NASA’s Pandora Begins Studying at Least 20 Exoplanet Atmospheres

A planet crosses the face of a distant star, and the starlight reaching Earth carries a faint trace of its atmosphere. NASA’s Pandora mission has begun making those observations, targeting at least 20 exoplanets — worlds outside our solar system — and the stars they orbit.

The problem is that the signal does not come from the planet alone. During a transit, some light passes through the exoplanet’s atmosphere, where molecules can imprint chemical fingerprints at characteristic wavelengths. But the host star also has brighter regions called faculae and cooler, darker areas similar to sunspots; those features change as the star rotates and can distort the atmospheric signal, including the search for water.

Pandora is designed to watch both sides of the problem at once. Its telescope, about 18 inches (45 centimeters) in diameter, will measure starlight in visible and near-infrared light while also recording the planet’s near-infrared spectrum during a transit. Over its year-long primary mission, NASA plans to observe each target 10 times, with every observation covering 24 hours and including a transit.

And so what, concretely? Astronomers should get a cleaner way to distinguish a planet’s chemistry from misleading changes on its star. That matters first for the interpretation of data from NASA’s James Webb Space Telescope, whose observing time cannot regularly support such extended looks, and later for observatories searching for potentially habitable worlds. Pandora’s near-infrared detector was originally developed as a spare for Webb.

The spacecraft is healthy and its instruments are performing as expected, NASA says. Elisa Quintana of NASA’s Goddard Space Flight Center leads the mission, with engineering and project management from Lawrence Livermore National Laboratory. The measurements will be valuable, but Pandora has only now entered science operations; the results still have to come from the planned observing campaign.