Water vapor and sand clouds detected in atmosphere of ‘fluffy’ planet

By Stephen Beech via SWNS

Water vapor and sand clouds have been detected in the atmosphere of a nearby planet.

A team of European astronomers used recent observations made with the James Webb Space Telescope (JWST) to study the atmosphere of the exoplanet WASP-107b.

Peering deep into the "fluffy" atmosphere of WASP-107b they discovered not only water vapor and sulfur dioxide but even silicate sand clouds.

The particles reside within a "dynamic" atmosphere, say scientists.

Astronomers worldwide are harnessing the advanced capabilities of the Mid-Infrared Instrument (MIRI) aboard the JWST to conduct ground-breaking observations of exoplanets – those orbiting stars other than our own sun.

WASP-107b is a "unique" gaseous exoplanet that orbits a star slightly cooler and less massive than our Sun.

The mass of the planet is similar to that of Neptune.

But it is much larger than Neptune, almost approaching the size of Jupiter.

Scientists say that characteristic renders WASP-107b rather "fluffy" when compared to the gas giant planets within our solar system.

The fluffiness of the exoplanet enables astronomers to look roughly 50 times deeper into its atmosphere compared to the depth of exploration achieved for a solar-system giant like Jupiter.

Their findings, published in the journal Nature, reveal the presence of water vapor, sulfur dioxide (SO2), and silicate clouds, but there was no trace of the greenhouse gas methane (CH4).

Scientists say the absence of methane hints at a potentially warm interior, offering a "tantalizing glimpse" into the movement of heat energy in the planet’s atmosphere.

They said the discovery of sulfur dioxide -known for the odor of burnt matches - was a major surprise.

Even though its host star emits a relatively small fraction of high-energy photons due to its cooler nature, the photons can reach deep into the planet’s atmosphere. That enables the chemical reactions required to produce sulfur dioxide to occur.

The team explained that high-altitude clouds partially obscure the water vapor and sulfur dioxide in the atmosphere.

While clouds have been inferred on other exoplanets, it marks the first instance where astronomers can definitively identify their chemical composition.

The astronomers said the clouds consist of small silicate particles, a familiar substance for humans found in many parts of the world as the primary constituent of sand.

Study lead author Prof. Leen Decin, of KU Leuven in Belgium, said: "JWST is revolutionizing exoplanet characterization, providing unprecedented insights at remarkable speed.

"The discovery of clouds of sand, water, and sulfur dioxide on this fluffy exoplanet by JWST's MIRI instrument is a pivotal milestone.

"It reshapes our understanding of planetary formation and evolution, shedding new light on our own Solar System."

He said that in contrast to Earth’s atmosphere, where water freezes at low temperatures, in gaseous planets reaching temperatures around 1000 degrees Celsius, silicate particles can freeze out to form clouds.

But in the case of WASP-107b with a temperature of around 500 degrees Celsius in the outer atmosphere, traditional models predicted that the silicate clouds should be forming deeper within the atmosphere, where temperatures are substantially higher.

Co-lead author Dr. Michiel Min said: "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 and 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 teams said that the continuous cycle of sublimation and condensation through vertical transport is responsible for the enduring presence of sand clouds in WASP-107b's atmosphere.

Co-lead author Dr. Achrène Dyrek, of CEA Paris, said: “JWST enables a deep atmospheric characterization of an exoplanet that does not have any counterpart in our Solar System, we are unraveling new worlds!”

Instrument specialist Dr. Bart Vandenbussche, also of KU Leuven, added: "With colleagues across Europe and the United States we have been building and testing the MIRI instrument for almost 20 years.

"It is rewarding to see our instrument unravel the atmosphere of this intriguing exoplanet."