A pseudo-oblique view of Jupiter’s cloud-tops

A pseudo-oblique view of Jupiter's cloud-tops
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Cool image time! The image to the right, cropped, reduced, and annotated to post here, was created on October 18, 2022 by citizen scientist Thomas Thomopoulos from one of the photos taken by Juno during its close fly-by of Jupiter in May 2018.

He created this three dimensional relief by assigning different elevation values across the image’s greyscale, with white having the highest elevation. This relief is thus not based on actual topography, but it provides a nice way to illustrate the cloud structures of Jupiter’s cloud tops. It also, as Thomopoulos notes, provide a good way to possibly “see a representation in relief of surface movements.” Nor is his topography based on greyscale far wrong, since in many Jupiter images the lighter colored clouds are generally higher because the darker ones are in shadow.

The map below provides the context and scale of this image.
» Read more

Lucy to fly past Earth on October 16th

Lucy solar panel graphic
Artist’s impression of solar panel

As part of its planned route to get to the Trojan asteroids in Jupiter’s orbit, the planetary probe Lucy is scheduled to fly only 220 miles above the Earth’s surface on October 16th.

Lucy will be passing the Earth at such a low altitude that the team had to include the effect of atmospheric drag when designing this flyby. Lucy’s large solar arrays increase this effect.

“In the original plan, Lucy was actually going to pass about 30 miles closer to the Earth,” says Rich Burns, Lucy project manager at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “However, when it became clear that we might have to execute this flyby with one of the solar arrays unlatched, we chose to use a bit of our fuel reserves so that the spacecraft passes the Earth at a slightly higher altitude, reducing the disturbance from the atmospheric drag on the spacecraft’s solar arrays.”

That solar array remains unlatched (as shown in the graphic above), but because it is almost completely deployed and is producing about 90% of its intended electricity, engineers have ceased efforts to complete deployment and latching.

Europa in true color

Europa in true color
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The photo to the right, cropped and reduced to post here, was taken on September 29, 2022 by the Jupiter orbiter Juno during its close fly-by of Europa. Citizen scientist Bjorn Jonsson has processed it to bring out the details. From his caption:

This is an approximately true color/contrast, reprocessed version of Europa image PJ45_1. It is more carefully processed than the version I posted very shortly after the raw image data was released. The color should be fairly close to Europa’s real color and probably slightly more accurate than the color of the earlier version I posted. North is up.

The Sun is coming from the right, so those are craters in the upper left, close to the shadowed limb of the planet. The red color has been known for decades, and appears in many cases to be seepage coming up from the many meandering ridges that criss-cross the planet’s surface. Their chemistry/make-up is not fully known at this time.

Juno came within 219 miles of Europa, the closest any spacecraft has come since the Galileo orbiter circled Jupiter in the 1990s. I was expecting close-up images of the surface, from that close distance, but have not yet seen any. Instead, most of the images released and processed by citizen scientists have been global images from farther away. Thus, at this moment it does not appear Juno took pictures at this closest distance.

NASA releases first Juno image from the first close fly-by of Europa in decades

First released Juno image of Europa
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Kevin Gill's processed Juno image of Europa
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NASA yesterday released the first image from the successful close fly-by by Juno of Jupiter’s moon Europa since the 1990s. That photo, reduced and sharpened, is above.

The first picture NASA’s Juno spacecraft took as it flew by Jupiter’s ice-encrusted moon Europa has arrived on Earth. Revealing surface features in a region near the moon’s equator called Annwn Regio, the image was captured during the solar-powered spacecraft’s closest approach, on Thursday, Sept. 29, at 2:36 a.m. PDT (5:36 a.m. EDT), at a distance of about 219 miles (352 kilometers).

This is only the third close pass in history below 310 miles (500 kilometers) altitude and the closest look any spacecraft has provided at Europa since Jan. 3, 2000, when NASA’s Galileo came within 218 miles (351 kilometers) of the surface.

Meanwhile, the raw images have been pouring in, and citizen scientists have been quickly processing them. The photo to the right is only one example, created by Kevin Gill. I have cropped it to show one section in full resolution.

Expect many more processed images, especially those taken at closest approach, in the coming days.

Jupiter’s north pole cyclones appear as stable as those at the south pole

The northern polar cyclones of Jupiter
Click for original figure.

