Atmospheric characterization of terrestrial exoplanets in the mid-infrared: biosignatures, habitability, and diversity

Abstract

Exoplanet science is one of the most thriving fields of modern astrophysics. A major goal is the atmospheric characterization of dozens of small, terrestrial exoplanets in order to search for signatures in their atmospheres that indicate biological activity, assess their ability to provide conditions for life as we know it, and investigate their expected atmospheric diversity. None of the currently adopted projects or missions, from ground or in space, can address these goals. In this White Paper, submitted to ESA in response to the Voyage 2050 Call, we argue that a large space-based mission designed to detect and investigate thermal emission spectra of terrestrial exoplanets in the mid-infrared wavelength range provides unique scientific potential to address these goals and surpasses the capabilities of other approaches. While NASA might be focusing on large missions that aim to detect terrestrial planets in reflected light, ESA has the opportunity to take leadership and spearhead the development of a large mid-infrared exoplanet mission within the scope of the “Voyage 2050” long-term plan establishing Europe at the forefront of exoplanet science for decades to come. Given the ambitious science goals of such a mission, additional international partners might be interested in participating and contributing to a roadmap that, in the long run, leads to a successful implementation. A new, dedicated development program funded by ESA to help reduce development and implementation cost and further push some of the required key technologies would be a first important step in this direction. Ultimately, a large mid-infrared exoplanet imaging mission will be needed to help answer one of humankind’s most fundamental questions: “How unique is our Earth?”

Exploring and Validating Exoplanet Atmospheric Retrievals with Solar System Analog Observations

“…The truncated spectrum is shown in Figure 14 where wavelength-independent uncertainties have been added to yield a SNR of 20 at 10 µm. Thus, adopted data quality is roughly consistent with under-study mid-infrared exo-Earth direct imaging mission concepts (Quanz et al 2021a), where studies have investigated wavelength coverage of 3-20 µm, resolving powers of 20-100, and SNRs of 5-20 (Konrad et al 2021).…”

Detailed chemical compositions of planet-hosting stars: II. Exploration of the interiors of terrestrial-type exoplanets

“…Exercised with caution, such an analysis (with a yet-large uncertainty) nevertheless offers an insight, in terms what we can learn already with the available data (essentially host stellar composition as well as planetary mass and radius) and with the bulk/interior models (with sensibly simplifications) that we can build, into the detailed properties of habitable-zone, terrestrial-type exoplanets, thus providing guidance for the target selections for future missions, such as PLATO (Rauer et al 2014;Nascimbeni et al 2022), Ariel (Turrini et al 2021), and LIFE (Quanz et al 2021(Quanz et al , 2022.…”

“…In reality, habitablezone terrestrial planets are unlikely to be an ideal Earth 2.0 and their mass and radius may vary. To test the effect of varying mass and radius (within the terrestrial regime) on the interiors, we assume two extreme cases for the size of a model terrestrial planet by referring to the definition of a rocky planet orbiting within the (empirical) habitable zone: 0.5 𝑅 ⊕ and 1.5 𝑅 ⊕ for the LIFE targets (Quanz et al 2021). The mass is not predefined but computed together with the interiors by keeping the planet to be in the terrestrial regime.…”

A Linear Formation Flying Astronomical Interferometer in Low Earth Orbit

“…O 3 is particularly useful as it can be used as a tracer for O 2 . These molecules are ideal for determining biosignatures, especially for life on Earth as we know it (Quanz et al, 2019;Kammerer & Quanz, 2017).…”

“…Again, due to budget cuts, Darwin was not funded and ceased being investigated in 2007. ESA is currently planning for the next 30 years as part of the Voyage 2050 process, and a revised Darwin-like mission LIFE (Large Interferometer For Exoplanets) (Quanz et al (2018); Quanz et al (2019)) is part of the discussion.…”