When were the First Exocontinents?

Greaves, Jane S. ORCID: https://orcid.org/0000-0002-3133-413X 2023. When were the First Exocontinents? Research Notes of the American Astronomical Society (RNAAS) 7 , 195. 10.3847/2515-5172/acf91a

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Abstract

Earth's biosphere was able to increase as continents emerged. I assess when continents could first appear on hypothetical rocky planets of nearby stars. Radiogenic heating of the planetary mantle is evaluated through stellar abundances of iron and silicon (core and mantle proxies) and thorium and potassium (mantle heating proxies). The heat per unit mantle mass is compared to a threshold on Earth after which large-scale continents appeared. Longer delays are inferred for some exoplanets, particularly those with high thorium, but earliest continents could have arisen 2 Gyr before those on Earth, among thin disk stars. In the thick disk, continents could appear 4–5 Gyr pre-Earth. Hence, subsolar-metalicity systems could be an important focus in searching for planets where life could be more advanced than on Earth. At least ∼2 worlds with such old continents are expected to be accessible to future space telescopes, such as Habitable Worlds Observatory.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Physics and Astronomy
Publisher:	IOP Press
ISSN:	2515-5172
Date of Acceptance:	1 September 2023
Last Modified:	01 May 2024 11:05
URI:	https://orca.cardiff.ac.uk/id/eprint/167069

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