22.08.2024
Using cameras designed for navigation, scientists count ‘fireflies’ to determine the amount of radiation the spacecraft receives during each orbit of Jupiter.
Scientists with NASA’s Juno mission have developed the first complete 3D radiation map of the Jupiter system. Along with characterizing the intensity of the high-energy particles near the orbit of the icy moon Europa, the map shows how the radiation environment is sculpted by the smaller moons orbiting near Jupiter’s rings.
The work relies on data collected by Juno’s Advanced Stellar Compass (ASC), which was designed and built by the Technical University of Denmark, and the spacecraft’s Stellar Reference Unit(SRU), which was built by Leonardo SpA in Florence, Italy. The two datasets complement each other, helping Juno scientists characterize the radiation environment at different energies.
Both the ASC and SRU are low-light cameras designed to assist with deep-space navigation. These types of instruments are on almost all spacecraft. But to get them to operate as radiation detectors, Juno’s science team had to look at the cameras in a whole new light.
Jupiter’s moon Europa was captured by the JunoCam instrument aboard NASA’s Juno spacecraft during the mission’s close flyby on Sept. 29, 2022.
“On Juno we try to innovate new ways to use our sensors to learn about nature, and we have used many of our science instruments in ways they were not designed for,” said Scott Bolton, Juno principal investigator from the Southwest Research Institute in San Antonio. “This is the first detailed radiation map of the region at these higher energies, which is a major step in understanding how Jupiter’s radiation environment works. This will help planning observations for the next generation of missions to the Jovian system.”
Counting Fireflies
Consisting of four star cameras on the spacecraft’s magnetometer boom, Juno’s ASC takes images of stars to determine the spacecraft’s orientation in space, which is vital to the success of the mission’s magnetic field experiment. But the instrument has also proved to be a valuable detector of high-energy particle fluxes in Jupiter’s magnetosphere. The cameras record “hard radiation,” or ionizing radiation that impacts a spacecraft with sufficient energy to pass through the ASC’s shielding.
“Every quarter-second, the ASC takes an image of the stars,” said Juno scientist John Leif Jørgensen of the Technical University of Denmark. “Very energetic electrons that penetrate its shielding leave a telltale signature in our images that looks like the trail of a firefly. The instrument is programmed to count the number of these fireflies, giving us an accurate calculation of the amount of radiation.”
Because of Juno’s ever-changing orbit, the spacecraft has traversed practically all regions of space near Jupiter.
ASC data suggests that there is more very high-energy radiation relative to lower-energy radiation near Europa’s orbit than previously thought. The data also confirms that there are more high-energy electrons on the side of Europa facing its orbital direction of motion than on the moon’s trailing side. This is because most of the electrons in Jupiter’s magnetosphere overtake Europa from behind due to the planet’s rotation, whereas the very high-energy electrons drift backward, almost like fish swimming upstream, and slam into Europa’s front side.
Jovian radiation data is not the ASC’s first scientific contribution to the mission. Even before arriving at Jupiter, ASC data was used to determine a measurement of interstellar dust impacting Juno. The imager also discovered a previously uncharted comet using the same dust-detection technique, distinguishing small bits of the spacecraft ejected by microscopic dust impacting Juno at a high velocity.
Dust Rings
Like Juno’s ASC, the SRU has been used as a radiation detector and a low-light imager. Data from both instruments indicates that, like Europa, the small “shepherd moons” that orbit within or close to the edge of Jupiter’s rings (and help to hold the shape of the rings) also appear to interact with the planet’s radiation environment. When the spacecraft flies on magnetic field lines connected to ring moons or dense dust, the radiation count on both the ASC and SRU drops precipitously. The SRU is also collecting rare low-light images of the rings from Juno’s unique vantage point.
“There is still a lot of mystery about how Jupiter’s rings were formed, and very few images have been collected by prior spacecraft,” said Heidi Becker, lead co-investigator for the SRU and a scientist at NASA’s Jet Propulsion Laboratory in Southern California, which manages the mission. “Sometimes we’re lucky and one of the small shepherd moons can be captured in the shot. These images allow us to learn more precisely where the ring moons are currently located and see the distribution of dust relative to their distance from Jupiter.”
Quelle: NASA
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Update: 13.09.2024
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NASA's Juno probe spots massive new volcano on Jupiter moon Io
Comparison with Galileo data reveals huge new volcano and lava flows.
An image of Jupiter's moon Io taken by NASA's Juno probe on Feb. 3, 2024 (left); and a comparison of Juno data from Feb. 2024 with Galileo spacecraft imagery of the same area in November 1997 (greyscale insert) reveals a new volcanic feature on the surface of Io. (Image credit: NASA/JPL-Caltech/SwRI/MSSS/Europlanet)
Researchers have spotted a huge new active volcano on Jupiter's moon Io by comparing images taken by two NASA missions more than a quarter of a century apart.
