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DIVerse Exoplanet Redox State Estimations

Project description

How planetary atmospheres lacking helium reveal more about planetary interiors

Planetary atmospheres hold vital clues about a planet’s interior and its potential for habitability. While most studies focus on biosignatures, understanding the redox state – a measure of chemical conditions that support prebiotic life – is equally important. Planets typically fall into two categories: Class I, with H2/He-dominated atmospheres and Class II, with oxidised volcanic atmospheres. A newly proposed planet category, Class X, features hydrogen-dominated atmospheres without helium, likely attributed to volcanic outgassing of oxygen-poor species. Observing these atmospheres could reveal how planetary interiors evolve. The ERC-funded DIVERSE project will use advanced models to explore how atmospheres lacking helium form and develop, and how these low-mean-molecular-weight atmospheres relate to planetary interiors.

Objective

New observational capabilities with the JWST and ARIEL space telescopes will strongly advance our ability to characterize exoplanetary atmospheres. While the community focusses mainly on biosignatures, in DIVERSE I will search for signatures of geophysical factors that influence habitability, specifically the diversity of planetary redox states. The redox state is of major importance for habitability, since reducing conditions favour prebiotic chemistry for life as we know it.

Atmospheres of rocky planets are typically divided into two distinct classes – H2/He-dominated (reduced) atmospheres of primordial origin – here denoted as Class I planets – or secondary (more oxidized) atmospheres of volcanic origin – here named Class II planets. In the Solar System, observations are limited to old, evolved atmospheres that became oxidized over time and do not allow to directly constrain the planets’ interior redox states. Furthermore, detection of reduced species such as CO or CH4 does not unambiguously link back to the interior redox state.

In contrast, if we were able to detect H2-dominated atmospheres lacking He – here called Class X planets – the most likely explanation would be strongly reduced degassing from the magma ocean or subsequent volcanism. Distinguishing Class I and X planets would truly allow to constrain the planetary redox state and indicate how it depends on observables such as stellar composition or planetary mass. Estimates on the distribution and observability of Class X planets are yet missing but became recently possible.

DIVERSE will build strong predictive, theoretical models, linking the interior evolution including core formation with atmospheric abundance and erosion models including the observability potential, to determine the diverse evolution pathways of reducing atmospheres of primary, secondary or hybrid origin. I will thus address whether (and for which planet classes) the atmosphere could indeed serve as a window into the interior.

Fields of science (EuroSciVoc)

Keywords

Programme(s)

Topic(s)

Funding Scheme

HORIZON-ERC - HORIZON ERC Grants

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Call for proposal

(opens in new window) ERC-2022-COG

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Host institution

FREIE UNIVERSITAET BERLIN
Net EU contribution
€ 1 993 270,00
Address
KAISERSWERTHER STRASSE 16-18
14195 Berlin
Germany
Region
Berlin Berlin Berlin
Activity type
Higher or Secondary Education Establishments
Links
Total cost
€ 1 993 270,00

Beneficiaries (1)