In reviewing five years of data from Juno, scientists now conclude that the polygon of large storms surrounding Jupiter’s north pole appear as stable as the same poloygon of storms found at the south pole.

Each polygon is made up of a central polar cyclone (PC) surrounded by a number of circum-polar cyclones (CPC). The image to the right, Figure 1 from the paper, compares the north polar storms from 2017 (top) to 2022 (bottom). During the five years of observations the whole polygon “rotated approximately 15° westward,” though it essentially maintained its structure.

After 5 years, the 8 + 1 North PCs structure and the 5 + 1 South one show very small changes; the lifetime of a single cyclone is therefore longer than 25 years and possibly longer than 75 years. Also, single cyclones have their peculiar morphology and this is often retained after 5 years, both in radiance and in morphology. In particular, this is the first time that we can observe the North CPCs system since the discovery in 2017, and we find that the structure is almost unperturbed.

The question that appears to remain unanswered by this data is whether these storms are deep-rooted to the interior of Jupiter or shallow structures. The stability suggests the latter, but this remains unproven.

Ganymede as seen by Juno

Ganymede as seen by Juno
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Cool image time! The picture to the right, cropped and reduced to post here, was taken on June 7, 2021 when Juno made a close fly-by of Jupiter’s moon Ganymede. It has been reprocessed to bring out the details by citizen scientist Brian Swift.

Note the bands and parallel light and dark ridges that criss-cross the planet. Scientist as yet do not understand what caused them. Note also the bright impact craters, suggesting the release of water ice from below.

This image anticipates Juno’s upcoming September 29, 2022 fly-by of Europa, one of Jupiter’s other Galilean moons. The orbiter will pass only 221 miles above its surface, and get the best images in decades, since the Galileo mission in the 1990s.

A hot wave in Jupiter’s upper atmosphere has been discovered, flowing away from the pole

Jupiter heat wave

Using data obtained by ground-based telescopes, scientists have discovered a hot wave, with temperatures in the range of 700 degrees Celsius (about 1,300 degrees Fahrenheit), rolling outward from Jupiter’s hot polar atmospheric regions, believed caused by the gas giant’s intense aurora.

Jupiter’s atmosphere, famous for its characteristic multicoloured vortices, is also unexpectedly hot: in fact, it is hundreds of degrees hotter than models predict. Due to its orbital distance millions of kilometres from the Sun, the giant planet receives under 4% of the amount of sunlight compared to Earth, and its upper atmosphere should theoretically be a frigid -70 degrees Celsius. Instead, its cloud tops are measured everywhere at over 400 degrees Celsius.

…Just like the Earth, Jupiter experiences auroras around its poles as an effect of the solar wind. However, while Earth’s auroras are transient and only occur when solar activity is intense, auroras at Jupiter are permanent and have a variable intensity. The powerful auroras can heat the region around the poles to over 700 degrees Celsius, and global winds can redistribute the heat globally around Jupiter.

The graphic above, adapted from the research presentation [pdf], shows that wave propagating away from the pole. The wave’s width is about the size of the Earth, with different sections moving from about 1,000 feet per second to 8,000 feet per second.

Jupiter’s endless interweaving storms

Jupiter's endless interweaving storms

Cool image time! The photo to the right, rotated so that north is up and then reduced slightly to post here, was created by citizen scientist Thomas Thomopoulos from a raw photo taken by Juno during its 44th orbit of Jupiter.

To bring out the details Thomopoulos enhanced the colors, then enlarged the entire photo and cropped the area of interest.

Unfortunately, the Juno team that releases these photos does not provide information for easily establishing scale. In an email to me Thomopoulos noted that the largest circular storm in the northern half of the image is likely a vortex, which on Jupiter tend to range from 600 to 3,500 miles in diameter. He also noted that Juno was a little less than 27,000 miles away from Jupiter when this photo was snapped on August 17, 2022. Thus, I suspect this particular vortex sits on the larger end of that size range, which makes it a little less than half the size of the Earth.

As for the colors, as with many similar Juno images, the white clouds appear to almost always sit at the top of these storms and jets, almost like thunderheads.

Though the largest feature here is that large vortex to the north, most of the gigantic Jupiter storms visible seem instead to form as bands, the storms churning about madly as they are driven along the gas giant’s very fast ten hour rotation period.

