Jupiter's Great Red Spot is perhaps its most iconic feature. It's a vast storm, a bloody-colored hurricane that is at least four centuries old, and larger in size than several Earths. It can be seen easily even in a small telescope, and is one of the most studied features in the solar system.
Yet for all that, it's still poorly understood. How has it lasted so long? What is going on inside of it? How did it form in the first place?
New observations using the Very Large Telescope (together with data from the Gemini, Subaru, and IRTF observatories) have taken us a step closer to finding the answers:
Cooooool. On top is an infrared view of the Spot (as well as its little brother, Oval BA, on the left) from the VLT taken in 2008, and on bottom, for comparison, is the same view from Hubble taken just days earlier. The VLT image was taken at a wavelength of 10.8 microns, about 14 times the wavelength our eye can see. Objects at just about the freezing point of water emit IR at that wavelength. On Jupiter, the atmosphere at a pressure about half of Earth's pressure at sea level emits at that temperature and wavelength.
What these images show is how Jupiter's atmosphere circulates up and down in the Spot. The core of the Spot, which appears red to our eye, is warm, and dark lanes are where the gas is being drawn down into Jupiter's depths. Because the center is warmer -- by just a few degrees -- it provides an upwelling in the middle of the Spot. This upwelling creates a weak clockwise flow of air, despite the storm's general counter-clockwise rotation.
More importantly, these observations link the color of the Spot to temperature, even if the exact mechanism for this link is unknown. But any clues we can find will help us understand this incredible hurricane bigger than some planets. Mind you, studying them on Jupiter gives us insight into how storms behave on Earth as well. Scientific observations thrive on diversity, on comparing one set of conditions to another, and seeing how the outcome changes.
Jupiter is vastly different than Earth, but by gazing at it we gaze back at ourselves. That's the way science works.