Tag Archives: #jupiter

Space Scientists Reveal Secret Behind Jupiter’s ‘Energy Crisis’ (Planetary Science)

New research published in Nature has revealed the solution to Jupiter’s ‘energy crisis’, which has puzzled astronomers for decades.

Space scientists at the University of Leicester worked with colleagues from the Japanese Space Agency (JAXA), Boston University, NASA’s Goddard Space Flight Center and the National Institute of Information and Communications Technology (NICT) to reveal the mechanism behind Jupiter’s atmospheric heating.

Now, using data from the Keck Observatory in Hawai’i, astronomers have created the most-detailed yet global map of the gas giant’s upper atmosphere, confirming for the first time that Jupiter’s powerful aurorae are responsible for delivering planet-wide heating.

Dr James O’Donoghue is a researcher at JAXA and completed his PhD at Leicester, and is lead author for the research paper.

He said: “We first began trying to create a global heat map of Jupiter’s uppermost atmosphere at the University of Leicester. The signal was not bright enough to reveal anything outside of Jupiter’s polar regions at the time, but with the lessons learned from that work we managed to secure time on one of the largest, most competitive telescopes on Earth some years later.

“Using the Keck telescope we produced temperature maps of extraordinary detail. We found that temperatures start very high within the aurora, as expected from previous work, but now we could observe that Jupiter’s aurora, despite taking up less than 10% of the area of the planet, appear to be heating the whole thing.

“This research started in Leicester and carried on at Boston University and NASA before ending at JAXA in Japan. Collaborators from each continent working together made this study successful, combined with data from NASA’s Juno spacecraft in orbit around Jupiter and JAXA’s Hisaki spacecraft, an observatory in space.”

Dr Tom Stallard and Dr Henrik Melin are both part of the School of Physics and Astronomy at the University of Leicester. Dr Stallard added: “There has been a very long-standing puzzle in the thin atmosphere at the top of every Giant Planet within our solar system.

“With every Jupiter space mission, along with ground-based observations, over the past 50 years, we have consistently measured the equatorial temperatures as being much too hot.

“This ‘energy crisis’ has been a long standing issue – do the models fail to properly model how heat flows from the aurora, or is there some other unknown heat source near the equator?

“This paper describes how we have mapped this region in unprecedented detail and have shown that, at Jupiter, the equatorial heating is directly associated with auroral heating.”

Aurorae occur when charged particles are caught in a planet’s magnetic field. These spiral along the field lines towards the planet’s magnetic poles, striking atoms and molecules in the atmosphere to release light and energy.

On Earth, this leads to the characteristic light show that forms the Aurora Borealis and Australis. At Jupiter, the material spewing from its volcanic moon, Io, leads to the most powerful aurora in the Solar System and enormous heating in the polar regions of the planet.

Although the Jovian aurorae have long been a prime candidate for heating the planet’s atmosphere, observations have previously been unable to confirm or deny this until now.

Previous maps of the upper atmospheric temperature were formed using images consisting of only several pixels. This is not enough resolution to see how the temperature might be changed across the planet, providing few clues as to the origin of the extra heat.

Researchers created five maps of the atmospheric temperature at different spatial resolutions, with the highest resolution map showing an average temperature measurement for squares two degrees longitude ‘high’ by two degrees latitude ‘wide’.

The team scoured more than 10,000 individual data points, only mapping points with an uncertainty of less than five per cent.

Models of the atmospheres of gas giants suggest that they work like a giant refrigerator, with heat energy drawn from the equator towards the pole, and deposited in the lower atmosphere in these pole regions.

These new findings suggest that fast-changing aurorae may drive waves of energy against this poleward flow, allowing heat to reach the equator.

Observations also showed a region of localised heating in the sub-auroral region that could be interpreted as a limited wave of heat propagating equatorward, which could be interpreted as evidence of the process driving heat transfer.

Planetary research at the University of Leicester spans the breadth of Jovian system, from the planet’s magnetosphere and atmosphere, out to its diverse collection of satellites.

Leicester researchers are members of the Juno mission made up of a global team astronomers observing the giant planet, and are leading Jupiter observations from the forthcoming James Webb Space Telescope. Leicester also plays a leading role in science and instrumentation on the European Space Agency (ESA)’s Jupiter Icy Moons Explorer (JUICE), due for launch in 2022.

‘Global upper-atmospheric heating on Jupiter by the polar aurorae’ is available in Nature.


Featured image: Jupiter is shown in visible light for context underneath an artistic impression of the Jovian upper atmosphere’s infrared glow. The brightness of this upper atmosphere layer corresponds to temperatures, from hot to cold, in this order: white, yellow, bright red and lastly, dark red. The aurorae are the hottest regions and the image shows how heat may be carried by winds away from the aurora and cause planet-wide heating. Credit: J. O'Donoghue (JAXA)/Hubble/NASA/ESA/A. Simon/J. Schmidt


Reference: O’Donoghue, J. et al, Global upper-atmospheric heating on Jupiter by the polar aurorae, Nature (2021). DOI: 10.1038/s41586-021-03706-w


Provided by University of Leicester

Hot And Dry: SPIRou Reveals the Atmosphere Of Hot Jupiter Tau Boötis b (Planetary Science)

Measuring the composition of the atmosphere of the hot Jupiter Tau Boötis b more precisely than ever, an iREx-led team of astronomers provides a better understanding of giant exoplanets.

Using the SPIRou spectropolarimeter on the Canada-France-Hawaii Telescope in Hawaii, a team led by Stefan Pelletier, a PhD student at Université de Montréal’s Institute for Research on Exoplanets (iREx), studied the atmosphere of the gas giant exoplanet Tau Boötis b, a scorching hot world that takes a mere three days to orbit its host star. 

