Tag Archives: #europa

Europa’s Interior May Be Hot Enough to Fuel Seafloor Volcanoes (Planetary Science)

Jupiter’s moon Europa has an icy crust covering a vast, global ocean. The rocky layer underneath may be hot enough to melt, leading to undersea volcanoes.

New research and computer modeling show that volcanic activity may have occurred on the seafloor of Jupiter’s moon Europa in the recent past – and may still be happening. NASA’s upcoming Europa Clipper mission, targeting a 2024 launch, will swoop close to the icy moon and collect measurements that may shed light on the recent findings.

Scientists have strong evidence that Europa harbors an enormous ocean between its icy crust and rocky interior. The new work shows how the moon may have enough internal heat to partially melt this rocky layer, a process that could feed volcanoes on the ocean floor. The recent 3D modeling of how this internal heat is produced and transferred is the most detailed and thorough examination yet of the effect this interior heating has on the moon.

The key to Europa’s rocky mantle being hot enough to melt lies with the massive gravitational pull Jupiter has on its moons. As Europa revolves around the gas giant, the icy moon’s interior flexes. The flexing forces energy into the moon’s interior, which then seeps out as heat (think of how repeatedly bending a paperclip generates heat). The more the moon’s interior flexes, the more heat is generated.

The research, published recently in Geophysical Research Letters, models in detail how Europa’s rocky part may flex and heat under the pull of Jupiter’s gravity. It shows where heat dissipates and how it melts that rocky mantle, increasing the likelihood of volcanoes on the seafloor.

Scientists’ findings suggest that the interior of Jupiter’s moon Europa may consist of an iron core, surrounded by a rocky mantle in direct contact with an ocean under the icy crust. New research models how internal heat may fuel volcanoes on the seafloor. Credit: NASA/JPL-Caltech/Michael Carroll

Volcanic activity on Europa has been a topic of speculation for decades. By comparison, Jupiter’s moon Io is obviously volcanic. Hundreds of volcanoes there erupt lava fountains and eject volcanic gas and dust up to 250 miles (400 kilometers) high – activity that is due to the same kind of internal heating caused by Jupiter’s pull. But Europa is farther away than Io is from its host planet, so scientists have wondered whether the effect would be similar under the icy surface.

Led by Marie Běhounková of Charles University in the Czech Republic, the authors further predicted that volcanic activity is most likely to occur near Europa’s poles – the latitudes where the most heat is generated. They also looked at how volcanic activity may have evolved over time. Long-lived energy sources give more opportunity for potential life to have developed.

Underwater volcanoes, if present, could power hydrothermal systems like those that fuel life at the bottom of Earth’s oceans. On Earth, when seawater comes into contact with hot magma, the interaction results in chemical energy. And it is chemical energy from these hydrothermal systems, rather than from sunlight, that helps support life deep in our own oceans. Volcanic activity on Europa’s seafloor would be one way to support a potential habitable environment in that moon’s ocean.

“Our findings provide additional evidence that Europa’s subsurface ocean may be an environment suitable for the emergence of life,” Běhounková said. “Europa is one of the rare planetary bodies that might have maintained volcanic activity over billions of years, and possibly the only one beyond Earth that has large water reservoirs and a long-lived source of energy.”

Direct Observations

NASA scientists will have the opportunity to put the new predictions to the test when Europa Clipper reaches its target in 2030. The spacecraft will orbit Jupiter and perform dozens of close flybys of Europa to map the moon and investigate its composition. Among the science data it collects, the spacecraft will survey the surface in detail and sample the moon’s thin atmosphere.

The surface and atmosphere observations will give scientists a chance to learn more about the moon’s interior ocean if the water percolates up through the icy crust. Scientists believe the exchange of material between the ocean and the crust would leave traces of seawater on the surface. They also believe the exchange may emit gas, and possibly even plumes of water vapor, with ejected particles that could contain materials coming from the seafloor.

