Hubble snaps new hi-res photo of Jupiter

Jupiter, as seen by Hubble in 2020
Click for full image.

Astronomers have used the Hubble Space Telescope to take a new global image of Jupiter, aimed to provide an global census of the gas giant’s storm systems.

This latest image of Jupiter, taken by NASA’s Hubble Space Telescope on August 25, 2020, was captured when the planet was 406 million miles from Earth. Hubble’s sharp view is giving researchers an updated weather report on the monster planet’s turbulent atmosphere, including a remarkable new storm brewing, and a cousin of the famous Great Red Spot region gearing up to change color – again.

The moon seen to the left is Europa. Hubble takes annual images of the planets outward from Earth in order to provide scientists this global view.

Juno’s 28th fly-by of Jupiter

Cool movie time! Below is a short movie created by citizen scientist Gerald Eichstädt from images taken by Juno as it swung past Jupiter on its 28th close pass since arriving in orbit in 2016.

In natural colors, Jupiter looks pretty pale. Therefore, the still images are approximately illumination-adusted, i.e. almost flattened, and consecutively gamma-stretched to the 4th power of radiometric values, in order to enhance contrast and color.

Like for all its previous flybys, Juno approached Jupiter roughly from north, and left Jupiter looking towards the soutern hemisphere. Closest approach to Jupiter was 3,500 km above the nominal IAU 1-bar level, and near 25.3 degrees north (planetocentric), according to long-term planning of November 2017.

Giant impact covered almost half of Gandymede’s surface

Artist's illustration of Ganydmede
Click for full illustration.

The uncertainty of science: Computer modeling and a review of images taken by Voyager 1 and 2 and the Galileo orbiter of Jupiter’s moon Ganymede now suggest the existence of a giant impact so large that it covers almost half the moon’s surface.

The artist’s illustration of Ganymede on the right, based on our presently incomplete set of global images, shows this impact area as the circular dark region.

Many furrows, or trough formations, have been observed on the surface of Ganymede, one of the Jovian moons. This research group comprehensively reanalyzed image data of Ganymede obtained by NASA’s Voyager 1, Voyager 2, and Galileo spacecrafts. The results revealed that almost all of these furrows appear to be arranged in concentric rings centered around a single point, indicating that this global multiring structure may be the remains of a giant crater. The radial extent of the multiring structures measured along Ganymede’s surface is 7800 km. For comparison, the mean circumference of Ganymede is only 16,530 km. If correct, this is the largest crater yet identified in the Solar System. The previous record holder with a 1900 km radius is on Calisto, another Jovian moon.

The conclusion reached here is very uncertain, since we really do not have a high resolution global map of Ganymede. All three spacecraft were only able to send back a scattering of high resolution images. The global map is based on Earth observations and images from the Hubble Space Telescope.

Lightning and mushballs on Jupiter

Artist's illustration of Jupiter lightning
Click for full illustration.

Using data from Juno, scientists now theorize that Jupiter produces what they dub “shallow lightning” as well as ammonia-water hailstones dubbed “mushballs.”

The image to the right, cropped and reduced to post here, is only an artist’s illustration of the lightning. Sadly Juno’s camera doesn’t have the resolution to capture such flashes.

An unexpected form of electrical discharge, shallow lightning originates from clouds containing an ammonia-water solution, whereas lightning on Earth originates from water clouds.

Other new findings suggest the violent thunderstorms for which the gas giant is known may form slushy ammonia-rich hailstones Juno’s science team calls “mushballs”; they theorize that mushballs essentially kidnap ammonia and water in the upper atmosphere and carry them into the depths of Jupiter’s atmosphere.

As with the InSight results below, there is much uncertainty with these results, especially the hypothesis of mushballs. These features fit their present data from Juno, but we must remember that the data is still somewhat superficial.

Jupiter’s south pole

The storms at the south pole of Jupiter
Click for full image.

Cool image time! The photo to the right, rotated and reduced to post here, was taken by Juno during its 28th close orbital fly-by of Jupiter, and then processed by citizen scientist Hemant Dara.