Storm fronts on Jupiter

Storm front on Jupiter
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Cool image time! The picture to the right, cropped and reduced to post here, was processed by citizen scientist Thomas Thomopoulos from a raw image taken by the Jupiter orbiter Juno on August 17, 2022.

The orbiter was 18,354 miles above the cloud tops when the image was snapped. It shows a stormy cloud band in the southern hemisphere.

You can get a sense of the processing that Thomospoulos did by comparing this image with the raw photo. The original has almost no contrast, either in color or in contrast. By enhancing both Thomospoulos makes the violent nature of these large storms, thousands of miles in size, quite visible.

Another Webb infrared image of Jupiter released

Jupiter as seen in the infrared by Webb
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The science team for the James Webb Space Telescope today released another infrared false-color image of Jupiter, this time processed for science instead of calibration of the telescope after launch.

That image is to the right, reduced to post here. From the caption:

Several exposures in three different filters were assembled to create this mosaic, after being corrected for the rotation of the planet. The combination of filters yields an image whose colors denote the height of the clouds and the intensity of auroral emissions.

The F360M filter (mapped to the red-orange colors) is sensitive to light reflected from the lower clouds and upper hazes. The red features in the polar regions are auroral emissions, caused by ions excited through collisions with charged particles at altitudes up to 1000 km above the cloud level. Auroral emission in red is evident in the northern and southern polar regions and reaches high above the limb of the planet. In the F212N filter (mapped to yellow-green colors), the gaseous methane in Jupiter’s atmosphere absorbs light; the greenish areas around the polar regions come from stratospheric hazes 100-200 km above the cloud level. The stratospheric haze that appears green in this composite is also concentrated in the polar regions, but extends down to equatorial latitudes and can also be seen along the limbs (edges) of the planet. The cyan channel holds the F150W2 filter, which is primarily sensitive to reflected light from the Jupiter’s deeper main cloud level at about one bar.

The Great Red Spot, the hazy equatorial region and myriad small storm systems appear white (or reddish-white) in this false-color image. Regions with little cloud cover appear as dark ribbons north of the equatorial region. Some dark regions — for example, those next to the Great Red Spot and in cyclonic features in the southern hemisphere — are also dark-colored when observed in visible wavelengths.

This image is part of the telescope’s early release science program.

Jupiter’s internal structure, based on Juno data

Jupiter's internal structure
Click for original figure.

Scientists using Juno data of Jupiter’s magnetic field, combined with computer modeling, have now produced a rough map of the gas giant’s internal structure.

The image to the right, figure 2, of their paper, shows that structure. I have annotated the figure to provide some sense of scale. The bold violet line indicates their conclusions about the size of the dynamo that drives Jupiter’s powerful magnetic field, comprising more than 80 percent of the planet’s internal diameter. From the caption:

The gray area depicts the core (0.2 RJ) and the possible dilute core region. The violet area between the dotted lines (0.68 and 0.84 RJ) depicts the [hydrogen-helium] phase separated layer. The top dotted line at 0.95 RJ depicts the depth where the jets decay down to the minimum. The arrows represent possible convection area with unknown origin depth.

While this is a good first hypothesis based on the available data, that data remains quite sparse and uncertain. Thus, the conclusions here must be taken with a great deal of skepticism.

The big storms at Jupiter’s poles are coherent and stable

Storms on Jupiter
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After four years of observations by Juno in orbit around Jupiter, scientists studying the storms at the gas giant’s poles have found that those storms are stable, long-lasting features. From the abstract of their paper:

These data have shown cyclones organized in snowflake-like structures. The Jupiter’s polar cyclones are long-lasting features, which did not disappear or merge during four years of observations.

The image to the right, posted by me earlier this week, shows several of these storms, or vortices, at Jupiter’s north pole. Previous work had documented the overall pattern, as described in the paper:

The observed vortices display geometrical symmetries around both poles: circumpolar cyclones (CPCs), organized in a regular pattern, surround a central one. At the north pole, eight circumpolar vortices form an octagonal structure, while at the south pole, five circumpolar vortices are arranged in a pentagonal pattern; both central polar vortices show some degree of displacements to the geometrical pole, about 0.5° for the Northern Polar Cyclone (NPC) and 1°-2° for the Southern Polar Cyclone (SPC).

While this research has found little change in these storms over four years, it is unknown what their long term evolution will be for an entire Jupiter year, twelve Earth years long.

