This wondrous image of Jupiter's south pole shows the arrangement of cyclones that is unique in our Solar System: five circumpolar cyclones perfectly arranged around a single polar cyclone. Image: NASA/SWRI/JPL/ASI/INAF/IAPS
When the Juno spacecraft arrived at Jupiter in July 2016, it quickly got to work. Among the multitude of stunning images of the planet were our first ever images of Jupiter’s poles. And what we saw there was a huge surprise: geometric arrangements of cyclones in persistent patterns.
Jupiter’s polar regions have always been a mystery to Earth-bound observers. The planet isn’t tilted much, which means the poles are always tantalizingly out of view. Other spacecraft visiting Jupiter have focused on the equatorial regions, but Juno’s circumpolar orbit is giving us good, close-up views of Jupiter’s poles.
“They are extraordinarily stable arrangements of such chaotic elements. We’d never seen anything like it.” – Morgan O’Neill, University of Chicago
Juno has a whole suite of instruments designed to unlock some of the mysteries surrounding Jupiter, including an infrared imager and a visible light camera. The polar regions are a particular focus for the mission, and astronomers were looking forward to their first views of Jupiter’s hidden poles. They were not disappointed when they got them.
Each of Jupiter’s poles is a geometric array of large cyclones arranged in persistent, polygonal patterns. At the north pole, eight storms are arranged around a single polar cyclone. In the south, one storm is encircled by five others.
Jupiter’s north pole is an arrangement of 8 cyclones around one central cyclone. Image: NASA/SWRI/JPL/ASI/INAF/IAPS
This was a stunning discovery, and quickly led to questions around the why and the how of these storm arrangements. Jupiter’s atmosphere is dominated by storm activity, including the well-known horizontal storm bands in the equatorial regions, and the famous Great Red Spot. But these almost artful arrangements of polar storms were something else.
The persistent arrangement of the storms is a puzzle. Our current understanding tells us that the storms should drift around and merge, but these storms do neither. They just turn in place.
A new paper published in Nature is looking deeper into these peculiar arrangements of storms. The paper is by scientists from an international group of institutions including the University of Chicago. It’s one of four papers dedicated to new observations from the Juno spacecraft.
One of the paper’s co-authors is Morgan O’Neill, a University of Chicago postdoctoral scholar. Remarking on the storms, she had this to say: “They are extraordinarily stable arrangements of such chaotic elements. We’d never seen anything like it.”
This image from Juno’s JunoCam captured the south pole in visible light only. It’s a puzzle why the north and south poles are so similar, yet have a different number of cyclones. Image: NASA/JPL-Caltech/SwRI/MSSS/Betsy Asher Hall/Gervasio Robles
The strange geometrical arrangement of Jupiter’s polar storms reminded O’Neill of something from the library of strange physical phenomena only observed under laboratory conditions. Back in the ’90s, scientists had used electrons to simulate a frictionless, turbulent 2-D fluid as it cools. In those conditions, they observed similar behaviour. Rather than merging like expected, small vortices clumped together and formed equally spaced arrays around a center. They called these arrays “vortex crystals.”
This could help explain what’s happening at Jupiter’s poles, but it’s too soon to be certain. “The next step is: Can you create a model that builds a virtual planet and predicts these flows?” O’Neill said. That’ll be the next step in understanding the phenomenon.
Maybe it’s not surprising that these delicate-looking storms at the poles are so persistent. After all, the Great Red Spot on Jupiter has been visible for over 200 years. Maybe Jupiter is just huge and stable.
But the polar cyclones still require an explanation. And whatever that explanation is, understanding what’s happening on Jupiter will help us understand other planets better.
This artist's conception illustrates the brown dwarf named 2MASSJ22282889-431026, observed by NASA's Hubble and Spitzer space telescopes. Brown dwarfs are more massive and hotter than planets but lack the mass required to become stars.
Image credit: NASA
When is a Brown Dwarf star not a star at all, but only a mere Gas Giant? And when is a Gas Giant not a planet, but a celestial object more akin to a Brown Dwarf? These questions have bugged astronomers for years, and they go to the heart of a new definition for the large celestial bodies that populate solar systems.
An astronomer at Johns Hopkins University thinks he has a better way of classifying these objects, and it’s not based only on mass, but on the company the objects keep, and how the objects formed. In a paper published in the Astrophysical Journal, Kevin Schlaufman made his case for a new system of classification that could helps us all get past some of the arguments about which object is a gas giant planet or a brown dwarf. Mass is the easy-to-understand part of this new definition, but it’s not the only factor. How the object formed is also key.
In general, the less massive a star, the cooler it is. Though stars smaller than our Sun can still sustain heat-producing fusion reactions, protostars that are too small cannot. These “failed” stars are commonly known as brown dwarfs, and a new definition puts their range from between 10-75 times the mass of Jupiter. This artist’s concept compares the size of a brown dwarf to that of Earth, Jupiter, a low-mass star, and the Sun. (Credit: NASA/JPL-Caltech/UCB).
Schlaufman is an assistant professor in the Johns Hopkins Department of Physics and Astronomy. He has set a limit for what we should call a planet, and that limit is between 4 and 10 times the mass of our Solar System’s biggest planet, Jupiter. Above that, you’ve got yourself a Brown Dwarf star. (Brown Dwarfs are also called sub-stellar objects, or failed stars, because they never grew massive enough to become stars.)
“An upper boundary on the masses of planets is one of the most prominent details that was missing.” – Kevin Schlaufman, Johns Hopkins University, Dept. of Physics and Astronomy.
Improvements in observing other solar systems have led to this new definition. Where previously we only had our own Solar System as reference, we now can observe other solar systems with increasing effectiveness. Schlaufman observed 146 solar systems, and that allowed him to fill in some of the blanks in our understanding of brown dwarf and planet formation.
An image of Jupiter showing its storm systems. According to a new definition, Jupiter would be considered a brown dwarf if it had grown to over 10 times its mass when it was formed. Image: Gemini
“While we think we know how planets form in a big picture sense, there’s still a lot of detail we need to fill in,” Schlaufman said. “An upper boundary on the masses of planets is one of the most prominent details that was missing.”
Let’s back up a bit and look at how Brown Dwarfs and Gas Giants are related.
Solar systems are formed from clouds of gas and dust. In the early days of a solar system, one or more stars are formed out of this cloud by gravitational collapse. They ignite with fusion and become the stars we see everywhere in the Universe. The leftover gas and dust forms into planets, or brown dwarfs. This is a simplified version of solar system formation, but it serves our purposes.
In our own Solar System, only a single star formed: the Sun. The gas giants Jupiter and Saturn gobbled up most of the rest of the material. Jupiter gobbled up the lion’s share, making it the largest planet. But what if conditions had been different and Jupiter had kept growing? According to Schlaufman, if it had kept growing to over 10 times the size it is now, it would have become a brown dwarf. But that’s not where the new definition ends.
