Fainter atmospheric signals may soon become distinguishable.
AUSTIN, United States | June 2026
Scientists have proposed equipping NASA’s future Habitable Worlds Observatory with a high-resolution infrared spectrograph capable of identifying extremely weak chemical signatures in the atmospheres of distant planets. The instrument could provide more than twelve times the spectral resolution available through the James Webb Space Telescope for comparable observations. Researchers believe the improvement would make it easier to distinguish planetary signals from the overwhelming light produced by nearby stars. The technology could therefore strengthen the search for environments capable of supporting life beyond the Solar System.
The proposal was developed by a team led by Daniel Jaffe of the University of Texas at Austin. Their objective is to add a compact near-infrared instrument to the Habitable Worlds Observatory, commonly known as HWO. The telescope is still being defined and is not expected to launch until the 2040s. Its principal mission would be to directly image potentially habitable planets and analyze the gases present in their atmospheres.
Spectroscopy works by separating light into its component wavelengths. Molecules absorb and emit light in distinctive patterns, creating chemical fingerprints that astronomers can identify from great distances. By studying those patterns, scientists can search for water vapor, carbon dioxide, oxygen, methane and other compounds associated with planetary climate or biological activity. No single molecule would prove that life exists, but combinations of gases could provide evidence worth investigating.
The James Webb Space Telescope has already transformed the study of exoplanet atmospheres. Its instruments can detect chemical compounds when planets pass in front of their stars or when their thermal emissions are sufficiently strong. However, Webb was not designed primarily to study Earth-like worlds orbiting Sun-like stars. Its spectral resolution, close to 3,600 in some relevant modes, can be insufficient when atmospheric features are weak or blended together.
Jaffe’s team proposes increasing that resolution to approximately 45,000. At that level, the spectrograph could separate closely spaced molecular lines that appear merged at lower resolution. Weak carbon dioxide signatures, for example, would become easier to identify against the surrounding background. The instrument would also improve scientists’ ability to determine whether an apparent feature originates from the planet, its star or the observing system itself.
Separating planetary light from stellar contamination is one of the greatest challenges in exoplanet science. A star can be billions of times brighter than a small rocky planet orbiting nearby. Coronagraphs are designed to block much of that light, allowing telescopes to search for the faint planet beside it. Even after suppression, however, residual starlight can interfere with the measurement.
High-resolution spectroscopy offers another layer of separation. The chemical lines from a planet move slightly because of its orbital motion, while features produced by the star follow a different velocity pattern. Astronomers can use these Doppler shifts to isolate the planetary spectrum from the remaining glare. The technique would increase the quality of the recovered data without requiring the coronagraph to eliminate every trace of stellar light.
The same capability could reveal more than atmospheric composition. Changes in spectral lines may allow researchers to calculate orbital velocities, atmospheric circulation and wind speeds. Repeated observations could show whether weather systems evolve over time or whether different regions of a planet have distinct atmospheric conditions. Scientists might eventually compare climates across several rocky worlds rather than simply determining whether an atmosphere exists.
Until recently, placing such a powerful infrared spectrograph aboard a space telescope appeared impractical. Traditional high-resolution instruments are large, heavy and difficult to cool. They can also generate electronic interference that affects the extremely faint signals astronomers are attempting to measure. Launching them would increase the mass, complexity and cost of an already ambitious mission.
Two technological advances have changed that assessment. Silicon immersion gratings and related diffractive components can achieve high spectral resolution inside a much smaller optical system. These devices allow light to travel through dense material, effectively increasing the optical path without requiring a physically enormous instrument. A compact spectrograph could therefore cover a broad infrared wavelength range while remaining compatible with spacecraft limitations.
The second advance involves avalanche photodiode arrays. These detectors can register very small numbers of incoming photons while producing extremely low readout noise and nearly negligible dark current. Dark current is the unwanted electrical signal generated by a detector even when no light is present. Reducing it is essential when the real astronomical signal may consist of only a few photons collected over long observations.
Together, the optical components and low-noise detectors could allow a future instrument to cover wavelengths between approximately 1.1 and 2 microns in a single exposure. That range contains important molecular information connected to habitability and atmospheric chemistry. Capturing it simultaneously would make observations more efficient and reduce inconsistencies caused by measuring separate wavelength regions at different times. Efficiency will be critical because access to a major space observatory will be limited and highly competitive.
The proposed technology has already been used successfully in ground-based astronomy, particularly through instruments such as the Immersion Grating Infrared Spectrometer. Space, however, presents different operating conditions involving vacuum, radiation, thermal extremes and limited possibilities for repair. The researchers therefore recommend launching a smaller demonstration mission before incorporating the system into HWO. Such a mission could validate the optics, detectors and electronic architecture under real orbital conditions.
Funding remains uncertain. The Habitable Worlds Observatory is still in an early planning phase, and NASA must evaluate competing scientific priorities, technical risks and budget constraints. Adding high-resolution infrared spectroscopy would increase the mission’s capabilities but also its cost and complexity. Researchers must demonstrate that the scientific benefits justify including the instrument in the final design.
The proposal does not promise the immediate discovery of extraterrestrial organisms. Atmospheric gases can be produced by geological, chemical or biological processes, and apparently promising signals may have nonliving explanations. Scientists would need multiple measurements and detailed planetary context before interpreting any observation as a possible biosignature. Greater spectral resolution would improve the evidence, not eliminate uncertainty.
Its importance lies in making subtle planetary information more accessible. The difference between finding a faint atmospheric molecule and missing it may depend on the ability to separate individual spectral lines. A telescope capable of doing that could identify promising worlds, reject misleading signals and study planetary climates with unprecedented precision. The search for life may ultimately advance not through a single dramatic image, but through technology able to extract meaning from almost invisible light.
Science moves forward by learning to see less. / La ciencia avanza al aprender a ver lo imperceptible.