Tag: Jupiter

Jet streams on Jupiter

12:55 pm

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.

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Dunes on Jupiter’s volcano moon Io?

9:35 am

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.

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Looking down into a Jupiter hurricane

11:25 am

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.

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Weird storms on Jupiter

9:03 am

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.

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Hubble’s 2021 survey of the outer solar system

2:18 pm

Jupiter in 2021 by Hubble
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Saturn in 2021 by Hubble
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Uranus in 2021 by Hubble
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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.

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The stormy atmosphere of Jupiter

9:07 am

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.

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Skimming over the cloud tops of Jupiter

8:29 am

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.

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New results about Jupiter published from Juno

1:01 pm

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.

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Pop-up clouds on Jupiter

9:12 am

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.

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

1:30 pm

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.

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

2:46 pm

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.

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

9:06 am

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.

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

10:49 am

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

11:27 am

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.
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Juno takes first close-up images of Ganymede since 2000

9:21 am

Ganymede as seen by Juno
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Ganymede as seen by Juno
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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.

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Jupiter’s changing and unchanging Great Red Spot

9:40 am

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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Looking into one of Jupiter’s smaller cyclones

9:47 am

A northern cyclone on Jupiter
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Cool image time! The photo to the right, cropped and reduced to post here, was taken by the Juno probe orbiting Jupiter and enhanced first by citizen scientist Kenneth Gill and then further enhanced by citizen scientist Navaneeth Krishnan.

Sadly all the link tells us about this storm is that it is in the northern hemisphere. Based upon the colors, my guess is that it located at the high latitude where Jupiter’s bands transition to the chaotic region of storms at the poles, as seen in this earlier wide image of the gas giant’s south pole.

No scale is provided, but an earlier image of other northern hemisphere storms suggests this storm would probably cover the state of Arizona.

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Europa Clipper to fly on commercial rocket, not SLS

11:30 pm

NASA managers have now decided unequivocally to not use SLS to launch Europa Clipper, and will instead choose a commercial rocket in about a year.

During a Feb. 10 presentation at a meeting of NASA’s Outer Planets Assessment Group (OPAG), leaders of the Europa Clipper project said the agency recently decided to consider only commercial launch vehicles for the mission, and no longer support a launch of the spacecraft on the SLS.

“We now have clarity on the launch vehicle path and launch date,” Robert Pappalardo, project scientist for Europa Clipper at the Jet Propulsion Laboratory, said. That clarity came in the form of a Jan. 25 memo from NASA’s Planetary Missions Program Office to “immediately cease efforts to maintain SLS compatibility” and move forward with a commercial launch vehicle, or CLV, he said.

Though this decision was expected following the approval of the most recent congressional budget for NASA, which contained language allowing NASA to abandon SLS if it thought it wise, this decision continues the string of recent stories that all point toward the eventually abandonment of SLS itself.

At the moment the rocket most likely to win the contract is the Falcon Heavy.

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Jupiter’s southern jet streams

9:21 am

Jupiter's southern jet streams
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Cool image time! The photo to the right, rotated and reduced slightly to post here, shows the southern jet streams in Jupiter’s atmosphere. From the press release:

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

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

According to data obtained by Juno, these bands of storms extend about 1,800 miles into Jupiter’s interior, much deeper than expected.

The Great Red Spot is at about 22 degrees south latitude, so this tells us that this picture covers Jupiter’s southern hemisphere from about the equator down to about 80 degrees.

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NASA extends mission of Juno and InSight probes

8:08 am

NASA has decided to extend the missions of Juno and InSight probes, giving both several more years to gather data.

InSight main goal for the two-year extension will be to gather more seismic data of Mars. They will also continue their efforts to get the heat sensor into the ground, but that will have a lower priority.

Juno will be able to slowly adjust its orbit to better study Jupiter’s north polar regions, thus developing a more complete first rough map of the gas giant’s internal structure and atmosphere. The changing orbit will also allow the first close fly-bys of some of Jupiter’s moons, the first in more than twenty years.