Their detailed analysis, presented in a paper published today in the Astronomical Journal, shows that the atmosphere of the gaseous planet contains carbon monoxide, as expected, but surprisingly no water, a molecule that was thought to be prevalent and should have been easily detectable with SPIRou. 

Tau Boötis b is a planet that is 6.24 times more massive than Jupiter and eight times closer to its parent star than Mercury is to the Sun. Located only 51 light-years from Earth and 40 per cent more massive than the Sun, its star, Tau Boötis, is one of the brightest known planet-bearing stars, and is visible to the naked eye in the Boötes constellation.

Tau Boötis b was one of the first exoplanets ever discovered, in 1996, thanks to the radial velocity method, which detects the slight back-and-forth motion of a star generated by the gravitational tug of its planet. Its atmosphere had been studied a handful of times before, but never with an instrument as powerful as SPIRou to reveal  its molecular content. 

Searching for water 

Assuming Tau Boötis b formed in a protoplanetary disk with a composition similar to that of our Solar System, models show that water vapour should be present in large quantities in its atmosphere. It should thus have been easy to detect with an instrument such as SPIRou.

“We expected a strong detection of water, with maybe a little carbon monoxide,” explained Pelletier. “We were, however, surprised to find the opposite: carbon monoxide, but no water.”

The team worked hard to make sure the results could not be attributed to problems with the instrument or the analysis of the data.

“Once we convinced ourselves the content of water was indeed much lower than expected on Tau Boötis b, we were able to start searching for formation mechanisms that could explain this,” said Pelletier.

Studying hot Jupiters to better understand Jupiter and Saturn

“Hot Jupiters like Tau Boötis b offer an unprecedented opportunity to probe giant planet formation”, said co-author Björn Benneke, an astrophysics professor and  Pelletier’s PhD supervisor at UdeM. “The composition of the planet gives clues as to where and how this giant planet formed.”

The key to revealing the formation location and mechanism of giant planets is imprinted in their molecular atmospheric composition. The extreme temperature of hot Jupiters allows most molecules in their atmospheres to be in gaseous form, and therefore detectable with current instruments. Astronomers can thus precisely measure the content of their atmospheres.

“In our Solar System, Jupiter and Saturn are really cold,” said Benneke. “Some molecules such as water are frozen and hidden deep in their atmospheres; thus, we have a very poor knowledge of their abundance. Studying hot Jupiters provides a way to better understand our own giant planets. The low amount of water on Tau Boötis b could mean that our own Jupiter is also drier than we had previously thought.” 

The Canada-France-Hawaii Telescope, that hosts the SPIRou instrument that allowed Pelletier and his team to analyse exoplanet Tau Boötis b. Credits: Canada-France-Hawaii Telescope/Cuillandre.

SPIRou: a unique instrument

Tau Boötis b is one of the first planets studied with the new SPIRou instrument since it was recently put into service at the Canada-France-Hawaii Telescope. This instrument was developed by researchers from several scientific institutions including UdeM.

“This spectropolarimeter can analyze the planet’s thermal light — the light emitted by the planet itself — in an unprecedentedly large range of colours, and with a resolution that allows for the identification of many molecules at once: water, carbon monoxide, methane, etc.” said co-author and iREx researcher Neil Cook, an expert on the SPIRou instrument. 

The team spent 20 hours observing the exoplanet with SPIRou between April 2019 and June 2020.

“We measured the abundance of all major molecules that contain either carbon or oxygen,” said Pelletier. “Since they are the two most abundant elements in the universe, after hydrogen and helium, that gives us a very complete picture of the content of the atmosphere.” 

Like most planets, Tau Boötis b does not pass in front of its star as it orbits around it, from Earth’s point of view. However, the study of exoplanet atmospheres has mostly been limited to “transiting” planets – those that cause periodic dips in the light of their star when they obscure part of their light.

“It is the first time that we get such precise measurements on the atmospheric composition of a non-transiting exoplanet,” said PhD student Caroline Piaulet, a co-author of the study.

“This work opens the door to studying in detail the atmospheres of a large number of exoplanets, even those that do not transit their star.” 

A composition similar to Jupiter

Through their analysis, Pelletier and his colleagues were able to conclude that Tau Boötis b’s atmospheric composition has roughly five times as much carbon as that found in the Sun, quantities similar to that measured for Jupiter. 

This may be a suggest that hot Jupiters could form much further from their host star, at distances that are similar to the giant planets in our Solar System, and have simply experienced a different evolution, which included a migration towards the star. 

“According to what we found for Tau Boötis b, it would seem that, at least composition-wise, hot Jupiters may not be so different from our own Solar System giant planets after all,” concluded Pelletier.

About this study 

Where is the water? Jupiter-like C/H ratio but strong H2O depletion found on Tau Boötis b using SPIRou,” by Stefan Pelletier et al., was published July 28th, 2021 in the Astronomical Journal. 

In addition to Stefan PelletierBjörn BennekeNeil Cook and Caroline Piaulet, the team includes Institute for research on exoplanets (iREx) members Antoine Darveau-BernierAnne BoucherLouis-Philippe CoulombeÉtienne ArtigauDavid LafrenièreSimon DelisleRomain AllartRené DoyonCharles Cadieux and Thomas Vandal, all based at Université de Montréal, and seven other co-authors from France, the United States, Portugal and Brazil. 

Funding was provided by the the Technologies for Exo-Planetary Science (TEPS) CREATE program, the Fonds de recherche du Québec – Nature et technologies (FRQNT), the Natural Sciences and Engineering Research Council of Canada (NSERC), the Trottier Family Foundation and the French National Research Agency (ANR).

Featured image: Artistic rendition of the exoplanet Tau Boötis b and its host star, Tau Boötis. Credit : ESO/L. Calçada.