Metallicity and Chemical Makeup
Mass is only part of it. What’s really behind his new classification is the way in which the object formed. This involves the concept of metallicity in stars.
Stars have a metallicity content. In astrophysics, this means the fraction of a star’s mass that is not hydrogen or helium. So any element from lithium on down is considered a metal. These metals are what rocky planets form from. The early Universe had only hydrogen and helium, and almost insignificant amounts of the next two elements, lithium and beryllium. So the first stars had no metallicity, or almost none.
This is an image of M80, an ancient globular cluster of stars. Since these stars formed in the early universe, their metallicity content is very low. This means that gas giants like Jupiter would be rare or non-existent here, while brown dwarfs are likely plentiful. Image: By NASA, The Hubble Heritage Team, STScI, AURA – Great Images in NASA Description, Public Domain, https://commons.wikimedia.org/w/index.php?curid=6449278
But now, 13.5 billion years after the Big Bang, younger stars like our Sun have more metal in them. That’s because generations of stars have lived and died, and created the metals taken up in subsequent star formation. Our own Sun was formed about 5 billion years ago, and it has the metallicity we expect from a star with its birthdate. It’s still overwhelmingly made of hydrogen and helium, but about 2% of its mass is made of other elements, mostly oxygen, carbon, neon, and iron.
This is where Schlaufman’s study comes in. According to him, we can distinguish between gas giants like Jupiter, and brown dwarfs, by the nature of the star they orbit. The types of planets that form around stars mirror the metallicity of the star itself. Gas giants like Jupiter are usually found orbiting stars with metallicity equal to or greater than our Sun. But brown dwarfs aren’t picky; they form around almost any star. Why?
Brown Dwarfs and Planets Form Differently
Planets like Jupiter are formed by accretion. A rocky core forms, then gas collects around it. Once the process is done, you have a gas giant. For this to happen, you need metals. If metals are present for these rocky cores to form, their presence will be reflected in the metallicity of the host star.
But brown dwarfs aren’t formed by accretion like planets are. They’re formed the same way stars are; by gravitational collapse. They don’t form from an initial rocky core, so metallicity isn’t a factor.
This brings us back to Kevin Schlaufman’s study. He wanted to find out the mass at which point an object doesn’t care about the metallicity of the star they orbit. He concluded that objects above 10 times the mass of Jupiter don’t care if the star has rocky elements, because they don’t form from rocky cores. Hence, they’re not planets akin to Jupiter; they’re brown dwarfs that formed by gravitational collapse.
What Does It Matter What We Call Them?
Let’s look at the Pluto controversy to understand why names are important.
The struggle to accurately classify all the objects we see out there in space is ongoing. Who can forget the plight of poor Pluto? In 2006, the International Astronomical Union (IAU) demoted Pluto, and stripped it of its long-standing status as a planet. Why?
Because the new definition of what a planet is relied on these three criteria:
a planet is in orbit around a star.
a planet must have sufficient mass to assume a hydrostatic equilibrium (a nearly round shape.)
a planet has cleared the neighbourhood around its orbit
The more we looked at Pluto with better telescopes, the more we realized that it did not meet the third criteria, so it was demoted to Dwarf Planet. Sorry Pluto.
Pluto was re-classified as a dwarf planet based on our growing understanding of its nature. Will Schlaufman’s new study help us more accurately classify gas giants and brown dwarfs? NASA’s New Horizons spacecraft captured this high-resolution enhanced color view of Pluto on July 14, 2015. Credit: NASA/JHUAPL/SwRI
Our naming conventions for astronomical objects are important, because they help people understand how everything fits together. But sometimes the debate over names can get tiresome. (The Pluto debate is starting to wear out its welcome, which is why some suggest we just call them all “worlds.”)
Though the Pluto debate is getting tiresome, it’s still important. We need some way of understanding what makes objects different, and names that reflect that difference. And the names have to reflect something fundamental about the objects in question. Should Pluto really be considered the same type of object as Jupiter? Are both really planets in the same sense? The IAU says no.
The same principle holds true with brown dwarfs and gas giants. Giving them names based solely on their mass doesn’t really tell us much. Schlaufman aims to change that.
His new definition makes sense because it relies on how and where these objects form, not simply their size. But not everyone will agree, of course.
A ring of cyclones swirls around Jupiter's south pole. Credit: NASA/JPL-Caltech/SwRI/MSSS/Betsy Asher Hall/Gervasio Robles
In addition to being the largest and most massive planet in our Solar system, Jupiter is also one of its more mysterious bodies. This is certainly apparent when it comes to Jupiter’s powerful auroras, which are similar in some ways to those on Earth. In recent years, astronomers have sought to study patterns in Jupiter’s atmosphere and magnetosphere to explain how aurora activity on this planet works..
For instance, an international team led by researchers from University College London recently combined data from the Juno probe with X-ray observations to discern something interesting about Jupiter’s northern and southern auroras. According to their study, which was published in the current issue of the scientific journal Nature – Jupiter’s intense, Jupiter’s X-ray auroras have been found to pulsate independently of each other.
Jupiter has spectacular aurora, such as this view captured by the Hubble Space Telescope. Credit: NASA, ESA, and J. Nichols (University of Leicester)
As already noted, Jupiter’s auroras are somewhat similar to Earth’s, in that they are also the result of charged particles from the Sun (aka. “solar wind”) interacting with Jupiter’s magnetic field. Because of the way Jupiter and Earth’s magnetic fields are structured, these particles are channeled to the northern and southern polar regions, where they become ionized in the atmosphere. This results in a beautiful light display that can be seen from space.
In the past, auroras have been spotted around Jupiter’s poles by NASA’s Chandra X-ray Observatory and by the Hubble Space Telescope. Investigating this phenomena and the mechanisms behind it has also been one of the goals of the Juno mission, which is currently in an ideal position to study Jupiter’s poles. With every orbit the probe makes, it passes from one of Jupiter’s poles to the other – a maneuver known as a perijove.
For the sake of their study, Dr. Dunn and his team were forced to consult data from the ESA’s XMM-Newton and NASA’s Chandra X-ray observatories. This is due to the fact that while it has already acquired magnificent images and data on Jupiter’s atmosphere, the Juno probe does not have an X-ray instrument aboard. Once they examined the X-ray data, Dr. Dunn and his team noticed a difference between Jupiter’s northern and southern auroras.
