Geology and Photometric Variation of Solar System Bodies with Minor Atmospheres: Implications for Solid Exoplanets

TL;DR

This paper reviews geological features of Solar System bodies with minor atmospheres and explores how their surface properties affect photometric observations, providing insights for characterizing similar exoplanets through future direct imaging.

Contribution

It offers a comprehensive overview of surface geology and photometric variations of Solar System bodies with minor atmospheres, informing exoplanet characterization strategies.

Findings

Surface albedo varies by 5-50% over a rotation due to geological processes.

Photometric variations depend on surface composition and particle distribution.

Detection of spin rotation rates requires specific photometric precision.

Abstract

A reasonable basis for future astronomical investigations of exoplanets lies in our best knowledge of the planets and satellites in the Solar System. Solar System bodies exhibit a wide variety of surface environments, even including potential habitable conditions beyond Earth, and it is essential to know how they can be characterized from outside the Solar System. In this study, we provide an overview of geological features of major Solar System solid bodies with minor atmospheres (i.e., the Terrestrial Moon, Mercury, the Galilean moons, and Mars) that affect surface albedo at local to global scale, and we survey how they influence point-source photometry in UV, visible, and near IR (i.e., the reflection-dominant range). We simulate them based on recent mapping products and also compile observed light curves where available. We show a 5-50% peak-to-trough variation amplitude in one spin rotation associated with various geological processes including heterogeneous surface compositions due to igneous activities, interaction with surrounding energetic particles, and distribution of grained materials. Some indications of these processes are provided by the amplitude and wavelength dependence of variation in combinations of the time-averaged spectra. We also estimate the photometric precision needed to detect their spin rotation rates through periodogram analysis. Our survey illustrates realistic possibilities for inferring the detailed properties of solid exoplanets with future direct imaging observations.