2.11.2020

Juno Data Indicates 'Sprites' or 'Elves' Frolic in Jupiter's Atmosphere

This illustration shows what a sprite could look like in Jupiter's atmosphere. Named after a mischievous, quick-witted character in English folklore, sprites last for only a few milliseconds. They feature a central blob of light with long tendrils of light extending down toward the ground and upward. In Earth's upper atmosphere, their interaction with nitrogen give sprites a reddish hue. At Jupiter, where the predominance of hydrogen in the upper atmosphere would likely give them a blue hue.

An instrument on the spacecraft may have detected transient luminous events - bright flashes of light in the gas giant's upper atmosphere.

New results from NASA's Juno mission at Jupiter suggest that either "sprites" or "elves" could be dancing in the upper atmosphere of the solar system's largest planet. It is the first time these bright, unpredictable and extremely brief flashes of light - formally known as transient luminous events, or TLE's - have been observed on another world. The findings were published on Oct. 27, 2020, in the Journal of Geophysical Research: Planets.

Scientists predicted these bright, superfast flashes of light should also be present in Jupiter's immense roiling atmosphere, but their existence remained theoretical. Then, in the summer of 2019, researchers working with data from Juno's ultraviolet spectrograph instrument (UVS) discovered something unexpected: a bright, narrow streak of ultraviolet emission that disappeared in a flash.

"UVS was designed to characterize Jupiter's beautiful northern and southern lights," said Giles, a Juno scientist and the lead author of the paper. "But we discovered UVS images that not only showed Jovian aurora, but also a bright flash of UV light over in the corner where it wasn't supposed to be. The more our team looked into it, the more we realized Juno may have detected a TLE on Jupiter."

Brief and Brilliant

Named after a mischievous, quick-witted character in English folklore, sprites are transient luminous events triggered by lightning discharges from thunderstorms far below. On Earth, they occur up to 60 miles (97 kilometers) above intense, towering thunderstorms and brighten a region of the sky tens of miles across, yet last only a few milliseconds (a fraction of the time it takes you to blink an eye).

Almost resembling a jellyfish, sprites feature a central blob of light (on Earth, it's 15 to 30 miles, or 24 to 48 kilometers, across), with long tendrils extending both down toward the ground and upward. Elves (short for Emission of Light and Very Low Frequency perturbations due to Electromagnetic Pulse Sources) appear as a flattened disk glowing in Earth's upper atmosphere. They, too, brighten the sky for mere milliseconds but can grow larger than sprites - up to 200 miles (320 kilometers) across on Earth.

Their colors are distinctive as well. "On Earth, sprites and elves appear reddish in color due to their interaction with nitrogen in the upper atmosphere," said Giles. "But on Jupiter, the upper atmosphere mostly consists of hydrogen, so they would likely appear either blue or pink."

Location, Location, Location

The occurrence of sprites and elves at Jupiter was predicted by several previously published studies. Synching with these predictions, the 11 large-scale bright events Juno's UVS instrument has detected occurred in a region where lightning thunderstorms are known to form. Juno scientists could also rule out that these were simply mega-bolts of lightning because they were found about 186 miles (300 kilometers) above the altitude where the majority of Jupiter's lightning forms - its water-cloud layer. And UVS recorded that the spectra of the bright flashes were dominated by hydrogen emissions.

A rotating, solar-powered spacecraft, Juno, arrived at Jupiter in 2016 after making a five-year journey. Since then, it has made 29 science flybys of the gas giant, each orbit taking 53 days.

"We're continuing to look for more telltale signs of elves and sprites every time Juno does a science pass," said Giles. "Now that we know what we are looking for, it will be easier to find them at Jupiter and on other planets. And comparing sprites and elves from Jupiter with those here on Earth will help us better understand electrical activity in planetary atmospheres."