Whereas the X-ray emissions at the north pole were erratic, increasing and decreasing in brightness, the ones at the south pole consistently pulsed once every 11 minutes. Basically, the auroras happened independently of each other, which is different from how auroras on Earth behave – i.e. mirroring each other in terms of their activity. As Dr. Dunn explained in a recent UCL press release:
“We didn’t expect to see Jupiter’s X-ray hot spots pulsing independently as we thought their activity would be coordinated through the planet’s magnetic field. We need to study this further to develop ideas for how Jupiter produces its X-ray aurora and NASA’s Juno mission is really important for this.”
The X-ray observations were conducted between May and June of 2016 and March of 2017. Using these, the team produced maps of Jupiter’s X-ray emissions and identified hot spots at each pole. The hot spots cover an area that is larger than the surface area of Earth. By studying them, Dr. Dunn and his colleagues were able to identify patterns of behavior which indicated that they behaved differently from each other.
Naturally, the team was left wondering what could account for this. One possibility they suggest is that Jupiter’s magnetic field lines vibrate, producing waves that carry charged particles towards the poles. The speed and direction of these particles could be subject to change over time, causing them to eventually collide with Jupiter’s atmosphere and generate X-ray pulses.
As Dr Licia Ray, a physicist from Lancaster University and a co-author on the paper, explained:
“The behavior of Jupiter’s X-ray hot spots raises important questions about what processes produce these auroras. We know that a combination of solar wind ions and ions of Oxygen and Sulfur, originally from volcanic explosions from Jupiter’s moon, Io, are involved. However, their relative importance in producing the X-ray emissions is unclear.”
And as Graziella Branduardi-Raymont- a professor from UCL’s Space & Climate Physics department and another co-author on the study – indicated, this research owes its existence to multiple missions. However, it was the perfectly-timed nature of the Juno mission, which has been in operation around Jupiter since July 5th, 2016, that made this study possible.
Composite images from the Chandra X-Ray Observatory and the Hubble Space Telescope show the hyper-energetic x-ray auroras at Jupiter. Credit: X-ray: NASA/CXC/UCL/STScI/W.Dunn et al.
“What I find particularly captivating in these observations, especially at the time when Juno is making measurements in situ, is the fact that we are able to see both of Jupiter’s poles at once, a rare opportunity that last occurred ten years ago,” he said. “Comparing the behaviours at the two poles allows us to learn much more of the complex magnetic interactions going on in the planet’s environment.”
Looking ahead, Dr. Dunn and his team hope to combine X-ray data from XMM-Newton and Chandra with data collected by Juno in order to gain a better understanding of how X-ray auroras are produced. The team also hopes to keep tracking the activity of Jupiter’s poles for the next two years using X-ray data in conjunction with Juno. In the end, they hope to see if these auroras are commonplace or an unusual event.
“If we can start to connect the X-ray signatures with the physical processes that produce them, then we can use those signatures to understand other bodies across the Universe such as brown dwarfs, exoplanets or maybe even neutron stars,” said Dr. Dunn. “It is a very powerful and important step towards understanding X-rays throughout the Universe and one that we only have while Juno is conducting measurements simultaneously with Chandra and XMM-Newton.”
In the coming decade, the ESA’s proposed JUpiter ICy moons Explorer (JUICE) probe is also expected to provide valuable information on Jupiter’s atmosphere and magnetosphere. Once it arrives in the Jovian system in 2029, it too will observe the planet’s auroras, mainly so that it can study the effect these have on the Galilean Moons (Io, Europa, Ganymede and Callisto).
A ring of cyclones swirls around Jupiter's south pole. Credit: NASA/JPL-Caltech/SwRI/MSSS/Betsy Asher Hall/Gervasio Robles
Since it established orbit around Jupiter in July of 2016, the Juno mission has been sending back vital information about the gas giant’s atmosphere, magnetic field and weather patterns. With every passing orbit – known as perijoves, which take place every 53 days – the probe has revealed more interesting things about Jupiter, which scientists will rely on to learn more about its formation and evolution.
During its latest pass, the probe managed to provide the most detailed look to date of the planet’s interior. In so doing, it learned that Jupiter’s powerful magnetic field is askew, with different patterns in it’s northern and southern hemispheres. These findings were shared on Wednesday. Oct. 18th, at the 48th Meeting of the American Astronomical Society’s Division of Planetary Sciencejs in Provo, Utah.
Ever since astronomers began observing Jupiter with powerful telescopes, they have been aware of its swirling, banded appearance. These colorful stripes of orange, brown and white are the result of Jupiter’s atmospheric composition, which is largely made up of hydrogen and helium but also contains ammonia crystals and compounds that change color when exposed to sunlight (aka. chromofores).
Illustration of NASA’s Juno spacecraft firing its main engine to slow down and go into orbit around Jupiter. Credit: NASA/Lockheed Martin
Until now, researchers have been unclear as to whether or not these bands are confined to a shallow layer of the atmosphere or reach deep into the interior of the planet. Answering this question is one of the main goals of the Juno mission, which has been studying Jupiter’s magnetic field to see how it’s interior atmosphere works. Based on the latest results, the Juno team has concluded that hydrogen-rich gas is flowing asymmetrically deep in the planet.
Another interesting find was that Jupiter’s gravity field varies with depth, which indicated that material is flowing as far down as 3,000 km (1,864 mi). Combined with information obtained during previous perijoves, this latest data suggests that Jupiter’s core is small and poorly defined. This flies in the face of previous models of Jupiter, which held that the outer layers are gaseous while the interior ones are made up of metallic hydrogen and a rocky core.
As Tristan Guillot – a planetary scientist at the Observatory of the Côte d’Azur in Nice, France, and a co-author on the study – indicated during the meeting, “This is something that was not expected. We were not sure at all whether we would be able to see that… It’s clear that giant planets have a lot of secrets.”
This artist’s illustration shows Juno’s Microwave Radiometer observing deep into Jupiter’s atmosphere. The image shows real data from the 6 MWR channels, arranged by wavelength. Credit: NASA/SwRI/JPL
But of course, more passes and data are needed in order to pinpoint how strong the flow of gases are at various depths, which could resolve the question of how Jupiter’s interior is structured. In the meantime, the Juno scientists are pouring over the probe’s gravity data hoping to see what else it can teach them. For instance, they also want to know how far the Great Red Spot extends into the amotpshere.
This anticyclonic storm, which was first spotted in the 17th century, is Jupiter’s most famous feature. In addition to being large enough to swallow Earth whole – measuring some 16,000 kilometers (10,000 miles) in diameter – wind speeds can reach up to 120 meters per second (432 km/h; 286 mph) at its edges. Already the JunoCam has snapped some very impressive pictures of this storm, and other data has indicated that the storm could run deep.
