The Surface UV Environment on Planets Orbiting M-Dwarfs: Implications for Prebiotic Chemistry & Need for Experimental Follow-Up

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 due to 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, and especially the origin of RNA. Characterizing the UV environment on M-dwarfs planets is relevant to 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 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 and TRAPPIST-1. 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.

Sukrit Ranjan, Robin D. Wordsworth, Dimitar D. Sasselov
(Submitted on 5 May 2017)

Comments: 18 pages; 6 figures; submitted, under review
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1705.02350 [astro-ph.EP] (or arXiv:1705.02350v1 [astro-ph.EP] for this version)
Submission history
From: Sukrit Ranjan [view email]
[v1] Fri, 5 May 2017 18:01:04 GMT (207kb,D)

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