Io casts a crisp circular shadow on the the cloud tops in Jupiter's atmosphere in this JunoCam image processed by Kevin Gill. Image Credit: NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill https://creativecommons.org/licenses/by/2.0/
The JunoCam onboard NASA’s Juno spacecraft continues to provide we Earthbound humans with a steady stream of stunning images of Jupiter. We can’t get enough of the gas giant’s hypnotic, other-worldly beauty. This image of Io passing over Jupiter is the latest one to awaken our sense of wonder.
This image was processed by Kevin Gill, a NASA software engineer who has produced other stunning images of Jupiter.
This stunning image comes from the Juno spacecraft. Citizen scientist Kevin M. Gill created it using images from Juno's JunoCam imager. Image Credit: NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill
There’s something about Jupiter that mesmerizes those who gaze at it. It’s intricate, dazzling clouds are a visual representation of the laws of nature that’s hard to turn away from. And even though the Juno spacecraft has been at Jupiter for almost three years now, and has delivered thousands of images of the gas giant’s colourful, churning clouds, we can’t seem to satisfy our appetite.
An amazingly active Io, Jupiter's "pizza moon" shows multiple volcanoes and hot spots in this photo taken with Juno's infrared camera. Credit: NASA / JPL-Caltech / SwRI / ASI / INAF /JIRAM / Roman Tkachenko
Thanks to a mission extension, NASA’s Juno probe continues to orbit Jupiter, being only the second spacecraft in history to do so. Since it arrived around the gas giant on July 5th, 2016, Juno has managed to gather a great deal of information on Jupiter’s atmosphere, magnetic and gravity environment, and its interior structure.
In that time, the probe has also managed to capture some breathtaking images of Jupiter as well. But on December 21st, during the probe’s sixteenth orbit of the gas giant, the Juno probe changed things up when four of its cameras captured images of the Jovian moon Io, showcasing its polar regions and spotting what appeared to be a volcanic eruption.
JunoCam captured these images of the Great Red Spot during the July 2017 fly-by of Jupiter. The composite images provide a richly-detailed look at the storm. Image: Sánchez-Lavega et al. 2018; composed by G. Eichstadt and J. Cowart
For almost 200 years humans have been watching the Great Red Spot (GRS) on Jupiter and wondering what’s behind it. Thanks to NASA’s Juno mission, we’ve been getting better and better looks at it. New images from JunoCam reveal some of the deeper detail in our Solar System’s longest-lived storm.
Atmospheric features in Jupiter’s northern hemisphere, captured by color-enhanced images from NASA’s Juno spacecraft. Credit: NASA/JPL-Caltech/SwRI/MSSS/Gerald Eichstäd/Seán Doran
In July of 2016, the Juno spacecraft established orbit around Jupiter, becoming the first spacecraft since the Galileoprobe to study the planet directly. Since that time, the probe has been sending back vital information about Jupiter’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 exciting things about this gas giant. Continue reading “Another Juno Flyby, Another Amazing Sequence of Images of Jupiter”
Infrared image of the southern hemisphere of Jupiter’s moon Io taken by NASA's Juno spacecraft on Dec. 16, 2017. Credits: NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM
When the Juno spacecraft arrived in orbit around Jupiter in 2016, it became the second spacecraft in history to study Jupiter directly – the first being the Galileo probe, which orbited Jupiter between 1995 and 2003. With every passing orbit (known as a perijove, which take place every 53 days), the spacecraft has revealed more about Jupiter’s atmosphere, weather patterns, and magnetic environment.
In addition, Juno recently discovered something interesting about Jupiter’s closest orbiting moon Io. Based on data collected by its Jovian InfraRed Auroral Mapper (JIRAM) instrument, Juno detected a new heat source close to the south pole of Io that could indicate the presence of a previously undiscovered volcano. This is just the latest discovery made by the probe during its mission, which NASA recently extended to 2021.
Annotated image of the new heat source in the southern hemisphere of the Jupiter moon Io. Credits: NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM
The infrared data was collected on Dec. 16th, 2017, when the Juno spacecraft was about 470,000 km (290,000 mi) away from Io. As Alessandro Mura, a Juno co-investigator from the National Institute for Astrophysics (INAF) in Rome, explained in a recent NASA press release:
“The new Io hotspot JIRAM picked up is about 200 miles (300 kilometers) from the nearest previously mapped hotspot. We are not ruling out movement or modification of a previously discovered hot spot, but it is difficult to imagine one could travel such a distance and still be considered the same feature.”