The moon flybys could begin in mid-2021 with an encounter with Ganymede, Jupiter’s largest moon, at a distance of roughly 600 miles (1,000 kilometers), Bolton said last year.

After a series of distant passes, Juno will swoop just 200 miles (320 kilometers) above Europa in late 2022 for a high-speed flyby. Only NASA’s Galileo spacecraft, which ended its mission in 2003, has come closer to Europa.

There are two encounters with Jupiter’s volcanic moon Io planned in 2024 at distances of about 900 miles (1,500 kilometers), according to the flight plan presented by Bolton last year. Juno will be able to look for changes on the surfaces of Jupiter’s moons since they were last seen up close by NASA’s Voyager and Galileo probes.

While it will take images, Juno’s camera is not particularly high resolution. The main effort will be to use its instruments to study the surface make-up of the moons.

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Congress frees Europa Clipper from SLS

9:10 am

It appears that Congress has at last removed its requirement that the unmanned probe Europa Clipper must be launched on the continually delayed and very expensive SLS rocket.

Almost unnoticed, tucked into the 2021 fiscal NASA funding section of the recently passed omnibus spending bill, is a provision that would seem to liberate the upcoming Europa Clipper mission from the Space Launch System (SLS).

According to Space News, the mandate that the Europa Clipper mission be launched on an SLS remains in place only if the behind-schedule and overpriced heavy lift rocket is available and if concerns about hardware compatibility between the probe and the launcher are resolved. Otherwise, NASA is free to search for commercial alternatives to get the Europa Clipper to Jupiter’s ice-shrouded moon.

Not only will this secure Europa Clipper’s launch schedule, which had deadlines imposed by orbital mechanics that SLS was not going to meet, the more than $1 billion in savings by using a SpaceX Falcon Heavy will allow the probe to do more while giving NASA more money for other planetary missions.

This is excellent news. It signals that Congress’s long love affair with SLS because of the ample pork it sends to many districts might finally be waning. If so, there is a good chance it will finally be killed, freeing up its bloated budget.

Sadly, in a sane world some of those savings would be used to reduce the overall federal deficit even as some was also used to expand NASA’s space effort. We are not in a sane world, however, so expect no reduction in the federal budget, at all.

Still, this is a move by Congress towards some fiscal responsibility that will make NASA’s efforts more efficient. For that small improvement we should be grateful.

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The conjunction of Jupiter and Saturn, as seen from the Moon

9:21 am

Jupiter and Saturn as seen by LRO
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With Jupiter and Saturn closer to each other in the sky than they have been in about 800 years, the science team for Lunar Reconnaissance Orbiter (LRO) decided to aim that lunar orbiter at the two gas giants to get a picture.

The photo to the right, cropped and expanded to post here, was also enhanced by the science team to brighten Saturn so that it would match Jupiter. As they note at the link,

[LRO] captured this view just a few hours after the point of closest separation (0.1°) between the two giant planets. With the sharp focus of the NAC [camera], you can see that the two planets are actually separated by about 10 Jupiter diameters

Both planets however look fuzzy in the image, probably because the camera was not designed to obtain sharp images from this distance. Nonetheless, this is a very cool photo.

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Trump administration asks Senate to remove SLS requirement for Europa Clipper

8:55 am

The Trump administration has requested the Senate to change the language in its NASA spending bill to remove its requirement that Europa Clipper be launched on SLS.

NASA wants the option to launch the Europa probe using commercial rockets, such as SpaceX’s Falcon Heavy. It also says that there are technical reasons that make using SLS problematic, and worse, the agency simply does not have enough SLS rockets to fly its planned (but unfunded) manned Artemis missions and also launch Europa Clipper.