In fact, on July 10th, 2017, the Juno probe passed withing 9,000 km (5,600 mi) of the Great Red Spot, which took place during its sixth orbit (perijove six) of Jupiter. With it’s suite of eight scientific instruments directed at the storm, the probe obtained readings that indicated that the Great Red Spot could also extend hundreds of kilometers into the interior, or possibly even deeper.
As David Stevenson, a planetary scientist at the California Institute of Technology and a co-author on the study, said during the meeting, “It’s not yet clear that it is so deep it will show up in gravity data. But we’re trying”.
Jupiter’s Great Red Spot, as imaged by the Juno spacecraft’s JunoCam at a distance of just 9,000 km (5,600 mi) from the atmosphere. Credit : NASA/SwRI/MSSS/TSmith
Other big surprises which Juno has revealed since it entered orbit around Jupiter include the clusters of cyclones located at each pole. These were visible to the probe’s instruments in both the visible and infrared wavelengths as it made its first maneuver around the planet, passing from pole to pole. Since Juno is the first space probe in history to orbit the planet this way, these storms were previously unknown to scientists.
In total, Juno spotted eight cyclonic storms around the north pole and five around the south pole. Scientists were especially surprised to see these, since computer modelling suggests that such small storms would not be stable around the poles due to the planet’s swirling polar winds. The answer to this, as indicated during the presentation, may have to do with a concept known as vortex crystals.
As Fachreddin Tabataba-Vakili – a planetary scientist at NASA’s Jet Propulsion Laboratory and a co-author on the study – explained, such crystals are created when small vortices form and persist as the material in which they are embedded continues to flow. This phenomenon has been seen on Earth in the form of rotating superfluids, and Jupiter’s swirling poles may possess similar dynamics.
In the short time that Juno has been operating around Jupiter, it has revealed much about the planet’s atmosphere, interior, magnetic field and internal dynamics. Long after the mission is complete – which will take place in February of 2018 when the probe is crashed into Jupiter’s atmosphere – scientists are likely to be sifting through all the data it obtained, hoping to solve any remaining mysteries from the Solar System’s largest and most massive planet.
Between the orbits of Mars and Jupiter lies a disk of rocks, small bodies and planetoids known as the Main Asteroid Belt. The existence of this Belt was first theorized in the 18th century, based on observations that indicated a regular pattern in the orbits of Solar planets. By the following century, regular discoveries began to be made in the space between Mars and Jupiter, prompting astronomers to theorize where the Belt came from.
For a long time, scientists debated whether the Belt was the remains of a planet that broke up, or remnants left over from the early system that failed to become a planet. But a new study by a pair of astronomers from the University of Bordeaux has offered a different take. According to their theory, the Asteroid Belt began as an empty space which was gradually filled by rocks and debris over time.
For the sake of their study – which recently appeared in the journal Science Advances under the title “The Empty Primordial Asteroid Belt” – astronomers Sean N. Raymond and Andre Izidoro of the University of Bordeaux considered the current scientific consensus, which is that the Main Belt was once much more densely packed and became depleted of mass over time.
Artist’s impression of how the Asteroid Belt could have become filled with C-type and S-type asteroids over time. Credit: Sean Raymond/planetplanet.net
As Dr. Raymond explained to Universe Today via email:
“The standard picture is that the building blocks of the Solar System — what we call planetesimals, generally thought of as 10-100 km-scale bodies — started off in a smooth distribution across the Sun’s planet-forming disk. The problem is, that puts a couple of times Earth’s mass in the asteroid belt, where there is now less than a thousandth of an Earth mass. The challenge in this picture is therefore to understand how the belt lost 99.9% of its mass (but not 100%).”
To this, Dr. Raymond and Dr. Izodoro considered the alternate possibility that perhaps the primordial belt started as an empty space. In accordance with this theory, there were no planetesimals – i.e. Ceres, Vesta, Palla, and Hygeia – orbiting between Mars and Jupiter as there are today. This began as a thought experiment which, as Dr. Raymond admits, sounded a bit crazy at first.
However, he and Dr. Izodoro soon realized that several protoplanetary disks like the one they were envisioning had already been discovered in other star systems. For example, in 2014, the Atacama Large Millimeter/submillimeter Array in Chile photographed a planet-forming disk of dust and gas (aka, a protoplanetary disk) in the HL Tauri system, a very young star located about 450 light years away in the Taurus constellation.
As the image (shown below) revealed, the dust in this disk is not smooth, but consists of several broad regions and less dense regions. “The exact explanation for the structure in this disk is still debated but pretty much all models invoke drifting dust,” said Raymond. “And planetesimals form when drifting dust piles up into sufficiently-dense rings. So, dust rings should (we think) produce rings of planetesimals.”
Image of the HL Tau planet-forming disk taken with the Atacama Large Millimeter Array. Credit: ALMA (ESO/NAOJ/NRAO)
To test this hypothesis, they constructed a model of the early Solar System which included an empty Main Belt region. As they moved the simulation forward, they found that the formation of the disk was related to the formation of the rocky planets, and would gradually become what we see today. As Raymond indicated:
“What we found is that the growth of the rocky planets is not 100% efficient. A fraction of planetesimals is gravitationally kicked outward and stranded in the asteroid belt. The orbits of captured bodies matches closely those of S-type asteroids. The efficiency of implanting S-types in the belt is quite low, only about 1 in 1000. However, recall that the belt is almost empty. There is a total of about 4 hundred-thousandths of an Earth-mass in S-types in the present-day belt. Our simulations typically implanted a few times that amount. Given that some are lost during later evolution of the Solar System, this matches both the distribution and amount of S-type asteroids in the belt.
They then combined this model with previous work which looked at the growth of Jupiter and Saturn and how this would effect the Solar System. In this study, they showed the C-type asteroids would be deposited in the Belt over time, and that these asteroids would also be responsible for delivering water to Earth. When they combined the distribution of implanted C-type and S-type asteroids with their current work, they found that it matched the present-day distribution of asteroids.
Interestingly enough, this is not the first theory Raymond and Izodoro have come up with to address the Asteroid Belt’s missing mass. Back in 2011, Raymond was a co-author on the study that proposed the Grand Tack model, in which he and his colleagues proposed that Jupiter migrated from its original orbit after it formed. At first, the planet moved closer to Mars’ current orbit, then back out towards where it is today.
Diagram comparing two possible explanations for how the Asteroid Belt formed. Credit: Sean Raymond/planetplanet.net
In the process, the asteroid belt would have been cleared, and Mars would have been deprived of mass, thus leading to its diminutive size – relative to Earth and Venus. This resolved a key problem with classical theories of Asteroid Belt formation, which was known as the “small Mars problem”. In short, all previous simulations of Solar planet formation tended to produce Mars analogs that were far more massive than Mars is today.