The south pole of Jupiter is seen in this annotated image of data from the ultraviolet spectrograph (UVS) instrument aboard NASA's Juno spacecraft. Bands of bright white and blue near the south pole are Jupiter's southern aurora. But researchers also noticed an unusual bright flash of light well away from the auroral region, highlighted here by the yellow circle at about the 10 o'clock position (between longitudinal lines 270 and 240). Juno scientists believe it could be an indication of a bright, unpredictable, and extremely brief flash of light — known as a transient luminous event — that was triggered by lightning discharges from thunderstorms far below. The data for this UVS image was acquired on April 10, 2020.

More About the Mission

JPL, a division of Caltech in Pasadena, California, manages the Juno mission for the principal investigator, Scott Bolton, of the Southwest Research Institute in San Antonio. Juno is part of NASA's New Frontiers Program, which is managed at NASA's Marshall Space Flight Center in Huntsville, Alabama, for the agency's Science Mission Directorate in Washington. Lockheed Martin Space in Denver built and operates the spacecraft.

Quelle: NASA

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Update: 13.12.2020

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NASA's Juno Spacecraft Updates Quarter-Century Jupiter Mystery

The spacecraft has been collecting data on the gas giant's interior since July 2016. Some of its latest findings touch on "hot spots" in the planet's atmosphere.

Twenty-five years ago, NASA sent history's first probe into the atmosphere of the solar system's largest planet. But the information returned by the Galileo probe during its descent into Jupiter caused head-scratching: The atmosphere it was plunging into was much denser and hotter than scientists expected. New data from NASA's Juno spacecraft suggests that these "hot spots" are much wider and deeper than anticipated. The findings on Jupiter's hot spots, along with an update on Jupiter's polar cyclones, were revealed on Dec. 11, during a virtual media briefing at the American Geophysical Union's fall conference. 

"Giant planets have deep atmospheres without a solid or liquid base like Earth," said Scott Bolton, principal investigator of Juno at the Southwest Research Institute in San Antonio. "To better understand what is happening deep into one of these worlds, you need to look below the cloud layer. Juno, which recently completed its 29^thclose-up science pass of Jupiter, does just that. The spacecraft's observations are shedding light on old mysteries and posing new questions – not only about Jupiter, but about all gas giant worlds."

The latest longstanding mystery Juno has tackled stems from 57 minutes, 36 seconds of data Galileo beamed back on Dec. 7, 1995. When the probe radioed back that its surroundings were dry and windy, surprised scientists attributed the finding to the fact that the 75-pound (34-kilogram) probe had descended into the atmosphere within one of Jupiter's relatively rare hot spots – localized atmospheric "deserts" that traverse the gas giant's northern equatorial region. But results from Juno's microwave instrument indicate that the entire northern equatorial belt – a broad, brown, cyclonic band that wraps around the planet just above of the gas giant's equator – is generally a very dry region.

The implication is that the hot spots may not be isolated "deserts," but rather, windows into a vast region in Jupiter's atmosphere that may be hotter and drier than other areas. Juno's high-resolution data show that these Jovian hot spots are associated with breaks in the planet's cloud deck, providing a glimpse into Jupiter's deep atmosphere. They also show the hot spots, flanked by clouds and active storms, are fueling high-altitude electrical discharges recently discovered by Juno and known as "shallow lightning." These discharges, which occur in the cold upper reaches of Jupiter's atmosphere when ammonia mixes with water, are a piece of this puzzle.

"High up in the atmosphere, where shallow lightning is seen, water and ammonia are combined and become invisible to Juno's microwave instrument. This is where a special kind of hailstone that we call 'mushballs' are forming," said Tristan Guillot, a Juno co-investigator at the Université Côte d'Azur in Nice, France. "These mushballs get heavy and fall deep into the atmosphere, creating a large region that is depleted of both ammonia and water. Once the mushballs melt and evaporate, the ammonia and water change back to a gaseous state and are visible to Juno again."

Jupiter Weather Report

Last year the Juno team reported on the cyclones of the south pole. At that time, Juno's Jovian Infrared Auroral Mapper instrument captured images of a new cyclone appearing to attempt to join the five established cyclones revolving around the massive central cyclone at the south pole.

