TechUsing ESPRESSO to unlock Jupiter's secrets. New ways to study gas giants' winds

Using ESPRESSO to unlock Jupiter's secrets. New ways to study gas giants' winds

Jupiter photographed by the Juno probe
Jupiter photographed by the Juno probe
Images source: © Caltech, MSSS, SwRI | evin M. Gill
10:43 AM EST, December 29, 2023

Over 5,000 confirmed exoplanets have been discovered by astronomers worldwide. According to scientists at the University of Lisbon, initial explorations were centered on the discovery of gas giants. These celestial bodies share similarities and stark contrasts with planets like Jupiter and Saturn.

Exploring Jupiter's atmosphere

Technological advancements and tools such as ESPRESSO have made it possible for scientists to study the atmospheres of distant, extrasolar planets. Yet, many enigmas about the atmospheres of planets within our solar system remain. For the first time in history, Lisbon-based researchers have tapped into the potential of the ESPRESSO instrument to explore Jupiter's atmosphere. This spectrograph is integral to the Very Large Telescope (VLT) the European Southern Observatory owns.

Using ESPRESSO, scientists can measure Jupiter's wind speeds by analyzing the sunlight's reflection, which varies based on these speeds. The Doppler effect, a phenomenon previously leveraged with other spectrographs to study Venus, was instrumental to this endeavor.

"Jupiter's visible atmospheric layer, the clouds as seen from Earth, consists of ammonia, ammonium hydrosulfide, and water, giving the planet its characteristic red bands," explains Pedro Machado, the author of a paper published in the Universe magazine (

"Frozen ammonia constitutes the upper cloud layers in the pressure zone ranging from 0.6 to 0.9 bar. Water clouds, conversely, form in the densest, lowest strata and significantly influence atmospheric dynamics," he adds.

Through ESPRESSO, researchers have accurately measured wind speeds on Jupiter, which range from 37 to 266 miles per second.

However, the precision of the telescope presented specific challenges. "One of the greatest difficulties was navigating the planetary disk, i.e., accurately determining where we were observing. It resulted from the incredibly high resolution of the VLT," explains the planetologist.

"We were achieving wind speed measurements with accuracy up to a few meters per second. Meanwhile, at the equator, Jupiter rotates at over 6 miles per second. Furthermore, due to its gaseous nature, unlike a rocky planet, rotation speed varies based on geographical breadth," the specialist points out.

The researchers corroborated their results with previously collected data acquired primarily via space-operating instruments.

New insights from further observations using this novel technique will allow analysis of how Jupiter's winds fluctuate over time. This will create a comprehensive model of the planet's atmospheric circulation.

Methodologies similar to the one used for studying Jupiter are also intended to examine other gas giants in our solar system, beginning with Saturn.

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