By Matthew Williams
May 28, 2025
In the search for life in the universe (also known as astrobiology), scientists use strategies that have different names. For example, there is the “Follow the Water” approach and searches for signs of oxygen gas, carbon dioxide, methane, ammonia and other compounds associated with life here on earth. Together, these are referred to as “biosignatures” (or “biomarker”), which relate to evidence of biological activity and processes. This search has been improved by the next generation instruments such as the James Webb Space Telescope (JWST), and others will follow soon.
This includes the Habitable World Observatory (HWO), the first telescope that was specially developed for astrobiology surveys (which will come onto the market until the 2040s). In preparation, scientists refine their strategies to identify these signatures to exoplanets. In a recently carried out work, geophysicists from the University of Chicago carried out simulations to determine how telescopes such as the HWO were able to demonstrate oxygen gas (O2) and ozone (O3) through direct imaging studies. Their results indicate that contrary to expectations, the presence of clouds could improve the detection of these biosignatures.
Research was led by Huanzhou Yang, a doctoral student of the Ministry of Geophysical Sciences at the University of Chicago. Michelle Hu, a student of the Demille Group Atomic/Molecular/Optical (AMO) Physics Group in Uchicago, and Dorian S. Abbot, professor for geophysical sciences in Uchicago joined him. The paper, which recently describes its results, appeared online and was recorded for publication in the Astrophysical Journal (probably published in a few weeks).
Your browser does not support HTML5 video.
The area of exoplanet studies has grown suddenly in the past 20 years, with more than 5,900 confirmed planets have so far confirmed. So far, the vast majority of the proven people have been found using indirect methods, especially the transit method (transitphotometry) and the radial speed method (Doppler spectroscopy). So far, only a small percentage (1.4%) has been discovered using the direct imaging method, in which astronomers analyze the light directly from the atmosphere or surface of an exoplanet.
This is changing thanks to the next generation of the next generation such as the James Webb Space Telescope (JWST) and future space and floor base (A La HWO) that use coronographies and spectrometers. While coronographers block light of parent star and enable astronomers to examine light directly from the atmospheres or surfaces of circulation exoplanets, enable spectrometers of astronomers to record absorption characteristics that show which chemical signatures are available so that they place a lower restrictions on the habitability of the planets.
Thanks to these highly developed instruments and thousands of exoplanets that are available for their studies, the field changes from the discovery to characterization. However, clouds are often considered a barrier for the detection of bisignatures to exoplanets, which is surprising when you consider that they are part of the water cycle of the earth and are closely related to the habitability of our planet. As Yang today said Universe by e -Mail:
“Evidence of atmospheric components on exoplanets is based on the fact that the radiation absorption is highly sensitive to wavelengths, which is a unique feature for every gas pecies. This enables us to analyze what components are available. Absorption features of the gases in every wavelength, which means that our ability to demonstrate the gasspeetzies. “
As Yang added, this applies to transit recognitions in which astronomers analyze light during a transit by the atmosphere of an exoplanet. For direct imaging studies, however, clouds could increase the observation signal for biosignatures by increasing the reflected light. The high reflection capacity of clouds enables more photons to be recognized by telescopes, which can compensate for their effects in blocking the gas absorption information. In order to assess this potential, Yang and his team carried out simulations with the community aerosol and radiation model for atmospheres (Carma).
Your browser does not support HTML5 video.
This general section microphysics code simulates the presence of various aerosols in planetary atmospheres. They simulated clouds with the Planetary Spectrum Generator (PSG), a radiation transmission model suite, which synthesize spectra from planetary atmospheres and surfaces based on different planetary parameters. For their purposes, they selected two simple biosignatures (O2 and O3), which were well examined and for which the results can be transferred to other biosignatures. Said yang:
“The potential to demonstrate the bisignature (such as oxygen and ozone) depends on the removal of the exoplanets to us, the temperature of the host stars, the frequency of biosignatures, the state of the atmosphere of the exoplanets (including clouds), etc.
The effects of this research could be far-reaching missions for upcoming missions, including the HWO, the Nancy Grace Roman space telescope (RST) and ground-based observatories such as the extremely large telescope (ELT), the huge Magellan telescope (GMT) and the thirty meter high telescope (TMT). As Yang said, one of the most remarkable snack bars from their results is the way it offers additional trust in direct surveys and their ability to recognize bisignatures to exoplanets:
“In comparison to transit surveys, which mainly observe planets around M stars, these surveys are better in order to observe larger planets, or circle the hotter stars like the earth in the solar system,” he said. “These planets have more often atmospheres and are better candidates for habitable planets. Second, the further analysis of some transit survey goals is limited due to the existence of clouds. Now we can see this as an advantage for direct imaging surveys and set these goals with priority.
Further reading: Arxiv
