Combination of visible light from Hubble Space telescope and infrared imagery (left) of Jupiter by the Gemini Observatory (right). This shows how darker, brighter areas in visible are infrared-bright, while warmer dark belts in IR are IR.
Combining infrared imagery (left half) from the Gemini Observatory with visible light (right), this shows how darker areas in visible are darker in infrared and warmer dark belts in IR-bright. Photo: Gemini: International Gemini Observatory/NOIRLab/NSF/AURA, M.H. Wong (UC Berkeley) et al. Acknowledgments: M. Zamani; Hubble: NASA/ESA/NOIRLab/NSF/AURA/M.H. Wong and I. de Pater (UC Berkeley) et al. Acknowledgments: M. Zamani
Juno, a Jupiter-divebombing spacecraft, has revealed new information about Jupiter's depths, including the size of the Great Red Spot, its stripes and the strange and regular cyclones that swarm at its poles.
Juno is a space mission's armored tank, built to withstand strong radiation from Jupiter's powerful magnetic fields. The electrically charged ions that have been blasted from its volcanic moon Io by Jupiter's magnetism are caught up and accelerated to high speeds, until they hit the atmosphere at its poles. The environment can fry any spacecraft that comes close to Jupiter.
Juno is close at hand: Juno's extremely elliptical orbit takes Juno as far as 2.7 million km, but then it descends to just 4,000 km above its cloud tops. It speeds past at 200,000km per hour.
Juno has several detectors that can probe Jupiter's innermost parts. Its main purpose is to find out what is going on there. The Microwave Radiometer (or MWR) is one of the main instruments. It can detect microwave radiation. This long wavelength light, which is emitted from gas located hundreds of kilometers below Jupiter's atmosphere and passes directly through the upper layers, is called "long wavelength light". MWR can detect ammonia and water deep below Jupiter's atmosphere and trace its movements.
Hubble captured Jupiter and Europa (upper left) in visible light on 25 Aug 2020. Credit: NASA and ESA.
Juno has passed Jupiter 37 times since arriving there in 2016. This includes several passes over the Great Red Spot. This anticyclonic system (high-pressure system) has been around for at least centuries. MWR data from a few years ago showed that the Spot was deep, up to 350 km below the cloud tops.
New results prove it extends to at least 500 km, which is incredible. Remember that the distance between the top and bottom of big storms is usually only a few kilometers.
Jupiter is a giant. It's 130,000km across, ten times as wide as Earth, and 1,000 times larger than Earth. There is plenty of room for the big.
Illustration of Jupiter's Great Red Spot size: Large enough to submerge the entire Earth in. Photo: JunoCam Image dаta: NASA/JPL-Caltech/SwRI/MSSS; JunoCam Image processing by Kevin M. Gill (CC BY); Earth Image: NASA
It's even more remarkable how this depth was calculated. Because the Spot's atmosphere has a different density to the surrounding atmosphere, the amount of gas it contains is also different. This causes Jupiter's gravity to change very subtly, and Juno will travel at a different speed as it passes the Spot. Engineers and scientists measured Juno's speed with an accuracy of 0.01 millimeters per sec It could also be used to measure its velocity changes. This was used to calculate the Spot's weight, which gave it its volume and depth. Whoa.
Combining infrared imagery (left half) from the Gemini Observatory with visible light (right), this shows how darker areas in visible are darker in infrared and warmer dark belts in IR-bright. Photo: Gemini: International Gemini Observatory/NOIRLab/NSF/AURA, M.H. Wong (UC Berkeley) et al. Acknowledgments: M. Zamani; Hubble: NASA/ESA/NOIRLab/NSF/AURA/M.H. Wong and I. de Pater (UC Berkeley) et al. Acknowledgments: M. Zamani
New results were also found using data from the MWR. Jupiter's visible light images show bright areas and dark belts. These are similar to jet winds that move through Jupiter's atmosphere in opposing directions. MWR data shows that the brightness of the belts and zones changes relative to visible light. Air near the cloud tops makes them appear brighter. Zones appear darker because they are cooler.
New MWR data shows that the gas becomes suddenly cooler as it goes deeper. Similar changes occur in the oceans of Earth. This must be due to the heat transport deep within the planet. As pressure rises, the gas will get warmer further down (deeper than MWR is able to see). The researchers also observed ammonia in the zones and belts moving in a circulating fashion, which is similar to Earth's Ferrel cells. These cells transport water to our planet's mid-latitudes, and can affect weather. These new data will allow scientists to better understand Jupiter's atmospheric motions.
Juno thermal infrared data from Jupiter's north Pole (brighter = warmter) shows eight cyclones circling around a central one. Credit: NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM Photo: NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM
Juno's orbit is unlike any other. It passes directly above both poles and can see them better than from Earth. Early results revealed that both poles were covered by vortices, which are large storms, that stretched over 1,000 kilometers. There are eight vortices at the north pole, which are arranged in two sets of four, each one slightly rotated with respect to the other. At the south pole, there are five, in a near perfect pentagon. It is one of the most bizarre planetary features that I have ever seen.
These vortices appear to be remarkably stable, according to the new MWR results. They jostle each other a little, but then they move away when they come across each other again. The mild oscillating motion is slow and steady. This suggests, as with the Red Spot storm, that the storms are very deep in the atmosphere.
Juno's south pole thermal infrared data shows five large cyclones around a central polar one. Credit: NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM Photo: NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM
Jupiter is quite different from Earth. This is partly due to the fact that it's much larger than Earth. Jupiter's atmosphere is mostly hydrogen and it's thousands of kilometers deep. The liquid ocean of hydrogen then merges into Jupiter's atmosphere, which becomes metallic. It acts in the same way as metals with electrons free to conduct electricity. We didn't know if it had one before Juno. Some models predicted it wouldn't have one, but others said it did. Juno observations confirmed that it does have one, sorta, but it is mushy, indistinct. It's a mashup of both, in a sense.
These are just a few of the many details, but they are only a small part of the story about how Jupiter functions on the inside. While some things can be done from Earth, it's impossible to fully understand the vast and strange world of Jupiter. Juno is, fortunately, right there.