Reference: Stefan Pelletier et al, Where Is the Water? Jupiter-like C/H Ratio but Strong H2O Depletion Found on τ Boötis b Using SPIRou, The Astronomical Journal (2021). DOI: 10.3847/1538-3881/ac0428


Provided by University of Montreal

Hubble Finds First Evidence of Water Vapor at Jupiter’s Moon Ganymede (Planetary Science)

For the first time, astronomers have uncovered evidence of water vapor in the atmosphere of Jupiter’s moon Ganymede. This water vapor forms when ice from the moon’s surface sublimates — that is, turns from solid to gas.

Scientists used new and archival datasets from NASA’s Hubble Space Telescope to make the discovery, published in the journal Nature Astronomy.

Previous research has offered circumstantial evidence that Ganymede, the largest moon in the solar system, contains more water than all of Earth’s oceans. However, temperatures there are so cold that water on the surface is frozen solid. Ganymede’s ocean would reside roughly 100 miles below the crust; therefore, the water vapor would not represent the evaporation of this ocean.

Astronomers re-examined Hubble observations from the last two decades to find this evidence of water vapor.

In 1998, Hubble’s Space Telescope Imaging Spectrograph took the first ultraviolet (UV) images of Ganymede, which revealed colorful ribbons of electrified gas called auroral bands, and provided further evidence that Ganymede has a weak magnetic field.

The similarities in these UV observations were explained by the presence of molecular oxygen (O2). But some observed features did not match the expected emissions from a pure O2 atmosphere. At the same time, scientists concluded this discrepancy was likely related to higher concentrations of atomic oxygen (O).

As part of a large observing program to support NASA’s Juno mission in 2018, Lorenz Roth of the KTH Royal Institute of Technology in Stockholm, Sweden led the team that set out to measure the amount of atomic oxygen with Hubble. The team’s analysis combined the data from two instruments: Hubble’s Cosmic Origins Spectrograph in 2018 and archival images from the Space Telescope Imaging Spectrograph (STIS) from 1998 to 2010.

To their surprise, and contrary to the original interpretations of the data from 1998, they discovered there was hardly any atomic oxygen in Ganymede’s atmosphere. This means there must be another explanation for the apparent differences in these UV aurora images.

Roth and his team then took a closer look at the relative distribution of the aurora in the UV images. Ganymede’s surface temperature varies strongly throughout the day, and around noon near the equator it may become sufficiently warm that the ice surface releases (or sublimates) some small amounts of water molecules. In fact, the perceived differences in the UV images are directly correlated with where water would be expected in the moon’s atmosphere.

In 1998, Hubble's Space Telescope Imaging Spectrograph (STIS) took these first ultraviolet (UV) images of Ganymede, which revealed a particular pattern in the observed emissions from the moon's atmosphere.
In 1998, Hubble’s Space Telescope Imaging Spectrograph took these first ultraviolet images of Ganymede, which revealed a particular pattern in the observed emissions from the moon’s atmosphere. The moon displays auroral bands that are somewhat similar to aurora ovals observed on Earth and other planets with magnetic fields. This was an illustrative evidence for the fact that Ganymede has a permanent magnetic field. The similarities in the ultraviolet observations were explained by the presence of molecular oxygen. The differences were explained at the time by the presence of atomic oxygen, which produces a signal that affects one UV color more than the other.Credits: NASA, ESA, Lorenz Roth (KTH)

“So far only the molecular oxygen had been observed,” explained Roth. “This is produced when charged particles erode the ice surface. The water vapor that we measured now originates from ice sublimation caused by the thermal escape of water vapor from warm icy regions.”

This finding adds anticipation to ESA (European Space Agency)’s upcoming mission, JUICE, which stands for JUpiter ICy moons Explorer. JUICE is the first large-class mission in ESA’s Cosmic Vision 2015-2025 program. Planned for launch in 2022 and arrival at Jupiter in 2029, it will spend at least three years making detailed observations of Jupiter and three of its largest moons, with particular emphasis on Ganymede as a planetary body and potential habitat.

Ganymede was identified for detailed investigation because it provides a natural laboratory for analysis of the nature, evolution and potential habitability of icy worlds in general, the role it plays within the system of Galilean satellites, and its unique magnetic and plasma interactions with Jupiter and its environment.

“Our results can provide the JUICE instrument teams with valuable information that may be used to refine their observation plans to optimize the use of the spacecraft,” added Roth.

Right now, NASA’s Juno mission is taking a close look at Ganymede and recently released new imagery of the icy moon. Juno has been studying Jupiter and its environment, also known as the Jovian system, since 2016.

Video: Astronomers have used new and archival datasets from NASA’s Hubble Space Telescope to uncover evidence of water vapor in the atmosphere of Jupiter’s moon Ganymede. The vapor is present due to the thermal excitation of water molecules from the moon’s icy surface. Previous research has offered circumstantial evidence for the moon containing more water than all of Earth’s oceans. However, temperatures there are so cold that water on the surface freezes and the ocean lies roughly 100 miles below the crust.Credits: NASA’s Goddard Space Flight Center

Understanding the Jovian system and unravelling its history, from its origin to the possible emergence of habitable environments, will provide us with a better understanding of how gas giant planets and their satellites form and evolve. In addition, new insights will hopefully be found on the habitability of Jupiter-like exoplanetary systems.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.

