# Large Interferometer For Exoplanets (LIFE): VIII. Where is the phosphine? Observing exoplanetary PH3 with a space based MIR nulling interferometer

**Authors:** D. Angerhausen, M. Ottiger, F. Dannert, Y. Miguel, C. Sousa-Silva, J. Kammerer, F. Menti, E. Alei, B. S. Konrad, H. S. Wang, S. P. Quanz, the LIFE collaboration  
**arXiv:** [2211.04975](https://arxiv.org/abs/2211.04975)  
**Date:** 2022-11-09  
**Summary page:** https://www.summarizepaper.com/en/paper/2211.04975v1/

## Key points

- The search for biosignatures in exoplanetary atmospheres is a key focus of current exoplanet research.
- Phosphine (PH3) has been identified as a potential biosignature molecule and could be crucial in understanding the exotic chemistry occurring in (exo)planetary atmospheres.
- The Large Interferometer For Exoplanets (LIFE) concept aims to identify which science cases for PH3 chemistry are observable with a space-based mid-infrared nulling interferometric observatory.
- Using chemical kinetics and radiative transfer calculations, the LIFE team produced forward models of informative observational cases for their observation simulator software.
- LIFE can produce highly informative observations in a relatively small amount of time. For example, it takes only about one hour to find phosphine in a warm giant around a G star at 10 pc and about ten hours to detect phosphine concentrations of 220 ppb (H2 case) and 310 ppm (CO2 case) in H2 or CO2 dominated temperate super-Earths around M star hosts at 5 pc.
- The study also compared the observation times needed to get significant detections of phosphine using JWST and LIFE. The results showed that LIFE performs more than an order of magnitude faster than JWST for comparable scenarios with similar signal-to-noise ratios.
- The next steps for the team will be to simulate more examples and run full Bayesian retrievals to get more quantitative assessments on the limits of phosphine detectability.
- Investigating atmospheric properties for a statistically significant number of temperate terrestrial exoplanets is one of the major achievements expected from exoplanet research this century.
- While ground-based projects and other space-based missions will likely deliver an initial comprehensive observational set of exoplanetary atmospheres, LIFE aims to investigate the atmospheric properties of primarily temperate terrestrial exoplanets using an interferometer.
- These efforts will help us better understand planetary diversity and identify potential biosignatures or even technosignatures.

## Summary

The search for biosignatures in exoplanetary atmospheres is a key focus of current exoplanet research. Phosphine (PH3) has been identified as a potential biosignature molecule and could be crucial in understanding the exotic chemistry occurring in (exo)planetary atmospheres. To this end, the Large Interferometer For Exoplanets (LIFE) concept aims to identify which science cases for PH3 chemistry are observable with a space-based mid-infrared nulling interferometric observatory. Using chemical kinetics and radiative transfer calculations, the LIFE team produced forward models of informative observational cases for their observation simulator software. The team found that LIFE can produce highly informative observations in a relatively small amount of time. For example, it takes only about one hour to find phosphine in a warm giant around a G star at 10 pc and about ten hours to detect phosphine concentrations of 220 ppb (H2 case) and 310 ppm (CO2 case) in H2 or CO2 dominated temperate super-Earths around M star hosts at 5 pc. The study also compared the observation times needed to get significant detections of phosphine using JWST and LIFE. The results showed that LIFE performs more than an order of magnitude faster than JWST for comparable scenarios with similar signal-to-noise ratios. The next steps for the team will be to simulate more examples and run full Bayesian retrievals to get more quantitative assessments on the limits of phosphine detectability. These results will inform crucial questions and decisions in the early design phase of a mission like LIFE. Overall, investigating atmospheric properties for a statistically significant number of temperate terrestrial exoplanets is one of the major achievements expected from exoplanet research this century. While ground-based projects and other space-based missions will likely deliver an initial comprehensive observational set of exoplanetary atmospheres, LIFE aims to investigate the atmospheric properties of primarily temperate terrestrial exoplanets using an interferometer. These efforts will help us better understand planetary diversity and identify potential biosignatures or even technosignatures.