The House has already removed that requirement in its version of the bill. The Senate has not, probably because the chairman of the Senate Appropriations Committee, Richard Shelby (R-Alabama), is a big fan of SLS (much of it built in his state), and has acted for years to pump money into that project.

If the requirement is not removed, Europa Clipper’s launch will likely be delayed by several years, and cost $1.5 billion more.

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Orbit of pristine comet in outer solar system is shifting inward

10:43 am

The orbit of a pristine comet that until now has kept it in the outer solar system, where it never got warm enough shed any material, is now shifting inward to join what is dubbed the Jupiter-family of comets, whose orbits are generally within that of Jupiter.

Although it has likely lost some supervolatile ices such as carbon dioxide ice (also known as dry ice) in the outer solar system beyond Jupiter, it is unlikely to have ever been in the inner solar system (where Earth, the other rocky planets, and [Jupiter-family comets] orbit), which is warm enough for water ice to sublime (‘evaporate’ from solid to gas),” Steckloff said. “This means that [Comet 2019] LD2 is a pristine comet, and presents a unique opportunity to observe how pristine [Jupiter-family comets] behave as their water ice begins to sublime for the first time and drive comet activity. Moreover, this transition is likely to finish in only 40 years from now, which is a blink of an eye for astronomy. This means that people alive today will be able to follow this object all the way through its transition into the [Jupiter-family] population.”

In 2019, when 2019 L2 was first identified, it was thought to be an asteroid that had suddenly become active, like a comet. Astronomers soon realized this was a mistake, that it was a comet whose orbit was being changed by its interaction with Jupiter.

The new data refines this conclusion, and confirms that observations of 2019 L2 will provide a lot of information about the make-up of the early solar system. More important, the comet’s orbit will allow for many observations, over a long period of time, unlike most comets that zip around the Sun in a year or so and then are gone.

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Jupiter’s stormy southern polar regions

2:46 pm

Jupiter's polar regions
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Cool image time! The photo to the right shows the southern polar regions of Jupiter. The image, taken by Juno during its 29th close-fly of Jupiter, was enhanced by a citizen scientist who only goes by the nickname Flury-21. This in fact was this person’s first try at enhancing a Juno image. He or she did a nice job, but provided no additional information other than saying that he “used lightroom to enhance the image and mostly used the dehaze effect.”

Works nicely nonetheless to illustrate how the bands that dominate Jupiter’s equatorial and mid-latitude regions disappear at the pole. Instead, the pole is a region of chaotic independent hurricanes, many bigger than North America. Other images from Juno suggest that they change relatively quickly. For example, compare this image of the south pole with an earlier one taken during the 28th fly-by. While we might not be looking at the same hemisphere, it is hard to believe there is no overlap between both images. Yet I can find no corresponding features.

The two images of course were taken months apart, and thus it is not surprising the storms have changed completely. However, I also suspect, given their size, that even over this time span some storms have survived, but changed so much it is hard to link them together. The only way to do this would be to have an orbiter close enough all the time to make movies. Unfortunately, Juno cannot do this, and I don’t expect any orbiter like this to reach Jupiter for many decades.

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Analyzing the evolving “small” storms in Jupiter’s atmosphere

12:09 pm

The vortices in Jupiter's polar regions
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The cool image to the right is another Juno photo of Jupiter enhanced by citizen scientist Gerald Eichstädt. This time Eichstädt also did some analysis of the motions and interactions of many vortices found in the northern polar regions of Jupiter. The image to the right has been cropped and reduced to post here, with the state of Arizona, about 400 by 300 miles in size, added for scale. There is more annotation in the full image.

As Eichstädt writes:

Large vortices in an atmosphere layer of a rotating planet can be roughly split into two classes, cyclonic and anticyclonic vortices.

Based on this rough classification, two interacting vortices can either be of the same or of opposite sign. Tightly interacting vortices of opposite sign tend to mutually propel each other, hence the whole pair, if they are of similar strength and size.

