Constraining the Limitations of NEATM-like Models: A Case Study with Near-Earth Asteroid (285263) 1998 QE2

Near-Earth asteroids (NEAs) are a key test bed for investigations into planet formation, asteroid dynamics, and planetary defense initiatives. These studies rely on understanding NEA sizes, albedo distributions, and regolith properties. Simple thermal models are a commonly used method for determining these properties; however, they have inherent limitations owing to the simplifying assumptions they make about asteroid shapes and properties. With the recent collapse of the Arecibo Telescope and a decrease of direct size measurements, as well as future facilities such as LSST and NEO Surveyor coming online soon, these models will play an increasingly important role in our knowledge of the NEA population. Therefore, it is key to understand the limits of these models. In this work we constrain the limitations of simple thermal models by comparing model results to more complex thermophysical models, radar data, and other existing analyses. Furthermore, we present a method for placing tighter constraints on inferred NEA properties using simple thermal models. These comparisons and constraints are explored using the NEA (285263) 1998 QE2 as a case study. We analyze QE2 with a simple thermal model and data from both the NASA IRTF SpeX instrument and NEOWISE mission. We determine an albedo between 0.05 and 0.10 and thermal inertia between 0 and 425J m−2 s−1/2 K−1. We find that overall the simple thermal model is able to well constrain the properties of QE2; however, we find that model uncertainties can be influenced by topography, viewing geometry, and the wavelength range of data used. © 2023. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

The volatile composition of 81P/Wild 2 from ground-based high-resolution infrared spectroscopy

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Volatiles and Refractories in Surface-Bounded Exospheres in the Inner Solar System

Volatiles and refractories represent the two end-members in the volatility range of species in any surface-bounded exosphere. Volatiles include elements that do not interact strongly with the surface, such as neon (detected on the Moon) and helium (detected both on the Moon and at Mercury), but also argon, a noble gas (detected on the Moon) that surprisingly adsorbs at the cold lunar nighttime surface. Refractories include species such as calcium, magnesium, iron, and aluminum, all of which have very strong bonds with the lunar surface and thus need energetic processes to be ejected into the exosphere. Here we focus on the properties of species that have been detected in the exospheres of inner Solar System bodies, specifically the Moon and Mercury, and how they provide important information to understand source and loss processes of these exospheres, as well as their dependence on variations in external drivers

Volatile Abundances, Extended Coma Sources, and Nucleus Ice Associations in Comet C/2014 Q2 (Lovejoy)

High-resolution infrared spectra of comet C/2014 Q2 Lovejoy were acquired with NIRSPEC at the W. M. Keck Observatory on two post-perihelion dates (UT 2015 February 2 and 3). H2O was measured simultaneously with CO, CH3OH, H2CO, CH4, C2H6, C2H4, C2H2, HCN, and NH3 on both dates, and rotational temperatures, production rates, relative abundances, H2O ortho-to-para ratios, and spatial distributions in the coma were determined. The first detection of C2H4 in a comet from ground-based observations is reported. Abundances relative to H2O for all species were found to be in the typical range compared with values for other comets in the overall population to date. There is evidence of variability in rotational temperatures and production rates on timescales that are small compared with the rotational period of the comet. Spatial distributions of volatiles in the coma suggest complex outgassing behavior. CH3OH, HCN, C2H6, and CH4 spatial distributions in the coma are consistent with direct release from associated ices in the nucleus and are peaked in a more sunward direction compared with co-measured dust. H2O spatial profiles are clearly distinct from these other four species, likely due to a sizable coma contribution from icy grain sublimation. Spatial distributions for C2H2, H2CO, and NH3 suggest substantial contributions from extended coma sources, providing further evidence for distinct origins and associations for these species in comets. CO shows a different spatial distribution compared with other volatiles, consistent with jet activity from discrete nucleus ice sources. © 2022. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]