Abstract DGP2026-21

Understanding Venus’ surface composition and volcanic activity is key to studying the planet’s evolution and present-day state. Multiple evidences indicate that Venus has been volcanically active in the past and is likely active today: - observations from Venus Express revealed thermal anomalies and emissivity variations consistent with differences between fresh and weathered basaltic materials, suggesting recently active volcanic hot spots [1-4]; - gravity, topography, and surface deformation associated with these regions further support the presence of mantle plume activity beneath the surface [5,6]; - temporal variations in atmospheric sulfur dioxide (SO₂) measured by Pioneer Venus and Venus Express might reflect episodic volcanic outgassing [7-9]. More recently, reanalysis of Magellan radar data has identified surface changes consistent with active volcanic eruptions [10,11]. However, key questions regarding Venus’ surface composition and the intensity and timing of recent magmatic activity remain unresolved, largely due to limited data. Upcoming missions - NASA’s VERITAS and DAVINCI, and ESA’s EnVision - will investigate Venus with unprecedented detail. As part of the payload on VERITAS and EnVision, the Venus Emissivity Mapper (VenSpec-M on EnVision/VEM on VERITAS), a push-broom multispectral imager, will target atmospheric windows in the 1 μm spectral region [12]. VenSpec-M/VEM is equipped with a 14-band filter assembly (0.79 – 1.51 μm) and an InGaAs detector. Its key science goals include mapping the main surface rock types based on Fe content, monitor the planet for signs of active volcanism through thermal anomaly signatures, and, on EnVision, combining surface-atmosphere observations with the VenSpec-H [13] and VenSpec-U [14] spectrometers, to study volcanic plumes and gas exchanges.
A critical preparatory activity for VenSpec-M/VEM involves laboratory spectroscopy. Spectral measurements at DLR’s Planetary Spectroscopy Laboratory (PSL) cover basaltic and granitic samples, emissivity of mineral mixtures [15], comparison between emissivity on altered versus unaltered Venus’s analogs [16] and samples and measurements collected from field campaigns [17].
These laboratory efforts are extended through the VenSpec Suite, where coordinated experiments are planned to simulate Venus’ surface and atmospheric conditions, generating reference spectra to link instrument observations to realistic surface scenarios [18].
Laboratory emissivity measurements are needed for radiative transfer models, helping translate surface spectral properties into top-of-atmosphere radiance and providing uncertainty estimates for VenSpec-M/VEM observations. Combined with geodynamic modeling, these data support investigations of mantle composition effects on surface emissivity and volcanic processes.
In summary, VenSpec-M/VEM data, supported by laboratory spectroscopy, will advance our understanding of Venus’ surface composition and volcanic activity, providing new insight into the planet’s geologic evolution and the connections between its interior, surface, and atmosphere.

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