Dr. Ross Irwin received his bachelor of science in geological sciences from Virginia Tech in 1997 and a PhD in environmental sciences from the University of Virginia in 2005. He completed a post-doctoral appointment at the Center for Earth and Planetary Studies in 2010. For two years he worked for the Planetary Science Institute as a visiting scientist at NASA Goddard Space Flight Center. He returned to CEPS as a staff scientist in 2012 and began a term as chair of the department in 2019.
Dr. Irwin's research focuses on relationships between the environment, geologic processes, and landforms. These projects include analyses of data returned by robotic spacecraft, studies of Mars-analog features on Earth, and planetary geologic mapping.
His studies of Mars focus on the evolution of the ancient cratered landscape of the Martian highlands, including the oldest preserved surfaces on Mars, networks of river valleys, former lake basins, and layered sedimentary deposits. A goal of this work is to constrain the hydrology of streams that flowed across Mars more than three billion years ago. The size of ancient river channels constrains the flow of rivers, showing that Martian watersheds generated a centimeter per day of runoff at times. Studies of former lake basins, some of which overflowed, suggest that it did not necessarily rain often. The wettest periods appear to have been fairly dry by Earth's standards, perhaps like Utah or Nevada in the United States. Estimating the total erosion at various locations across the highlands provides further insight into the long-term climate and water budget. Modeling the evolution of the landscape helps to constrain the long-term geologic processes.
Studies of Mars analogs on Earth include theater-headed valleys (box canyons), shorelines of ice-age paleolakes, inverted channels, and ephemeral desert rivers. Many river valleys on Mars are long, narrow box canyons, with steep sidewalls and a cliff at the head. Sites in the western United States and northern Chile help to determine the roles of runoff, groundwater, rock layers, and fractures in forming these canyons. Inverted channels form where sediments deposited in river channels are left behind as ridges, as fine-grained deposits around them are eroded away. Wave-cut terraces such as those around ice-age paleolakes of the western United States may have formed on early Mars, but they were likely too small to be preserved.
Geologic mapping projects have included part of the Margaritifer Terra region of Mars at 1:1 million scale and participation in a U.S. Geological Survey global geologic map of Mars at 1:25,000,000 scale.
We are studying inverted and volcanic channels using satellite data of Mars and in the field on Earth to better understand how they form.
Branching river valleys show that Mars once had flowing water on its surface.
Comparison of theater-headed river valleys on Mars with box canyons on Earth helps us to better understand both planets.
Using preserved river channels, scientists at the National Air and Space Museum have been able to constrain the size of floods in Martian rivers more than 3.5 billion years ago.
The oldest craters on Mars are much more eroded and filled by younger deposits than are craters on the airless moon and Mercury.
Valley networks are frequently cited as the best evidence that liquid water once existed on Mars. Currently, we are examining valley networks in other areas of Mars with the goal of understanding potential global and regional climatic differences.