Transmission Spectroscopy of Exo-Solar Systems in the TESS Era

Venus has long been thought of only as a lifeless, desolate world, that has remained that way since the birth of the solar system. However, recent studies using 3-D climate models have illustrated that Venus could have maintained habitable temperatures up to 1 Gyr ago. This finding further increased the need to understand the processes that are responsible for Earth and Venus being so dramatically different today, despite their similarities in size and mass. One method for identifying the reasons for the difference between Earth and Venus will be studying analogous exo-planetary systems with both a terrestrial planet in the Venus zone (VZ) and in the habitable zone (HZ). This will involve comparing their atmospheres, whose properties will be derived using transmission spectroscopy. This will not be a simple task however, as previous works have shown that retrieval algorithms can have difficulty correctly determining whether a given transit spectrum is derived from a Venus- or Earth-like planet. To avoid the ambiguities associated with retrieval methods, this work will determine whether the relative size of CO2 features in transmission spectra in the near-infrared can be used as a proxy for whether a planet is more Earth-like or Venus-like. Modelled transmission spectra will be created for a potential exo-Earth and exo-Venus, which will include several cloud and haze scenarios for each planet. Comparing the array of spectra from each planet will determine whether the truncation of features caused by clouds and hazes can cause an Earth-like planet to appear as a Venus-like planet with heavy cloud cover.