Featured image: This image presents Jupiter’s moon Ganymede as seen by the NASA’s Hubble Space Telescope in 1996. Ganymede is located half a billion miles (over 600 million km) away, and Hubble can follow changes on the moon and reveal other characteristics at ultraviolet and near-infrared wavelengths. Astronomers have now used new and archival datasets from Hubble to reveal evidence of water vapor in the atmosphere of Jupiter’s moon Ganymede for the first time, which is present due to the thermal escape of water vapor from the moon’s icy surface.Credits: NASA, ESA, John Spencer (SwRI Boulder)


Reference: Roth, L., Ivchenko, N., Gladstone, G.R. et al. A sublimated water atmosphere on Ganymede detected from Hubble Space Telescope observations. Nat Astron (2021). https://doi.org/10.1038/s41550-021-01426-9


Provided by NASA

Jupiter’s Super Polar Cyclones are Here to Stay (Planetary Science)

Weizmann Institute scientists reveal how gigantic cyclones remain stable at both of Jupiter’s poles

Until recently, before NASA’s Juno space probe entered its orbit around the planet Jupiter, no one knew that powerful cyclones, approximately the size of Australia, rage across its polar regions. Jupiter’s storms, as opposed to their earthly variety, do not disperse, hardly change, and are clearly not associated with flying rooftops and damp weather reporters. In an article published today in Nature Geoscience, researchers from the Weizmann Institute of Science reveal the mysteries of Jupiter’s cyclones: which forces are at work fixing these gargantuan storms to their polar locations, and why their numbers and locations remain more or less constant over time.

“We can think of Jupiter as an ideal climate laboratory,” says Prof. Yohai Kaspi of Weizmann’s Earth and Planetary Sciences Department. Earth is an intricate and multivariable system: it has oceans and an atmosphere, continents, biology – and of course, human activity. Jupiter, on the other hand, the largest planet in our solar system, is composed of gas and is therefore a far easier system to study, one that we can create predictions for and test hypotheses on. The data required for these predictions and hypotheses is collected by Juno – a research probe that was launched by NASA in 2011 and entered Jupiter’s orbit mid-2016. Kaspi, a NASA co-investigator on the Juno mission, witnessed one of its more exciting findings: the cyclone storms swirling around the planet’s poles.

“If we look at older images of Jupiter taken before 2016,” says Kaspi, “we see that the poles were commonly represented as large grey areas because no one knew then what they actually look like.” The reason for that lies in the fact that the solar system is organized on the same plane, which is very close to the plane of Jupiter’s equator. Therefore, past observations of the planet that were carried out from Earth, or from earlier space missions, could for the most part only capture Jupiter’s lower latitudes. Hence, one of the Juno mission’s noteworthy innovations is its polar orbit, which allowed researchers to observe in detail Jupiter’s tumultuous poles for the first time. This is exactly how the cyclones were exposed, surprisingly organized and resembling a round tray of cinnamon rolls, along latitude 84°N and S. Moreover, data gathered from Juno’s many orbits around Jupiter indicate that the number of cyclones remains fixed – eight are active around the north pole and five around the south. “This discovery was very surprising at the time,” says Kaspi, “because we expected the poles to be more or less symmetric.” In a previous study, Kaspi used the lack of symmetry in Jupiter’s gravitational field to determine the depth of the strong east-west wind belts that are characteristic of the planet’s atmosphere.

Kaspi: “The poles of Jupiter and the other gaseous planets are, perhaps, the last spots in the solar system that are still left to explore”

On Earth, tropical cyclonic storms form in areas where the water temperature exceeds 26 degrees Celsius – usually in the center of the Atlantic and Pacific Oceans – and they drift in a circular motion toward the poles, owing to a pull resulting from the planet’s spin. On Jupiter, on the other hand, strong jet streams prevent these storms from forming below latitude 60º – only above it are the currents weak enough to allow cyclones to rage on. What causes these particular storms on Jupiter to settle at latitude 84º? According to the new study, Jupiter’s cyclones are indeed attracted to the poles, but the polar storm located in the center of the ring of cyclones pushes them away, preventing them from reaching the pole itself.

“As long at the cyclones remain at a distance from the pole – they are attracted to it. But the nearer they venture – the more strongly they are repelled,” says doctoral student Nimrod Gavriel from Kaspi’s research group, whose thesis focuses on elucidating this phenomenon. “The question is whether the repulsion effect is strong enough to resist the pole’s attraction. Latitude 84º is where these forces even up.” Gavriel and Kaspi propose a mathematical model that considers the diameter of the polar cyclone (which is larger at the south pole than in the north), the possible minimal distance between each cyclone, the surface area around latitude 84º and the size of the cyclones and their spin, and that accurately predicts the presence of eight cyclones across the north pole. As for the south pole, based on their calculations, the number of cyclones should be 5.62. This number is consistent with the data collected by Juno: in reality this number cannot exist, but the five southern storms often separate into six storms, as observed during the probe’s eighteenth and thirty-fourth orbits around Jupiter. The proposed model also explains why this phenomenon is absent on Jupiter’s closest neighboring planet – Saturn.

“We are trying to understand atmospheric dynamics at a large scale, and providing a successful explanation for the phenomenon of Jupiter’s polar cyclones gives us the confidence that we truly know what’s going on there,” says Kaspi. This confidence may be paramount for us here on Earth, since a deeper understanding of cyclones could aid meteorologists to predict, for example, how the heating up of our planet will affect the movement of storms across it – a challenge that humanity will most likely face in the near future. But Kaspi’s fascination with the exploration of Jupiter is more straightforward: “There are no new islands to discover in the Pacific, and most planetary bodies in the solar system have already been mapped. The poles of Jupiter and the other gaseous planets are, perhaps, the last spots in the solar system that are still left to explore.”

Juno hovering above Jupiter’s south pole. In orbit around the solar system’s largest planet since 2016. Visualization: NASA

“We are expecting more valuable data to come in from Juno during the next couple of years,” Kaspi adds, following the recent extension of the Juno Mission to 2025. “Owing to gradual changes in the spacecraft’s polar orbit, it is now getting closer and closer to Jupiter’s north pole, allowing us to gain information about this polar region from several specialized instruments,” he concludes.

Science numbers: The diameter of each of Jupiter’s cyclones is about 4,000-5,000 kilometers, and they spin at velocities up to 360 kilometers per hour.