"That sixth cyclone, the baby of the group, appeared to be changing the geometric configuration at the pole – from a pentagon to a hexagon," said Bolton. "But, alas, the attempt failed; the baby cyclone got kicked out, moved away, and eventually disappeared."

At present, the team doesn't have an agreed-upon theory regarding how these giant polar vortices form – or why some appear stable while others are born, grow, and then die relatively quickly. Work continues on atmospheric models, but at present no one model appears to explain everything. How new storms appear, evolve, and are either accepted or rejected is key to understanding the circumpolar cyclones, which might help explain how the atmospheres of such giant planets work in general. 

More About the Mission

JPL, a division of Caltech in Pasadena, California, manages the Juno mission for the principal investigator, Scott Bolton, of the Southwest Research Institute in San Antonio. Juno is part of NASA's New Frontiers Program, which is managed at NASA's Marshall Space Flight Center in Huntsville, Alabama, for the agency's Science Mission Directorate in Washington. Lockheed Martin Space in Denver built and operates the spacecraft.

Quelle: NASA

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Update: 11.02.2021

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Deep Jet Streams in Jupiter’s Atmosphere

This view of Jupiter’s turbulent atmosphere from NASA’s Juno spacecraft includes several of the planet’s southern jet streams. Using data from Juno’s instruments, scientists discovered that Jupiter’s powerful atmospheric jet streams extend far deeper than previously imagined. Evidence from Juno shows the jet streams and belts penetrate about 1,800 miles (3,000 kilometers) down into the planet.

 

The storm known as the Great Red Spot is also visible on the horizon, nearly rotated out of view as Juno sped away from Jupiter at about 30 miles per second (48 kilometers per second), which is more than 100,000 mph (160,900 kilometers per hour). 

 

Citizen scientist Tanya Oleksuik created this color-enhanced image using data from the JunoCam camera. The original image was taken on Dec. 30, 2020 as the Juno spacecraft performed its 31st close flyby of Jupiter. At the time, the spacecraft was about 31,000 miles (about 50,000 kilometers) from the planet’s cloud tops, at a latitude of about 50 degrees South.

 

JunoCam's raw images are available for the public to peruse and process into image products at https://missionjuno.swri.edu/junocam/processing.  More information about NASA citizen science can be found at https://science.nasa.gov/citizenscience and https://www.nasa.gov/solve/opportunities/citizenscience.

More information about Juno is at https://www.nasa.gov/juno and https://missionjuno.swri.edu. For more about this finding and other science results, see https://www.missionjuno.swri.edu/science-findings.

Quelle: NASA

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Update: 29.03.2021

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NASA’s Juno Reveals Dark Origins of One of Jupiter’s Grand Light Shows

This illustration depicts ultraviolet polar aurorae on Jupiter and Earth. While the diameter of the Jovian world is 10 times larger than that of Earth, both planets have markedly similar aurora.

Credits: NASA/JPL-Caltech/SwRI/UVS/STScI/MODIS/WIC/IMAGE/ULiège

 

The gas-giant orbiter is illuminating the provenance of Jovian polar light shows.

 

New results from the Ultraviolet Spectrograph instrument on NASA’s Juno mission reveal for the first time the birth of auroral dawn storms – the early morning brightening unique to Jupiter’s spectacular aurorae. These immense, transient displays of light occur at both Jovian poles and had previously been observed only by ground-based and Earth-orbiting observatories, notably NASA’s Hubble Space Telescope. Results of this study were published March 16 in the journal AGU Advances.

First discovered by Hubble’s Faint Object Camera in 1994, dawn storms consist of short-lived but intense brightening and broadening of Jupiter’s main auroral oval – an oblong curtain of light that surrounds both poles – near where the atmosphere emerges from darkness in the early morning region. Before Juno, observations of Jovian ultraviolet aurora had offered only side views, hiding everything happening on the nightside of the planet. 

“Observing Jupiter’s aurora from Earth does not allow you to see beyond the limb, into the nightside of Jupiter’s poles. Explorations by other spacecraft – Voyager, Galileo, Cassini – happened from relatively large distances and did not fly over the poles, so they could not see the complete picture,” said Bertrand Bonfond, a researcher from the University of Liège in Belgium and lead author of the study. “That’s why the Juno data is a real game changer, allowing us a better understanding what is happening on the nightside, where the dawn storms are born.”