As Europa Clipper measures the moon’s gravity and magnetic field, anomalies in those areas, especially toward the poles, could help confirm the volcanic activity predicted by the new research.

“The prospect for a hot, rocky interior and volcanoes on Europa’s seafloor increases the chance that Europa’s ocean could be a habitable environment,” said Europa Clipper Project Scientist Robert Pappalardo of NASA’s Jet Propulsion Laboratory in Southern California. “We may be able to test this with Europa Clipper’s planned gravity and compositional measurements, which is an exciting prospect.”

More About the Mission

Missions such as Europa Clipper help 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 the Johns Hopkins Applied Physics Lab (APL) in Maryland for the agency’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 and Europa Clipper can be found here:


Featured image: This illustration, updated as of December 2020, depicts NASA’s Europa Clipper spacecraft. The mission, targeting a 2024 launch, will investigate whether Jupiter’s moon Europa and its internal ocean have conditions suitable for life. Credit: NASA/JPL-Caltech

Reference: Běhounková, M., Tobie, G., Choblet, G., Kervazo, M., Melwani Daswani, M., Dumoulin, C., & Vance, S. D. (2021). Tidally induced magmatic pulses on the oceanic floor of Jupiter’s moon Europa. Geophysical Research Letters, 48, e2020GL090077. https://doi.org/10.1029/2020GL090077

Provided by JPL NASA

NASA Extends Juno Mission to Jupiter (Planetary Science)

NASA has extended the Juno mission to explore Jupiter through September 2025, expanding the science goals to include the overall Jovian system, made up of the planet and its rings and moons. In addition to continuing to explore our Solar System’s largest planet, NASA’s planetary orbiter will rendezvous with three of the most intriguing Jovian moons.

NASA has extended the Juno mission, led by Scott Bolton of Southwest Research Institute, to explore Jupiter through September 2025, expanding the science goals to include the overall Jovian system, made up of the planet and its rings and moons. Juno includes a public outreach instrument that allows citizen scientists to participate in the mission, processing JunoCam data to create images such as this highly enhanced “Orange Marble” image of Jupiter. © Courtesy of NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill/Navaneeth Krishnan 

“Since its first orbit in 2016, Juno has delivered one revelation after another about the inner workings of this massive gas giant,” said Southwest Research Institute’s Scott Bolton, Juno principal investigator. “With the extended mission, we will answer fundamental questions that arose during Juno’s prime mission while reaching beyond the planet to explore Jupiter’s ring system and largest satellites.”

Proposed in 2003 and launched in 2011, Juno arrived at Jupiter on July 4, 2016. The prime mission operations will be completed in July 2021. The extended mission includes 42 additional orbits including close passes of Jupiter’s north polar cyclones and flybys of the Galilean moons Ganymede, Europa and Io, as well as the first extensive exploration of Jupiter’s ring system. 

The extended mission represents an efficient advance for NASA’s Solar System exploration strategy. The data Juno collects will complement the goals of the next generation of missions to the Jovian system — NASA’s Europa Clipper and ESA’s JUpiter ICy moons Explorer (JUICE). Juno’s investigation of Jupiter’s volcanic moon Io addresses many science goals identified by the National Academy of Sciences for a future Io explorer mission.

The extended mission’s science campaigns expand on discoveries Juno has already made about Jupiter’s interior structure, internal magnetic field, magnetosphere and atmosphere, including its deep atmosphere, polar cyclones and auroras.

“With this extension, Juno becomes its own follow-on mission,” said Steve Levin, Juno project scientist at NASA’s Jet Propulsion Laboratory (JPL). “Close-up observations of the poles, radio occultations, satellite flybys, and focused magnetic field studies combine to make a new mission, the next logical step in our exploration of the Jovian system.”

For example, scientists will target Jupiter’s enigmatic “Great Blue Spot,” an isolated patch near the planet’s equator exhibiting an intense magnetic field, deploying high spatial resolution magnetic surveys during six flybys. As Juno’s orbit evolves, multiple flybys of Ganymede (2), Europa (3), and Io (11) are planned en route to multiple passages through Jupiter’s tenuous rings.