Featured image: Six cyclones in Jupiter’s south pole as captured by Juno’s infrared lens in February 2017. Surprisingly organized and resembling a round tray of cinnamon rolls. Photo credit: NASA


Reference: The number and location of Jupiter’s circumpolar cyclones explained by vorticity dynamics, Gavriel N. and Kaspi Y. (2021) Nature Geoscience.


Provided by Weizmann Institute of Science

NASA’s Juno Tunes Into Jovian Radio Triggered by Jupiter’s Volcanic Moon Io (Planetary Science)

The Juno Waves instrument “listened” to the radio emissions from Jupiter’s immense magnetic field to find their precise locations.

By listening to the rain of electrons flowing onto Jupiter from its intensely volcanic moon Io, researchers using NASA’s Juno spacecraft have found what triggers the powerful radio emissions within the monster planet’s gigantic magnetic field. The new result sheds light on the behavior of the enormous magnetic fields generated by gas-giant planets like Jupiter.

Jupiter has the largest, most powerful magnetic field of all the planets in our solar system, with a strength at its source about 20,000 times stronger than Earth’s. It is buffeted by the solar wind, a stream of electrically charged particles and magnetic fields constantly blowing from the Sun. Depending on how hard the solar wind blows, Jupiter’s magnetic field can extend outward as much as two million miles (3.2 million kilometers) toward the Sun and stretch more than 600 million miles (over 965 million kilometers) away from the Sun, as far as Saturn’s orbit.

The multicolored lines in this conceptual image represent the magnetic field lines that link Io’s orbit with Jupiter’s atmosphere. Radio waves emerge from the source and propagate along the walls of a hollow cone (gray area). Juno, its orbit represented by the white line crossing the cone, receives the signal when Jupiter’s rotation sweeps that cone over the spacecraft. Credit: NASA/GSFC/Jay Friedlander

Jupiter has several large moons that orbit within its massive magnetic field, with Io being the closest. Io is caught in a gravitational tug-of-war between Jupiter and the neighboring two of these other large moons, which generates internal heat that powers hundreds of volcanic eruptions across its surface.

These volcanoes collectively release one ton of material (gases and particles) per second into space near Jupiter. Some of this material splits up into electrically charged ions and electrons and is rapidly captured by Jupiter’s magnetic field. As Jupiter’s magnetic field sweeps past Io, electrons from the moon are accelerated along the magnetic field toward Jupiter’s poles. Along their way, these electrons generate “decameter” radio waves (so-called decametric radio emissions, or DAM). The Juno Waves instrument can “listen” to this radio emission that the raining electrons generate.

Video: Juno tunes into one of its favorite radio stations. Hear the decametric radio emissions triggered by the interaction of Io with Jupiter’s magnetic field. The Waves instrument on Juno detects radio signals whenever Juno’s trajectory crosses into the beam which is a cone-shaped pattern. This beam pattern is similar to a flashlight that is only emitting a ring of light rather than a full beam. Juno scientists then translate the radio emission detected to a frequency within the audible range of the human ear. Credit: University of Iowa/SwRI/NASA

The researchers used the Juno Waves data to identify the precise locations within Jupiter’s vast magnetic field where these radio emissions originated. These locations are where conditions are just right to generate the radio waves; they have the right magnetic field strength and the right density of electrons (not too much and not too little), according to the team.

“The radio emission is likely constant, but Juno has to be in the right spot to listen,” said Yasmina Martos of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the University of Maryland, College Park.

The radio waves emerge from the source along the walls of a hollow cone aligned with and controlled by the strength and shape of the magnetic field of Jupiter. Juno receives the signal only when Jupiter’s rotation sweeps that cone over the spacecraft, in the same way a lighthouse beacon shines briefly upon a ship at sea. Martos is lead author of a paper about this research published in June 2020 in the Journal of Geophysical Research, Planets.

Data from Juno allowed the team to calculate that the energy of the electrons generating the radio waves was far higher than previously estimated, as much as 23 times greater. Also, the electrons do not necessarily need to come from a volcanic moon. For example, they could be in the planet’s magnetic field (magnetosphere) or come from the Sun as part of the solar wind, according to the team.

More about this project and the Juno Mission

The research was funded by the Juno Project under NASA Grants NNM06AAa75c and 699041X to the Southwest Research Institute in San Antonio, Texas, and NASA Grant NNN12AA01C to NASA’s Jet Propulsion Laboratory, a division of Caltech in Pasadena, California. The team is composed of researchers from NASA Goddard, the National Institute of Technology (KOSEN) in Tokyo, Japan; Niihama College in Niihama, Ehime, Japan, the University of Iowa, Iowa City; and the Technical University of Denmark in Kongens Lyngby, Denmark. NASA JPL manages the Juno mission for the principal investigator, Scott J. Bolton, of the Southwest Research Institute. 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.

More information about Juno is available at:

https://www.nasa.gov/juno

https://www.missionjuno.swri.edu

Featured image: This processed image of Io by New Horizons shows the 290-kilometer-high (180-mile-high) plume of the volcano Tvashtar near Io’s north pole. Also visible is the Prometheus volcano’s much smaller plume in the 9 o’clock direction. The top of the Masubi volcano’s plume appears as an irregular bright patch near the bottom. Credit: NASA/JHUAPL/SwRI


Reference: Martos, Y. M., Imai, M., Connerney, J. E. P., Kotsiaros, S., & Kurth, W. S. (2020). Juno reveals new insights into Io-related decameter radio emissions. Journal of Geophysical Research: Planets, 125, e2020JE006415. https://doi.org/10.1029/2020JE006415


Provided by NASA JPL

Surface of Jupiter’s Moon Europa Churned by Small Impacts (Planetary Science)

Jupiter’s moon Europa and its global ocean may currently have conditions suitable for life. Scientists are studying processes on the icy surface as they prepare to explore.