While not the first Juno image of the poles of Jupiter, this photo illustrates very well the evolution of the gas giant’s deep atmosphere as you move from the equator to the pole. From the equator to the high mid-latitudes the planet’s rotation, producing a day only 10 hours long, organizes that atmosphere into jet streams that form the bands that astronomers have spied from Earth since the first telescopes.

At the pole the influence of that rotation seems to wane, or at least influence the atmosphere differently, so that the storms seem to form randomly and incoherently.

The image also shows that there appear to be several types of storms at the south pole. Some appear as tight spirals, similar to hurricanes. Others appear chaotic, with no consistent shape, almost like clouds on Earth.

The processes that would explain all this are not yet understood, in the slightest, and won’t be until we get orbiters at Jupiter able to watch the atmosphere continuously, as we do here on Earth. Then it will be possible to assemble movies of the formation and dissipation of these storms, and begin (only begin) to decipher what causes them.

New storm outbreak on Jupiter

Clyde's Spot
Click for full image.

A new storm, dubbed Clyde’s spot after its discoverer, developed suddenly in late May on Jupiter, and has been imaged by Juno during its most recent close fly-by of the gas giant planet.

The image to the right, cropped to post here, focuses in on this spot. It is the feature in the center of the full image, with the Great Red Spot to the upper left.

The new feature was discovered by amateur astronomer Clyde Foster of Centurion, South Africa. Early on the morning of May 31, 2020, while imaging Jupiter with his telescope, Foster noticed a new spot, which appeared bright as seen through a filter sensitive to wavelengths of light where methane gas in Jupiter’s atmosphere has strong absorption. The spot was not visible in images captured just hours earlier by astronomers in Australia.

On June 2, 2020, just two days after Clyde Foster’s observations, Juno performed its 27th close flyby of Jupiter. The spacecraft can only image a relatively thin slice of Jupiter’s cloud tops during each pass. Although Juno would not be travelling directly over the outbreak, the track was close enough that the mission team determined the spacecraft would obtain a detailed view of the new feature, which has been informally dubbed “Clyde’s Spot.”

The feature is a plume of cloud material erupting above the upper cloud layers of the Jovian atmosphere. These powerful convective “outbreaks” occasionally erupt in this latitude band, known as the South Temperate Belt

The coolest thing about this is that the storm was spotted by an amateur, using a ground-based telescope, within hours of its inception.

That Jupiter Trojan comet-like asteroid was neither an asteroid nor a Trojan

Astronomers have now found that the asteroid that had suddenly become active, like a comet, and they had thought was part of the asteroids in Jupiter orbit called Trojans, was neither an asteroid nor a Trojan.

Instead, it is an actual comet captured in a strange unstable orbit around Jupiter.

[W]hen amateur astronomer Sam Deen used software on the Jet Propulsion Laboratory’s solar-system dynamics website to calculate the object’s orbit, he found P/2019 LD2 recently had a close encounter with Jupiter that left its orbit unstable. The model showed that the comet had likely been a Centaur, part of a family of outer solar system asteroids, with an orbit reaching out to Saturn. Then, on February 17, 2017, it passed about 14 million kilometers from Jupiter, an encounter that sent the comet on a wild ride and inserted it into an odd Jupiter-like orbit.

Yet although the swing past Jupiter put P/2019 LD2 into a Jupiter-like orbit, it didn’t move it near to one of the two Lagrange points where the combination of gravitational forces from Jupiter and the Sun hold Trojan asteroids. Instead of being 60° — one-sixth of the giant planet’s orbit — from Jupiter, P/2019 LD2 is only 21° ahead of Jupiter.

The orbit is unstable. It will bring the comet to within 3 million miles of Jupiter in 2063, but beyond that predictions are impossible. The exact closeness of that approach cannot be predicted with much precision, partly because of the chaotic nature of the orbit, and partly because of the random orbital changes that can occur because the comet is venting.

Europa’s mysterious stained grooves

Europa's jumbled icepack
Click for full image.

From 1995 to 2003 the Galileo orbiter circled Jupiter 34 times. During those orbits the spacecraft made numerous close fly-bys of Jupiter’s moons, including eleven past the tantalizingly mysterious moon Europa.

