Prebiosignature Molecules Can Be Detected in Temperate Exoplanet Atmospheres with JWST

Abstract

The search for biosignatures on exoplanets connects the fields of biology and biochemistry to astronomical observation, with the hope that we might detect evidence of active biological processes on worlds outside the solar system. Here we focus on a complementary aspect of exoplanet characterization connecting astronomy to prebiotic chemistry: the search for molecules associated with the origin of life, prebiosignatures. Prebiosignature surveys in planetary atmospheres offer the potential to both constrain the ubiquity of life in the galaxy and provide important tests of current prebiotic syntheses outside of the laboratory setting. Here, we quantify the minimum abundance of identified prebiosignature molecules that would be required for detection by transmission spectroscopy using JWST. We consider prebiosignatures on five classes of terrestrial planets: an ocean planet, a volcanic planet, a post-impact planet, a super-Earth, and an early-Earth analog. Using a novel modeling and detection test pipeline, with simulated JWST noise, we find the detection thresholds of hydrogen cyanide ( HCN ), hydrogen sulfide (H2S), cyanoacetylene (HC3N), ammonia (NH3), methane (CH4), acetylene (C2H2), sulfur dioxide (SO2), nitric oxide (NO), formaldehyde (CH2O), and carbon monoxide (CO) in a variety of low-mean-molecular-weight (<5) atmospheres. We test the dependence of these detection thresholds on an M dwarf target star and the number of observed transits, finding that a modest number of transits (1–10) are required to detect prebiosignatures in numerous candidate planets, including TRAPPIST-1e with a high-mean-molecular-weight atmosphere. We find that the Near Infrared Spectrograph G395M/H instrument is best suited for detecting most prebiosignatures.

Mid-infrared detectors for space electronics based on InAs-core/InP-shell nanowires

“…Moreover, searching for biosignatures lying in MIR spectral range on exoplanets can reveal evidence of active biological processes on worlds beyond the Solar System. Studying molecules in exoplanet atmospheres associated with life (biosignatures) and its origins (prebiosignatures) such as, hydrogen cyanide (HCN), hydrogen sulfide (H2S), cyanoacetylene (HCN), carbon monoxide (CO), methane (CH4), acetylene (C2H2), ammonia (NH), nitric oxide (NO), and formaldehyde (CH2O), can give us insight into the geochemical and physical processes occurring on terrestrial exoplanets (Claringbold et al (2023)).…”

Using a Quench Level Approximation to Estimate the Effect of Metallicity on the Abundances of N-bearing Species in H2-dominated Atmospheres

“…Major nitrogen-bearing species, such as HCN and NH 3 , have been detected in exoplanet atmospheres (Cabot et al 2019;Giacobbe et al 2021;Carleo et al 2022;Guilluy et al 2022). With JWST, we are entering the golden era for the atmospheric characterization of exoplanets, and conclusive detections of nitrogen chemistry are possible (MacDonald & Madhusudhan 2017; Tsai et al 2021;Claringbold et al 2023). The recent detection of SO 2 in WASP-39 b provides the first-ever signature of photochemistry (Alderson et al 2023;Rustamkulov et al 2023), which is very promising.…”