However, the Grand Tack hypothesis still contained theoretical uncertainties, which prompted Raymond and Izodoro to consider the the Empty Primordial Belt theory. “Our new result lends credence to an alternate model in which planetesimals never formed in the asteroid belt at all,” he said. “Different pieces of this new alternative model have been developed in recent years, and I think they add up to make a solid alternative to the Grand Tack model.”
Looking ahead, Raymond says that he and Izodoro hope to conduct further studies and simulations to see if either theory can be confirmed or falsified. “That’s the next step,” he said. “Until the next (seemingly-)crazy idea!”
Reconstructed view of Jupiter's northern lights through the filters of the Juno Ultraviolet Imaging Spectrograph instrument on Dec. 11, 2016, as the Juno spacecraft approached Jupiter, passed over its poles, and plunged towards the equator. Credit: NASA/JPL-Caltech/Bertrand Bonfond
Even after decades of study, Jupiter’s atmosphere continues to be something of a mystery to scientists. Consistent with the planet’s size, its atmosphere is the largest in the Solar System, spanning over 5,000 km (3,000 mi) in altitude and boasting extremes in temperature and pressure. On top of that, the planet’s atmosphere experiences the most powerful auroras in the Solar System.
Studying this phenomena has been one of the main goals of the Juno probe, which reached Jupiter on July 5th, 2016. However, after analyzing data collected by the probe’s instruments, scientists at Johns Hopkins University Applied Physics Laboratory (JHUAPL) were surprised to find that Jupiter’s powerful magnetic storms do not have the same source as they do on Earth.
The study which details these findings, “Discrete and Broadband Electron Acceleration in Jupiter’s Powerful Aurora“, recently appeared in the scientific journal Nature. Led by Barry Mauk, a scientist with the JHUAPL, the team analyzed data collected by Juno’s Ultraviolet Spectrograph (UVS) and Jovian Energetic Particle Detector Instrument (JEDI) to study Jupiter’s polar regions.
Ultraviolet auroral images of Jupiter from the Juno Ultraviolet Spectrograph instrument. Credit: NASA/SwRI/Randy Gladstone
As with Earth, on Jupiter, auroras are the result of intense radiation and Jupiter’s magnetic field. When this magnetosphere aligns with charged particles, it has the effect of accelerating electrons towards the atmosphere at high energy levels. In the course of examining Juno’s data, the JHUAPL team observed signatures of electrons being accelerated toward the Jovian atmosphere at energy levels of up to 400,000 electron volts.
This is roughly 10 to 30 times higher than what is experienced here on Earth, where only several thousand volts are typically needed to generate the most intense aurora. Given that Jupiter has the most powerful auroras in the Solar System, the team was not surprised to see such powerful forces at work within the planet’s atmosphere. What was surprising, however, was that this was not the source of the most intense auroras.
As Dr. Mauk, who leads the investigation team for the APL-built JEDI instrument and was the lead author on the study , explained in a JHUAPL press release:
“At Jupiter, the brightest auroras are caused by some kind of turbulent acceleration process that we do not understand very well. There are hints in our latest data indicating that as the power density of the auroral generation becomes stronger and stronger, the process becomes unstable and a new acceleration process takes over. But we’ll have to keep looking at the data.”
Image compiled using data from Juno’s Ultraviolet Spectrograph, which marks the path of Juno’s readings of Jupiter’s auroras. Credit: NASA/SwRI/Randy Gladstone
These findings could have significant implications for the study of Jupiter, who’s composition and atmospheric dynamics continue to be a source of mystery. It also has implications or the study of extra-solar gas giants and planetary systems. In recent decades, the study of these systems has revealed hundreds of gas giants that have ranged in size from being Neptune-like to many times the size of Jupiter (aka. “Super-Jupiters”).
These gas giants have also shown significant variations in orbit, ranging from being very close to their respective suns to very far (i.e. “Hot Jupiters” to “Cold Gas Giants”). By studying Jupiter’s ability to accelerate charged particles, astronomers will be able to make more educated guesses about space weather, radiation environments, and the risks they pose to space missions.
This will come in handy when it comes time to mount future missions to Jupiter, as well as deep-space and maybe even interstellar space. As Mauk explained:
“The highest energies that we are observing within Jupiter’s auroral regions are formidable. These energetic particles that create the auroras are part of the story in understanding Jupiter’s radiation belts, which pose such a challenge to Juno and to upcoming spacecraft missions to Jupiter under development. Engineering around the debilitating effects of radiation has always been a challenge to spacecraft engineers for missions at Earth and elsewhere in the solar system. What we learn here, and from spacecraft like NASA’s Van Allen Probes and MMS that are exploring Earth’s magnetosphere, will teach us a lot about space weather and protecting spacecraft and astronauts in harsh space environments. Comparing the processes at Jupiter and Earth is incredibly valuable in testing our ideas of how planetary physics works.”
Before the Juno mission is scheduled to wrap up (in February of 2018), the probe is likely to reveal a great many things about the planet’s composition, gravity field, magnetic field and polar magnetosphere. In so doing, it will address long-standing mysteries about how the planet formed and evolved, which will also shed light on the history of the Solar System and extra-solar systems.
The outer planets of our Solar System at approximately relative sizes. From left, Jupiter, Saturn, Uranus and Neptune. Credit: Lunar and Planetary Institute
Between the planets of the inner and outer Solar System, there are some stark differences. The planets that resides closer to the Sun are terrestrial (i.e. rocky) in nature, meaning that they are composed of silicate minerals and metals. Beyond the Asteroid Belt, however, the planets are predominantly composed of gases, and are much larger than their terrestrial peers.
This is why astronomers use the term “gas giants” when referring to the planets of the outer Solar System. The more we’ve come to know about these four planets, the more we’ve come to understand that no two gas giants are exactly alike. In addition, ongoing studies of planets beyond our Solar System (aka. “extra-solar planets“) has shown that there are many types of gas giants that do not conform to Solar examples. So what exactly is a “gas giant”?
Definition and Classification:
By definition, a gas giant is a planet that is primarily composed of hydrogen and helium. The name was originally coined in 1952 by James Blish, a science fiction writer who used the term to refer to all giant planets. In truth, the term is something of a misnomer, since these elements largely take a liquid and solid form within a gas giant, as a result of the extreme pressure conditions that exist within the interior.
The four gas giants of the Solar System (from right to left): Jupiter, Saturn, Uranus and Neptune. Credit: NASA/JPL
What’s more, gas giants are also thought to have large concentrations of metal and silicate material in their cores. Nevertheless, the term has remained in popular usage for decades and refers to all planets – be they Solar or extra-solar in nature – that are composed mainly of gases. It is also in keeping with the practice of planetary scientists, who use a shorthand – i.e. “rock”, “gas”, and “ice” – to classify planets based on the most common element within them.