Aside from Juno and Galileo, many NASA missions have visited or passed through the Jovian System in the past few decades. These have including the Pioneer 10 and 11 missions in 1973/74, the Voyager 1 and 2 missions in 1979, and the Cassini and New Horizons missions in 2000 and 2007, respectively. Each of these missions managed to snap pictures of the Jovians moons on their way to the outer Solar System.
Annotated image of the new heat source close to the south pole of Io, with a scale depicting the range of temperatures displayed in the infrared image. Credits: NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM
Combined with ground-based observations, scientists have accounted for over 150 volcanoes on the surface of Io so far, with estimates claiming there could over 400 in total. Since it entered Jupiter’s orbit on July 4th, 2016, the Juno probe has traveled nearly 235 million km (146 million mi) from one pole to other. On July 16th, Juno will conduct its 13th perijove maneuver, once again passing low over Jupiter’s cloud tops at a distance of about 3,400 km (2,100 mi).
During these flybys, Juno probes beneath the upper atmosphere to study the planet’s auroras to learn more about it’s structure, atmosphere and magnetosphere. By shedding light on these characteristics, the Juno probe will also teach us more about the planet’s origins and evolution. This in turn will teach scientists a great deal more about the formation and evolution of our Solar System, and perhaps how life began here.
The Juno Infrared Auroral Mapper (JIRAM) captured this infrared image of Jupiter's south pole. This part of Jupiter cannot be seen from Earth. Image: NASA/JPL-Caltech/SwRI/MSSS
Since it arrived in 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 things about Jupiter that scientists will rely on to learn more about its formation and evolution.
Interestingly, some of the most recent information to come from the mission involves how two of its moons affect one of Jupiter’s most interesting atmospheric phenomenon. As they revealed in a recent study, an international team of researchers discovered how Io and Ganymede leave “footprints” in the planet’s aurorae. These findings could help astronomers to better understand both the planet and its moons.
Infrared images obtained by the Cassini probe, showing disturbances in Jupiter’s aurorae caused by Io and Ganymede. Credit: (c) Science (2018).
Much like aurorae here on Earth, Jupiter’s aurorae are produced in its upper atmosphere when high-energy electrons interact with the planet’s powerful magnetic field. However, as the Juno probe recently demonstrated using data gathered by Ultraviolet Spectrograph (UVS) and Jovian Energetic Particle Detector Instrument (JEDI), Jupiter’s magnetic field is significantly more powerful than anything we see on Earth.
In addition to reaching power levels 10 to 30 times greater than anything higher than what is experienced here on Earth (up to 400,000 electron volts), Jupiter’s norther and southern auroral storms also have oval-shaped disturbances that appear whenever Io and Ganymede pass close to the planet. As they explain in their study:
“A northern and a southern main auroral oval are visible, surrounded by small emission features associated with the Galilean moons. We present infrared observations, obtained with the Juno spacecraft, showing that in the case of Io, this emission exhibits a swirling pattern that is similar in appearance to a von Kármán vortex street.”
A Von Kármán vortex street, a concept in fluid dynamics, is basically a repeating pattern of swirling vortices caused by a disturbance. In this case, the team found evidence of a vortex streaming for hundreds of kilometers when Io passed close to the planet, but which then disappeared as the moon moved farther away from the planet.
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
The team also found two spots in the auroral belt created by Ganymede, where the extended tail from the main auroral spots eventually split in two. While the team was not sure what causes this split, they venture that it could be caused by interaction between Ganymede and Jupiter’s magnetic field (since Ganymede is the only Jovian moon to have its own magnetic field).
These features, they claim, suggest that magnetic interactions between Jupiter and Ganymede are more complex than previously thought. They also indicate that neither of the footprints were where they expected to find them, which suggests that models of the planet’s magnetic interactions with its moons may be in need of revision.
Studying Jupiter’s magnetic storms is one of the primary goals of the Juno mission, as is learning more about the planet’s interior structure and how it has evolved over time. In so doing, astronomers hope to learn more about how the Solar System came to be. NASA also recently extended the mission to 2021, giving it three more years to gather data on these mysteries.
And be sure to enjoy this video of the Juno mission, courtesy of the Jet Propulsion Laboratory:
NASA / JPL-Caltech / SwRI / ASI / INAF /JIRAM / Roman Tkachenko
An amazingly active Io, Jupiter’s “pizza moon” shows multiple volcanoes and hot spots in this photo taken with Juno’s infrared camera. Credit: NASA / JPL-Caltech / SwRI / ASI / INAF /JIRAM / Roman Tkachenko
Volcanic activity on Io was discovered by Voyager 1 imaging scientist Linda Morabito. She spotted a little bump on Io’s limb while analyzing a Voyager image and thought at first it was an undiscovered moon. Moments later she realized that wasn’t possible — it would have been seen by earthbound telescopes long ago. Morabito and the Voyager team soon came to realize they were seeing a volcanic plume rising 190 miles (300 km) off the surface of Io. It was the first time in history that an active volcano had been detected beyond the Earth. For a wonderful account of the discovery, click here.
