Jupiter is not here to screw around.
Concurrent observations of the solar system’s mightiest planet by Hubble Space Telescope, the Gemini Observatory, and the Juno spacecraft show that Jupiter’s thunderstorms are ridiculously huge, towering skyward for 80 kilometers or more, powered by heat from below and water in the atmosphere. That’s five times taller than similar storm systems on Earth.
I technically live in the midwestern plains of the U.S., and I’ve seen some powerful and terrifying storms. Jupiter’s make these look like friendly breezes.
Juno has orbited Jupiter since July 2016. It’s on a long, elliptical orbit that takes it from several million kilometers out to so close to the planet that it almost skims the cloud tops, screaming past at 200,000 kilometers per hour. It’s equipped with a lot of different detectors, including one that senses radio waves emitted when lightning zaps in Jupiter’s atmosphere.
That happens a lot. A recent study showed Jupiter crackles with lightning from between 2,000 to 60,000 times per second. Per second. That means there must be a lot of storm cloud activity on the planet too, and that’s where Gemini and Hubble come in. They observed Jupiter at the same time Juno is on closest approach, to get the best possible observations of these storms.
Gemini North is an 8.1-meter behemoth in Hawaii and is sensitive to infrared light. Looking in thermal infrared (4.7 microns, a wavelength about five times longer than the reddest light our eyes can see) — essentially making a heat map of the planet — Gemini saw this:
Holy Jovian emissivity! That’s gorgeous.
It’s the highest-resolution image of Jupiter ever taken from Earth, with features as small as 400 km across visible (for comparison, the planet is 140,000 km across). They accomplished this through “lucky imaging,” taking a lot of short exposures (it helps that Jupiter is bright) to minimize the blurring that our own atmosphere produces. They can then pick the highest-quality images from the 350 or so taken to assemble into a mosaic that produces such a sharp map of the planet.
You can see the familiar banding, but it looks more like a jack-o-lantern in these colors. Bright features are warmer, and dark cooler. The interior of Jupiter is very hot, left over from its formation billions of years ago, and that heat leaks out where the atmosphere is clear. Where it’s dark it’s cloudy, and where it’s bright the air is clear.
Hubble, on the other hand, sees in visible light (as well as into the ultraviolet and infrared, but not as far in IR as Gemini). It sees sunlight reflecting off the clouds, so it sees the cloud tops. There’s haze as well in the air there, which is good at scattering ultraviolet light, so Hubble can detect that as well.
Along with Juno measuring the lightning, this gives scientists a three-dimensional view of the storm clouds! They can combine the power of these three machines to figure out how deep the clouds go, where they are creating lightning, and even the composition of the clouds.
What they found sounds familiar: Dry cool air sinks, while warm air laden with water vapor rises and makes clouds. This is pretty much how convection works in a cumulonimbus cloud on Earth, too. However, while these thunderclouds on Earth reach heights of 15 km from their base or so, Jupiter’s are 80 kilometers high. Yegads.
Convection like this is somewhat rare on Jupiter, but at different latitudes over the past few years wind conditions have been right to get them. Lightning is in part the result of liquid condensing in these rising and falling winds, and the only liquid known to exist at these atmospheric heights is water. This makes these clouds seem more Earth-like as well, except in their colossal scale.
Speaking of huge things, they also took a look at Jupiter’s Great Red Spot, a persistent vortex that has been spinning in Jupiter’s upper atmosphere for centuries. Juno has probed it deeply, and planetary scientists have learned a lot about it. Despite that, a longstanding mystery about it is that dark regions are seen inside the Spot, and it wasn’t known if they were dark clouds made of some unknown material, or clear spots in the air allowing us to peer deeper into the atmosphere where it’s darker.
The concurrent Gemini and Hubble observations have apparently solved this. Hubble sees the location of the dark spots clearly, and Gemini can sense the warmth coming from them. What they found, at least in this instance, is that the dark regions are warmer, consistent with them being clear patches in the air, gaps between the clouds allowing heat from within to leak upwards. This will help scientists better understand the powerful forces shaping this single storm that is bigger than worlds.
Observations like these are called synoptic, meaning in general “observing together.” It’s a powerful method of learning a lot more about an object or process, because the Universe likes to do things that emit different kinds of light at the same time. Between the radio flashes of lightning, the infrared emission from warmth, and the optical sunlight bouncing off the clouds, we can understand the mechanics of Jupiter’s immensely complex atmosphere, and see how all the pieces fit together.
Over a thousand Earths could fit inside Jupiter. It’s immense. There are a lot of pieces, and a lot to see.
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