A crowd of Jupiter hurricanes

Storms on Jupiter
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Cool image time! The photo to the right, cropped and reduced to post here, was taken on July 5, 2022 during Juno’s 43rd close fly-by of Jupiter, and was enhanced by citizen scientist Brian Swift. It shows a group of storms, what planetary scientists have labeled “vortices” near Jupiter’s north pole.

These powerful storms can be over 30 miles (50 kilometers) in height and hundreds of miles across. Figuring out how they form is key to understanding Jupiter’s atmosphere, as well as the fluid dynamics and cloud chemistry that create the planet’s other atmospheric features. Scientists are particularly interested in the vortices’ varying shapes, sizes, and colors. For example, cyclones, which spin counter-clockwise in the northern hemisphere and clockwise in the southern, and anti-cyclones, which rotate clockwise in the northern hemisphere and counter-clockwise in the southern hemisphere, exhibit very different colors and shapes.

The image highlights the type of storm Juno scientists are asking the pubic to category in a new citizen scientist project called Jovian Vortex Hunter. You go to its website and go through Juno images, noting and categorizing them. So far more than 2,400 volunteers have marked up more than 375,000 storms.

Webb infrared image of Jupiter & Europa

Jupiter and Europa as seen by Webb
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During the commissioning phase after deployment, the James Webb Space Telescope took images of Jupiter and several asteroids in order test the telescope’s instruments. The photo to the right, cropped and reduced to post here, shows both Jupiter and its moon Europa to the left.

Fans of Jupiter will recognize some familiar features of our solar system’s enormous planet in these images seen through Webb’s infrared gaze. A view from the NIRCam instrument’s short-wavelength filter shows distinct bands that encircle the planet as well as the Great Red Spot, a storm big enough to swallow the Earth. The iconic spot appears white in this image because of the way Webb’s infrared image was processed.

…Clearly visible at left is Europa, a moon with a probable ocean below its thick icy crust, and the target of NASA’s forthcoming Europa Clipper mission. What’s more, Europa’s shadow can be seen to the left of the Great Red Spot. Other visible moons in these images include Thebe and Metis.

The false color differences indicated differences in heat but it is not explained whether brighter is colder or warmer in this photo.. As one of my readers below correctly notes, Europa’s shadow tells us that darker is cooler. This one image shows that the Red Spot and Jupiter’s equatorial regions and poles are generally warm.

Jet streams on Jupiter

Jet streams on Jupiter
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Cool image time! The photo to the right, cropped and reduced to post here, was created from a raw image from the Jupiter orbiter Juno by citizen scientist Sergio Diaz-Ruiz. As he notes in his caption:

Several jet streams at high latitude, near the north pole of the planet, crowned by clouds, contrast with a dark oval just over the center.

The original was taken on February 25, 2022 during Juno’s fortieth close approach to Jupiter. As Diaz-Ruiz notes, the contrast with the dark oval and the higher lighter clouds is striking. It is almost as if thermals rising over that oval are pushing the lighter clouds away.

This is only the fourth Juno image that Diaz-Ruiz has processed. All are quite stunning, and worth a look.

Dunes on Jupiter’s volcano moon Io?

Dunes on Io?
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The uncertainty of science: According to a just published paper, scientists now propose that the dune-like ridges long known to exist on Io, Jupiter’s volcano-covered moon, might actually be dunes, even though Io has no real atmosphere.

The photo to the right, cropped, reduced, and annotated to post here, was taken by the Galileo while it orbited Jupiter from 1995 to 2003. It illustrates what the scientists believe is the proposed process:

McDonald and his colleagues used mathematical equations to simulate the force required to move grains on Io and calculated the path those grains would take. The study simulated the movement of a single grain of basalt or frost, revealing that the interaction between flowing lava and sulfur dioxide beneath the moon’s surface creates venting that is dense and fast moving enough to form large dune-like features on the moon’s surface, according to the statement.

In what might be a monumental understatement about the reality of interplanetary geology, McDonald said this in the press release: “This work tells us that the environments in which dunes are found are considerably more varied than the classical, endless desert landscapes on parts of Earth.”

Damn right. The possibility of unexpected geology of all kinds on the millions of planets, moon, and asteroids not yet studied is endless, and guaranteed.

Looking down into a Jupiter hurricane

Looking down into a Jupiter hurricane
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Cool image time! The photo to the right, cropped and reduced to post here, was created by citizen scientists Kevin Gill and Navaneeth Krishnan from a raw image taken by Juno during its 40th close fly-by of Jupiter in February 2022.