Linda Morabito spotted the puzzling plume off Io’s limb in this photo, taken on March 8, 1979, three days after Voyager 1’s encounter with Jupiter. It really does look like another moon poking out from behind Io. A second plume over the terminator (border between day and night) catches the rays of the rising Sun. Credit: NASA / JPL
Today, we know that Io boasts more than 130 active volcanoes with an estimated 400 total, making it the most volcanically active place in the Solar System. Juno used its Jovian Infrared Aurora Mapper (JIRAM) to take spectacular photographs of Io during Perijove 7 last July, when we were all totally absorbed by close up images of Jupiter’s Great Red Spot.
Io is captured here by NASA’s Galileo spacecraft. Deposits of sulfur dioxide frost appear in white and grey hues while yellowish and brownish hues are probably due to other sulfurous materials. Bright red materials, such as the prominent ring surrounding Pele (lower left), and “black” spots mark areas of recent volcanic activity. Credit: NASA / JPL / University of Arizona
Juno’s Io looks like it’s on fire. Because JIRAM sees in infrared, a form of light we sense as heat, it picked up the signatures of at least 60 hot spots on the little moon on both the sunlight side (right) and the shadowed half. Like all missions to the planets, Juno’s cameras take pictures in black and white through a variety of color filters. The filtered views are later combined later by computers on the ground to create color pictures. Our featured image of Io was created by amateur astronomer and image processor Roman Tkachenko, who stacked raw images from this data set to create the vibrant view.
This map shows thermal emission from erupting volcanoes on Io. The larger the spot, the larger the thermal emission. Credit: NASA/JPL-Caltech/Bear Fight Institute
Io’s hotter than heck with erupting volcano temperatures as high as 2,400° F (1,300° C). Most of its lavas are made of basalt, a common type of volcanic rock found on Earth, but some flows consist of sulfur and sulfur dioxide, which paints the scabby landscape in unique colors.
This five-frame sequence taken by NASA’s New Horizons spacecraft on March 1, 2007 captures the giant plume from Io’s Tvashtar volcano.
Located more than 400 million miles from the Sun, how does a little orb only a hundred miles larger than our Moon get so hot? Europa and Ganymede are partly to blame. They tug on Io, causing it to revolve around Jupiter in an eccentric orbit that alternates between close and far. Jupiter’s powerful gravity tugs harder on the moon when its closest and less so when it’s farther away. The “tug and release”creates friction inside the satellite, heating and melting its interior. Io releases the pent up heat in the form of volcanoes, hot spots and massive lava flows.
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.
Jupiter’s south pole. captured by the JunoCam on Feb. 2, 2017, from an altitude of about 62,800 miles (101,000 kilometers) above the cloud tops.
Credits: NASA/JPL-Caltech/SwRI/MSSS/John Landino
In the early 1960s, scientists developed the gravity-assist method, where a spacecraft would conduct a flyby of a major body in order to increase its speed. Many notable missions have used this technique, including the Pioneer, Voyager,Galileo, Cassini, andNew Horizons missions. In the course of many of these flybys, scientists have noted an anomaly where the increase in the spacecraft’s speed did not accord with orbital models.
This has come to be known as the “flyby anomaly”, which has endured despite decades of study and resisted all previous attempts at explanation. To address this, a team of researchers from the University Institute of Multidisciplinary Mathematics at the Universitat Politecnica de Valencia have developed a new orbital model based on the maneuvers conducted by the Juno probe.
The study, which recently appeared online under the title “A Possible Flyby Anomaly for Juno at Jupiter“, was conducted by Luis Acedo, Pedro Piqueras and Jose A. Morano. Together, they examined the possible causes of the so-called “flyby anomaly” using the perijove orbit of the Juno probe. Based on Juno’s many pole-to-pole orbits, they not only determined that it too experienced an anomaly, but offered a possible explanation for this.
Artist’s impression of the Pioneer 10 probe, launched in 1972 and now making its way out towards the star Aldebaran. Credit: NASA
To break it down, the speed of a spacecraft is determined by measuring the Doppler shift of radio signals from the spacecraft to the antennas on the Deep Space Network (DSN). During the 1970s when the Pioneer 10 and 11 probes were launched, visiting Jupiter and Saturn before heading off towards the edge of the Solar System, these probes both experienced something strange as they passed between 20 to 70 AU (Uranus to the Kuiper Belt) from the Sun.