 

Researchers found dawn storms are born on the nightside of the gas giant. As the planet rotates, the soon-to-be dawn storm rotates with it into the dayside, where these complex and intensely bright auroral features grow even more luminous, emitting anywhere from hundreds to thousands of gigawatts of ultraviolet light into space. The jump in brightness implies that dawn storms are dumping at least 10 times more energy into Jupiter's upper atmosphere than typical aurora.

 

This video clip depicts the evolution of a dawn storm in Jupiter’s polar aurorae. The imagery for the video was collected using data from the from the Ultraviolet Spectrograph instrument aboard NASA’s Juno spacecraft.

Credits: NASA/JPL-Caltech/SwRI/UVS/ULiège

 

 

“When we looked at the whole dawn storm sequence, we couldn’t help but notice that they are very similar to a type of terrestrial auroras called substorms,” said Zhonghua Yao, co-author of the study at the University of Liège.”

 

Substorms result from brief disturbances in the Earth’s magnetosphere – the region of space controlled by the planet’s magnetic field – that release energy high into the planet’s ionosphere. The similarity between terrestrial and Jovian substorms is surprising because the magnetospheres of Jupiter and Earth are radically different. On Earth, the magnetosphere is essentially controlled by the interaction of the solar wind – the stream of charged particles flowing from the Sun – with Earth’s magnetic field. Jupiter’s magnetosphere is mostly populated by particles escaping from the volcanic moon Io, which then get ionized and trapped around the gas giant via its magnetic field.

 

These new findings will allow scientists to further study the differences and similarities driving the formation of aurora, providing a better understanding how these most beautiful of planetary phenomena occur on worlds both within our solar system and beyond.

 

“The power that Jupiter possesses is amazing. The energy in these dawn aurorae is yet another example of how powerful this giant planet really is,” said Scott Bolton, principal investigator of Juno from the Southwest Research Institute in San Antonio. “The dawn storm revelations are another surprise from the Juno mission, which is constantly rewriting the book on how giant planet’s work. With NASA’s recent mission extension, we’re looking forward to many more new insights and discoveries.”

Quelle: NASA

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Update: 12.04.2021

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New research reveals secret to Jupiter's curious aurora activity

Auroral displays continue to intrigue scientists, whether the bright lights shine over Earth or over another planet. The lights hold clues to the makeup of a planet's magnetic field and how that field operates.

New research about Jupiter proves that point -- and adds to the intrigue.

Peter Delamere, a professor of space physics at the University of Alaska Fairbanks Geophysical Institute, is among an international team of 13 researchers who have made a key discovery related to the aurora of our solar system's largest planet.

The team's work was published April 9, 2021, in the journal Science Advances. The research paper, titled "How Jupiter's unusual magnetospheric topology structures its aurora," was written by Binzheng Zhang of the Department of Earth Sciences at the University of Hong Kong; Delamere is the primary co-author.

Research done with a newly developed global magnetohydrodynamic model of Jupiter's magnetosphere provides evidence in support of a previously controversial and criticized idea that Delamere and researcher Fran Bagenal of the University of Colorado at Boulder put forward in a 2010 paper -- that Jupiter's polar cap is threaded in part with closed magnetic field lines rather than entirely with open magnetic field lines, as is the case with most other planets in our solar system.

"We as a community tend to polarize -- either open or closed -- and couldn't imagine a solution where it was a little of both," said Delamere, who has been studying Jupiter since 2000. "Yet in hindsight, that is exactly what the aurora was revealing to us."

Open lines are those that emanate from a planet but trail off into space away from the sun instead of reconnecting with a corresponding location in the opposite hemisphere.

On Earth, for example, the aurora appears on closed field lines around an area referred to as the auroral oval. It's the high latitude ring near -- but not at -- each end of Earth's magnetic axis.

