The Surface UV Environment on Planets Orbiting M Dwarfs: Implications for Prebiotic Chemistry and the Need for Experimental Follow-up

By S. Ranjan, R. Wordsworth, D. Sasselov. 2017

119 citations recorded by the source corpus.

Potentially habitable planets orbiting M dwarfs are of intense astrobiological interest because they are the only rocky worlds accessible to biosignature search over the next 10+ years because of a confluence of observational effects. Simultaneously, recent experimental and theoretical work suggests that UV light may have played a key role in the origin of life on Earth, especially the origin of RNA. Characterizing the UV environment on M-dwarf planets is important for understanding whether life as we know it could emerge on such worlds. In this work, we couple radiative transfer models to observed M-dwarf spectra to determine the UV environment on prebiotic Earth-analog planets orbiting M dwarfs. We calculate dose rates to quantify the impact of different host stars on prebiotically important photoprocesses. We find that M-dwarf planets have access to 100–1000 times less bioactive UV fluence than the young Earth. It is unclear whether UV-sensitive prebiotic chemistry that may have been important to abiogenesis, such as the only known prebiotically plausible pathways for pyrimidine ribonucleotide synthesis, could function on M-dwarf planets. This uncertainty affects objects like the recently discovered habitable-zone planets orbiting Proxima Centauri, TRAPPIST-1, and LHS 1140. Laboratory studies of the sensitivity of putative prebiotic pathways to irradiation level are required to resolve this uncertainty. If steady-state M-dwarf UV output is insufficient to power these pathways, transient elevated UV irradiation due to flares may suffice; laboratory studies can constrain this possibility as well.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/c7d444add40530de69819c2e5afda6c35a0b3e00

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

Citations in the corpus

Exoplanet Biosignatures: A Review of Remotely Detectable Signs of Life (2017, background): “In addition, the low quiescent (nonflaring) nearultraviolet (NUV) spectrum of M dwarfs may also drastically limit the rate of prebiotic photoprocesses, creating an obstacle for the origin of life on these worlds (Ranjan et al., 2017).”
Stellar Flares from the First TESS Data Release: Exploring a New Sample of M Dwarfs (2019, background): “Indeed, recent work suggests that flares might be the only means for delivering the UV photons which have been proposed to be required to initiate life on exoplanets around M dwarf stars (Ranjan et al. 2017; Rimmer et al. 2018).”