The natural evolution of Juno’s polar orbit around the gas giant provides new science opportunities that the extended mission capitalizes on.

“The mission designers have done an amazing job crafting an extended mission that conserves the mission’s single most valuable resource — fuel,” said Ed Hirst, Juno project manager from NASA JPL. “Gravity assists from multiple satellite flybys steer our spacecraft through the Jovian system while providing a wealth of science opportunities.”

JPL, a division of Caltech in Pasadena, California, manages the Juno mission for the principal investigator, Dr. 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.

Provided by Southwest Research Institute

Europa Glows: Radiation Does A Bright Number On Jupiter’s moon (Planetary Science)

As the icy, ocean-filled moon Europa orbits Jupiter, it withstands a relentless pummeling of radiation. Jupiter zaps Europa’s surface night and day with electrons and other particles, bathing it in high-energy radiation. But as these particles pound the moon’s surface, they may also be doing something otherworldly: making Europa glow in the dark.

This illustration of Jupiter’s moon Europa shows how the icy surface may glow on its nightside, the side facing away from the Sun. Variations in the glow and the color of the glow itself could reveal information about the composition of ice on Europa’s surface. Credit: NASA/JPL-Caltech

New research from scientists at NASA’s Jet Propulsion Laboratory in Southern California details for the first time what the glow would look like, and what it could reveal about the composition of ice on Europa’s surface. Different salty compounds react differently to the radiation and emit their own unique glimmer. To the naked eye, this glow would look sometimes slightly green, sometimes slightly blue or white and with varying degrees of brightness, depending on what material it is.

Scientists use a spectrometer to separate the light into wavelengths and connect the distinct “signatures,” or spectra, to different compositions of ice. Most observations using a spectrometer on a moon like Europa are taken using reflected sunlight on the moon’s dayside, but these new results illuminate what Europa would look like in the dark.

“We were able to predict that this nightside ice glow could provide additional information on Europa’s surface composition. How that composition varies could give us clues about whether Europa harbors conditions suitable for life,” said JPL’s Murthy Gudipati, lead author of the work published Nov. 9 in Nature Astronomy.

That’s because Europa holds a massive, global interior ocean that could percolate to the surface through the moon’s thick crust of ice. By analyzing the surface, scientists can learn more about what lies beneath.

Shining a Light

Scientists have inferred from prior observations that Europa’s surface could be made of a mix of ice and commonly known salts on Earth, such as magnesium sulfate (Epsom salt) and sodium chloride (table salt). The new research shows that incorporating those salts into water ice under Europa-like conditions and blasting it with radiation produces a glow.

That much was not a surprise. It’s easy to imagine an irradiated surface glowing. Scientists know the shine is caused by energetic electrons penetrating the surface, energizing the molecules underneath. When those molecules relax, they release energy as visible light.

“But we never imagined that we would see what we ended up seeing,” said JPL’s Bryana Henderson, who co-authored the research. “When we tried new ice compositions, the glow looked different. And we all just stared at it for a while and then said, ‘This is new, right? This is definitely a different glow?’ So we pointed a spectrometer at it, and each type of ice had a different spectrum.”

To study a laboratory mockup of Europa’s surface, the JPL team built a unique instrument called Ice Chamber for Europa’s High-Energy Electron and Radiation Environment Testing (ICE-HEART). They took ICE-HEART to a high-energy electron beam facility in Gaithersburg, Maryland, and started the experiments with an entirely different study in mind: to see how organic material under Europa ice would react to blasts of radiation.

They didn’t expect to see variations in the glow itself tied to different ice compositions. It was—as the authors called it—serendipity.

“Seeing the sodium chloride brine with a significantly lower level of glow was the ‘aha’ moment that changed the course of the research,” said Fred Bateman, co-author of the paper. He helped conduct the experiment and delivered radiation beams to the ice samples at the Medical Industrial Radiation Facility at the National Institute of Standards and Technology in Maryland.