The images of the new volcano were taken by NASA's Juno spacecraft and its JunoCam as it made a flyby of Io — the solar system's most volcanic body — on Feb. 3 this year. The images were captured on the nightside of Io, illuminated only by reflected sunlight from Jupiter.
Comparison with Galileo spacecraft imagery of the same area, just south of Io's equator, taken in November 1997, revealed that there was previously no volcanic feature in that location, meaning the vast feature and its after-effects have appeared at some point during the last 27 years.
The findings, which reinforce just how volcanically active Io is, were presented at the Europlanet Science Congress (EPSC) in Berlin this week.
"Our recent JunoCam images show many changes on Io, including this large, complicated volcanic feature that appears to have formed from nothing since 1997," said Michael Ravine, Advanced Projects Manager at Malin Space Science Systems, Inc, which designed, developed and operates JunoCam for the NASA Juno Project, in a Europlanet statement.
Io, which is slightly larger than Earth's moon, is caught between the colossal Jupiter and its fellow Galilean moons Europa and Ganymede. These gravitational forces tug on Io's interior, generating frictional heat, and resulting in widespread volcanic activity across its surface. The eruptions are thought to eject molten sulfur and its compounds.
Juno launched in 2011 and reached the Jupiter system in 2016. The spacecraft completed its primary mission in July 2021 but is conducting an extended mission until September 2025. JunoCam data are published on the mission's webpages.
Quelle: SC
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Update: 29.01.2025
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NASA's Juno Mission Captures Close-Ups of Polar Storms on Jupiter
During its 65th close flyby of Jupiter on Sept. 20, 2024, NASA's Juno spacecraft captured this series of images as it approached the giant planet and swung low over its north polar region.
Juno's recent orbits have provided exceptionally clear views of Jupiter's circumpolar cyclones. At closest approach in this series of images, the Juno spacecraft was about 6,800 miles (11,000 kilometers) above the cloud tops, at a latitude of 82 degrees north of the equator.
Citizen scientist Brian Swift made this image using raw data from the JunoCam instrument, applying digital processing techniques to enhance color and clarity.
Quelle: NASA
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Update: 30.01.2025
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NASA Juno Mission Spots Most Powerful Volcanic Activity on Io to Date
A massive hotspot — larger the Earth’s Lake Superior — can be seen just to the right of Io’s south pole in this annotated image taken by the JIRAM infrared imager aboard NASA’s Juno on Dec. 27, 2024, during the spacecraft’s flyby of the Jovian moon.
Credit: NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM
Even by the standards of Io, the most volcanic celestial body in the solar system, recent events observed on the Jovian moon are extreme.
Scientists with NASA’s Juno mission have discovered a volcanic hot spot in the southern hemisphere of Jupiter’s moon Io. The hot spot is not only larger than Earth’s Lake Superior, but it also belches out eruptions six times the total energy of all the world’s power plants. The discovery of this massive feature comes courtesy of Juno’s Jovian Infrared Auroral Mapper (JIRAM) instrument, contributed by the Italian Space Agency.
“Juno had two really close flybys of Io during Juno’s extended mission,” said the mission’s principal investigator, Scott Bolton of the Southwest Research Institute in San Antonio. “And while each flyby provided data on the tormented moon that exceeded our expectations, the data from this latest — and more distant — flyby really blew our minds. This is the most powerful volcanic event ever recorded on the most volcanic world in our solar system — so that’s really saying something.”
Images of Io captured in 2024 by the JunoCam imager aboard NASA’s Juno show significant and visible surface changes (indicated by the arrows) near the Jovian moon’s south pole. These changes occurred between the 66th and 68th perijove, or the point during Juno’s orbit when it is closest to Jupiter.
Credit: NASA/JPL-Caltech/SwRI/MSSS Image processing by Jason Perry
The source of Io’s torment: Jupiter. About the size of Earth’s Moon, Io is extremely close to the mammoth gas giant, and its elliptical orbit whips it around Jupiter once every 42.5 hours. As the distance varies, so does the planet’s gravitational pull, which leads to the moon being relentlessly squeezed. The result: immense energy from frictional heating that melts portions of Io’s interior, resulting in a seemingly endless series of lava plumes and ash venting into its atmosphere from the estimated 400 volcanoes that riddle its surface.
Close Flybys
Designed to capture the infrared light (which isn’t visible to the human eye) emerging from deep inside Jupiter, JIRAM probes the gas giant’s weather layer, peering 30 to 45 miles (50 to 70 kilometers) below its cloud tops. But since NASA extended Juno’s mission, the team has also used the instrument to study the moons Io, Europa, Ganymede, and Callisto.
During its extended mission, Juno’s trajectory passes by Io every other orbit, flying over the same part of the moon each time. Previously, the spacecraft made close flybys of Io in December 2023 and February 2024, getting within about 930 miles (1,500 kilometers) of its surface. The latest flyby took place on Dec. 27, 2024, bringing the spacecraft within about 46,200 miles (74,400 kilometers) of the moon, with the infrared instrument trained on Io’s southern hemisphere.
