Brief résumé 1997: MSci Physics with Space Science, University College London, UK 2001: PhD Geophysics, University College London. PhD title: “Small scale tectonism on Venus: an experimental and image based study”. Used fracture mechanics principles and high-pressure, high-temperature fracture mechanics experiments to model formation of closely space parallel fractures (CSPF) on Venus. Mapped CSPF on Venus using Magellan radar data. JGR 109 E03 (2004), JVGR 132 (2004) : Postdoc, Arizona State University. Working with Prof. Ron Greeley, ran experiments in the NASA Ames MARSWIT low-pressure chamber to simulate dust devils on Mars. Also performed dust devil ‘chasing’ fieldwork in Nevada desert and catalogued dust devil tracks on Mars from MOC images. JGR 108 E5 (2003), JGR 108 E8 (2003) GRL 30, 16 (2003) : Postdoc, Oxford University, then at Planetary Science Institute, Tucson, with Dr. Mary Bourke studying aeolian dunes on Mars using MOC and THEMIS data. Recently submitted 1st PI proposal to NASA MDAP programme. 2005: Postdoc, MAGE program, Université de Paris-Sud, France. Matt Balme: MAGE Postdoc

An Investigation of Martian Gully Features Using HRSC Images Matt Balme, Université de Paris Sud Aims: i) Determine spatial distribution and orientation of gully features on Mars ii) Investigate morphology, size and age of formation of gullies. Rationale: Formation process responsible for gullies still controversial. This large area, high-resolution survey (HRSC) seeks to determine the formation mechanism and thus constrain when and if liquid H 2 O existed on the (near) surface - a vital question for astrobiology, climate and geologic evolution and future exploration. Image: NASA/JPL/Malin Space Science Systems.

Key Gully Features 1. Morphological Classification ‘Type’ examples display alcove, channel and distal debris apron (fans) regions. Some gullies show no (or small) alcoves, some have no visible debris fans. To be classified as a gully, the channel must be present, even if very small 2. Age, Associations and Distribution i) Generally un-cratered, superpose other young terrains (dunes, polygons) ii) Generally ‘pristine’, not dusty iii) Alcoves often associated with layers iv) Start near steepest part of slope v) Found on crater wall, central peaks, walls of pits, scarps vi) Generally found at latitudes >30 o vii) Appear to form in clusters, do not appear to have orientation preference Image: NASA/JPL/Malin Space Science Systems.

Competing models of formation 1. Genesis by aqueous processes i)Seep onto surface from deep or shallow aquifer ii)Melting of near-surface ice by insolation iii)Melting underneath ‘pasted on’ ice mantle on slopes 2. Genesis by non-aqueous processes i)CO 2 is ‘wet’ channel forming fluid; source is shallow aquifer ii)CO 2 is ‘dry’ channel forming fluid; CO 2 source is snow or frost iii)‘Dry’ channel forming processes by mass wasting of aeolian deposits 3. Model Constraints Aqueous process must explain how water can flow with subliming ‘Dry’ processes seem unlikely to cause alcove erosion into wall of slopes Aquifer CO 2 model unrealistic for ‘seeping’; more likely to form a geyser! Aquifer models do not explain how sufficient fluid becomes contained within small volumes such as central peaks and rims of crater Melting of surface ice (deposited in a different climate epoch) seems the best model but predicts skewed orientation distribution (not yet seen).

This study: Uses HRSC data to measure orientation and distribution of gullies Has advantage of imaging large areas at high resolution: Other studies have used ‘targeted’ images from MOC which might have skewed the data and imposed ‘clustering’ that is an artefact of the spatial distribution of the images Will help determine whether gullies are associated with regions where ice was deposited, have a distribution controlled by latitude or show other regional trends