A moon that’s visible in a dark sky may not seem unusual; we see our own Moon because it reflects sunlight. But Europa’s glow is caused by an entirely different mechanism, the scientists said. Imagine a moon that glows continuously, even on its nightside—the side facing away from the Sun.

“If Europa weren’t under this radiation, it would look the way our moon looks to us—dark on the shadowed side,” Gudipati said. “But because it’s bombarded by the radiation from Jupiter, it glows in the dark.”

Set to launch in the mid-2020s, NASA’s upcoming flagship mission Europa Clipper will observe the moon’s surface in multiple flybys while orbiting Jupiter. Mission scientists are reviewing the authors’ findings to evaluate if a glow would be detectable by the spacecraft’s science instruments. It’s possible that information gathered by the spacecraft could be matched with the measurements in the new research to identify the salty components on the moon’s surface or narrow down what they might be.

“It’s not often that you’re in a lab and say, ‘We might find this when we get there,'” Gudipati said. “Usually it’s the other way around—you go there and find something and try to explain it in the lab. But our prediction goes back to a simple observation, and that’s what science is about.”

Missions such as Europa Clipper help 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.

References: Gudipati, M.S., Henderson, B.L. & Bateman, F.B. Laboratory predictions for the night-side surface ice glow of Europa. Nat Astron (2020). https://doi.org/10.1038/s41550-020-01248-1 link: https://www.nature.com/articles/s41550-020-01248-1

Provided by NASA

Astronomers Presented The Evidence For Sulfur-bearing Species On Callisto’s Leading Hemisphere (Planetary Science)

Sulfur is one of the key elements required for life as we know it. Measuring the abundance, distribution, and spectral signature of sulfur on ocean worlds like the icy Galilean moons Callisto, Ganymede, and Europa is therefore important for assessing their astrobiological potential. The innermost Galilean moon Io erupts substantial quantities of sulphur rich materials into orbit. Much of the erupted sulphur is then ionized and subsequently trapped in Jupiter’s magnetosphere. These trapped sulfur ions are delivered primarily to the trailing hemispheres of Europa and Ganymede by Jupiter’s co-rotating plasma, spurring a cascade of radiolytic surface chemistry. The flux of magnetospheric S ions is lower at the orbit of Callisto but is still sufficient to drive radiolytic modification of its surface.


In the recent paper, Richard Cartwright and colleagues investigated whether sulfur-bearing species are present on the icy Galilean moon Callisto by analyzing eight near-infrared reflectance spectra collected over a wide range of sub-observer longitudes.

They measured the band areas and depths of a 4-µm feature in these spectra, which has been attributed to sulfur dioxide (SO2), as well as carbonates, in previously collected datasets of this moon. All eight spectra they collected display the 4-µm band. The four spectra collected over Callisto’s leading hemisphere display significantly stronger 4-µm bands compared to the four trailing hemisphere spectra (>3σ difference). They compared the central wavelength position and shape of Callisto’s 4-µm band to laboratory spectra of various sulfur-bearing species and carbonates. Their comparison demonstrates that Callisto’s 4-µm band has a spectral signature similar to thermally-altered sulfur, as well as a 4.025 µm feature attributed to disulfanide (HS2). They considered possible origin scenarios to explain the presence of 4-µm band on Callisto which I explained below.

Delivery of S-bearing dust from the irregular satellites: Dust grains (∼10 – 1000 µm diameters) ejected from the giant planets’ retrograde irregular satellites should experience Poynting-Robertson drag and slowly migrate inward on decaying orbits. Eventually, the orbits of these dust grains overlap the orbital zone of the classical satellites, and they subsequently collide with the leading hemispheres of the outermost moons. The irregular satellites of the giant planets are darker and spectrally redder than the classical moons. The accumulation of irregular satellite dust can therefore explain why the leading hemispheres of the outer moons Callisto, Iapetus and Titania and Oberon are spectrally redder and darker than their trailing hemispheres.