Hence the difference between Jupiter and Saturn on the one and, and Uranus and Neptune on the other. Due to the high concentrations of volatiles (such as water, methane and ammonia) within the latter two – which planetary scientists classify as “ices” – these two giant planets are often called “ice giants”. But since they are composed mainly of hydrogen and helium, they are still considered gas giants alongside Jupiter and Saturn.
Classification:
Today, Gas giants are divided into five classes, based on the classification scheme proposed by David Sudarki (et al.) in a 2000 study. Titled “Albedo and Reflection Spectra of Extrasolar Giant Planets“, Sudarsky and his colleagues designated five different types of gas giant based on their appearances and albedo, and how this is affected by their respective distances from their star.
Class I: Ammonia Clouds – this class applies to gas giants whose appearances are dominated by ammonia clouds, and which are found in the outer regions of a planetary system. In other words, it applies only to planets that are beyond the “Frost Line”, the distance in a solar nebula from the central protostar where volatile compounds – i.e. water, ammonia, methane, carbon dioxide, carbon monoxide – condense into solid ice grains.
These cutaways illustrate interior models of the giant planets. Jupiter is shown with a rocky core overlaid by a deep layer of metallic hydrogen. Credit: NASA/JPL
Class II: Water Clouds – this applies to planets that have average temperatures typically below 250 K (-23 °C; -9 °F), and are therefore too warm to form ammonia clouds. Instead, these gas giants have clouds that are formed from condensed water vapor. Since water is more reflective than ammonia, Class II gas giants have higher albedos.
Class III: Cloudless – this class applies to gas giants that are generally warmer – 350 K (80 °C; 170 °F) to 800 K ( 530 °C; 980 °F) – and do not form cloud cover because they lack the necessary chemicals. These planets have low albedos since they do not reflect as much light into space. These bodies would also appear like clear blue globes because of the way methane in their atmospheres absorbs light (like Uranus and Neptune).
Class IV: Alkali Metals – this class of planets experience temperatures in excess of 900 K (627 °C; 1160 °F), at which point Carbon Monoxide becomes the dominant carbon-carrying molecule in their atmospheres (rather than methane). The abundance of alkali metals also increases substantially, and cloud decks of silicates and metals form deep in their atmospheres. Planets belonging to Class IV and V are referred to as “Hot Jupiters”.
Class V: Silicate Clouds – this applies to the hottest of gas giants, with temperatures above 1400 K (1100 °C; 2100 °F), or cooler planets with lower gravity than Jupiter. For these gas giants, the silicate and iron cloud decks are believed to be high up in the atmosphere. In the case of the former, such gas giants are likely to glow red from thermal radiation and reflected light.
Artist’s concept of “hot Jupiter” exoplanet, a gas giant that orbits very close to its star. Credit: NASA/JPL-Caltech)
Exoplanets:
The study of exoplanets has also revealed a wealth of other types of gas giants that are more massive than the Solar counterparts (aka. Super-Jupiters) as well as many that are comparable in size. Other discoveries have been a fraction of the size of their solar counterparts, while some have been so massive that they are just shy of becoming a star. However, given their distance from Earth, their spectra and albedo have cannot always be accurately measured.
As such, exoplanet-hunters tend to designate extra-solar gas giants based on their apparent sizes and distances from their stars. In the case of the former, they are often referred to as “Super-Jupiters”, Jupiter-sized, and Neptune-sized. To date, these types of exoplanet account for the majority of discoveries made by Kepler and other missions, since their larger sizes and greater distances from their stars makes them the easiest to detect.
In terms of their respective distances from their sun, exoplanet-hunters divide extra-solar gas giants into two categories: “cold gas giants” and “hot Jupiters”. Typically, cold hydrogen-rich gas giants are more massive than Jupiter but less than about 1.6 Jupiter masses, and will only be slightly larger in volume than Jupiter. For masses above this, gravity will cause the planets to shrink.
Exoplanet surveys have also turned up a class of planet known as “gas dwarfs”, which applies to hydrogen planets that are not as large as the gas giants of the Solar System. These stars have been observed to orbit close to their respective stars, causing them to lose atmospheric mass faster than planets that orbit at greater distances.
For gas giants that occupy the mass range between 13 to 75-80 Jupiter masses, the term “brown dwarf” is used. This designation is reserved for the largest of planetary/substellar objects; in other words, objects that are incredibly large, but not quite massive enough to undergo nuclear fusion in their core and become a star. Below this range are sub-brown dwarfs, while anything above are known as the lightest red dwarf (M9 V) stars.
An artist’s conception of a T-type brown dwarf. Credit: Tyrogthekreeper/Wikimedia Commons
Like all things astronomical in nature, gas giants are diverse, complex, and immensely fascinating. Between missions that seek to examine the gas giants of our Solar System directly to increasingly sophisticated surveys of distant planets, our knowledge of these mysterious objects continues to grow. And with that, so is our understanding of how star systems form and evolve.
Jupiter's Great Red Spot, as imaged by the Juno spacecraft's JunoCam at a distance of just 9,000 km (5,600 mi) from the atmosphere. Credit : NASA/SwRI/MSSS/TSmith
Earlier this week, on Monday, July 10th, the Juno mission accomplished an historic feet as it passed directly over Jupiter’s most famous feature – the Great Red Spot. This massive anticyclonic storm has been raging for centuries, and Juno’s scheduled flyby was the closest any mission has ever come to it. It all took place at 7:06 p.m. PDT (11:06 p.m. EDT), just days after the probe celebrated its first year of orbiting the planet.
And today – Wednesday, July 12th, a few days ahead of schedule – NASA began releasing the pics that Juno snapped with its imager – the JunoCam – to the public. As part of the missions’ seventh orbit around the planet (perijove 7) these images are the closest and most detailed look of Jupiter’s Great Red Spot to date. And as you can clearly see by going to the JunoCam website, the pictures are a sight to behold!
And as always, citizen scientists and amateur astronomers are already busy processing the images. This level of public involvement in a NASA mission is something quite new. Prior to every perijove, NASA has asked for public input on what features they would like to see imaged. These Points of Interest (POIs), as they are called, are then photographed, and the public has had the option of helping to process them for public consumption.
As Scott Bolton – the associate VP at the Southwest Research Institute (SwRI) and the Principle Investigator (PI) of the Juno mission – said in a NASA press release, “For generations people from all over the world and all walks of life have marveled over the Great Red Spot. Now we are finally going to see what this storm looks like up close and personal.” And in just the past two days, several processed images have already come in.
Consider the images that were processed by Jason Major – an amateur astronomer and graphic designer who created the astronomy website Lights in the Dark. In the image above (his own work), we see a cropped version of the original JunoCam image in order to put Jupiter’s Great Red Spot center-frame. It was then color-adjusted and enhanced to mark the boundaries of the storm’s “eye” and the swirling clouds that surround it more clearly.