Basically, the probes were both 386,000 km (240,000 mi) farther from where existing models predicted they would be. This came to be known as the “Pioneer anomaly“, which became common lore within the space physics community. While the Pioneer anomaly was resolved, the same phenomena has occurred many times since then with subsequent missions. As Dr. Acebo told Universe Today via email:
“The “flyby anomaly” is a problem in astrodynamics discovered by a JPL’s team of researchers lead by John Anderson in the early 90s. When they tried to fit the whole trajectory of the Galileo spacecraft as it approached the Earth on December, 8th, 1990, they found that this only can be done by considering that the ingoing and outgoing pieces of the trajectory correspond to asymptotic velocities that differ in 3.92 mm/s from what is expected in theory.
“The effect appears both in the Doppler data and in the ranging data, so it is not a consequence of the measurement technique. Later on, it has also been found in several flybys performed by Galileo again in 1992, the NEAR [Near Earth Asteroid Rendezvous mission] in 1998, Cassini in 1999 or Rosetta and Messenger in 2005. The largest discrepancy was found for the NEAR (around 13 mm/s) and this is attributed to the very close distance of 532 Km to the surface of the Earth at the perigee.”
NASA’s Juno spacecraft launched on August 6, 2011 and should arrive at Jupiter on July 4, 2016. Credit: NASA / JPL
Another mystery is that while in some cases the anomaly was clear, in others it was on the threshold of detectability or simply absent – as was the case with Juno‘s flyby of Earth in October of 2013. The absence of any convincing explanation has led to a number of explanations, ranging from the influence or dark matter and tidal effects to extensions of General Relativity and the existence of new physics.
However, none of these have produced a substantive explanation that could account for flyby anomalies. To address this, Acedo and his colleagues sought to create a model that was optimized for the Juno mission while at perijove – i.e. the point in the probe’s orbit where it is closest to Jupiter’s center. As Acedo explained:
“After the arrival of Juno at Jupiter on July, 4th, 2016, we had the idea of developing our independent orbital model to compare with the fitted trajectories that were being calculated by the JPL team at NASA. After all, Juno is performing very close flybys of Jupiter because the altitude over the top clouds (around 4000 km) is a small fraction of the planet’s radius. So, we expected to find the anomaly here. This would be an interesting addition to our knowledge of this effect because it would prove that it is not only a particular problem with Earth flybys but that it is universal.”
Their model took into account the tidal forces exerted by the Sun and by Jupiter’s larger satellites – Io, Europa, Ganymede and Callisto – and also the contributions of the known zonal harmonics. They also accounted for Jupiter’s multipolar fields, which are the result of the planet oblate shape, since these play a far more important role than tidal forces as Juno reaches perijove.
Illustration of NASA’s Juno spacecraft firing its main engine to slow down and go into orbit around Jupiter. Lockheed Martin built the Juno spacecraft for NASA’s Jet Propulsion Laboratory. Credit: NASA/Lockheed Martin
In the end, they determined that an anomaly could also be present during the Juno flybys of Jupiter. They also noted a significant radial component in this anomaly, one which decayed the farther the probe got from the center of Jupiter. As Acebo explained:
“Our conclusion is that an anomalous acceleration is also acting upon the Juno spacecraft in the vicinity of the perijove (in this case, the asymptotic velocity is not a useful concept because the trajectory is closed). This acceleration is almost one hundred times larger than the typical anomalous accelerations responsible for the anomaly in the case of the Earth flybys. This was already expected in connection with Anderson et al.’s initial intuition that the effect increases with the angular rotational velocity of the planet (a period of 9.8 hours for Jupiter vs the 24 hours of the Earth), the radius of the planet and probably its mass.”
They also determined that this anomaly appears to be dependent on the ratio between the spacecraft’s radial velocity and the speed of light, and that this decreases very fast as the craft’s altitude over Jupiter’s clouds changes. These issues were not predicted by General Relativity, so there is a chance that flyby anomalies are the result of novel gravitational phenomena – or perhaps, a more conventional effect that has been overlooked.
In the end, the model that resulted from their calculations accorded closely with telemetry data provided by the Juno mission, though questions remain. “Further research is necessary because the pattern of the anomaly seems very complex and a single orbit (or a sequence of similar orbits as in the case of Juno) cannot map the whole field,” said Acebo. “A dedicated mission is required but financial cuts and limited interest in experimental gravity may prevent us to see this mission in the near future.”
It is a testament to the complexities of physics that even after sixty years of space exploration – and one hundred years since General Relativity was first proposed – that we are still refining our models. Perhaps someday we will find there are no mysteries left to solve, and the Universe will make perfect sense to us. What a terrible day that will be!