I don’t have a scale, but I would guess that this storm is at least a thousand miles across. The depth is harder to measure, but we looking down into a deep whirlpool for sure.

To bring out the details Gill and Krishnan enhanced the colors significantly. The original is quite bland in comparison, with this storm being the faint dark spot just below the center near the photo’s left edge.

Weird storms on Jupiter

Storms on Jupiter
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Cool image time! The photo to the right, reduced to post here, was taken during Juno’s 38th close fly-by of Jupiter. It was enhanced and released yesterday by citizen scientist Kevin Gill to bring out the storm details, both of the large white storm at the bottom of the photo and the oblong eddy in the center.

Note the white puffy clouds sticking up from both larger cyclones. These tiny thunderheads are probably about the size of a very large Earth storm, but I am guessing. I don’t know the scale, but I suspect the Earth would fit within this image.

The oblong storm is actually an eddy that is swirling around the white and more stable storm below it.

Hubble’s 2021 survey of the outer solar system

Jupiter in 2021 by Hubble
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Saturn in 2021 by Hubble
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Uranus in 2021 by Hubble
Click for full Uranus image.

Neptune in 2021 by Hubble
Click for full Neptune image.

NASA today released the annual survey of images taken each year by the Hubble Space Telescope of the large planets that comprise the outer solar system, Jupiter, Saturn, Uranus, and Neptune.

These Hubble images are part of yearly maps of each planet taken as part of the Outer Planets Atmospheres Legacy program, or OPAL. The program provides annual, global views of the outer planets to look for changes in their storms, winds, and clouds. Hubble’s longevity, and unique vantage point, has given astronomers a unique chance to check in on the outer planets on a yearly basis. Knowledge from the OPAL program can also be extended far beyond our own solar system in the study of atmospheres of planets that orbit stars other than our Sun.

The four photos, all either cropped or reduced slightly to post here, are to the right. Each shows some changes in these planets since the previous survey images the year before.

On Jupiter for example the equatorial region shows several new storms, with that band remaining a deep orange color longer than expected.

On Saturn the various bands have continued to show the frequent and extreme color changes that the telescope has detected since it began these survey images back in the 1990s.

The photo of Uranus meanwhile looks at the gas giant’s northern polar regions, where it is presently spring. The increased sunlight and ultraviolet radiation has thus caused the upper atmosphere at the pole to brighten. The photo also confirms that the size of this bright “polar hood” continues to remain the same, never extending beyond the 43 degree latitude where scientists suspect a jet streams acts to constrain it.

The image of Neptune, the farthest and thus hardest planet for Hubble to see, found that the dark spot in the planet’s northern hemisphere appears to have stopped moving south and now appears to be heading north. Also,

In 2021, there are few bright clouds on Neptune, and its distinct blue with a singular large dark spot is very reminiscent of what Voyager 2 saw in 1989.

The stormy atmosphere of Jupiter

Jupiter's South South Temperate Belt
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Cool image time! The photo to the right, cropped to post here, was created by citizen scientist Thomas Thomopoulo from a Juno image taken during its 16th close pass of Jupiter in 2018. To bring out the different colors of the clouds he enhanced the resolution and color contrast.

We have no scale, but I would guess the distances seen exceed several thousand miles. The area covered is what is called Jupiter’s South South Temperate Belt, the visible belt at about 40 degrees south latitude that circles the South Polar Region (which is the darker purple swirls in the bottom left). This belt is difficult to observe from Earth because of its high latitude, with the curve of Jupiter’s limb beginning to bend away from view.

Skimming over the cloud tops of Jupiter

Skimming over the cloud tops of Jupiter
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Cool image time! The computer visualization above is based on a orbital image of Jupiter taken by Juno, but processed by citizen scientist Ryan Cornell to give, as he puts it, a view “as if we had a low orbit above the clouds.”

I estimate the scale of these clouds is quite large, with the Earth easily fitting inside the orange band on the right. The sharp horizon edge is a not accurate, however, as the clouds would have a decidedly fuzzy boundary, possibly many thousand miles in extent.

Nonetheless, it is a fun image that begins to give us a sense of Jupiter’s upper atmosphere.