The image to the right was taken during the eighth fly-by of Europa. It is one of three Galileo images of Europa that scientists have pulled from the Galileo archive and subjected to modern computer processing in order to improve what can be seen. The other two can be found here and here. From the release for the image to the right:

All three images were captured along the same longitude of Europa as Galileo flew by on Sept. 26, 1998, in the spacecraft’s 17th orbit of Jupiter (orbit E17). It was the eighth of Galileo’s 11 targeted flybys of Europa. High-resolution images were taken through a clear filter in grayscale (black and white). Using lower-resolution, color images of the same region from a different flyby (orbit E14), technicians recently mapped color onto the higher-resolution images.

In other words, they laid the colors from a lower resolution color image on top of the high resolution black & white image so that we could see these three images in color. The blue and white areas are made of up water ice, while the reddish areas are made up of “more non-ice materials.”

The vagueness for describing the non-ice materials is intentional, as scientists still do not know what they made of. They do believe that this material came from the planet’s interior, as the red material is always found aligned with the cracks, fissures, and grooves, as illustrated clear by this image.

What has always struck me about this surface of Europa since I first saw similar Galileo images back in 1998 and wrote about them for the magazine The Sciences is how much it resembles the Arctic ice pack as seen by early explorers during their attempts to reach the North Pole, jumbled jigsaw pieces of ice packed together but moving slowly so that the cracks between them shift and change over time.

The resemblance adds weight to the theory that there is a liquid ocean below Europa’s icepack, and the red material hints at some intriguing chemistry coming from that ocean.

Jupiter in glorious color

Jupiter in glorious color
Click for full image.

Cool image time! The photograph on the right, reduced to post here, was color enhanced by citizen scientist Emma Walimaki from the original Juno image in order to bring out the features and storms visible in the upper storm layers of Jupiter.

The photo was taken during Juno’s 25th close fly-by of the gas giant, and thus we are only seeing a small portion of Jupiter’s sphere.

In comparing this image with the original, it appears that Walimaki simply made the colors that were already there brighter and more distinctive. Thus, these colors represent real data. Jupiter’s cloud tops are really blue, orange, tan, and brown, unlike Earth’s consistently and boringly white water clouds.

Juno’s first measurement of water content on Jupiter

The uncertainty of science: Scientists today released their first measurements from Juno of the amount of water found in Jupiter’s atmosphere.

The Juno science team used data collected during Juno’s first eight science flybys of Jupiter to generate the findings. They initially concentrated on the equatorial region because the atmosphere there appears more well-mixed, even at depth, than in other regions. From its orbital perch, the radiometer was able to collect data from a far greater depth into Jupiter’s atmosphere than the Galileo probe – 93 miles (150 kilometers), where the pressure reaches about 480 psi (33 bar).

“We found the water in the equator to be greater than what the Galileo probe measured,” said Cheng Li, a Juno scientist at the University of California, Berkeley. “Because the equatorial region is very unique at Jupiter, we need to compare these results with how much water is in other regions.”

These results remain very preliminary, especially because they have not yet gathered data at higher latitudes. Regardless the amount so far detected, 0.25% of all molecules in Jupiter’s atmosphere. seems remarkably small, suggesting that Jupiter has relatively little hydrogen or oxygen in its atmosphere.

Europa Clipper faces budget overruns

NASA’s $4.25 billion dollar mission to orbit the Jupiter moon Europa now faces cost overruns that threaten its launch in 2023.

The management of NASA’s Europa Clipper mission, facing dwindling cost reserves while still years away from launch, is looking at cost saving options that would preserve the mission’s science.

In a Feb. 3 presentation at a meeting of the Outer Planets Assessment Group in Houston, Jan Chodas, project manager for Europa Clipper at the Jet Propulsion Laboratory, said she was looking for ways to restore cost reserves that had declined precipitously in the last year.

Chodas said that Europa Clipper had met a JPL recommendation of 25% cost reserves, known at the lab as unallocated future expenses (UFE), when it completed a final “delta” preliminary design review in June 2019. By November, though, those reserves had fallen to just 12%, a level deemed “unacceptably low” for a mission not scheduled for launch until at least 2023.

