What Lies Beneath Jupiter’s Great Red Spot?

A: A volcano is an unlikely explanation for the mysterious red storm observed on the surface of Jupiter since the early 19th century. The planet has been found to be mostly gas, lacking a defined crust to rupture in an Earth-style volcanic eruption that would release hot materials from the interior of the planet.

The spot remains a mystery, and it is not even certain that the storm reported by scientists in 1831 is the same one seen now. The exact nature of the chemical reactions that produce its red-orange color is also not known.

The latest observations by the Juno spacecraft, combined with historical records, show significant changes in the size, shape and motion of the Great Red Spot. It has shrunk in diameter in recent decades, NASA scientists reported in 2017 in Astronomical Journal, but has increased in height and depth, with its hot, swirling gases reaching at least 200 miles below the surface. The spot has recently started to drift westward at a faster rate than ever before.

It has also become brighter, and its color has become more intensely orange since 2014, possibly because it is exposed to more ultraviolet radiation at higher altitudes.