arXiv subjects

James B. Garvin

Publications and source records attributed to James B. Garvin.

5 recordsLinked to original sources

arXiv2026

The Venus Benchmark: Resolving Degeneracies in Terrestrial Exoplanet Spectra with DAVINCI

The characterization of terrestrial exoplanets with thick, CO$_2$-dominated atmospheres via transmission and emission spectroscopy is limited by degeneracies between atmospheric composition, cloud structure, and surface conditions. These degeneracies are particularly acute for planets in or near the Venus Zone, where sulfuric acid aerosol layers and deep-atmosphere opacity render the lower atmosphere and surface spectroscopically inaccessible via many optical/IR wavelengths. Venus provides the only accessible analog to such worlds, yet current knowledge of its full atmospheric profile relies on decades-old in situ data with known limitations. Here we demonstrate that the forthcoming DAVINCI (Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging) mission will provide the comprehensive, high-fidelity atmospheric profile data necessary to resolve many of these degeneracies. We quantify how atmospheric profile uncertainties translate into uncertainties in modeled transmission and thermal emission spectra of CO$_2$-dominated terrestrial worlds, and show that the spread in the modeled Venus benchmark spectrum arising from current atmospheric profile uncertainties will decrease by factors of $\sim$4--5 for transmission and $\sim$5--15$\times$ for thermal emission after DAVINCI, providing a correspondingly improved benchmark and prior for the modeling of exoplanets with Venus-like atmospheres. We further demonstrate that these improvement factors are larger for the cloud-free atmospheric case, where the opacity floor is set by gas-phase processes rather than aerosols, because the pre-DAVINCI data are most discrepant in the sub-cloud region. Our results highlight the importance of Venus for the atmospheric characterization of rocky exoplanets in the JWST and HWO era, and demonstrate how DAVINCI measurements will directly improve exoplanet atmospheric modeling.

astro-ph.EP↗

arXiv2026

The Expected Yield of Venus Zone Terrestrial Planets from PLATO

The characterization of terrestrial exoplanets and the conditions that lead to divergent climate outcomes is a primary goal of exoplanetary science. The Venus Zone (VZ) provides a framework for identifying planets that may have experienced runaway greenhouse processes similar to Venus, and the statistical properties of such planets bear directly on models of planetary habitability. Here we present a quantitative estimate of the expected yield of VZ terrestrial planets from ESA's PLATO (PLAnetary Transits and Oscillations of stars) mission. We combine the predicted PLATO planet yield for Earth-size ($0.8$--$1.25~R_\oplus$) and super-Earth ($1.25$--$2.0~R_\oplus$) planets with empirical occurrence rates for VZ terrestrial planets derived from Kepler data. Under conservative assumptions, we estimate that PLATO will detect $\sim$170--280 VZ terrestrial planets ($0.8$--$2.0~R_\oplus$), including $\sim$40--80 Earth-size ($0.8$--$1.25~R_\oplus$) planets, during a nominal 4-year mission. For the bright P1 sample ($V \leq 11$), we estimate $\sim$50--85 terrestrial and $\sim$13--22 Earth-size VZ detections, enabling radial velocity mass determination and atmospheric characterization of the most favorable targets with JWST and future facilities. We discuss the implications of this yield for comparative studies of Earth-Venus divergence, synergies with the DAVINCI, VERITAS, and EnVision missions to Venus, and the role of PLATO in advancing our understanding of the runaway greenhouse boundary.

astro-ph.EP↗

arXiv2026

The Zhamanshin Impact Event: Potential Implications for Environmental Responses and Biological Linkages on Earth and Beyond

At least one large-body (diameter > 1.1 km) hypervelocity cratering event occurred during ~ 0.8-0.90 Ma (Zhamanshin, Kazakhstan) in the Middle Pleistocene Transition period. Analysis designed to reduce uncertainty in the dimensions of the Zhamanshin structure employing high resolution topography demonstrated that it likely generated a ~ 26.5 km diameter multi-ring crater. This is at least two times larger than the current best estimates. Using a range of accepted impactor sizes, velocities, compositions, and angles of impact, such impacts typically yield kinetic energies of impact over 240,000 Megatons (TNT). Explosive energetic events of this magnitude (e.g., Yellowstone Caldera) at other times (K-Pg) have created global environmental effects. The factor of two discrepancy in the dimensions of Zhamanshin increases the kinetic energy yield by factors of 7-10, with significantly larger environmental consequences. This justifies examination of rapid climate transitions linked to biological consequences, including those related to environmental perturbations, at ~0.9 Ma.

astro-ph.EP↗

arXiv2022

Revealing the Mysteries of Venus: The DAVINCI Mission

The Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI) mission described herein has been selected for flight to Venus as part of the NASA Discovery Program. DAVINCI will be the first mission to Venus to incorporate science-driven flybys and an instrumented descent sphere into a unified architecture. The anticipated scientific outcome will be a new understanding of the atmosphere, surface, and evolutionary path of Venus as a possibly once-habitable planet and analog to hot terrestrial exoplanets. The primary mission design for DAVINCI as selected features a preferred launch in summer/fall 2029, two flybys in 2030, and descent sphere atmospheric entry by the end of 2031. The in situ atmospheric descent phase subsequently delivers definitive chemical and isotopic composition of the Venus atmosphere during a cloud-top to surface transect above Alpha Regio. These in situ investigations of the atmosphere and near infrared descent imaging of the surface will complement remote flyby observations of the dynamic atmosphere, cloud deck, and surface near infrared emissivity. The overall mission yield will be at least 60 Gbits (compressed) new data about the atmosphere and near surface, as well as first unique characterization of the deep atmosphere environment and chemistry, including trace gases, key stable isotopes, oxygen fugacity, constraints on local rock compositions, and topography of a tessera.

astro-ph.EP↗

arXiv2020

Deep Atmosphere of Venus Probe as a Mission Priority for the Upcoming Decade

This is a white paper submitted to the Planetary Science and Astrobiology Decadal Survey. The deep atmosphere of Venus is largely unexplored and yet may harbor clues to the evolutionary pathways for a major silicate planet with implications across the solar system and beyond. In situ data is needed to resolve significant open questions related to the evolution and present-state of Venus, including questions of Venus' possibly early habitability and current volcanic outgassing. Deep atmosphere "probe-based" in situ missions carrying analytical suites of instruments are now implementable in the upcoming decade (before 2030), and will both reveal answers to fundamental questions on Venus and help connect Venus to exoplanet analogs to be observed in the JWST era of astrophysics.

astro-ph.IM↗