Dr. Dave Schleicher
PhD University of Maryland, 1983
Dr. Schleicher joined the Lowell Observatory science staff in 1985. He and his team typically observe nearly a dozen comets over the course of many months each year. Some are new comets while others have small orbits which return them near the Sun repeatedly. These investigations can, therefore, examine how comets evolve over time, and distinguish evolutionary effects from inherent variations in composition due to differing conditions in the outer proto-solar nebula from which the solar system formed.
Because comets are believed to be the most pristine objects remaining from the time of solar system formation available for chemical studies, comets provide a unique probe of these conditions. Dr. Schleicher and his team routinely measure five molecular species as part of the Lowell Observatory program of compositional studies of comets in the visible and near-ultraviolet portions of the spectrum. The chemical composition is determined by first measuring the amount of light emitted by various molecules within a comet’s coma or head. These photometric measurements are then converted to the number of molecules of each species which must be present to produce the measured light.
In 1986, Dr. Schleicher and former Lowell Observatory Director Dr. Robert Millis discovered the periodic variability of Comet Halley. This profoundly affected the interpretation of all observations of the comet, including those from the Giotto and Vega spacecraft.