Alexander Michael Morgan

Planetary Science Institute

The deflated surfaces of the alluvial fans in Saheki crater reveal the most detailed record of fan stratigraphy and evolution found, to date, on Mars. During deposition of at least the uppermost 100 m of fan deposits, discharges from the source basin consisted of channelized flows transporting sediment (which we infer to be primarily sand- and grav...

Data in this article are related to the research article “The global distribution and morphologic characteristics of fan-shaped sedimentary landforms on Mars”. We used globally available image and topographic data to document the location of every fan-shaped sedimentary landform on the surface of Mars. We mapped fan outlines and associated drainage...

Fan-shaped sedimentary landforms on Mars are important geomorphic markers of past water flow and characterizing the distribution and morphology of these features can yield insights into the planet's climatic evolution. We present a new database of 1501 martian fan-shaped sedimentary landforms that builds upon previous surveys and uses Context Camer...

Early Mars had rivers, but the cause of Mars' wet-to-dry transition remains unknown. Past climate on Mars can be probed using the spatial distribution of climate-sensitive landforms. We analyzed global databases of water-worked landforms and identified changes in the spatial distribution of rivers over time. These changes are simply explained by co...

Early Mars had rivers, but the cause of Mars's wet-to-dry transition remains unknown. Past climate on Mars can be probed using the spatial distribution of climate-sensitive landforms. We analyzed global databases of water-worked landforms and identified changes in the spatial distribution of rivers over time. These changes are simply explained by c...

The history of rivers on Mars is an important constraint on Martian climate evolution. The timing of relatively young, alluvial fan-forming rivers is especially important, as Mars’s Amazonian atmosphere is thought to have been too thin to consistently support surface liquid water. Previous regional studies suggested that alluvial fans formed primar...

The surface environment of early Mars had an active hydrologic cycle, including flowing liquid water that carved river valleys1–3 and filled lake basins4–6. Over 200 of these lake basins filled with sufficient water to breach the confining topography4,6, causing catastrophic flooding and incision of outlet canyons7–10. Much past work has recognized...

The history of rivers on Mars is an important constraint on Martian climate evolution. The timing of relatively young, alluvial fan-forming rivers is especially important, as Mars' Amazonian atmosphere is thought to have been too thin to consistently support surface liquid water. Previous regional studies suggested that alluvial fans formed primari...

We present an inventory of alluvial fans and deltas within martian impact craters based on a systematic global survey of Context Camera images. Our database includes 314 fan‐hosting craters, with a total of 890 alluvial fans and 114 deltas. Alluvial fans and deltas are more widespread than previously reported (∼40°N to 54°S) and are strongly banded...

The Atacama Desert contains the driest regions on Earth, with significant rain occurring only a few times per century, based on sparse historical records. However, the frequency and magnitude of rainfall remains speculative. On March 24e26 of 2015, an unusual storm caused rainfall rates and quantities to exceed many historical records. Of interest...

Extensive exposures of a light-toned deposit (LTD) occurs on the northeastern interior slope of the Hellas basin. This deposit is on the floors of all but the youngest craters greater than 30 km in diameter in the study region centered at 83°E and 30°S, as well as in exposures on crater interior and exterior walls, on intercrater plains, and the no...

Knowledge of modern terrestrial surface processes, and their relationship with climate, has been key to deciphering Earth's past and making predictions about its future. These mechanistic understandings also give us the ability to decode geologic and atmospheric processes on other solid surface bodies throughout the solar system. The desire to disc...

Estimates of river paleodischarges have been used to constrain the former climate of Mars. Paleodischarge has been calculated using mechanistic approximations of the channel bed‐shear stress at the threshold of particle motion or correlative width‐discharge relations derived from empirical terrestrial hydraulic geometry data. We apply both these me...

Along a 200 km transect of the Atacama Desert in northern Chile a series of mudflow-dominated alluvial fans derive from the volcanic Andean foothills, flowing onto the hyperarid interior basin at about 1100 m elevation. The fan systems, centered at about 20.5°S, 69.4ºW are active at about decadal frequency. Individual flows extend 20-30 km across t...

We investigated the range of Titan climate evolution hypotheses, regulated by the role, sources, and availability of methane. We analyzed all available image data (principally SAR) of Titan's landscape through the T-86 encounter, starting with focused examinations of terrains that carry the markers of climate evolution. Traditional geologic and geo...

Alluvial fans in the Atacama may constitute a strong analog to those on Mars, with fans in both environments forming from hundreds of individual runoff events.

Characteristics of the Saheki Crater fans suggest that they formed during the late Hesperian to early Amazonian periods, possibly under conditions similar to those that were prevalent during the formation of fans in the Atacama Desert, Chile.

Numerous alluvial fans have been identified in the southern martian highlands. We use a landform-evolution model to simulate growth of these fans to infer the prevalent local climatic conditions during their formation.

We present results of a series of large-scale experiments to measure the coefficient of restitution for 1-m-diameter rocky bodies in impacts with collision speeds up to ∼1.5 m s−1. The experiments were conducted in an outdoor setting, with two 40-ton cranes used to suspend the ∼1300-kg granite spheres pendulum-style in mutual contact at the bottoms...