Listen: Dr Navid Constantinou in conversation with Stephen O’Doherty.
Scientists from Australia and the United States have helped to solve the mystery underlying Jupiter’s coloured bands in a new study on the interaction between atmospheres and magnetic fields. Jupiter is by far the largest planet in our solar system. Unlike Earth, Jupiter has no solid surface – it is a gaseous planet, consisting mostly of hydrogen and helium.
Several strong jet streams flow west to east in Jupiter’s atmosphere that are, in a way, similar to Earth’s jet streams. Clouds of ammonia at Jupiter’s outer atmosphere are carried along by these jet streams to form Jupiter’s coloured bands, which are shades white, red, orange, brown and yellow.
Secrets below Jupiter’s clouds
The fifth planet from the Sun, and the most massive in our solar system, Jupiter has a long history surprising scientists—all the way back to 1610 when Galileo Galilei found the first moons beyond Earth. That discovery changed the way we see the universe.
Dr Navid Constantinou from the Research School of Earth Sciences at The Australian National University (ANU), one of the researchers on the study, said that until recently little was known about what happened below Jupiter’s clouds.
“We know a lot about the jet streams in Earth’s atmosphere and the key role they play in the weather and climate, but we still have a lot to learn about Jupiter’s atmosphere,” he said.
“Scientists have long debated how deep the jet streams reach beneath the surfaces of Jupiter and other gas giants, and why they do not appear in the sun’s interior.”
98% of our solar system is the sun and the rest, 2%, half of it is Jupiter
Lessons from alien, distant world
On Open House Dr Constantinou explained there were good reasons for studying such an alien and distant world as Jupiter.
“One reason is because it is sure that the underlying laws of physics are the same if you are on Earth or on Jupiter. If you understand fluid dynamics and how the atmospheric dynamics work in Jupiter you can get intuition and understand how things work on earth as well. Another reason space scientists want to study Jupiter in particular is because Jupiter is very massive and it consists of more than half of the mass of our solar system if you take out the sun.” he says.
Jupiter is really, really HUGE
It is hard to imagine just how enormous Jupiter is, as an indication, eleven Earths could fit across Jupiter’s equator and if Earth were the size of a grape, Jupiter would be the size of a basketball.
“98% of our solar system is the sun and the rest, 2%, half of it is Jupiter. People think if we want to understand the history of how our solar system evolved we better first understand Jupiter. So that’s the motivation why people send spacecraft there to study Jupiter itself.” says Dr Constantinou.
Juno has a peek
Recent evidence from NASA’s spacecraft Juno indicates these jet streams reach as deep as 3,000 kilometres below Jupiter’s clouds. The photograph at the top of the page captures the intensity of the jets and vortices in Jupiter’s North North Temperate Belt.
It was taken by Juno on May 23, 2018 as Juno performed its 13th close flyby of Jupiter. At the time, the spacecraft was about 7,900 kilometers from the tops of the clouds of the gas giant planet.
The North North Temperate Belt is the prominent reddish-orange band left of center. It rotates in the same direction as the planet and is predominantly cyclonic, which in the northern hemisphere means its features spin in a counter-clockwise direction. Within the belt are two gray-colored anticyclones. Although the region as a whole appears chaotic, there is an alternating pattern of rotating, lighter-colored features on the zone’s north and south sides.
Infrared shows warmer, deeper emissions
Scientists think the large-scale dark regions are places where the clouds are deeper, based on infrared observations made at the same time by Juno’s JIRAM experiment and Earth-based supporting observations. Those observations show warmer, and thus deeper, thermal emission from these regions.
To the right of the bright zone, and farther north on the planet, Jupiter’s striking banded structure becomes less evident and a region of individual cyclones can be seen, interspersed with smaller, darker anticyclones.
First of all you see these marvellous bands. These bands turn out to be strong jet streams.
Atmosphere of Earth and other planets
Dr Constantinou’s background is in atmospherics and fluid dynamics which he says was a big factor in studying Jupiter.
“My main motivation is I want to understand how really how planetary that is, geophysical fluid dynamics works. By geophysical I mean earth and also the atmosphere on other planets.” he says.
Bands are jet streams
“The atmospheric flow on Jupiter turns out to be a bit simpler than the atmosphere flow on earth. You see, first of all, you see these marvellous bands. These bands turn out to be strong jet streams – strong air currents that flow in Jupiter’s atmosphere. In the boundary between each band there is a strong wind flow going either west to east or from east to west.”