To save money, they are “streamlining hardware testing and scaling back work on flight spare hardware. The project has also reduced the frequency of meetings of the mission’s science team.”

When the reserves in a government budget get this low, it almost always guarantees that the budget will go over. When the reserves get this low this early in the project, it almost always guarantees that the budget will go over, by a lot.

There have been other indications that Europa Clipper’s budget is in trouble. In March NASA canceled one science instrument to save money.

Making matter worse has been our lovely Congress, which has required this mission fly on its bloated, over-budget, and behind schedule SLS rocket, a mandate that is also costing the project an additional $1.5 billion (for the launch) while threatening its launch date (because of SLS delays). NASA would rather have the option to launch Clipper on the more reliable commercial and already operational Falcon Heavy, for about $100 million, thereby saving more than a billion dollars while guaranteeing its launch date. Congress so far has refused to budge, and has in fact insisted that the mission be delayed several years if necessary for getting it on SLS.

Meanwhile, Clipper itself is doing what too many big NASA projects routinely do, go overbudget.

Our federal government. Doesn’t its management skills just warm your heart?

A new Juno flyover movie above Jupiter

Citizen scientist Brian Swift has created a new movie from images taken by Juno during its December 25th close pass of Jupiter, the 24th such flyby of the spacecraft’s mission.

I have embedded the movie below. While it isn’t as spectacular as previous movies (see here, here, here, and especially here and here), as it appears that either Juno did not get quite as close, or Swift did not shape it to give that impression, it is still most breathtaking.

First image of Ganymede’s north pole

Ganymede's north polar region

During Juno’s 24th close approach to Jupiter the spacecraft was able to take the first images ever of the north pole of Ganymede, the largest moon in the solar system. The image to the right was processed by citizen scientist Roman Tkacenko, and shows a variety of light and dark features.

The Juno science team decided for some reason to highlight a different set of images processed by citizen scientist Gerald Eichstädt, using the same data. I prefer Tkacenko’s version, because he focused in on the planet itself, making it easier to see what’s there.

In either case, however, the fuzziness of the image reminds me of planetary astronomy in my early childhood. Images like this, taken by telescopes on Earth, were the best we had of any planet beyond the Moon. Made it very hard to understand what was there, or what it meant.

Movie of Jupiter’s south pole storms

Clip from animation of Jupiter's south polar storms

Cool image time! Citizen scientist Gerald Eichstädt has used images taken by Juno of Jupiter’s south polar storms to produce an animation that shows the evolution of those storms over a short time period.

The movie is more a computer model than an assemblage of images.

A fluid dynamical 2D model rotating with Jupiter’s System III rotation rate is started with a map of PJ19 (Juno’s 19th close approach) vorticity measurements of the south polar region between 75 and 90 degrees south (azimuthal, equidistant, planetocentric) as initial condition. The vorticity map is based on a sequence of PJ19 JunoCam images.

Relative vorticities are encoded in color, blue for cyclonic, orange for anticyclonic relative vorticity. The animated gif covers 48 hours, with one frame per real-time hour. Played with 25 fps, the result is a 90,000-fold time-lapsed animation.

I have embedded the animation below the fold. It is quite impressive.
» Read more

New storm spotted at Jupiter’s south pole

New cyclone at Jupiter's south pole
Click for full image.

New images from Juno have revealed the formation of a new Texas-sized cyclone joining the circle of storms around Jupiter’s south pole.

In the infrared Juno image to the right, the new storm is the small bright cyclone in the lower right.

[D]uring Juno’s 22nd science pass [on November 3], a new, smaller cyclone churned to life and joined the fray. “Data from Juno’s Jovian Infrared Auroral Mapper [JIRAM] instrument indicates we went from a pentagon of cyclones surrounding one at the center to a hexagonal arrangement,” said Alessandro Mura, a Juno co-investigator at the National Institute for Astrophysics in Rome. “This new addition is smaller in stature than its six more established cyclonic brothers: It’s about the size of Texas. Maybe JIRAM data from future flybys will show the cyclone growing to the same size as its neighbors.”

