Nature Astronomy Scientific Journal

A crucial factor governing the habitability of exoplanets is the availability of bioessential elements such as nitrogen (N) and phosphorous (P), which foster prebiotic chemistry and sustain life after its emergence. However, concentrations of P and N in planetary mantles vary, owing to initial availability and oxidation conditions during planet formation, and thus their characterization and availability in planetary environments are challenging. Here we use a core-formation model to show that moderate oxygen fugacity during core formation is the key parameter to the availability of these two elements, with the existence of a narrow ‘chemical Goldilocks zone’ that allows both P and N to be present with the right abundances in the mantle. Earth falls within this zone, whereas planets with more reducing/oxidizing conditions will sequester P/N into the core, hindering their availability for life. Future observations refining estimates of the oxygen fugacity prevalent during exoplanet core formation will be crucial to properly evaluate exoplanetary habitability and correctly interpret possible biosignatures.

Earth’s surface is deficient in available forms of many elements considered limiting for prebiotic chemistry. In contrast, many extraterrestrial rocky objects are rich in these same elements. Limiting prebiotic ingredients may, therefore, have been delivered by exogenous material; however, the mechanisms by which exogeneous material may be reliably and non-destructively supplied to a planetary surface remains unclear. Today, the flux of extraterrestrial matter to Earth is dominated by fine-grained cosmic dust. Although this material is rarely discussed in a prebiotic context due to its delivery over a large surface area, concentrated cosmic dust deposits are known to form on Earth today due to the action of sedimentary processes. Here we combine empirical constraints on dust sedimentation with dynamical simulations of dust formation and planetary accretion to show that localized sedimentary deposits of cosmic dust could have accumulated in arid environments on early Earth, in particular glacial settings that today produce cryoconite sediments. Our results challenge the widely held assumption that cosmic dust is incapable of fertilizing prebiotic chemistry. Cosmic dust deposits may have plausibly formed on early Earth and acted to fertilize prebiotic chemistry.

Publications in Nature Astronomy by NOMIS researchers

The chemical habitability of Earth and rocky planets prescribed by core formation

Cosmic dust fertilization of glacial prebiotic chemistry on early Earth