It’s easy to see the impact of space debris on our Moon, where the ancient, battered surface is covered with craters and scars. Jupiter’s icy moon Europa withstands a similar trouncing – along with a punch of super-intense radiation. As the uppermost surface of the icy moon churns, material brought to the surface is zapped by high-energy electron radiation accelerated by Jupiter.

NASA-funded scientists are studying the cumulative effects of small impacts on Europa’s surface as they prepare to explore the distant moon with the Europa Clipper mission and study the possibilities for a future lander mission. Europa is of particular scientific interest because its salty ocean, which lies beneath a thick layer of ice, may currently have conditions suitable for existing life. That water may even make its way into the icy crust and onto the moon’s surface.

In this zoomed-in image of Europa’s surface, captured by NASA’s Galileo mission, the thin, bright layer, visible atop a cliff in the center shows the kind of areas churned by impact gardening. Credit: NASA/JPL-Caltech

New research and modeling estimate how far down that surface is disturbed by the process called “impact gardening.” The work, published July 12 in Nature Astronomy, estimates that the surface of Europa has been churned by small impacts to an average depth of about 12 inches (30 centimeters) over tens of millions of years. And any molecules that might qualify as potential biosignatures, which include chemical signs of life, could be affected at that depth.

That’s because the impacts would churn some material to the surface, where radiation would likely break the bonds of any potential large, delicate molecules generated by biology. Meanwhile, some material on the surface would be pushed downward, where it could mix with the subsurface.

“If we hope to find pristine, chemical biosignatures, we will have to look below the zone where impacts have been gardening,” said lead author Emily Costello, a planetary research scientist at the University of Hawaii at Manoa. “Chemical biosignatures in areas shallower than that zone may have been exposed to destructive radiation.”

Going Deeper

While impact gardening has long been understood to be likely taking place on Europa and other airless bodies in the solar system, the new modeling provides the most comprehensive picture yet of the process. In fact, it is the first to take into account secondary impacts caused by debris raining back down onto Europa’s surface after being kicked up by an initial impact. The research makes the case that Europa’s mid- to high-latitudes would be less affected by the double whammy of impact gardening and radiation.

“This work broadens our understanding of the fundamental processes on surfaces across the solar system,” said Cynthia Phillips, a Europa scientist at NASA’s Jet Propulsion Laboratory in Southern California and a co-author of the study. “If we want to understand the physical characteristics and how planets in general evolve, we need to understand the role impact gardening has in reshaping them.”

Managed by JPL for NASA, Europa Clipper will help develop that understanding. The spacecraft, targeting a 2024 launch, will conduct a series of close flybys of Europa as it orbits Jupiter. It will carry instruments to thoroughly survey the moon, as well as sample the dust and gases that are kicked up above the surface.

More About the Mission

Missions such as Europa Clipper contribute to the field of astrobiology, the interdisciplinary research on the variables and conditions of distant worlds that could harbor life as we know it. While Europa Clipper is not a life-detection mission, it will conduct detailed reconnaissance of Europa and investigate whether the icy moon, with its subsurface ocean, has the capability to support life. Understanding Europa’s habitability will help scientists better understand how life developed on Earth and the potential for finding life beyond our planet.

Managed by Caltech in Pasadena, California, JPL leads the development of the Europa Clipper mission in partnership with APL for NASA’s Science Mission Directorate in Washington. The Planetary Missions Program Office at NASA’s Marshall Space Flight Center in Huntsville, Alabama, executes program management of the Europa Clipper mission.

More information about Europa can be found here:

europa.nasa.gov

Featured image: This color view of Jupiter’s moon Europa was captured by NASA’s Galileo spacecraft in the late 1990s. Scientists are studying processes that affect the surface as they prepare to explore the icy body. Credit: NASA/JPL-Caltech/SETI Institute


Reference: E. S. Costello et al, Impact gardening on Europa and repercussions for possible biosignatures, Nature Astronomy (2021). DOI: 10.1038/s41550-021-01393-1


Provided by NASA JPL

Scientists Solve 40-year Mystery Over Jupiter’s X-ray Aurora (Planetary Science)

A research team co-led by UCL has solved a decades-old mystery as to how Jupiter produces a spectacular burst of X-rays every few minutes.

The X-rays are part of Jupiter’s aurora – bursts of visible and invisible light that occur when charged particles interact with the planet’s atmosphere. A similar phenomenon occurs on Earth, creating the northern lights, but Jupiter’s is much more powerful, releasing hundreds of gigawatts of energy, enough to briefly power all of human civilisation*.

In a new study, published in Science Advances, researchers combined close-up observations of Jupiter’s environment by NASA’s satellite Juno, which is currently orbiting the planet, with simultaneous X-ray measurements from the European Space Agency’s XMM-Newton observatory (which is in Earth’s own orbit).

The research team, led by UCL and the Chinese Academy of Sciences, discovered that X-ray flares were triggered by periodic vibrations of Jupiter’s magnetic field lines. These vibrations create waves of plasma (ionised gas) that send heavy ion particles “surfing” along magnetic field lines until they smash into the planet’s atmosphere, releasing energy in the form of X-rays.

Co-lead author Dr William Dunn (UCL Mullard Space Science Laboratory) said: “We have seen Jupiter producing X-ray aurora for four decades, but we didn’t know how this happened. We only knew they were produced when ions crashed into the planet’s atmosphere.

“Now we know these ions are transported by plasma waves – an explanation that has not been proposed before, even though a similar process produces Earth’s own aurora. It could, therefore, be a universal phenomenon, present across many different environments in space.”

X-ray auroras occur at Jupiter’s north and south poles, often with clockwork regularity – during this observation Jupiter was producing bursts of X-rays every 27 minutes.