Similar to the irregular satellites, Jupiter’s trojan asteroid population includes a group of objects with reddish surfaces. It has been hypothesized that this red-colored trojan asteroid group is populated by captured Kuiper Belt Objects (KBOs) that formed beyond an H2S ‘snow line’ in the primordial Kuiper Belt. Dynamical simulations indicate that giant planet migration in the early Solar System scattered large numbers of KBOs into the giant planet zone, and some of these objects were likely captured by Jupiter into its trojan asteroid and irregular satellite populations. Along with capture of H2S-rich KBOs in Jupiter’s L4 and L5 Lagrange points, perhaps H2S-bearing KBOs were captured into Jupiter’s irregular satellite population, providing a source of H2S and other S-bearing species that could be delivered to Callisto’s leading hemisphere within dust grains. Although sublimation and space weathering should remove volatile rich deposits from the surfaces of Jovian irregular satellites, H2S and other volatiles could be retained beneath their regoliths and subsequently excavated and ejected in dust grains by impact events. Albeit, it is uncertain how long H2S could survive within dust grains before colliding with Callisto, nor whether H2S delivered to Callisto would survive long enough to be radiolytically modified into other S-bearing species. Laboratory work that explores the longevity of H2S under conditions relevant to the surface of Callisto are needed to further investigate this scenario.

Delivery of magnetospheric S ions: Volcanoes on Io erupt large volumes of S-rich material into orbit. Much of the
erupted sulfur is then ionized and gets trapped in Jupiter’s magnetosphere. These trapped S ions are delivered to the more distant icy Galilean moons, primarily bombarding the trailing hemispheres of Europa and Ganymede.

In contrast, Cartwright et al. numerical modeling work showed that energetic O and S ions (1 – 100 KeV) trapped in Jupiter’s magnetosphere might preferentially bombard Callisto’s leading hemisphere. This hemispherical dichotomy results from interactions between Jupiter’s magnetosphere and Callisto’s intense ionosphere, which largely blocks these lower energy O and S ions from accessing its trailing side, unlike Europa and Ganymede, which do not have substantial ionospheres. Radiolytic sulfur chemistry, induced by implanted S ions, could therefore be operating across Callisto’s leading hemisphere, explaining the stronger 4-µm band they detected on this hemisphere.

Exposure of native S-rich deposits: Alternatively, the species contributing to the 4-µm band could be native to Callisto and are exposed by dust-driven regolith overturn, which should preferentially operate on the leading hemispheres of tidally-locked moons. In this scenario, native deposits of S-bearing species exposed by dust collisions could be modified by UV photolysis and charged particle radiolysis, forming new S-rich constituents, such as S2-bearing species and perhaps CS-bearing species as well. Larger impact events might also excavate S-rich deposits from greater depths in Callisto’s subsurface, albeit, analysis of NIMS data indicates that the 4-µm band is not spatially associated with craters on Callisto’s leading hemisphere, unlike CO2 which showed in earlier studies.

Figure: Left: Eight SpeX spectra of Callisto’s leading and trailing hemisphere (1σ uncertainties shown as blue and green error bars, respectively), normalized to 1 at 4.12 µm and offset vertically for clarity. The spectra are numbered (1 – 8) using the same sequence shown in Tables 1 and 2. Right: ‘Grand average’ leading and trailing hemisphere spectra of Callisto (1σ uncertainties shown as blue and green error bars, respectively), normalized to 1 at 4.12 µm and offset vertically for clarity. The dashed lines at 3.1, 3.87, 4.02, and 4.57 µm highlight the central wavelengths of the H2O ice Fresnel peak and the 3.9-µm, 4-µm, and 4.6-µm bands, respectively. The 4-µm and 4.6-micron bands are stronger on Callisto’s leading hemisphere, whereas the 3.9-µm band does not display apparent hemispherical asymmetries in its band strength. Other, more subtle bands that are possibly present include features centered near 2.97, 3.05, and 3.4 µm, which appear to be stronger on Callisto’s leading hemisphere, and a band centered near 3.75 µm, which appears to be slightly stronger on Callisto’s trailing side (see Figure A4 for closer looks at these subtle bands). All spectra have been lightly smoothed using a 9 pixel-wide boxcar function between 2.75 and 4.2 µm and a 27 pixel-wide boxcar function between 4.45 and 5.05 µm. Wavelength regions where strong telluric bands are present are shown as
gray-toned zones.

