Could scientists uncover signs of life within the clouds of exoplanets? A recently submitted manuscript delves into this question, focusing on the identification of microbial biosignatures in exoplanetary atmospheres and clouds. The research aims to advance methods for detecting life on exoplanets, potentially expanding our understanding of life beyond Earth.
In their investigation, the research team conducted laboratory experiments using seven strains of airborne microbes sourced from Earth”s atmosphere. These included strains related to Modestobacter versicolor, Roseomonas vinacea, Micrococcus luteus, Massilia niabensis, and Noviherbaspirillum soli, as well as the species Curtobacterium aetherium and Curtobacterium oceanosedimentum. The researchers employed spectroscopy to analyze the light reflected by these samples, aiming to determine whether their spectral features could indicate biosignatures in the atmospheres of exoplanets.
The findings revealed that each microbial sample displayed distinct biosignatures, which could potentially be utilized to identify them in the clouds and atmospheres of exoplanets. The researchers concluded, “Here, we present an additional path for searching for life on Earth-like exoplanets: the search for biopigments as signs of life in clouds. The first reflectance spectra of aerial life demonstrate UV-protective biopigment signatures, offering a critical spectral reference to guide the detection and interpretation of potential biosignatures in the reflected light of Earth-like exoplanets during upcoming missions.”
This research is motivated by past studies, including a seminal 1976 analysis by American astronomer Carl Sagan and Australian-American astrophysicist Ed Salpeter, which explored the potential for life in Jupiter”s clouds. They proposed various types of organisms, such as “Sinkers,” “Floaters,” “Hunters,” and “Scavengers,” hypothesizing their existence within distinct ecological niches in Jupiter”s atmosphere.
Another driving factor behind this study is the Habitable Worlds Observatory (HWO), a planned space telescope set for launch in the 2040s. HWO aims to utilize spectroscopy to observe and analyze 25 habitable exoplanets for biosignatures. The researchers suggest that their findings could assist HWO in detecting these biosignatures.
In addition to exoplanets, HWO is expected to explore galaxy evolution, star formation, and solar system objects. The James Webb Space Telescope (JWST) has already employed spectroscopy to examine several exoplanet atmospheres, such as those of WASP-39 b and WASP-17 b, located approximately 700 and 1,324 light-years from Earth, respectively. JWST successfully detected water, carbon dioxide, and carbon monoxide in the atmosphere of WASP-39 b, while quartz particles were identified in the upper atmosphere of WASP-17 b.
Recently, JWST published two papers in “The Astrophysical Journal Letters” discussing the atmosphere of TRAPPIST-1 e, an Earth-sized exoplanet in its host star”s habitable zone. However, the results did not definitively confirm the presence of an atmosphere around TRAPPIST-1 e, highlighting the need for further research to verify atmospheric existence.
The TRAPPIST-1 system, located about 41 light-years from Earth, contains seven known Earth-sized planets, three of which orbit within the habitable zone of their star. It is speculated that all seven planets are tidally locked, similar to how Earth”s Moon is perpetually aligned with our planet.
As researchers continue to investigate the potential for life in exoplanet atmospheres and clouds, the scientific community eagerly anticipates new insights in the years ahead. This research underscores the importance of ongoing exploration and discovery in the quest to understand life beyond our planet.