Io Brings the Heat
“JIRAM detected an event of extreme infrared radiance — a massive hot spot — in Io’s southern hemisphere so strong that it saturated our detector,” said Alessandro Mura, a Juno co-investigator from the National Institute for Astrophysics in Rome. “However, we have evidence what we detected is actually a few closely spaced hot spots that emitted at the same time, suggestive of a subsurface vast magma chamber system. The data supports that this is the most intense volcanic eruption ever recorded on Io.”
The JIRAM science team estimates the as-yet-unnamed feature spans 40,000 square miles (100,000 square kilometers). The previous record holder was Io’s Loki Patera, a lava lake of about 7,700 square miles (20,000 square kilometers). The total power value of the new hot spot’s radiance measured well above 80 trillion watts.
Picture This
The feature was also captured by the mission’s JunoCam visible light camera. The team compared JunoCam images from the two previous Io flybys with those the instrument collected on Dec. 27. And while these most recent images are of lower resolution since Juno was farther away, the relative changes in surface coloring around the newly discovered hot spot were clear. Such changes in Io’s surface are known in the planetary science community to be associated with hot spots and volcanic activity.
An eruption of this magnitude is likely to leave long-lived signatures. Other large eruptions on Io have created varied features, such as pyroclastic deposits (composed rock fragments spewed out by a volcano), small lava flows that may be fed by fissures, and volcanic-plume deposits rich in sulfur and sulfur dioxide.
Juno will use an upcoming, more distant flyby of Io on March 3 to look at the hot spot again and search for changes in the landscape. Earth-based observations of this region of the moon may also be possible.
“While it is always great to witness events that rewrite the record books, this new hot spot can potentially do much more,” said Bolton. “The intriguing feature could improve our understanding of volcanism not only on Io but on other worlds as well.”
Quelle: NASA
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Update: 8.03.2025
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Juno reveals dozens of lava lakes on Jupiter’s moon Io
High-resolution images offer a glimpse at what might lie within the gas giant’s most fiery moon
Jupiter’s moon Io, seen here in a photo from the Galileo spacecraft, is the most volcanically active body in the solar system. JPL/NASA, UNIVERSITY OF ARIZONA
Jupiter’s moon Io, the most volcanically active body in the solar system, is littered with hundreds of erupting volcanoes. High-resolution images now reveal several dozen lava lakes, researchers report in the February Journal of Geophysical Research: Planets. These lakes are far larger than their analogs on Earth, and their structure sheds light on how magma moves beneath the surface of Io.
Io’s volcanism — probably present over the moon’s entire 4.6-billion-year existence — was discovered when the Voyager spacecraft flew by in 1979. The volcanic activity is caused by the intense gravitational pulls of Jupiter and nearby moons, which deform Io by tens of meters. “This squeezing is heating the body,” says Alessandro Mura, a planetary scientist at Italy’s National Institute for Astrophysics in Rome.
Using infrared images from NASA’s Juno spacecraft, which has orbited Jupiter since 2016, Mura’s team pinpointed more than 40 lava lakes ranging in diameter from about 10 to 100 kilometers. That’s much larger than the lava lakes found on Earth, which tend to measure tens to hundreds of meters across.
Volcanic activity and lava flows are known to be more extreme on other worlds, says Einat Lev, a volcanologist at Columbia University’s Lamont-Doherty Earth Observatory in Palisades, N.Y., who was not involved in the research. “A lot of planetary flows are much bigger” than Earth’s, she says.
Previous studies have reported lava lakes on Io but with only limited detail, Mura and colleagues note. The researchers found that most of the newly analyzed lava lakes are hottest at their perimeters. This suggests that these lakes are largely capped by a cooler crust of solidified lava.
That idea makes sense given the conditions on Io, says Alfred McEwen, a planetary geologist at the University of Arizona in Tucson who was not involved in the research. “It’s very, very cold. A crust starts forming immediately.”
Molten lava remains exposed at the lake edges probably because of how the lakes interact with their surroundings, Mura and his colleagues propose. Io’s lava lakes sit within caldera-like features with steep or even vertical walls, so as a lake fills or drains, its outer crust scrapes against those walls, breaking up the crust there and exposing fresh lava.
The findings also shed light on how magma moves beneath Io’s surface and feeds these lakes. None of the analyzed lakes had a hot spot in the middle, Mura notes, suggesting that magma doesn’t simply upwell at a lake’s center.
He and his team hope to understand whether multiple lava lakes are fed by a common magma reservoir. In that case, different lakes might change in size in lockstep. Such observations could help reveal details about the plumbing that powers Io’s volcanism, Mura says. “These can be a glimpse beneath the surface of Io.”
Quelle: ScienceNews