On his website, Major described the method he used to bring this image to life:
“[T]he image above is my first rendering made from a map-projected PNG file which centers and fully-frames the giant storm in contrast- and color-enhanced detail… The resolution is low but this is what my “high-speed” workflow is set up for—higher resolution images will take more time and I’m anticipating some incredible versions to be created and posted later today and certainly by tomorrow and Friday by some of the processing superstars in the imaging community (Kevin, Seán, Björn, Gerald, I’m looking at you!)”
Above is another one of Major’s processed images, which was released shortly after the first one. This image shows the GRS in a larger context, using the full JunoCam image, and similarly processed to show contrasts. The same image was processed and submitted to the Juno website by amateur astronomers Amadeo Bellotti and Oliver Jenkins – though their submissions are admittedly less clear and colorful than Major’s work.
Other images include “Juno Eye“, a close up of Jupiter’s northern hemisphere that was processed by our good friend, Kevin M. Gill. Shown below, this image is a slight departure from the others (which focused intently on Jupiter’s Great Red Spot) to capture a close-up of the swirls in Jupiter’s northern polar atmosphere. Much like the GRS, these swirls are eddies that are created by Jupiter’s extremely high winds.
The Juno mission reached perijove – i.e. the point in its orbit where it is closest to Jupiter’s center – on July 10th at 6:55 p.m. PDT (9:55 p.m. EDT). At this time, it was about 3,500 km (2,200 mi) above Jupiter’s cloud tops. Eleven minutes and 33 seconds later, it was passing directly over the anticyclonic storm at a distance of about 9,000 km (5,600 mi); at which time, all eight of its instruments were trained on the feature.
In addition to the stunning array of images Juno has sent back, its suite of scientific instruments have gathered volumes of data on this gas giant. In fact, the early science results from the mission have shown just how turbulent and violent Jupiter’s atmosphere is, and revealed things about its complex interior structure, polar aurorae, its gravity and its magnetic field.
The Juno mission reached Jupiter on July 5th, 2016, becoming the second probe in history to establish orbit around the planet. By the time the mission is scheduled to end in 2018 (barring any mission extensions), scientist hope to have learned a great deal about the planet’s structure and history of formation.
Given that this knowledge is likely to reveal things about the early history and formation of the Solar System, the payoffs from this mission are sure to be felt for many years to come after it is decommissioned.
In the meantime, you can check out all the processed images by going to the JunoCam sight, which is being regularly updated with new photos from Perijove 7!
True color mosaic of Jupiter, based on images taken by the narrow angle camera onboard NASA's Cassini spacecraft on December 29, 2000, during its closest approach to the giant planet at a distance of approximately 10 million kilometers (6.2 million miles). Credits: NASA/JPL/Space Science Institute
When the Juno mission reached Jupiter on July 5th, 2016, it became the second mission in history to establish orbit around the Solar System’s largest planet. And in the course of it conducting its many orbits, it has revealed some interesting things about Jupiter. This has included information about its atmosphere, meteorological phenomena, gravity, and its powerful magnetic fields.
And just yesterday – on Monday, July 10th at 7:06 p.m. PDT (11:06 p.m. EDT) – just days after the probe celebrated its first year of orbiting the planet, the Juno mission passed directly over Jupiter’s most famous feature – the Great Red Spot. This massive anticyclonic storm has been a focal point for centuries, and Juno’s scheduled flyby was the closest any mission has ever come to it.
Jupiter’s Great Red Spot was first observed during the late 17th century, either by Robert Hooke or Giovanni Cassini. By 1830, astronomers began monitoring this anticyclonic storm, and have noted periodic expansions and regressions in its size ever since. Today, it is 16,000 kilometers (10,000 miles) in diameter and reaches wind speeds of 120 meters per second (432 km/h; 286 mph) at the edges.
The Juno spacecraft isn’t the first one to visit Jupiter. Galileo went there in the mid 90’s, and Voyager 1 snapped a nice picture of the clouds on its mission. Credit: NASA
As part of its sixth orbit of Jupiter’s turbulent cloud tops, Juno passed close to Jupiter’s center (aka. perijove), which took place at 6:55 p.m. PDT (9:55 p.m. EDT). Eleven minutes later – at 7:06 p.m. PDT (10:06 p.m. EDT) – the probe flew over the Great Red Spot. In the process, Juno was at a distance of just 9,000 km (5,600 miles) from the anticyclonic storm, which is the closest any spacecraft has ever flown to it.
During the flyby, Juno had all eight of its scientific instruments (as well its imager, the JunoCam) trained directly on the storm. With such an array aimed at this feature, NASA expects to learn more about what has been powering this storm for at least the past three and a half centuries. As Scott Bolton, the principal investigator of Juno at the Southwest Research Institute (SwRI), said prior to the event in a NASA press release:
“Jupiter’s mysterious Great Red Spot is probably the best-known feature of Jupiter. This monumental storm has raged on the Solar System’s biggest planet for centuries. Now, Juno and her cloud-penetrating science instruments will dive in to see how deep the roots of this storm go, and help us understand how this giant storm works and what makes it so special.”
This perijove and flyby of the Giant Red Spot also comes just days after Juno celebrated its first anniversary around Jupiter. This took place on July 4th at 7:30 p.m. PDT (10:30 p.m. EDT), at which point, Juno had been in orbit around the Jovian planet for exactly one year. By this time, the spacecraft had covered a distance of 114.5 million km (71 million mi) while orbiting around the planet.
This artist’s illustration shows Juno’s Microwave Radiometer observing deep into Jupiter’s atmosphere. The image shows real data from the 6 MWR channels, arranged by wavelength. Credit: NASA/SwRI/JPL
The information that Juno has collected in that time with its advanced suite of instruments has already provided fresh insights into Jupiter’s interior and the history of its formation. And this information, it is hoped, will help astronomers to learn more about the Solar System’s own history of formation. And in the course of making its orbits, the probe has been put through its paces, absorbing radiation from Jupiter’s powerful magnetic field.
As Rick Nybakken, the project manager for Juno at NASA’s Jet Propulsion Laboratory, put it:
“The success of science collection at Jupiter is a testament to the dedication, creativity and technical abilities of the NASA-Juno team. Each new orbit brings us closer to the heart of Jupiter’s radiation belt, but so far the spacecraft has weathered the storm of electrons surrounding Jupiter better than we could have ever imagined.”
The Juno mission is set to conclude this coming February, after completing 6 more orbits of Jupiter. At this point, and barring any mission extensions, the probe will be de-orbited to burn up in Jupiter’s outer atmosphere. As with the Galileo spacecraft, this is meant to avoid any possibility of impact and biological contamination with one of Jupiter’s moons.
