How habitable are M-dwarf Exoplanets? Modeling surface conditions and exploring the role of melanins in the survival of Aspergillus niger spores under exoplanet-like radiation

TL;DR

This study models the surface conditions of M-dwarf exoplanets and experimentally demonstrates that melanin-rich Aspergillus niger spores can survive extreme radiation, highlighting potential microbial resilience in extraterrestrial environments.

Contribution

It introduces a combined modeling and microbiological approach to assess exoplanet habitability and the protective role of melanins in microbial survival under space-like radiation conditions.

Findings

Proxima b and TRAPPIST-1 e may have habitable surface temperatures.

A. niger spores can survive superflare radiation with shielding.

Melanin enhances spore survival and germination under radiation.

Abstract

Exoplanet habitability remains a challenging field due to the large distances separating Earth from other stars. Using insights from biology and astrophysics, we studied the habitability of M-dwarf exoplanets by modeling their surface temperature and flare UV and X-ray doses using the Martian atmosphere as a shielding model. Analyzing the Proxima Centauri and TRAPPIST-1 systems, our models suggest that Proxima b and TRAPPIST-1 e are likeliest to have temperatures compatible with surface liquid water, as well as tolerable radiation environments. Results of the modeling were used as a basis for microbiology experiments to assess spore survival of the melanin-rich fungus Aspergillus niger to exoplanet-like radiation (UV-C and X-rays). Results showed that A. niger spores can endure superflare events on M-dwarf planets when shielded by a Mars-like atmosphere or by a thin layer of soil or water. Melanin-deficient spores suspended in a melanin-rich solution showed higher survival rates and germination efficiency when compared to melanin-free solutions. Overall, the models developed in this work establish a framework for microbiological research in habitability studies. Finally, we showed that A. niger spores can survive harsh radiation conditions of simulated exoplanets, also emphasizing the importance of multifunctional molecules like melanins in radiation shielding beyond Earth.