281-3 Understanding Venus Orbital Spectroscopy

Session: Petrology, Volcanology, and Mantle Plumes across the Solar System, Part II

Presenting Author:

M. Dyar

Authors:

Dyar, M. Darby¹, Ytsma, Cai R², Breitenfeld, Laura B³, Maturilli, Alessandro⁴, Alemanno, Giulia⁵, Adeli, Solmaz⁶, Garland, Stephen⁷, Smrekar, Suzanne⁸

(1) Planetary Science Institute, Freeport, ME, USA, (2) Cai Consulting, Strathaven, United Kingdom, (3) Planetary Science Institute, Tucson, Arizona, USA, (4) DLR, Berlin, Germany, (5) DLR, Berlin, Germany, (6) DLR, Berlin, Germany, (7) DLR, Berlin, Germany, (8) Jet Propulsion Laboratory, Pasadena, CA, USA,

Abstract:

An important science goal of past and upcoming missions to Venus is using remote-sensed spectra to distinguish between basalt and felsic compositions, thus constraining surface formation mechanisms. Band selection on these missions is constrained by sparse windows in the dense, CO₂-rich atmosphere through which VNIR observations can be made. Extensive atmospheric scattering limits spectroscopic footprints. Different missions exploit different bands within those windows. VIRTIS (Venus Express) employed three bands, while the VEM/Venspec-M instruments on VERITAS/EnVision use six-band emissivity spectra acquired on the nightside. DAVINCI uses its three-band VISOR instrument to measure emissivity on nightside flybys and reflectance with its two-band VenDI spectrometer during a dayside descent.

 

Interpreting these data requires non-traditional approaches given the very small wavelength range of the windows between ~0.80 to 1.20 um and a new paradigm for rock type identification and geochemical classification is needed. To support such models for interpretation of orbital data, acquisition of high-temperature emissivity data is also in its infancy, so spectra available for modeling are currently limited. This talk explores what is possible using such limited data and sets expectations for interpreting spectra to derive rock types.

 

Calibrated laboratory measurements of rock standards at 440°C suggest that basalt and felsic rocks easily be distinguished using mission-specific optical bands. Predicted precision of these measurements on Venus is about 4% or better, while accuracy is constrained by observations of Soviet-era landing sites. Using the latter, the amount of FeO in surface rocks can be estimated using a multivariate algorithm that will allow the continuum of igneous rock types between basalt and rhyolite (or their intrusive analogs) to be identified. Even prior to landing site observations, relative emissivity measurements using ratios between band intensities and slopes between them can also be used to discriminate between basalt and felsic rocks using parametric and non-parametric machine learning algorithms. In general, three- and six-band instruments offer higher accuracy in distinguishing rock types.

 

This research was partially conducted at the Jet Propulsion Laboratory, California Institute of Technology under contract with NASA.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9810

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.