Jupiter as seen by the Juno spacecraft during the Perijove 5 pass on March 27, 2017. Processed using raw data. Credit: NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill.
The original plans for the Juno mission to Jupiter didn’t include a color camera. You don’t need color images when the mission’s main goals are to map Jupiter’s magnetic and gravity fields, determine the planet’s internal composition, and explore the magnetosphere.
But a camera was added to the manifest, and the incredible images from the JunoCam have been grabbing the spotlight.
As an instrument where students and the public can choose the targets, JunoCam is a “public outreach” camera, meant to educate and captivate everyday people.
“The whole endeavor of JunoCam was to get the public to participate in a meaningful way,” said Candy Hansen, Juno co-investigator at the Planetary Science Institute in Tucson, Arizona, speaking at a press conference last week to showcase Juno’s science and images.
And participate they have. Hundreds of ‘amateur’ image processing enthusiasts have been processing raw data from the JunoCam, turning them into stunning images, many reminiscent of a swirling Van Gogh ‘starry night’ or a cloudscape by Monet.
The swirling cloudtops of Jupiter, as seen by Juno during Perijove 5 on March 27, 2017. Credit: NASA/JPL-Caltech/SwRI/MSSS/Sophia Nasr.
“The contributions of the amateurs are essential,” Hansen said. “I cannot overstate how important the contributions are. We don’t have a way to plan our data without the contributions of the amateur astronomers. We don’t have a big image processing team, so we are completely relying on the help of our citizen scientists.”
Jupiter as seen by Juno during Perijove 6 in May, 2017. Credit: NASA/SwRI/MSSS/Gerald Eichstädt / Seán Doran.
Click on this image to have access to a 125 Megapixel upscaled print portrait.
Featured here are images processed by Seán Doran, Sophia Nasr, Kevin Gill and Jason Major. Like hundreds of others around the world, they anxiously await for data to arrive to Earth, where it is uploaded to the public Juno website. Then they set to work to turn the data into images.
“What I find the most phenomenal of all is that this takes real work,” Hansen said. “When you download a JunoCam image and process it, it’s not something you do in five minutes. The pictures that we get that people upload back onto our site, they’ve invested hours and hours of their own time, and then generously returned that to us.”
This video shows Juno’s trajectory from Perijove 6, and is based on work by Gerald Eichstädt, compiled and edited by Seán Doran. “This is real imagery projected along orbit trajectory,” Doran explained on Twitter.
Intricate swirls on Jupiter Jupiter, from Juno’s Perijove 6 pass on May 19, 2017. Credit: NASA/JPL-Caltech/SwRI /MSSS/Kevin M. Gill.Details of Jupiter’s swirling gas clouds, as seen by Juno during the Perijove 6 pass in May, 2017. Credit: NASA / SwRI / MSSS / Gerald Eichstädt / Seán Doran.
JunoCam was built by Malin Space Science Systems, which has cameras on previous missions like the Curiosity Mars Rover, the Mars Global Surveyor and the Mars Color Imager on the Mars Reconnaissance Orbiter. To withstand the harsh radiation environment at Jupiter, the camera required special protection and a reinforced lens.
Whenever new images arrive, many of us feel exactly like editing enthusiast Björn Jónsson:
I never expected I'd ever say this but: The latest @NASAJuno images of Jupiter are the most spectacular images of Jupiter I've ever seen. pic.twitter.com/7HawZ9RSwe
Even the science team has expressed their amazement at these images.
“Jupiter looks different than what we expected,” said Scott Bolton, Juno’s principal investigator at the Southwest Research Institute. “Jupiter from the poles doesn’t look anything like it does from the equator. And the fact the north and south pole don’t look like each other, makes us wonder if the storms are stable, if they going to stay that way for years and years like the the Great Red Spot. Only time will tell us what is true.”
A sequence of images of Jupiter from Juno’s Perijove 6 pass during May, 2017. Credit: NASA / SwRI / MSSS / Gerald Eichstädt / Seán Doran.
Part of what makes these images so stunning is that Juno is closer to Jupiter than any previous spacecraft.
“Juno has an elliptical orbit that brings it between the inner edges of Jupiter’s radiation belt and the planet, passing only 5,000 km above the cloud tops,” Juno Project Manager Rick Nybakken told me in my book ‘Incredible Stories From Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos.’ “This close proximity to Jupiter is unprecedented, as no other mission has conducted their science mission this close to the planet. We’re right on top of Jupiter, so to speak.”
Juno engineers designed the mission to enable the use of solar panels, which prior to Juno, have never been used on a spacecraft going so far from the Sun. Juno orbits Jupiter in a way that the solar panels are always pointed towards the Sun and the spacecraft never goes behind the planet. Juno’s orbital design not only enabled an historic solar-powered mission, it also established Juno’s unique science orbit.
White oval on Jupiter during Juno’s Perijove 4 pass on February 2, 2017. Processed from raw data. Credit: NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill.Uncalibrated, processed raw image from Juno’s Perijove 6 pass of Jupiter on May 19, 2017. Credit: NASA/SwRI/MSSS/Jason Major.
Juno spacecraft launched from Cape Canaveral on August 5, 2011. After traveling five years and 1.7 billion miles Juno arrived in orbit at Jupiter on July 4, 2016. The mission will last until at least February 2018, making 11 science orbits around Jupiter, instead of the 32 laps originally planned. Last year, engineers detected a problem with check valves in the propulsion system, and NASA decided to forego an engine burn to move Juno into a tighter 14-day orbit around Jupiter. The current 53.4 day orbit will be maintained, but depending on how the spacecraft responds, NASA could extend the mission another three years to give Juno more flybys near Jupiter.
The next science flyby will occur on July 11, when Juno will get some close-up views of the famous Great Red Spot.
Thanks to everyone who works on these images.
Animation of six images acquired by NASA’s Juno spacecraft on March 27, 2017. Credit: NASA/JPL-Caltech/SwRI/MSSS/Jason Major.This enhanced color view of Jupiter’s south pole was created by citizen scientist Gabriel Fiset using data from the JunoCam instrument on NASA’s Juno spacecraft. Oval storms dot the cloudscape. Approaching the pole, the organized turbulence of Jupiter’s belts and zones transitions into clusters of unorganized filamentary structures, streams of air that resemble giant tangled strings. The image was taken on Dec. 11, 2016 at 9:44 a.m. PST (12:44 p.m. EST), from an altitude of about 32,400 miles (52,200 kilometers) above the planet’s beautiful cloud tops. Credits: NASA/JPL-Caltech/SwRI/MSSS/Gabriel Fiset