Probing the weather layer down to 30 to 45 miles (50 to 70 kilometers) below Jupiter’s cloud tops, JIRAM captures infrared light emerging from deep inside Jupiter. Its data indicate wind speeds of the new cyclone average 225 mph (362 kph) – comparable to the velocity found in its six more established polar colleagues.

Because of Juno’s orbit we do not get continuous views of the gas giant’s cloud-tops, so we can’t see the moment-by-moment evolution of these storms, which makes it impossible to obtain a full understanding of their formation or disappearance. Even then it will likely take centuries of observations to even begin to get a fuller understanding of the meteorology of Jupiter.

Cloud stream on Jupiter

Cloud stream on Jupiter
Click for full image.

Cool image time! The photo to the right, taken by Juno on November 3, was enhanced by citizen scientist Björn Jónsson to bring out the colors. It shows a band of repeating large storms, with tiny white thunderheads popping up within them.

The dark areas at the edges of the swirls are likely not an aspect of the clouds but shadows created because the white swirls sit higher than the surrounding gases.

Sadly the press release does not give us a scale. The image was taken from a distance of 3,200 miles. I suspect each cloud swirl would likely cover much of the Earth.

Jupiter’s thunderheads

The cloud tops of Jupiter
Click for full image.

Using raw Juno images, citizen scientist Gerald Eichstädt has created the processed and color enhanced image to the right, cropped to post here. From the Juno press release:

This view from NASA’s Juno spacecraft captures colorful, intricate patterns in a jet stream region of Jupiter’s northern hemisphere known as “Jet N3.”

Jupiter’s cloud tops do not form a simple, flat surface. Data from Juno helped scientists discover that the swirling bands in the atmosphere extend deep into the planet, to a depth of about 1,900 miles (3,000 kilometers). At center right, a patch of bright, high-altitude “pop-up” clouds rises above the surrounding atmosphere.

Some of the darker areas are darker mostly because they are lower and therefore in shadow.

The raw image was taken on May 29, 2019 when Juno was about 6,000 miles away. Unfortunately, they do not provide a scale, but I suspect that the image is probably close to the size of the entire Earth.

Juno completes long engine burn to avoid Jupiter’s shadow

In order to avoid a twelve-hour plunge through Jupiter’s shadow that would have likely sucked all power from Juno’s solar powered systems and killed the spacecraft, mission engineers have successfully used its attitude thrusters to complete a 10.5 long engine burn.

Juno began the maneuver yesterday, on Sept. 30, at 7:46 p.m. EDT (4:46 p.m. PDT) and completed it early on Oct. 1. Using the spacecraft’s reaction-control thrusters, the propulsive maneuver lasted five times longer than any previous use of that system. It changed Juno’s orbital velocity by 126 mph (203 kph) and consumed about 160 pounds (73 kilograms) of fuel. Without this maneuver, Juno would have spent 12 hours in transit across Jupiter’s shadow – more than enough time to drain the spacecraft’s batteries. Without power, and with spacecraft temperatures plummeting, Juno would likely succumb to the cold and be unable to awaken upon exit.

“With the success of this burn, we are on track to jump the shadow on Nov. 3,” said Scott Bolton, Juno principal investigator at the Southwest Research Institute in San Antonio.

This burn did not use the spacecraft’s main engine, which they fear has a problem that would produce a catastrophic failure if fired. Instead, they used Juno’s small attitude thrusters, which explains the length of the maneuver. In fact, this 10.5 hour burn might actually be the longest chemical engine burn in space ever. While ion engines routinely fire for this long or longer, as far as I can remember no chemical engine in space has ever fired even close to this length of time.

Movie of Juno’s 22 close fly-by of Jupiter

As he has done previously, citizen scientist Gerald Eichstädt has created a movie using Juno images of the spacecraft’s twenty-second fly-by of Jupiter.

I have embedded the movie below the fold. This fly-by included the images of Io’s shadow posted by other citizen scientists earlier. Because the movie shows this shadow in the context of the fly-by (near its lowest altitude), it illustrates why the shadow appears far larger than it is, relative to the entire planet.