Within that ring on Earth, however, and as with some other planets in our solar system, is an empty spot referred to as the polar cap. It's a place where magnetic field lines stream out unconnected -- and where the aurorae rarely appear because of it. Think of it like an incomplete electrical circuit in your home: No complete circuit, no lights.

Jupiter, however, has a polar cap in which the aurora dazzles. That puzzled scientists.

The problem, Delamere said, is that researchers were so Earth-centric in their thinking about Jupiter because of what they had learned about Earth's own magnetic fields.

The arrival at Jupiter of NASA's Juno spacecraft in July 2016 provided images of the polar cap and aurora. But those images, along with some captured by the Hubble Space Telescope, couldn't resolve the disagreement among scientists about open lines versus closed lines.

So Delamere and the rest of the research team used computer modeling for help. Their research revealed a largely closed polar region with a small crescent-shaped area of open flux, accounting for only about 9 percent of the polar cap region. The rest was active with aurora, signifying closed magnetic field lines.

Jupiter, it turns out, possesses a mix of open and closed lines in its polar caps.

"There was no model or no understanding to explain how you could have a crescent of open flux like this simulation is producing," he said. "It just never even entered my mind. I don't think anybody in the community could have imagined this solution. Yet this simulation has produced it."

"To me, this is a major paradigm shift for the way that we understand magnetospheres."

What else does this reveal? More work for researchers.

"It raises many questions about how the solar wind interacts with Jupiter's magnetosphere and influences the dynamics," Delamere said.

Jupiter's aurorally active polar cap could, for example, be due to the rapidity of the planet's rotation -- once every 10 hours compared to Earth's once every 24 hours -- and the enormity of its magnetosphere. Both reduce the impact of the solar wind, meaning the polar cap magnetic field lines are less likely to be torn apart to become open lines.

And to what extent does Jupiter's moon Io affect the magnetic lines within Jupiter's polar cap? Io is electrodynamically linked to Jupiter, something unique in our solar system, and as such is constantly stripped of heavy ions by its parent planet.

As the paper notes, "The jury is still out on the magnetic structure of Jupiter's magnetosphere and what exactly its aurora is telling us about its topology."

Quelle: AAAS

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Update: 5.06.2021

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NASA’s Juno to Get a Close Look at Jupiter’s Moon Ganymede

Left to right: The mosaic and geologic maps of Jupiter’s moon Ganymede were assembled incorporating the best available imagery from NASA’s Voyager 1 and 2 spacecraft and NASA’s Galileo spacecraft.

 

Credit: USGS Astrogeology Science Center/Wheaton/NASA/JPL-Caltech

The first of the gas-giant orbiter’s back-to-back flybys will provide a close encounter with the massive moon after over 20 years.

On Monday, June 7, at 1:35 p.m. EDT (10:35 a.m. PDT), NASA’s Juno spacecraft will come within 645 miles (1,038 kilometers) of the surface of Jupiter’s largest moon, Ganymede. The flyby will be the closest a spacecraft has come to the solar system’s largest natural satellite since NASA’s Galileo spacecraft made its penultimate close approach back on May 20, 2000. Along with striking imagery, the solar-powered spacecraft’s flyby will yield insights into the moon’s composition, ionosphere, magnetosphere, and ice shell. Juno’s measurements of the radiation environment near the moon will also benefit future missions to the Jovian system.

Ganymede is bigger than the planet Mercury and is the only moon in the solar system with its own magnetosphere – a bubble-shaped region of charged particles surrounding the celestial body.

“Juno carries a suite of sensitive instruments capable of seeing Ganymede in ways never before possible,” said Juno Principal Investigator Scott Bolton of the Southwest Research Institute in San Antonio. “By flying so close, we will bring the exploration of Ganymede into the 21st century, both complementing future missions with our unique sensors and helping prepare for the next generation of missions to the Jovian system – NASA’s Europa Clipper and ESA’s [European Space Agency’s] JUpiter ICy moons Explorer [JUICE] mission.”

