An Analytic Function of Lunar Surface Temperature for Exospheric Modeling

We present an analytic expression to represent the lunar surface temperature as a function of Sun-state latitude and local time. The approximation represents neither topographical features nor compositional effects and therefore does not change as a function of selenographic latitude and longitude. The function reproduces the surface temperature measured by Diviner to within +/-10 K at 72% of grid points for dayside solar zenith angles of less than 80, and at 98% of grid points for nightside solar zenith angles greater than 100. The analytic function is least accurate at the terminator, where there is a strong gradient in the temperature, and the polar regions. Topographic features have a larger effect on the actual temperature near the terminator than at other solar zenith angles. For exospheric modeling the effects of topography on the thermal model can be approximated by using an effective longitude for determining the temperature. This effective longitude is randomly redistributed with 1 sigma of 4.5deg. The resulting ''roughened'' analytical model well represents the statistical dispersion in the Diviner data and is expected to be generally useful for future models of lunar surface temperature, especially those implemented within exospheric simulations that address questions of volatile transport

The case for studying other planetary magnetospheres and atmospheres in Heliophysics

Heliophysics is the field that "studies the nature of the Sun, and how it influences the very nature of space - and, in turn, the atmospheres of planetary bodies and the technology that exists there." However, NASA's Heliophysics Division tends to limit study of planetary magnetospheres and atmospheres to only those of Earth. This leaves exploration and understanding of space plasma physics at other worlds to the purview of the Planetary Science and Astrophysics Divisions. This is detrimental to the study of space plasma physics in general since, although some cross-divisional funding opportunities do exist, vital elements of space plasma physics can be best addressed by extending the expertise of Heliophysics scientists to other stellar and planetary magnetospheres. However, the diverse worlds within the solar system provide crucial environmental conditions that are not replicated at Earth but can provide deep insight into fundamental space plasma physics processes. Studying planetary systems with Heliophysics objectives, comprehensive instrumentation, and new grant opportunities for analysis and modeling would enable a novel understanding of fundamental and universal processes of space plasma physics. As such, the Heliophysics community should be prepared to consider, prioritize, and fund dedicated Heliophysics efforts to planetary targets to specifically study space physics and aeronomy objectives

Science Opportunities offered by Mercury's Ice-Bearing Polar Deposits

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Lunar Volatiles and Solar System Science

Understanding the origin and evolution of the lunar volatile system is not only compelling lunar science, but also fundamental Solar System science. This white paper (submitted to the US National Academies' Decadal Survey in Planetary Science and Astrobiology 2023-2032) summarizes recent advances in our understanding of lunar volatiles, identifies outstanding questions for the next decade, and discusses key steps required to address these questions

Recommendations for Addressing Priority Io Science in the Next Decade

Io is a priority destination for solar system exploration. The scope and importance of science questions at Io necessitates a broad portfolio of research and analysis, telescopic observations, and planetary missions - including a dedicated New Frontiers class Io mission

The Science Case for Io Exploration

Io is a priority destination for solar system exploration, as it is the best natural laboratory to study the intertwined processes of tidal heating, extreme volcanism, and atmosphere-magnetosphere interactions. Io exploration is relevant to understanding terrestrial worlds (including the early Earth), ocean worlds, and exoplanets across the cosmos

Unusual Velocity Structures of Neutral Sodium Near Io's Wake

New high-resolution spectra of Io sodium have identified an unexpected velocity structure near Io's wake and Jupiter-facing hemisphere. We used the 3.6-m Telescopio Nazionale Galileo in the Canary Islands with its SARG echelle spectrograph at a resolving power R=115,000. The observations targeted Io as it neared eclipse behind Jupiter. The slit was oriented parallel to the jovian equator, enabling spectra ahead of of Io and behind it along the orbit. The region ahead of Io along the orbit is also the downstream wake region in a magnetospheric sense; the Galileo spacecraft showed this to be a region of cold, dense, stagnated plasma. Our spectra of this region in the hour before eclipse show three distinct spectral features. The first two are well known: the slow sodium "banana cloud" and fast sodium ejected in the anti-Jupiter direction and hence highly red-shifted. The unexpected third feature is clearly blue-shifted, indicating an ejection from Io towards Jupiter, either from Io's trailing or inner hemisphere. At present there are no known ejection mechanisms that satisfy the observed properties. We will present preliminary analysis of the spatial and velocity distributions of this feature, along with a discussion of plausible source mechanisms. This work has been supported by NSF's Planetary Astronomy Program, INAF/TNG, and the Dipartimento di Astronomia, Universit\ue0 di Padova