Invited comunication
P. Machado
Abstract
Transmission spectroscopy probes the atmospheric limb of a transiting planet. I will present our study using spectroscopic transmission techniques upon observations of the last Venus’ transit, related with the spectral region impacted by Mie scattering.
We retrieved transmission spectra of the atmosphere of Venus, using high resolution observations (FIRS/Dunn), our aim was to produce a case study where we compare the retrieved spectroscopic transmission observables on Venus with the datasets obtained by space probes and ground-based observations, which will consist in a valuable calibration template and an opportunity to assess the feasibility of the atmospheric characterization of Earth-size exoplanets near the habitable zone.
The solar radiation that interacted with the Venus’ atmosphere high layers (70 to 150 km), whence were transmitted from the top of the cloud deck up to above the mesopause, become affected by its interaction with the Venusian atmosphere. The atmosphere altitudes probed with this transmission spectroscopy technique on Venus present a lower absorption value at about 80 km due to the dominant diffusion regime, in the case of Venus, the most remarkable and extended spectral signature is that of Mie scattering by the upper haze, below that altitude large particles start to be dominant which turn the Rayleigh scattering more prominent which only could be reached at 2.65 microns or higher wavelengths.
Venus transmission spectrum obtained during its transit across the Sun will serve both as a comparison basis for transiting Earth-mass exoplanets to be observed in the future, and a proof of feasibility that such observations can effectively probe the atmospheres of exoplanets in this mass range. In addition, transit observations of Venus can bring precious information about how the atmosphere of a non-habitable world – observed as an exoplanet – differs from that of an habitable planet, such as Earth’s.
Planetary Science and Space Exploration 2024
Daejeon, South Korea
2024 July
