The detection, which was uniquely possible with Webb's Mid-Infrared Instrument, marks the first time silica (SiO2) particles have been spotted in an exoplanet atmosphere.
"We knew from Hubble observations that there must be aerosols - tiny particles making up clouds or haze - in WASP-17 b's atmosphere, but we didn't expect them to be made of quartz," said David Grant, a researcher at the University of Bristol in Britain and first author on a paper being published today in the Astrophysical Journal Letters.
Silicates make up the bulk of Earth, the Moon and other rocky objects in our solar system and are extremely common across the galaxy.
But the silicate grains previously detected in the atmospheres of exoplanets and brown dwarfs appear to be made of magnesium-rich silicates like olivine and pyroxene, not quartz alone - which is pure SiO2, according to NASA.
The result from the research team puts a new spin on our understanding of how exoplanet clouds form and evolve, said NASA.
"We fully expected to see magnesium silicates," said co-author Hannah Wakeford, also from the University of Bristol. "But what we're seeing instead are likely the building blocks of those, the tiny 'seed' particles needed to form the larger silicate grains we detect in cooler exoplanets and brown dwarfs."
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