» Read more

Storms on Jupiter

Storms on Jupiter
Click for full resolution image.

The image on the right, reduced to post here, was created by Citizen scientist Kevin Gill from recent Juno images taken of Jupiter, and shows in detail some of the many storms that fill Jupiter’s many bands of color.

We do not have a scale, but my guess is that these storms are probably about the size of the Earth, which means these storms are bigger than any hurricane you can imagine. If you click on the image to look at the full resolution photograph, you can see there are tiny white clouds clumped in the middle of the picture’s three biggest storms. Those clumps are probably also bigger than any single clouds you could find anywhere on Earth.

As I wrote in a post in April 2017 about a similar Juno image:

What should fill us with even more awe is that this only covers a very thin slice of the top of Jupiter’s deep atmosphere. The planet itself is about 89,000 miles in diameter, more than ten times larger than Earth. The depth of its atmosphere is not really known, but it must be deeper than several Earths, piled on top of each other. In that depth there must be many atmospheric layers, each thicker and denser than the one above, and each with its own weather systems and complexities.

It will take centuries of research, including the development of new engineering capable of accessing this place, to even begin to map out its meteorology. And this is only one gas giant, of what we now know must be millions and millions throughout the galaxy.

If we have the nerve and daring, the human race has the opportunity to go out there and never be bored. There will always be something unknown to discover.

All that still applies. We have only just begun our journey exploring the universe.

Io’s shadow on Jupiter

Io's shadow on Jupiter
Click for full image.

Citizen scientists Kevin Gill and Tanya Oleksuik have used raw images from Juno to create several really cool images of the eclipse shadow of Io moving across the face of Jupiter. The image above, by Gill, is what I think is the most dramatic. The other images are here, here, here, here, and here.

Oleksuik notes that the colors are not true, and are enhanced for drama. Also, the shadow in many of the images are much too large relative to the globe of Jupiter. The last link above gives a better sense of the true size of that shadow against Jupiter’s giant sphere. Io’s shadow only covers a tiny part of the surface. The reason it appears larger is that the whole image does not see the entire hemisphere.

Io volcano erupts like Ol’ Faithful

Having determined that Io’s largest volcano appears to erupt on a regularly schedule, scientists have predicted that a new eruption should occur sometime in the next week or so.

The volcano Loki is expected to erupt in mid-September, 2019, according to a poster by Planetary Science Institute Senior Scientist Julie Rathbun presented today.

“Loki is the largest and most powerful volcano on Io, so bright in the infrared that we can detect it using telescopes on the Earth,” Rathbun said. Based on more than 20 years of observations, Loki undergoes periodic brightenings when it erupts on a relatively regular schedule. In the 1990s, that schedule was approximately every 540 days. It currently appears to be approximately every 475 days. Rathbun discovered the 540-day periodicity, described in her 2002 paper “L. Loki, Io: A periodic volcano” that appeared in Geophysical Research Letters.

These same scientists successfully predicted Loki’s last eruption based on this data, but also warn that there is no guarantee the volcano will do what they say. As stock brokers are required to say, past performance is no guarantee of future results.

Stony-iron asteroid caused flash on Jupiter in August

According to an analysis of the data obtained from the light flash that occurred when an object hit Jupiter on August 7, scientists have estimated its probably make-up, mass, and size.

They estimate from the energy released by the flash that the impactor could have been an object around 12-16 metres in diameter and with a mass of about 450 tons that disintegrated in the upper atmosphere at an altitude of about 80 kilometres above Jupiter’s clouds. Sankar and Palotai’s models of the light-curve for the flash suggest the impactor had a density typical of stony-iron meteors, indicating that it was a small asteroid rather than a comet.

Their conclusions are strengthened because they were able to compare this flash with five other similar but not as bright flashes, all detected since 2010.

These recent detections, all by amateurs, are because of the higher quality equipment now available to ordinary people, including the use of computers and remote operation. This technology is making it possible for amateurs to discover things that once only professionals could find.

