Planetary geologist John Marshall specializes in the study of particulate matter –dust and sand-size materials that comprise nebulae clouds, volcanic eruptions, dust storms, sand dunes, beach and river sediments, and the regoliths of the terrestrial planets, rocky moons, and asteroids. These particles are being studied from three perspectives: (1) their electrostatic behavior – how they form aggregates in dust clouds and nebulae; (2) how they are transported by wind, water, and in the pyroclastic flows that surge down the sides of volcanoes, and (3) their microscopic properties – how their size, shape, and surface texture provide clues about processes which have shaped them, such as wind, water, and chemical action.
To study particle transport, John operated the Mars Wind Tunnel and the Venus Wind Tunnel at NASA Ames, and developed the Ames Venus Simulator. Currently he is part of a consortium of investigators developing a new wind tunnel to simulate aeolian action on Titan. To study the electrostatics of particles, John has flown his experiments on the KC 135 (zero-gravity) aircraft, and twice on Space Shuttle Columbia, as well as diving into dust devils in the Mojave Desert and conducting a number of laboratory simulations of Mars. Currently he is developing a Lunar Laboratory for NASA Ames and has successfully duplicated electrostatic levitation of dust as seen on the Moon.
Heavily involved in the flight world, he has developed instruments for three Mars missions, for Space Shuttle, and Space Station, as well as a coffee-can size X-ray analyzer for use on the Moon or Mars. At the moment, John’s fingers are crossed for a safe landing of the Phoenix mission to Mars. John is a co-investigator, and will be interpreting the first ever microscopic images of Martian soil to be transmitted back in the Spring of 2008.