The charged ion particles that hit the atmosphere originate from volcanic gas pouring into space from giant volcanoes on Jupiter’s moon, Io.

This gas becomes ionised (its atoms are stripped free of electrons) due to collisions in Jupiter’s immediate environment, forming a doughnut of plasma that encircles the planet.

Co-lead author Dr Zhonghua Yao (Chinese Academy of Sciences, Beijing) said: “Now we have identified this fundamental process, there is a wealth of possibilities for where it could be studied next. Similar processes likely occur around Saturn, Uranus, Neptune and probably exoplanets as well, with different kinds of charged particles ‘surfing’ the waves.” 

Co-author Professor Graziella Branduardi-Raymont (UCL Mullard Space Science Laboratory) said: “X-rays are typically produced by extremely powerful and violent phenomena such as black holes and neutron stars, so it seems strange that mere planets produce them too.

“We can never visit black holes, as they are beyond space travel, but Jupiter is on our doorstep. With the arrival of the satellite Juno into Jupiter’s orbit, astronomers now have a fantastic opportunity to study an environment that produces X-rays up close.”

For the new study, researchers analysed observations of Jupiter and its surrounding environment carried out continuously over a 26-hour period by the Juno and XMM-Newton satellites.

They found a clear correlation between waves in the plasma detected by Juno and X-ray auroral flares at Jupiter’s north pole recorded by X-MM Newton. They then used computer modelling to confirm that the waves would drive the heavy particles towards Jupiter’s atmosphere.

Why the magnetic field lines vibrate periodically is unclear, but the vibration may result from interactions with the solar wind or from high-speed plasma flows within Jupiter’s magnetosphere.

Jupiter’s magnetic field is extremely strong – about 20,000 times as strong as Earth’s – and therefore its magnetosphere, the area controlled by this magnetic field, is extremely large. If it was visible in the night sky, it would cover a region several times the size of our moon.

The work was supported by the Chinese Academy of Sciences, the National Natural Science Foundation of China, and the UK’s Science and Technology Facilities Council (STFC), Royal Society, and Natural Environment Research Council, as well as ESA and NASA.

* Jupiter’s X-ray aurora alone releases about a gigawatt, equivalent to what one power station might produce over a period of days.

Jupiter with false colour X-ray aurora overlaid

Links

Binzheng Zhang, Peter A. Delamere, Zhonghua Yao, Bertrand Bonfond, D. Lin, Kareem A. Sorathia, Oliver J. Brambles, William Lotko, Jeff S. Garretson, Viacheslav G. Merkin, Denis Grodent, William R. Dunn, John G. Lyon, “How Jupiter’s unusual magnetospheric topology structures its aurora”, Science Advances  09 Apr 2021: Vol. 7, no. 15, eabd1204 DOI: https://doi.org/10.1126/sciadv.abd1204

Image

  • Credit: ESA/NASA/Yao/Dunn. Bottom image: Overlaid image of Jupiter’s north pole from NASA’s satellite Juno and NASA’s Chandra X-ray telescope. The X-ray aurora (purple) is overlaid on a visible Junocam image.

Provided by UCL

Life Could Exist in the Clouds of Jupiter But Not Venus (Planetary Science)

Jupiter’s clouds have water conditions that would allow Earth-like life to exist, but this isn’t possible in Venus’ clouds, according to the groundbreaking finding of new research led by a Queen’s University Belfast scientist with participation of the University of Bonn. The study has been published in the journal Nature Astronomy.

For some decades, space exploration missions have looked for evidence of life beyond Earth where we know that large bodies of water, such as lakes or oceans, exist or have previously existed. However, the new research shows that it isn’t the quantity of water that matters for making life viable, but the effective concentration of water molecules – known as ‘water activity’.

The new study also found that research published by an independent team of scientists last year, claiming that the phosphine gas in Venus’ atmosphere indicates possible life in the sulphuric acid clouds of Venus, is not plausible.

Through this innovative research project, Dr John E. Hallsworth from the School of Biological Sciences at Queen’s and his team of international collaborators devised a method to determine the water activity of atmospheres of a planet. Using their approach to study the sulphuric acid clouds of Venus, the researchers found that the water activity was more than a hundred times below the lower limit at which life can exist on Earth.

Dr Hallsworth comments: “Our research shows that the sulphuric acid clouds in Venus have too little water for active life to exist, based on what we know of life on Earth. We have also found that the conditions of water and temperature within Jupiter’s clouds could allow microbial-type life to subsist, assuming that other requirements such as nutrients are present.”

Co-author of the report, an expert on physics and chemical biology of water, Dr Philip Ball, says: “The search for extraterrestrial life has sometimes been a bit simplistic in its attitude to water. As our work shows, it’s not enough to say that liquid water equates with habitability. We’ve got to think too about how Earth-like organisms actually use it – which shows us that we then have to ask how much of the water is actually available for those biological uses.” 

A plant scientist in extraterrestrial spheres

Dr Jürgen Burkhardt of the Institute of Crop Science and Resource Conservation (INRES), a member of the Phenorob Cluster of Excellence and the Transdisciplinary Research Area “Innovation and Technology for Sustainable Futures” at the University of Bonn, contributed to this study primarily by making calculations of water activity and sulphuric acid concentration in the cloud droplets of the Venusian atmosphere. The fact that a scientist researching plant nutrition is contributing to Life in the Venus Atmosphere is due to Dr Burkhardt’s earlier work. He had previously used the aerosol model used in the study to characterize the state of deposited hygroscopic aerosols on leaf surfaces.