According to authors, to further test these different origin hypotheses, follow up ground-based observations of the 4-µm band at complementary sub-observer longitudes are needed. Furthermore, new laboratory experiments that measure the spectral signature of substrates composed of H2O ice, S-bearing, and C-bearing species, performed under temperature and irradiation conditions relevant to the surface of Callisto, could provide key insight into origin and composition of the 4-µm band. These new experiments could also provide insight into whether a radiolytic cycle involving S, C, and H2O ice is occurring on Callisto, spurring the formation of species like OCS and CS2.

Their analysis thus, supports the presence of Sulfur bearing species on Callisto but is not consistent with the presence of SO2. The significantly stronger 4-µm band detected on Callisto’s leading hemisphere could result from collisions with H2S-rich dust grains that originate on Jupiter’s retrograde irregular satellites or implantation of magnetospheric S ions that originate from volcanic activity on Io.

References: Richard J. Cartwright, Tom A. Nordheim, Dale P. Cruikshank, Kevin P. Hand, Joseph E. Roser, William M. Grundy, Chloe B. Beddingfield, Joshua P. Emery, “Evidence for sulfur-bearing species on Callisto’s leading hemisphere: Sourced from Jupiter’s irregular satellites or Io?”, ArXiv, 2020. arXiv:2010.01395 https://arxiv.org/abs/2010.01395

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Hubble Captures Spectacular Photos of Jupiter and Its Icy Moon Europa (Planetary Science)

Two new photos, taken with the NASA/ESA Hubble Space Telescope, show Jupiter with its turbulent atmosphere and giant storms. One of the images also features Europa, one of Jupiter’s Galilean moons.

This image of Jupiter was taken by the NASA/ESA Hubble Space Telescope on August 25, 2020, when the planet was 653 million km (406 million miles) from Earth. Image credit: NASA / ESA / A. Simon, NASA’s Goddard Space Flight Center / M.H. Wong, University of California, Berkeley / OPAL Team.

A bright, white, stretched-out storm moving at 560 km per hour (348 mph) appeared at Jupiter’s mid-northern latitudes on August 18, 2020.

While it’s common for storms to pop up in this region, often several at once, this particular disturbance appears to have more structure behind it than observed in previous storms. Trailing behind the plume are small, counterclockwise dark clumps also not witnessed in the past.

Hubble shows that the Great Red Spot, rolling counterclockwise in the planet’s southern hemisphere, is ploughing into the clouds ahead of it, forming a cascade of white and beige ribbons.

The huge storm system is currently an exceptionally rich red color, with its core and outermost band appearing deeper red.

It now measures about 15,800 km (9,818 miles) across, and is still shrinking, as noted in telescopic observations dating back to 1930, but its rate of shrinkage appears to have slowed.