New results about Jupiter published from Juno

Three new papers published today in the journals Science and the Journal of Geophysical Research: Planets reveal in more detail the depth of Jupiter’s storms and clouds, using a variety of different sensors and techniques.

The papers can be found here, here, and here.

Juno’s microwave radiometer (MWR) allows mission scientists to peer beneath Jupiter’s cloud tops and probe the structure of its numerous vortex storms. The most famous of these storms is the iconic anticyclone known as the Great Red Spot. Wider than Earth, this crimson vortex has intrigued scientists since its discovery almost two centuries ago.

The new results show that the cyclones are warmer on top, with lower atmospheric densities, while they are colder at the bottom, with higher densities. Anticyclones, which rotate in the opposite direction, are colder at the top but warmer at the bottom.

The findings also indicate these storms are far taller than expected, with some extending 60 miles (100 kilometers) below the cloud tops and others, including the Great Red Spot, extending over 200 miles (350 kilometers). This surprise discovery demonstrates that the vortices cover regions beyond those where water condenses and clouds form, below the depth where sunlight warms the atmosphere.

The height and size of the Great Red Spot means the concentration of atmospheric mass within the storm potentially could be detectable by instruments studying Jupiter’s gravity field. Two close Juno flybys over Jupiter’s most famous spot provided the opportunity to search for the storm’s gravity signature and complement the MWR results on its depth.

With Juno traveling low over Jupiter’s cloud deck at about 130,000 mph (209,000 kph) Juno scientists were able to measure velocity changes as small 0.01 millimeter per second using a NASA’s Deep Space Network tracking antenna, from a distance of more than 400 million miles (650 million kilometers). This enabled the team to constrain the depth of the Great Red Spot to about 300 miles (500 kilometers) below the cloud tops.

The data from these two techniques confirms that the base of the Great Red Spot is somewhere between 200 to 300 miles below the cloud tops, much deeper than most of the other storms, though even those storms are deeper than expected.

Another paper published earlier in Geophysical Research Letters looked at the storms in Jupiter’s polar regions, and found their polygonal arrangement around the poles appears stable and caused by a balanced push between these surrounding storms, trying to move to the poles, and the storms at the poles pushing back.

Pop-up clouds on Jupiter

Pop-up clouds on Jupiter
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Cool image time! The photo above was cropped and enhanced by citizen scientist Gerald Eichstädt from a raw Juno image taken during that spacecraft’s 37th orbit. I have reduced it slightly to post here.

The photo shows what he calls “pop-up” clouds floating above a much larger cloud eddy. Unfortunately, Eichstädt provides no scale, but I suspect this image would easily cover the Earth, with those white clouds probably far larger than the biggest hurricane on Earth.

Hubble data detects persistent water vapor on one of Europa’s hemispheres

Using data from the Hubble Space Telescope spanning sixteen Earth years, scientists have detected the presence of water vapor on Europa, but strangely spread only across one of the moon’s hemispheres.

Previous observations of water vapor on Europa have been associated with plumes erupting through the ice, as photographed by Hubble in 2013. They are analogous to geysers on Earth, but extend more than 60 miles high. They produce transient blobs of water vapor in the moon’s atmosphere, which is only one-billionth the surface pressure of Earth’s atmosphere.

The new results, however, show similar amounts of water vapor spread over a larger area of Europa in Hubble observations spanning from 1999 to 2015. This suggests a long-term presence of a water vapor atmosphere only in Europa’s trailing hemisphere – that portion of the moon that is always opposite its direction of motion along its orbit. The cause of this asymmetry between the leading and trailing hemisphere is not fully understood.

First, it must be emphasized that the amounts of atmospheric water being discussed are tiny, so tiny that on Earth we might consider this a vacuum.

Second, that the water vapor is only seen on the trailing hemisphere suggests there is some sort of orbital influence involved, though what that influence is remains unknown.

Hopefully when Europa Clipper finally arrives in orbit around Jupiter in 2030, with a path that will fly past Europa fifty times, we will some clarity on these questions.

Data suggests the winds in Jupiter’s Great Red Spot are changing

Changing wind speeds in Great Red Spot
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Data accumulated from 2009 to 2020 by the Hubble Space Telescope suggest that the outer winds in Jupiter’s Great Red Spot have speeded up by about 8%, while the winds in the spot’s inner regions have slowed.