NASA Inspector General to Congress: Free Europa Clipper from SLS

In a letter to Congress on August 27, 2019, NASA’s inspector general has called for Congress to immediately abandon the legal requirement it imposed on Europa Clipper to fly on NASA’s SLS rocket, thereby allowing NASA to choose any commercial rocket to launch the spacecraft.

The letter [pdf] is amazingly blunt.

[W]e write to highlight an issue at NASA that we believe requires immediate action by Congress. Language in NASA’s appropriation legislation requires the Agency to launch a satellite to Europa, a moon of Jupiter, in 2023 on the yet-to-be-completed Space Launch System (SLS) rocket. However, because of developmental delays and, more significantly, NASA’s plans to use the first three SLS rockets produced for its Artemis lunar program, an SLS will not be available until 2025 at the earliest. Consequently, if completed on its projected schedule, the approximately $3 billion dollar Europa spacecraft (known as “Europa Clipper”) will need to be stored for at least 2 years at a cost of $3 to $5 million per month until an SLS becomes available. NASA recently added $250 million in Headquarters-held reserves to the project to address these storage and related personnel costs.

Congress could reduce risks to both the Europa mission and Artemis program while potentially saving taxpayers up to $1 billion by providing NASA the flexibility in forthcoming fiscal year (FY) 2020 appropriations legislation to determine the most cost effective and timely vehicle to launch the Europa Clipper mission in 2023 or whenever the satellite is completed.

As blunt as the letter is, the wording above is also very careful to hide the fact that the $1 billion savings will come, not from avoiding the launch delay, but from buying a private commercial launch vehicle (estimated launch cost about $100 million) versus using SLS (estimated launch cost of $1 billion to $4 billion).

Will Congress take this advice? It should, though I am pessimistic. Our Congress has not shown much interest in doing the smart thing when it comes to SLS for about a decade. Why should things change now?

Juno finds Jupiter’s core more extended and less dense than predicted

My headline above focuses on the real story here, that Juno has found that Jupiter’s solid core is more fuzzy and extended.

Unfortunately, the press release instead focuses on one theory, based on computer models, that might explain this discovery.

The research team ran thousands of computer simulations and found that a fast-growing Jupiter can have perturbed the orbits of nearby “planetary embryos,” protoplanets that were in the early stages of planet formation.

Liu said the calculations included estimates of the probability of collisions under different scenarios and distribution of impact angles. In all cases, Liu and colleagues found there was at least a 40% chance that Jupiter would swallow a planetary embryo within its first few million years. In addition, Jupiter mass-produced “strong gravitational focusing” that made head-on collisions more common than grazing ones.

Isella said the collision scenario became even more compelling after Liu ran 3D computer models that showed how a collision would affect Jupiter’s core. “Because it’s dense, and it comes in with a lot of energy, the impactor would be like a bullet that goes through the atmosphere and hits the core head-on,” Isella said. “Before impact, you have a very dense core, surrounded by atmosphere. The head-on impact spreads things out, diluting the core.”

This theory is all well and good, but we mustn’t take it too seriously. It relies entirely on computer models, and carries with it enormous assumptions about the early solar system that are as yet unproven.

That Jupiter’s core however is fuzzy and extended however is quite fascinating, highlighting once again how little we know about the universe.

Jupiter’s changing Great Red Spot, as seen by Juno

Montage of Jupiter's Great Red Spot since 2017
Click for full image.

Citizen scientist Björn Jónsson has compiled the montage to the right, reduced to post here, of the five times Jupiter’s Great Red Spot (GRS) was imaged by Juno during its repeated orbital fly-bys.

The mosaics show how the GRS and nearby areas have changed over the course of the Juno mission. The mosaics cover planetographic latitudes 4.7 to 38 degrees south.

The resolution of the source data is highly variable and this can be seen in some of the mosaics. The viewing geometry also varies a lot. Some of the images were obtained almost directly above the GRS (in particular some of the perijove 7 images) whereas other images were obtained at an oblique viewing angle (in particular the perijove 17 images).

These are approximately true color/contrast mosaics but there may be some inaccuracies in areas where the original images were obtained at a highly oblique angle. The contrast is also lower in these areas.

