According to a new study, Jupiter's Great Red Spot (GRS) is growing taller even as the storm's perimeter continues to shrink. The GRS is a colossal swirling storm that has been raging continuously on Jupiter's cloud surface since its discovery in 1831, though its shape and size has altered dramatically in that time, and scientists aren't sure how much longer it will persevere.
Jupiter is the largest planet in our solar system, with a volume over 1,300 times that of the Earth. Its surface is a mesmerizingly complex and chaotic swirl of clouds, pockmarked with giant storms, the most massive of which is known as the Great Red Spot.
When it was first discovered, the GRS could have easily swallowed three full Earth-sized planets within its expanse. However, Jupiter's most iconic feature has been observed to be shrinking for decades, and now covers a region only a little larger than the disk of one Earth-sized world. The future of this grantedly still massive storm is in question, with scientists unsure as to whether the GRS is likely to stabilize, or disappear entirely.
The new research suggests that as the storm shrinks, it is also growing taller. The international team of scientists involved in the research drew on a mixture of historical archives and data collected by NASA spacecraft, going back as early as the Voyager 1 & 2 probes.
The archival information allowed the team to observe long-term changes in the shape, color, size and drift of the GRS. High-spatial resolution spacecraft data, including a series of annual observations of the gas giant carried out by the Hubble Space Telescope, helped the team to track the constantly changing spectral characteristics and internal structure of the monster storm.
The historical observations revealed that, with the exception of a brief growth period in the 1920s, that the GRS has been shrinking in length since 1878.
It had been expected that, as the storm's perimeter contracted, the internal winds would spin faster. The new analysis of the Jovian data suggests that this is not the case, and that the shrinking has instead caused the storm to stretch higher into Jupiter's atmosphere.
Alongside the literal heightening of the storm, the paper notes that the GRS is drifting westward – against the easterly rotation of the planet – at a significantly faster rate than had previously been the case. The findings challenge the previous assumption that the speed of travel of the storm was relatively uniform.
The team also noted that, since 2014, the spot has been steadily becoming more intensely orange-colored. This could be because more of the chemicals that give the storm its color are being drawn up through the atmosphere towards the upper cloud layers. Once there, they are subjected to higher levels of sunlight, which cause them to take on a darker hue.
NASA's Juno spacecraft is currently in orbit around Jupiter, braving the fierce radiation belts that surround the planet on a mission to unravel some of the mysteries that continue to pervade the enigmatic gas giant, and its dynamic and ever-changing GRS.
The study has been published in the Astronomical Journal.
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