The change in wind speeds they have measured with Hubble amount to less than 1.6 miles per hour per Earth year. “We’re talking about such a small change that if you didn’t have eleven years of Hubble data, we wouldn’t know it happened,” said Simon. “With Hubble we have the precision we need to spot a trend.” Hubble’s ongoing monitoring allows researchers to revisit and analyze its data very precisely as they keep adding to it. The smallest features Hubble can reveal in the storm are a mere 105 miles across, about twice the length of the state of Rhode Island.

“We find that the average wind speed in the Great Red Spot has been slightly increasing over the past decade,” Wong added. “We have one example where our analysis of the two-dimensional wind map found abrupt changes in 2017 when there was a major convective storm nearby.”

The graphic above shows the different wind speeds between the spot’s inner and outer regions, not the increase in speed described in this press release.

To put it mildly, these results are uncertain. We simply could be seeing the long term random fluctuations in the storm, or the change could simply be a reflection of the data’s margin of error. Moreover, since the data covers only the top layer of the Great Red Spot, it tells us nothing about the storm’s deeper regions or its more fundamental origins.

1st water vapor in Ganymede’s atmosphere, detected using data from Hubble

Using Hubble data, astronomers have detected the first evidence of water vapor in the atmosphere of Jupiter’s largest moon, Ganymede.

Though larger than the blistering planet Mercury, the Jovian moon Ganymede is no place to go sunbathing. Located ½-billion miles from the Sun, the water ice on its surface is frozen solid in frigid temperatures as low as minus 300 degrees Fahrenheit. This makes the ice as hard as rock. Still, a rain of charged particles from the Sun is enough to turn the ice into water vapor at high noon on Ganymede.

This is the first time such evidence has been found, courtesy of the Hubble Space Telescope’s spectroscopic observations of aurora on Ganymede spanning two decades. The auroras are used to trace the presence of oxygen, which then is linked to the presence of water molecules sputtering off the surface. Ganymede has a deep ocean located an estimated 100 miles below the surface. That’s too deep for water vapor to be leaking out.

This detection has a margin of uncertainty, but it provides a baseline for the up close observations planned for Europe’s JUICE orbiter, set to launch in ’22 and arrive in Jupiter orbit in ’29. JUICE’s study focus will be the three Galilean moons that appear to have lots of ice, Ganymede, Calisto, and Europa.

Juno team creates dramatic animation of Ganymede/Jupiter fly-by

Using images from Juno’s fly-by of both Ganymede and Jupiter on June 7th and 8th, the science team has produced a dramatic animation, with background music, showing that fly-by from the point of view of the spacecraft.

I have embedded it below the fold.

The 3:30-minute-long animation begins with Juno approaching Ganymede, passing within 645 miles (1,038 kilometers) of the surface at a relative velocity of 41,600 mph (67,000 kph). The imagery shows several of the moon’s dark and light regions (darker regions are believed to result from ice sublimating into the surrounding vacuum, leaving behind darkened residue) as well as the crater Tros, which is among the largest and brightest crater scars on Ganymede.

It takes just 14 hours, 50 minutes for Juno to travel the 735,000 miles (1.18 million kilometers) between Ganymede and Jupiter, and the viewer is transported to within just 2,100 miles (3,400 kilometers) above Jupiter’s spectacular cloud tops. By that point, Jupiter’s powerful gravity has accelerated the spacecraft to almost 130,000 mph (210,000 kph) relative to the planet.

Among the Jovian atmospheric features that can be seen are the circumpolar cyclones at the north pole and five of the gas giant’s “string of pearls” – eight massive storms rotating counterclockwise in the southern hemisphere that appear as white ovals. Using information that Juno has learned from studying Jupiter’s atmosphere, the animation team simulated lightning one might see as we pass over Jupiter’s giant thunderstorms.

The lightning shown on Jupiter, while entertaining, is a complete fantasy. The flashes are much too bright and large. At the scale created, some would cover the Earth. In reality, that lightning wouldn’t be visible until you are very very close, and even then probably difficult to spot in the vastness of Jupiter.

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Craters on Ganymede’s striped surface

Craters on Ganymede
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Cool image time! The photo to the right, cropped to post here, is a color enhanced section taken from of one of the images taken by Juno when it did a close fly-by of the Jupiter moon Ganymede back on June 7, 2021.

The enhancement was done by citizen scientist Navaneeth Krishnan, using a wider Juno image of Ganymeded enhanced by citizen scientist Kevin Gill. That wider image is below, and marks the area covered by this first image with a white box.

