Paper No. 222-12
Presentation Time: 11:20 AM
NIGHTSIDE THERMAL EMISSION OF VENUS THROUGH THE WISPR WINDOW
IZENBERG, Noam1, LUSTIG-YAEGER, Jacob1, GILMORE, Martha2, MAYORGA, Laura C.3, MAY, Erin M.1, VOURLIDAS, Angelos1, HESS, Phillip N.4, WOOD, Brian E.4, HOWARD, Russel A.1, RAOUAFI, Nour E.1 and ARNEY, Giada5, (1)Space Exploration Sector, Johns Hopkins Applied Physics Laboratory, 11100 Johns Hopkins Rd., Laurel, MD 20723, (2)Earth and Environmental Sciences, Wesleyan University, 265 Church St, Middletown, CT 06459-3138, (3)Johns Hopkins APL, 11100 Johns Hopkins Rd, Laurel, MD 20723, (4)Space Science Division, Naval Research Laboratory, 4555 Overlook Ave., SW, Washington, DC 20375, (5)NASA Goddard Spaceflight Center, Greenbelt, MD 20771
During its third and fourth Venus Gravity Assists (VGA3 and VGA4) Parker Solar Probe (PSP) turned its Wide-field Imager for Solar PRobe (WISPR) optical telescopes to the Venus nightside resulting in surprising observations of the surface through a theorized, but until-then unobserved near-visible window through the thick, cloudy CO2 atmosphere. We use these broadband observations below 0.8 μm to examine the origins of the Venus night side flux and confirm the presence of this new atmospheric window through which to observe the surface geology of Venus. The WISPR images are well explained by emission from the hot Venus surface escaping through a new atmospheric window in the optical with an overlying emission component from the atmosphere that is consistent with O2 nightglow, particularly at the limb. The surface thermal emission correlates strongly with surface elevation (via temperature) and emission angle. Tessera and plains units have distinct WISPR brightness values. Controlling for elevation, Ovda Regio tessera is brighter than Thetis Regio; likewise the volcanic plains of Sogolon Planitia are brighter than the surrounding regional plains units. WISPR brightness at 0.8 μm is predicted to be positively correlated to FeO content in minerals, thus the brighter units may have a different starting composition, be less weathered, and/or have larger particle sizes
We examine the potential for Venus surface science using the WISPR flyby observations. We correlate WISPR emission to mapped geologic units, simulate thermal emission from the surface through the Venus atmosphere, and discuss potential contributions to observed spatial variability. For this analysis we reproject earlier Magellan-based datasets for surface radar reflectance, altimetry, and radar emissivity to the WISPR perspective, and apply an atmospheric radiative transfer model to compare to WISPR observations. We validate WISPR band photometry and show WISPR images correlation with known Venus surface features and specific geologic units, and discuss the implications of our findings for determining compositional variation on the surface, and for future explorations of Venus.
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