Some of the changes are remarkable, considering the short time involved. For example, note the appearance of the large white storm below the Spot in the third image, taken in December 2018. It wasn’t there in April 2018, and was gone by Feburary 2019. This doesn’t mean it had dissipated. Instead, the storm is in a different band which moves at a different speed than the band that the Spot is in. It has thus simply moved away.

This movement is even more remarkable when we remember that the Great Red Spot is about the width of the Earth.

New Hubble image of Jupiter

Jupiter as seen by Hubble in 2019
Click for full image.

The Hubble science team today released a new global image the telescope took of Jupiter on June 27, 2019. The photograph on the right is that image, reduced and cropped to post here. As noted by the press release about the Great Red Spot,

The Great Red Spot is a towering structure shaped like a wedding cake, whose upper haze layer extends more than 3 miles (5 kilometers) higher than clouds in other areas. The gigantic structure, with a diameter slightly larger than Earth’s, is a high-pressure wind system called an anticyclone that has been slowly downsizing since the 1800s. The reason for this change in size is still unknown.

A worm-shaped feature located below the Great Red Spot is a cyclone, a vortex around a low-pressure area with winds spinning in the opposite direction from the Red Spot. Researchers have observed cyclones with a wide variety of different appearances across the planet. The two white oval-shaped features are anticyclones, like small versions of the Great Red Spot.

Another interesting detail is the color of the wide band at the equator. The bright orange color may be a sign that deeper clouds are starting to clear out, emphasizing red particles in the overlying haze.

In many ways Hubble’s images of Jupiter are comparable to those taken by Juno, except that Hubble can’t zoom in as close.

The great storms of Jupiter

The Great Red Spot and its trailing storms
Click for full image.


During its most recent close approach of Jupiter, Juno took the above image of the gas giant’s Great Red Spot from a distance of 26,697 miles above the cloud tops. As noted at the link,

This view highlights the contrast between the colorful South Equatorial Belt and the mostly white Southern Tropical Zone, a latitude that also features Jupiter’s most famous phenomenon, the persistent, anticyclonic storm known as the Great Red Spot.

Just for fun, I cropped out at full resolution the bright storm just to the west of the Great Red Spot, as shown on the right.

It is important to understand the vastness of this image’s scale. You could almost fit two full Earths within the Great Spot. The close-up covers only a slightly smaller range of size. Thus, that tiny bright storm would be the largest hurricane ever seen on Earth, able to cover almost the entire Pacific Ocean.

Jupiter’s changing Great Red Spot

The changing Great Red Spot
Click for full resolution image.

Using Juno images produced during four different orbits, beginning in July 2017 through February 2019, citizen scientist Björn Jónsson has created a montage, reduced in resolution to post on the right, that shows the changes that have occurred in Jupiter’s Great Red Spot during that time. As he writes,

This is a montage of four map-projected [Spot] mosaics processed from images obtained during these perijoves (at the time of this writing perijove 20 is the most recent perijove). The mosaics show how the [Spot] and nearby areas have changed over the course of the Juno mission. The mosaics cover planetographic latitudes 4.7 to 38 degrees south.

The resolution of the source data is highly variable and this can be seen in some of the mosaics. The viewing geometry also varies a lot. Some of the images were obtained almost directly above the [Spot] (in particular some of the perijove 7 images) whereas other images were obtained at an oblique viewing angle (in particular the perijove 17 images).

These are approximately true color/contrast mosaics but there may be some inaccuracies in areas where the original images were obtained at a highly oblique angle. The contrast is also lower in these areas.

What strikes me the most is how the Spot itself seems relatively unchanged, while the bands and surrounding cloud formations changed significantly during this time.

Jupiter in 3D

Jupiter in 3D

Cool image time! Using images from Juno, a citizen scientist going under the nom de plume YobiRoby has created the height map image to the right, showing three-dimensionality of the cloud surface of Jupiter.

Though they provide no details to go with this image, it appears it is centered on Jupiter’s Great Red Spot, the larger of the two big storms that are visible. While the smaller storm appears raised like a mound above the surrounding cloudtops, the Great Red Spot instead appears to be a mound that is depressed below the cloudtops.

1 2 3 5