Cloudy Jupiter

For years, scientists believed that Jupiter’s clouds were made of ammonia ice.

It turns out they may have been wrong.

Instead, a collaborative study between professional and amateur astronomers recently found that they are likely formed of ammonium hydrosulfide mixed with smog.

Steven Hill, an amateur astronomer with a Ph.D in astrophysics and co-author of the study, was able to map the abundance of ammonia and cloud-top pressure in Jupiter’s atmosphere just by using a commercially available telescope and a few specially colored filters.

His observations suggest that Jupiter’s clouds are too deeply embedded within the planet’s warm atmosphere to be composed of ammonia ice.

Lead researcher Patrick Irwin applied Hill’s study method to observations of Jupiter captured by the Multi Unit Spectroscopic Explorer (MUSE) instrument at the European Southern Observatory’s Very Large Telescope (VLT) in Chile.

MUSE uses spectroscopy – a technique analyzing the light that passes through or reflects off a substance – to determine the light from Jupiter’s atmosphere, allowing scientists to detect the gases, map ammonia levels, and measure the height of the planet’s clouds.

Computer simulations of how light interacts with gases and clouds matched Hill’s findings and showed that the primary layer of Jupiter’s clouds had to be much deeper than previously thought.

The clouds are in a region where pressure and temperature are higher, meaning that pure ammonia ice can’t be present because the space is too warm for the condensation of ammonia to happen.

Previous analysis had hinted similar results but the findings were difficult to corroborate because they involved using extremely complex methods that only a few researchers worldwide could implement.

The amateurs’ method, however, led to similar findings that could be confirmed.

According to the researchers, in areas where moist, ammonia-rich air rises, the ammonia is broken down or mixed with photochemical products – chemicals created by sunlight-induced reactions – more quickly than ammonia ice can form.

The main cloud layer, therefore, may be composed of ammonium hydrosulfide mixed with photochemical, smoggy products, which are responsible for the red and brown colors seen in images of Jupiter.