A multiwavelength observation in ultraviolet/visible/near-infrared light of Jupiter obtained by Hubble on August 25, 2020 is giving astronomers an entirely new view of the giant planet. Hubble’s near-infrared imaging, combined with ultraviolet views, provides a unique panchromatic look that offers insights into the altitude and distribution of the planet’s haze and particles. This complements Hubble’s visible-light pictures that show the ever-changing cloud patterns. In this photo, the parts of Jupiter’s atmosphere that are at higher altitude, especially over the poles, look red as a result of atmospheric particles absorbing ultraviolet light. Conversely, the blue-hued areas represent the ultraviolet light being reflected off the planet. A new storm at upper left, which erupted on August 18, 2020, is grabbing the attention of scientists in this multiwavelength view. The ‘clumps’ trailing the white plume appear to be absorbing ultraviolet light, similar to the center of the Great Red Spot, and Red Spot Jr. directly below it. This provides the astronomers with more evidence that this storm may last longer on Jupiter than most storms. Image credit: NASA / ESA / A. Simon, NASA’s Goddard Space Flight Center / M.H. Wong, University of California, Berkeley / OPAL Team.

The astronomers are noticing that another feature has changed: Oval BA, nicknamed as Red Spot Jr., which appears just below the Great Red Spot in the new images.

For the past few years, Oval BA has been fading in color to its original shade of white after appearing red in 2006.

However, now the core of this storm appears to be darkening to a reddish hue. This could hint that Red Spot Jr. is on its way to reverting to a color more similar to that of its cousin.

The images also show that Jupiter is clearing out its higher-altitude white clouds, especially along the planet’s equator, which is enveloped in an orangish hydrocarbon smog.

In one of the two images, the icy moon Europa is visible to the left of Jupiter.

Hubble also captured a new multiwavelength observation in ultraviolet/visible/near-infrared light of Jupiter, which is giving astronomers an entirely new view of the giant planet.

The telescope’s near infrared imaging, combined with ultraviolet views, provides a unique panchromatic look that offers insights into the altitude and distribution of the planet’s haze and particles.

This complements Hubble’s visible-light picture that shows the ever-changing cloud patterns.

This article is based on press-releases provided by the National Aeronautics and Space Administration and the European Space Agency.

Jupiter’s Ocean Moons Raise Big tides In Each Other’s Subsurface Sea (Planetary Science)

According to recent study done by Hay, Antony and Matsuyama, investigated moon‐moon tides for the first time in the Galilean moons and showed that they can cause significant heating through the excitation of high‐frequency resonant tidal waves in their subsurface oceans. The heating occurs both in the crust and ocean and can exceed that of other tidal sources and radiogenic decay if the ocean is inviscid enough.

The Jupiter moon Europa, seen here by NASA’s Galileo spacecraft, harbors a huge ocean beneath its icy shell. Europa’s fellow Galilean moons raise powerful tides in that subsurface sea (Image: © NASA/JPL-Caltech/SETI Institute)

Hay and his colleagues modeled the gravitational interactions among Jupiter’s four large Galilean moons — lo, Europa, Callisto and Ganymede. The latter three are thought to harbor huge oceans of liquid water beneath their icy shells, whereas powerfully volcanic lo might have a subsurface sea of molten rock.

The researchers determined that the Galilean moons have an outsized influence on each other thanks to “tidal resonance” — basically, a reinforcing sync-up of a gravitational tug and the natural rocking of the satellites’ oceans. The moons are more tidally resonant with each other than with Jupiter, which explains why the giant planet’s powerful pull doesn’t translate into bigger tidal effects.

As an example: Hay and his team calculated that Jupiter’s tug could generate a tidal wave in Europa’s buried ocean if that sea were about 660 feet (200 meters) deep. Little Io, by contrast, could get a strong wave going in a Europan ocean 50 miles (80 kilometers) deep.

Astronomers suspect that Europa’s sea, one of the most promising abodes for alien life in the solar system, is more than 50 miles deep, but nobody knows the actual figure. Tidal resonance among the Galilean moons could help them nail that measurement down, however. If moon-moon tides are strong enough, the icy surfaces of Europa, Callisto and Ganymede could pulse in and out.

References: Hamish C. F. C. Hay, Antony Trinh and Isamu Matsuyama, “Powering the Galilean Satellites with Moon‐Moon Tides”, Geophysical Research Letters, Volume 47, Issue 15, 2020 doi: https://doi.org/10.1029/2020GL088317 link: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2020GL088317