In this one picture we can see many of the geological mysteries that have puzzled scientists since the Galileo orbiter first took close-up images back in the 1990s. We can see patches of grooved terrain with the grooves in the different patches often oriented differently. We can also see bright and dark patches that while they overlay the grooved terrain they bear no correspondence to those grooved patches. And on top of it all are these small craters, impacts that obviously occurred after the formation of the grooves.
» Read more

Juno takes first close-up images of Ganymede since 2000

Ganymede as seen by Juno
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Ganymede as seen by Juno
Click for full image.

On June 7th the Jupiter orbiter Juno made its first close fly-by of Ganymede, taking the first close-up images of this Jupiter moon since the orbiter Galileo flew past in 2000.

The first two images from NASA Juno’s June 7, 2021, flyby of Jupiter’s giant moon Ganymede have been received on Earth. The photos – one from the Jupiter orbiter’s JunoCam imager and the other from its Stellar Reference Unit star camera – show the surface in remarkable detail, including craters, clearly distinct dark and bright terrain, and long structural features possibly linked to tectonic faults.

…Using its green filter, the spacecraft’s JunoCam visible-light imager captured almost an entire side of the water-ice-encrusted moon. Later, when versions of the same image come down incorporating the camera’s red and blue filters, imaging experts will be able to provide a color portrait of Ganymede. Image resolution is about 0.6 miles (1 kilometer) per pixel.

In addition, Juno’s Stellar Reference Unit, a navigation camera that keeps the spacecraft on course, provided a black-and-white picture of Ganymede’s dark side (the side opposite the Sun) bathed in dim light scattered off Jupiter. Image resolution is between 0.37 to 0.56 miles (600 to 900 meters) per pixel.

Both images are to the right, each slightly reduced to post here. These images of this moon of Jupiter, the largest moon in the solar system and about 26% larger than the planet Mercury, reveal many of the same unsolved geological mysteries uncovered when the Galileo orbiter photographed it two decades ago. As I wrote in my Chronological Encyclopedia

Closer inspection of Ganymede revealed a strange topography, including patches of grooved terrain (not unlike the surface of a vinyl record) overlaying other patches of grooved terrain, the different patches oriented in random and totally unrelated directions. Moreover, the surface is overlain by bright and dark patches (the bright patches thought to be caused by water frost) that often had no apparent correspondence to topographical features. Planetary geologists could only scratch their heads in wonderment.

Jupiter’s changing and unchanging Great Red Spot

The changing Great Red Spot of Jupiter
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In a paper published in March in the Journal of Geophysical Research: Planets, scientists (using images from amateurs, the Hubble Space Telescope, and Juno, scientists) have mapped out the interactions between Jupiter’s Great Red Spot, the longest known storm on the gas giant, and the smaller storms that interact with it as they zip past.

The series of images to the right come from figure 5 of their paper, showing the Spot over a period of three days. The Spot in these images is about 9,000 miles across, less than half the size it had been back in the late 1800s.

The black arrows mark the shifting location and shape of one smaller vortice as it flowed past the Spot from east to west along its northern perimeter, ripping off portions of the Spot as it passed. From the paper’s absract:

During its history, the [Great Red Spot] has shrunk to half its size since 1879, and encountered many smaller anticyclones and other dynamical features that interacted in a complex way. In 2018–2020, while having a historically small size, its structure and even its survival appeared to be threatened when a series of anticyclones moving in from the east tore off large fragments of the red area and distorted its shape. In this work, we report observations of the dynamics of these interactions and show that as a result the [Spot] increased its internal rotation velocity, maintaining its vorticity but decreasing its visible area, and suffering a transient change in its otherwise steady 90‐day oscillation in longitude.

…From the analysis of the reflectivity of the [Spot] and flakes and model simulations of the dynamics of the interactions we find that these events are likely to have been superficial, not affecting the full depth of the [Spot]. The interactions are not necessarily destructive but can transfer energy to the [Spot], maintaining it in a steady state and guaranteeing its long lifetime.

In other words, the changes seen only involved the Spot’s cloud tops, even if those tops were many miles thick. The storm itself is much deeper, with its base embedded strongly inside Jupiter and largely unaffected by these passing smaller storms.

Why the Spot exists and remains so long-lived remains an unsolved mystery.

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