NASA Finds Clouds Made of Sand in 'Fluffy' Exoplanet's Atmosphere

Using data from NASA's James Webb Space Telescope, astronomers have detected clouds made up of silicate, or sand, in the atmosphere of a nearby exoplanet, or planet outside our solar system.

WASP-107b—which lies 200 light-years from Earth, in the constellation Virgo—is a unique gaseous world that orbits a star a little cooler and less massive than our sun.

What makes it unusual is that it has a mass about the size of Neptune, but a size closer to that of Jupiter, whose diameter is nearly three times larger.

This, the team said, makes WASP-107b somewhat "fluffy" in comparison with the gas giants found in our Solar System, but also allows us to peer 50 times deeper into its atmosphere.

Analyzing Webb's data, the researchers found not only silicate clouds but also water and the toxic gas sulfur dioxide, all contained within a dynamic atmosphere in which material is vigorously circulated around—including via rain made from sand.

The study was undertaken by astrophysicist Leen Decin of KU Leuven in Belgium and her colleagues, using observations made by the Mid-Infrared Instrument on Webb, which the team credit with "revolutionizing" our study of exoplanets.

When it comes to WASP-107b, Decin told Newsweek, "there exists no analogue [……] in our own Solar System.

"In addition, we have seen that the chemical pathways taken to form specific molecules and solid sand particles are completely different from what we know here on Earth.

"It is only by opening up our mind, by exploring that terra incognita of extraterrestrial chemical processes, that we could understand what is happening in the atmosphere of this extreme planet."

The presence of the clouds so high up in WASP-107b's atmosphere presented something of a conundrum to the researchers.

Just as water freezes at low temperatures in Earth's atmosphere, silicate particles—what we might call sand—can freeze out to form clouds in the upper atmosphere of gaseous worlds, where temperatures reach 1,832 Fahrenheit (1,000 Celsius).

However, with WASP-107b's outer atmosphere only some 932 Fahrenheit (500 Celsius), scientists had expected the silicate clouds to form deeper in the atmosphere, where temperatures are substantially higher, and not in the outer layers.

Paper co-author Michiel Min—an astronomer at the University of Amsterdam—said in a statement: "The fact that we see these sand clouds high up in the atmosphere must mean that the sand rain droplets evaporate in deeper, very hot layers.

"The resulting silicate vapor is efficiently moved back up, where they recondense to form silicate clouds once more.

"This is very similar to the water vapor and cloud cycle on our own Earth, but with droplets made of sand."

The team's analysis also revealed that WASP-107b's atmosphere contains both water and sulfur dioxide—the gas that gives burnt matches their characteristic smell.

Scientists have previously predicted that this compound would be found around WASP-107b but this is the first time the gas has been detected there.

The researchers explained that the planet's fluffy nature is responsible for forming the sulfur dioxide.

Even though WASP-107b's host star is cool, and releases a relatively limited number of high-energy photons, they are still able to penetrate deep into the planet's atmosphere and drive sulfur dioxide-producing reactions.

With their initial study complete, the team are continuing to analyze exoplanets using data collected by the Webb telescope. Although this effort is ongoing, Decin concluded, "it is clear that many new surprises and new insights will follow!"

The full findings of the study were published in the journal Nature.