Dr. Jürgen Burkhardt – from the Institute of Crop Science and Resource Conservation (INRES) at the University of Bonn.© Photo: Maximilian Meyer

“These aerosols allow microorganisms to survive under certain conditions,” Burkhardt says. A shared interest in this habitat and its very specific physicochemical conditions, such as high acid concentrations and minimal amounts of water, led to contact years ago with the study’s first author, John Hallsworth. Experimental electron microscopy studies by Hallsworth and Burkhardt on this topic had already resulted in two earlier joint publications that also addressed the question of extraterrestrial life.

Participating institutions and funding:

Co-authors of this paper include planetary scientist Christopher P. McKay (NASA Ames Research Center, CA, USA); atmosphere chemistry expert Thomas Koop (Bielefeld University, Germany); expert on physics and chemical biology of water Philip Ball (London, UK); biomolecular scientist Tiffany D. Dallas (Queen’s University Belfast); biophysics-of-lipid-membrane expert Marcus K. Dymond (University of Brighton, UK); theoretical physicist María-Paz Zorzano (Centro de Astrobiologia [CSIC-INTA], Spain); micrometeorology and aerosol expert Juergen Burkhardt (University of Bonn, Germany); expert on acid-tolerant microorganisms Olga V. Golyshina (Bangor University, UK); and atmospheric physicist and planetary scientist Javier Martín-Torres (University of Aberdeen, UK).

The research was funded by Research Councils UK (RCUK) | Biotechnology and Biological Sciences Research Council (BBSRC) and Ministry of Science and Innovation.

Featured image: Thunderclouds on Jupiter – based on images from the Juno mission’s Stellar Reference Unit camera (NASA).© NASA/JPL-Caltech/SwRI/MSSS/Gerald Eichstädt/Heidi N. Becker/Koji Kuramura


Publication: John E. Hallsworth et al.: Water activity in Venus’s uninhabitable clouds and other planetary atmospheres, Nature Astronomy, DOI: 10.1038/s41550-021-01391-3


Provided by University of Bonn

Experiments Validate the Possibility of Helium Rain Inside Jupiter and Saturn (Planetary Science)

Nearly 40 years ago, scientists first predicted the existence of helium rain inside planets composed primarily of hydrogen and helium, such as Jupiter and Saturn. However, achieving the experimental conditions necessary to validate this hypothesis hasn’t been possible — until now.

In a paper published today by Nature, scientists reveal experimental evidence to support this long-standing prediction, showing that helium rain is possible over a range of pressure and temperature conditions that mirror those expected to occur inside these planets.

“We discovered that helium rain is real, and can occur both in Jupiter and Saturn,” said Marius Millot, a physicist at Lawrence Livermore National Laboratory (LLNL) and co-author on the publication. “This is important to help planetary scientists decipher how these planets formed and evolved, which is critical to understanding how the solar system formed.”

“Jupiter is especially interesting because it’s thought to have helped protect the inner-planet region where Earth formed,” added Raymond Jeanloz, co-author and professor of earth and planetary science and astronomy at the University of California, Berkeley. “We may be here because of Jupiter.”

The international research team, which included scientists from LLNL, the French Alternative Energies and Atomic Energy Commission, the University of Rochester and the University of California, Berkeley, conducted their experiments at the University of Rochester’s Laboratory for Laser Energetics (LLE).

“Coupling static compression and laser-driven shocks is key to allow us to reach the conditions comparable to the interior of Jupiter and Saturn, but it is very challenging,” Millot said. “We really had to work on the technique to obtain convincing evidence. It took many years and lots of creativity from the team.”

The team used diamond anvil cells to compress a mixture of hydrogen and helium to 4 gigapascals, (GPa; approximately 40,000 times Earth’s atmosphere). Then, the scientists used 12 giant beams of LLE’s Omega Laser to launch strong shock waves to further compress the sample to final pressures of 60-180 GPa and heat it to several thousand degrees. A similar approach was key to the discovery of superionic water ice.

Using a series of ultrafast diagnostic tools, the team measured the shock velocity, the optical reflectivity of the shock-compressed sample and its thermal emission, finding that the reflectivity of the sample did not increase smoothly with increasing shock pressure, as in most samples the researchers studied with similar measurements. Instead, they found discontinuities in the observed reflectivity signal, which indicate that the electrical conductivity of the sample was changing abruptly, a signature of the helium and hydrogen mixture separating. In a paper published in 2011, LLNL scientists Sebastien Hamel, Miguel Morales and Eric Schwegler suggested using changes in the optical reflectivity as a probe for the demixing process.

“Our experiments reveal experimental evidence for a long-standing prediction: There is a range of pressures and temperatures at which this mixture becomes unstable and demixes,” Millot said. “This transition occurs at pressure and temperature conditions close to that needed to transform hydrogen into a metallic fluid, and the intuitive picture is that the hydrogen metallization triggers the demixing.”

Numerically simulating this demixing process is challenging because of subtle quantum effects. These experiments provide a critical benchmark for theory and numerical simulations. Looking ahead, the team will continue to refine the measurement and extend it to other compositions in the continued pursuit of improving our understanding of materials at extreme conditions.

The work was funded by LLNL’s Laboratory Directed Research and Development program and the Department of Energy’s Office of Science. In addition to Millot and Jeanloz, collaborators include Stephanie Brygoo and Paul Loubeyre of CEA; Peter Celliers and Jon Eggert from LLNL; and Ryan Rygg and Gilbert Collins from the University of Rochester.

Featured image: An international research team, including scientists from Lawrence Livermore National Laboratory, have validated a nearly 40-year-old prediction and experimentally shown that helium rain is possible inside planets such as Jupiter and Saturn (pictured). Image credit: NASA/JPL/Space Science Institute.


Reference: Brygoo, S., Loubeyre, P., Millot, M. et al. Evidence of hydrogen−helium immiscibility at Jupiter-interior conditions. Nature 593, 517–521 (2021). https://doi.org/10.1038/s41586-021-03516-0


Provided by LLNL