Nonphotosynthetic pigments as potential biosignatures

Area of Science:

• Astrobiology
• Planetary Science
• Spectroscopy

Background:

• Previous research on exoplanet biosignatures focused on photosynthetic pigments, like the vegetation red edge.
• Pigmentation in Earth organisms serves diverse adaptive purposes beyond photosynthesis.

Purpose of the Study:

• To investigate the diversity and detectability of nonphotosynthetic pigments as potential biosignatures.
• To assess the utility of broadband color versus spectral data for identifying these pigments on exoplanets.

Main Methods:

• Described environments hosting nonphotosynthetic biologically pigmented surfaces.
• Conducted lab experiments analyzing spectral and broadband color diversity of pigmented Earth organisms.
• Utilized 1-D and 3-D spectral models to simulate planetary reflectance.

Main Results:

• Nonphotosynthetic pigments can significantly impact a planet's disk-averaged spectrum if coverage is substantial.
• Broadband color alone is insufficient for distinguishing nonphotosynthetic pigments from photosynthetic or nonbiological surfaces.
• Atmospheric and cloud effects, along with biological diversity, complicate pigment detection.

Conclusions:

• Detecting widespread nonphotosynthetic pigments on exoplanets is challenging.
• Spectrally resolved data, rather than broadband color, is likely necessary for robust identification of biologically produced pigments.