamic, four- dimensional nature of the marine environment causes its own issues, boosting the need for a dedicated scientific effort in marine geomorphometry. This contribution offers the first comprehensive review of marine geomorphometry to date. It addresses all the five main steps of geomorphometry, from data collection to the application of terrain attributes and features. We focus on how these steps are relevant to marine geomorphometry and also highlight differences from terrestrial geomorphometry. We conclude with recommendations and reflections on the future of marine geomorphometry.peer-reviewe

Two complementary approaches in refining the search for liquid water and habitable environments on present-day Mars

All known active life requires liquid water. The correlation between liquid water and the presence of life on Earth has guided the search for life on other planets. For terrestrial-like life to exist in the harsh conditions that dominate the surfaces of other rocky planets, the minimum fundamental requirements of liquid water, nutrients, and chemical energy must be met. Within our solar system, Mars is a strong candidate for hospitable environments able to support life, due to the reservoirs of water within its crust and the strong likelihood of liquid water. The aim of this thesis is to refine the search for liquid water and environments that may be hospitable to life on Mars. Two complementary methodologies are developed and utilised to achieve this aim. Water requires a relatively narrow range of pressures and temperatures to occur in the liquid phase. The first approach of this thesis compares this range with the pressure-temperature conditions that occur within the Earth, the Earth’s active biosphere, and Mars. Temperature, pressure and water activity are examined to determine the extent to which they restrict life from some liquid water environments. The relevant thresholds are then applied to Mars and compared to models of where liquid water environments are likely to occur under present-day martian conditions. Extensive regions of the Earth may be inhospitable despite lying within the hydrosphere. Life is likely restricted from ~ 81% of the volume of the hydrosphere of Earth due to high temperature and/or low water activity. In contrast, the fraction of Mars that can support liquid water is five times larger than that of Earth, given estimates of an average martian brine. Many environments within the martian crust can potentially support life, with perennially habitable conditions extending from approximately 10 to 37 km beneath the surface. The surface and shallow regolith may also be habitable in the warmest regions of the planet. The second approach focuses on the shallow subsurface of Mars within the top ~20 m. The thermal behaviour of surface materials determines the occurrence of transient shallow liquid water and habitable temperatures for life. Ten classes of surface materials are identified from analysis of global martian thermal inertia and albedo, through the technique of algorithmic classification. These classes are interpreted as mixtures of dust, sand, duricrust, rocks and ice on the surface, and validated through comparisons with independent datasets. Low latitude locations of dark sand, duricrust and pebbles in Syrtis Major, Oxia Palus, Mawrth Vallis and eastern Meridiani Planum are identified as having high potential for hospitable liquid water environments at < 10 m depth. Dark, coarse, sand dominated surfaces are found in Syrtis Major and Aram Chaos and are predicted to be locations of low volume flows of liquid water, potentially analogous to the observed martian recurring slope lineae. This thesis identifies where habitable liquid water environments may occur on Mars, strengthening the astrobiological significance of the planet and providing direction for future robotic and satellite missions searching for life