The HWO observatory searches for signs of life on exoplanets
NASA is preparing its first flagship astrophysics mission: the Habitable Worlds Observatory (HWO). Its main objective is to search for signs of life on rocky exoplanets outside our solar system. A scientific team is evaluating how to characterize these worlds and interpret possible biosignatures, carefully considering detection errors. 🔭
Technical requirements for detecting biological pigments
To identify surface biosignatures, such as pigments on a planet's crust, the telescope needs specific parameters. A signal-to-noise ratio between 20 and 40 is required, operating in a spectral range of 500 to 1100 nanometers. Analyses of the HWO coronagraph indicate that to separate these biological signals from the abiotic background, it is crucial to use multiple spectral channels in parallel, covering the entire wavelength range without interruptions.
Key points of spectral detection:- Using all possible channels in the 500-1100 nm range greatly enhances detection capability.
- Probing strategies with restricted spectral ranges are not sufficient to isolate pigment features.
- These measurements would provide multiple lines of evidence to corroborate previous atmospheric findings.
Detecting surface pigments is the only way to find forms of life that perform anoxygenic photosynthesis, on worlds where oxygenic photosynthesis may never have evolved.
Expanding the horizon of detectable biology
Searching for surface biosignatures is a secondary but fundamental strategy. It not only serves to confirm atmospheric detections of gases like oxygen, but also radically expands the type of biology that the HWO could identify. This search allows tracking more primitive life that does not significantly alter its planet's atmosphere.
Advantages of searching for surface biosignatures:- Allows confirming and supporting atmospheric biosignature findings, reducing false positives.
- Enables detecting organisms with anoxygenic photosynthesis, which do not produce oxygen.
- Expands the spectrum of potentially habitable worlds that the mission can study.
A two-front search
The HWO strategy is comprehensive. While one part of the science focuses on analyzing exoplanet atmospheres for bioindicator gases, another directly explores their surfaces. Scanning a planet for the extraterrestrial equivalent of a layer of