Juno’s science instruments will begin collecting data about three hours before the spacecraft’s closest approach. Along with the Ultraviolet Spectrograph (UVS) and Jovian Infrared Auroral Mapper (JIRAM) instruments, Juno’s Microwave Radiometer’s (MWR) will peer into Ganymede’s water-ice crust, obtaining data on its composition and temperature.

Animation of a rotating globe of Ganymede, with a geologic map superimposed over a global color mosaic.

Credit: USGS Astrogeology Science Center/Wheaton/ASU/NASA/JPL-Caltech

“Ganymede’s ice shell has some light and dark regions, suggesting that some areas may be pure ice while other areas contain dirty ice,” said Bolton. “MWR will provide the first in-depth investigation of how the composition and structure of the ice varies with depth, leading to a better understanding of how the ice shell forms and the ongoing processes that resurface the ice over time.” The results will complement those from ESA’s forthcoming JUICE mission, which will look at the ice using radar at different wavelengths when it becomes the first spacecraft to orbit a moon other than Earth’s Moon in 2032.

Signals from Juno’s X-band and Ka-band radio wavelengths will be used to perform a radio occultation experiment to probe the moon’s tenuous ionosphere (the outer layer of an atmosphere where gases are excited by solar radiation to form ions, which have an electrical charge).

“As Juno passes behind Ganymede, radio signals will pass through Ganymede’s ionosphere, causing small changes in the frequency that should be picked up by two antennas at the Deep Space Network’s Canberra complex in Australia,” said Dustin Buccino, a signal analysis engineer for the Juno mission at JPL. “If we can measure this change, we might be able to understand the connection between Ganymede’s ionosphere, its intrinsic magnetic field, and Jupiter’s magnetosphere.”

Find out where Juno is at this moment with NASA’s interactive Eyes on the Solar System. With three giant blades stretching out some 66 feet (20 meters) from its cylindrical, six-sided body, the Juno spacecraft is a dynamic engineering marvel, spinning to keep itself stable as it makes oval-shaped orbits around Jupiter.

Three Cameras, Two Jobs

Normally, Juno’s Stellar Reference Unit (SRU) navigation camera is tasked with helping keep the Jupiter orbiter on course, but during the flyby it will do double duty. Along with its navigation duties, the camera – which is well shielded against radiation that could otherwise adversely affect it – will gather information on the high-energy radiation environment in the region near Ganymede by collecting a special set of images.

“The signatures from penetrating high-energy particles in Jupiter’s extreme radiation environment appear as dots, squiggles, and streaks in the images – like static on a television screen. We extract these radiation-induced noise signatures from SRU images to obtain diagnostic snapshots of the radiation levels encountered by Juno,” said Heidi Becker, Juno’s radiation monitoring lead at JPL.

Meanwhile, the Advanced Stellar Compass camera, built at the Technical University of Denmark, will count very energetic electrons that penetrate its shielding with a measurement every quarter of a second.

Also being enlisted is the JunoCam imager. Conceived to bring the excitement and beauty of Jupiter exploration to the public, the camera has provided an abundance of useful science as well during the mission’s almost five-year tenure at Jupiter. For the Ganymede flyby, JunoCam will collect images at a resolution equivalent to the best from Voyager and Galileo. The Juno science team will scour the images, comparing them to those from previous missions, looking for changes in surface features that might have occurred over four-plus decades. Any changes to crater distribution on the surface could help astronomers better understand the current population of objects that impact moons in the outer solar system.

Due to the speed of the flyby, the icy moon will – from JunoCam’s viewpoint – go from being a point of light to a viewable disk then back to a point of light in about 25 minutes. So that’s just enough time for five images.

“Things usually happen pretty quick in the world of flybys, and we have two back-to-back next week. So literally every second counts,” said Juno Mission Manager Matt Johnson of JPL. “On Monday, we are going to race past Ganymede at almost 12 miles per second (19 kilometers per second). Less than 24 hours later we’re performing our 33rd science pass of Jupiter – screaming low over the cloud tops, at about 36 miles per second (58 kilometers per second). It is going to be a wild ride.”