Earth has two jet streams
“These jet streams are similar to the jet streams we have here on Earth. On Earth we have two jet streams in each hemisphere that flow about 10 kilometres up in the atmosphere. We cannot see them if we take a picture from space, because the clouds are not so thick and colourful as in Jupiter. In Jupiter you just see them immediately. The clouds in Jupiter they contain ammonia and other colourful substances like that. Each jet stream, depending on if it is from west to east or east to west, induces some up-whirling and down-whirling circulation.” Dr Constantinou explained.
It would be a very harsh place to visit. Let’s see if I am invited to write the trip advisor review.
What it says about the Sun
The theory is that the magnetic fields suppress some of that activity. Dr Constantinou explained that it also tells us something about the sun – another a ‘gas giant’.
“This is also applicable in the sun. In the sun, there was a theory put forward, more or less, ten years ago, and people have tried to do numerical simulations of the fluid flow in the presence of magnetic fields. They saw, indeed, that numerical simulations suggested when the magnetic fields are strong enough the jet streams are suppressed. That’s what we explain in the recent paper.”
We predict a threshold for the magnetic field when it’s stronger- when we expect suppression of the jets. We also discuss the physical process behind that; what is actually going on and how are the jets suppressed when you have magnetic fields.” says Dr Constantinou.
Animated gif of Jupiter’s Great Red Spot
A passion for Jupiter
Dr Constantinou says he just loves his work and even admits “I would like to visit there it would be a very harsh place to visit. Let’s see if I am invited to write the trip advisor review. I will let you know” he joked on Open House.
Jupiter’s Great Red Spot is a gigantic storm that’s about twice the size of Earth and has raged for over a century
Co-researcher Dr Jeffrey Parker from Lawrence Livermore National Laboratory in the United States said their theory showed that jet streams were suppressed by a strong magnetic field.
“The gas in the interior of Jupiter is magnetised, so we think our new theory explains why the jet streams go as deep as they do under the gas giant’s surface but don’t go any deeper,” said Dr Parker.
Jet streams and earth’s climate
The polar and subtropical jet streams in Earth’s atmosphere shape the climate, especially in the mid-latitudes such as in Australia, Europe and North America.
“Earth’s jet streams have a huge impact on the weather and climate by acting as a barrier and making it harder for air on either side of them to exchange properties such as heat, moisture and carbon,” said Dr Constantinou.
Jupiter is a lab for atmospheric flow
The jet streams on Earth are wavy and irregular, while they are much straighter on Jupiter.
“There are no continents and mountains below Jupiter’s atmosphere to obstruct the path of the jet streams,” Dr Parker said.
“This makes the jet streams on Jupiter simpler. By studying Jupiter, not only do we unravel the mysteries in the interior of the gas giant, but we can also use Jupiter as a laboratory for studying how atmospheric flows work in general.”
The research involved mathematical calculations for the instability that leads to jet streams when magnetic fields are present, as well as work comparing the theoretical predictions with results from previous computer simulations. The study, Magnetic Suppression of Zonal Flows on a Beta Plane is published in The Astrophysical Journal.
Jupiter is big in pop culture
The biggest planet in our solar system, Jupiter also has a large presence in pop culture, including many movies, TV shows, video games and comics. Jupiter was a notable destination in the Wachowski siblings’ science fiction spectacle Jupiter Ascending, while various Jovian moons provide settings for Cloud Atlas, Futurama, Power Rangers, and Halo, among many others. In Men in Black when Agent J—played by Will Smith—mentions he thought one of his childhood teachers was from Venus, Agent K—played by Tommy Lee Jones—replies that she is actually from one of Jupiter’s moons.
NASA has a wonderful interactive site on Jupiter with loads of facts and images.
Speaking of moons
In July this year NASA announced twelve new moons orbiting Jupiter have been found—11 “normal” outer moons, and one that they’re calling an “oddball.” This brings Jupiter’s total number of known moons to a whopping 79—the most of any planet in our Solar System. Jupiter has 53 named moons. The Others are awaiting official names. There are many interesting moons orbiting the planet, but the ones of most scientific interest are the first four moons discovered beyond Earth—the Galilean satellites.
The planet Jupiter’s four largest moons are called the Galilean satellites after Italian astronomer Galileo Galilei, who first observed them in 1610. The German astronomer Simon Marius claimed to have seen the moons around the same time, but he did not publish his observations and so Galileo is given the credit for their discovery. These large moons, named Io, Europa, Ganymede, and Callisto, are each distinctive worlds.
Main Photo Credit: NASA/JPL-Caltech/SwRI/JunoCam 2018-06-14 This image captures the intensity of the jets and vortices in Jupiter’s North North Temperate Belt.
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