Mysterious Io

March Meeting
Via ZOOM (ID & Password Required)

Meeting & Speaker
Saturday, March 4, 2023 at 7:00 PM
 

Topic: "Mysterious Io"

Speaker: Dr. Jonathan Gradie 

Is there still room for synoptic ground-based observations of volcanic processes?

Abstract: The first report of a remarkable post-eclipse brightening of Io (for a few minutes when Io emerges from the shadow of Jupiter) was by Alan Binder in the early 1960s.  Subsequent searches through the 1970s by others at telescopes large (88" MKO) and small (24" at Steward Observatory) produced scattered and seemingly unreliable observations. Because of the intense UV absorption in Io's spectral reflectance, sulfur was assumed to be dominant on the surface leading to the theory that condensation/sublimation of thin SO2 atmosphere, photo-dynamic sulfur-bearing salts or sulfur allotropes might be the cause.  Synoptic observations of Io during the 1973 apparition (https://articles.adsabs.harvard.edu/full/seri/BAAS./0005//0000404.000.html, see abstracts by Morrison and by Gradie and Zellner) demonstrated that the spectral properties Io's surface were not uniform between leading to trailing sides and that the polarimetric properties of Io might be changing with time suggesting seemingly random time-dependent changes in the surface's scattering properties.  Were these time-dependent changes, which did not occur during eclipses, related to the elusive post-eclipse brightening or something else. The discovery of active explosive volcanism on Io by Voyager in 1979 seemed to put the issue on the backburner.  But, what if the polarimetric observations were detecting major resurfacing events on Io caused by its volcanoes?  Could an ongoing monitoring of Io's polarimetric properties provide evidence of the appearance of major volcanic plumes and their resurfacing characteristics?  This talk will provide a historical overview of the original ground-based observations (including some of the original data sheets!), how Voyager 1 & 2 changed the dialog and how 21^st Century technology and small telescopes might add to or understanding of the dynamics of this mysterious object (a challenge to the amateur astronomer).

Dr. Jonathan Gradie, Ph.D., a retired planetary scientist and entrepreneur, received a BS in Astronomy (1973) and Ph.D. in Planetary Sciences (1978) both from the University of Arizona. He his major focus was on applying polarization, photometric and infrared observations to understanding the properties of asteroids, comets and planetary satellites which he continued at Cornell University (6 years) and the University of Hawaii (for 32 years). Asteroid 3253 Gradie is named in recognition of this work. In the 1990s Dr. Gradie turned his attention to commercializing these remote sensing technologies to Earth observations and applications in medical imaging. Dr. Gradie, grew up in Putnam, CT, with dreams of being an astronomer but unaware of Seagrave Observatory a mere 15 miles east of his home. Fortunately, he discovered Seagrave and Skyscrapers upon returning to Northeast CT.