More About the Mission

JPL, a division of Caltech in Pasadena, California, manages the Juno mission for the principal investigator, Scott J. Bolton, of the Southwest Research Institute in San Antonio. Juno is part of NASA’s New Frontiers Program, which is managed at NASA’s Marshall Space Flight Center in Huntsville, Alabama, for the agency’s Science Mission Directorate in Washington. Lockheed Martin Space in Denver built and operates the spacecraft.

Quelle: NASA

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Update: 8.06.2021

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NASA’s Juno probe will get close to Jupiter’s moon Ganymede on Monday

Ganymede is bigger than Mercury

USGS Astrogeology Science Center/ Wheaton/ NASA/ JPL-Caltech

On Monday NASA’s Juno space probe, which has been orbiting Jupiter since 2016, will get a close-up look at Jupiter’s biggest moon Ganymede, the agency said in a press release. It will be the closest NASA has gotten to the largest moon in the solar system for more than 20 years— Galileo cruised by Ganymede in 2000— coming within 645 miles of its surface. The information Juno gathers will give insight into the moon’s composition and ice shell, as well as provide data for future missions to Jupiter.

“Juno carries a suite of sensitive instruments capable of seeing Ganymede in ways never before possible,” said principal investigator Scott Bolton of the Southwest Research Institute in San Antonio. “By flying so close, we will bring the exploration of Ganymede into the 21st century, both complementing future missions with our unique sensors and helping prepare for the next generation of missions to the Jovian system.”

Those missions include NASA’s Europa Clipper (launch date still TBD) and the European Space Agency’s JUpiter ICy moons Explorer [JUICE] mission, slated to launch next year and arrive at Jupiter in 2029 (and kudos to the ESA for going the extra mile on that acronym).

Ganymede is bigger than Mercury and is the only moon in the solar system with its own magnetosphere, which NASA describes as “a bubble-shaped region of charged particles” that surrounds it. The JunoCam, which has taken many of the most striking photos of Jupiter during its mission will only be able to snap about five images during the flyby, since Ganymede will appear and fade from view all within a 25-minute window. Three hours before Juno gets to its closest point near Ganymede, its science instruments will begin collecting data.

“Literally every second counts,” said Matt Johnson, Juno mission manager at NASA’s Jet Propulsion Laboratory. “On Monday, we are going to race past Ganymede at almost 12 miles per second (19 kilometers per second).” And less than 24 hours later, Juno will make its 33rd science pass of Jupiter, he added.

Juno is expected to get closest to Ganymede at about 1:35PM ET on Monday. You can track where Juno is now with NASA’s Eyes on the Solar System interactive.

Quelle: The Verge

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Update: 10.06.2021

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Mighty Jupiter moon Ganymede pictured in close-up

The American space agency's Juno probe has returned some close-in views of Ganymede - one of Jupiter's four Galilean moons and the largest natural satellite in the Solar System.

The imagery was acquired from a distance of about 1,000km.

It's the nearest any spacecraft has been to Ganymede in more than 20 years.

Juno's was an opportunity pass; its everyday duties are to study Jupiter. But the European Space Agency will soon send a dedicated mission.

The JUpiter ICy moon Explorer, or Juice for short, will make a series of fly-bys around two other Galilean moons, Callisto and Europa, before then putting itself in a settled orbit around Ganymede, expected to occur in 2032.

Juno's pictures show the impacted and cracked surface of the big moon in remarkable detail. They'll be compared with the pictures acquired by Nasa's Galileo (1995-2003) and Voyager (1979) probes to see if there have been any changes through time.

 

"This is the closest any spacecraft has come to this mammoth moon in a generation," said Juno Principal Investigator Scott Bolton of the Southwest Research Institute in San Antonio. "We are going to take our time before we draw any scientific conclusions, but until then we can simply marvel at this celestial wonder."

One of the fascinations of Ganymede - and of Callisto and Europa - is that they all likely have oceans of water below their ice surfaces.

Nasa says it will release colour imagery from Juno's Ganymede flyby shortly.

IMAGE COPYRIGHTESA