Tightly interacting vortex pairs of the same sign tend to merge. More distant like-signed vortex pairs may essentially repel each other. Interacting vortices tend to create filaments, some of which may split into fragments and further collapse into streets of small eddies.

He also notes that in future orbits Juno will provide closer views of this stormy region, as with the orbit the closest point shifts northward.

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Europa Clipper to be delayed because of SLS bottleneck

10:06 am

Because Boeing will be unable to provide an SLS rocket in time for the planned 2024 launch of Europa Clipper, once the probe is completed NASA will be forced to put it in storage.

The problem is that Congress has mandated that the Jupiter probe be launched on SLS, but has only funded the first two Artemis launches to the Moon. Boeing will also need at least three years to build it, meaning that even if the money from Congress appeared today, it would likely not be ready for its ’24 launch date.

In terms of rocket science, right now, Europa Clipper can launch on a commercial vehicle, like SpaceX’s Falcon Heavy or United Launch Alliance’s Delta-IV Heavy rocket, although the mission would then need a longer cruise time to reach its destination.

But in terms of the law, NASA’s hands are tied.

“Because of that, we’re planning to build the Europa Clipper and then put it into storage, because we’re not going to have an SLS rocket available until 2025,” Bridenstine said. “That’s the current plan. I don’t think that’s the right plan, but we’re going to follow the law.”

Though the common sense thing for Congress to do would be to release NASA from this mandate and allow the agency to pick the launch rocket, do not expect that to happen. Congress wants SLS because of all the pork it produces. They will not allow NASA to reduce its reliance on SLS one iota, if they can. Unless pressured publicly (which I think is NASA’s goal with this announcement), Congress will let Europa Clipper sit in a warehouse for years, at a cost of between $36 to $60 million per year, waiting for SLS.

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The face on Jupiter

9:56 am

The face on Jupiter!

Citizen scientist Gerald Eichstädt has created a two-image blink animation from Juno images of Jupiter that shows the changes in the two oppositely rotating storm vortices, shown on the right. As he notes.

Two vortices or eddies, one cyclonic, the other one anticyclonic, can propell themselves mutually and slowly within the overall context they are embedded in.

…The rotation of the two vortices is perceptible in the image sequence taken within nine minutes. The cyclonic eddy is located at the left, the anticyclonic one at the right. The motion of the vortex pair, however, is too slow to be resolved. But the morphology of the cloud tops points towards a relative upward motion in this rendition.

That the two storms also invoke face I am sure also had something to do with his decision to showcase this data. Unlike the face on Mars, this face is real, though relatively temporary. It will eventually break apart as Jupiter’s storms evolve.

The animation can be seen at the link.

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Juno science team proposes fly-bys of Jupiter’s moons

8:30 am

The Juno science team has proposed doing fly-bys of three of Jupiter’s moons, should NASA extend the mission beyond ’21.

Juno’s five-year primary mission phase ends in July 2021, and mission managers have proposed an extension that would continue operations until September 2025. The spacecraft’s additional orbits around Jupiter will bring Juno closer to the planet’s moons, allowing for a more diversified set of scientific targets.

…The moon flybys would begin in mid-2021 with an encounter with Ganymede, Jupiter’s largest moon, at a distance of roughly 600 miles (1,000 kilometers), according to Bolton.

After a series of distant passes, Juno would swoop just 200 miles (320 kilometers) above Europa in late 2022 for a high-speed flyby. Only NASA’s Galileo spacecraft, which ended its mission in 2003, has come closer to Europa.

There are two encounters with Jupiter’s volcanic moon Io planned in 2024 at distances of about 900 miles (1,500 kilometers), according to the flight plan presented by Bolton last month.

The extended mission would also allow scientists to get a better look at Jupiter’s north pole.

NASA will decide on the extension by the end of the year. From a cost and scientific perspective, it makes perfect sense to extend this mission for as long as possible. Compared to launching a new mission, extending an active one is far cheaper. It is also already in place.

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