NASA to needlessly kill Juno mission to Jupiter this month

If you were an alien looking at the Solar System, the first planet you’d notice, most likely, wouldn’t be Earth. It’s much easier to spot Jupiter for a variety of reasons, including:

• the fact that it emits its own infrared radiation, making it the only planet to emit more light on its own than it reflects from the Sun,
• the fact that it has the largest effect, of any planet, on the wobbling orbit of our parent star,
• the fact that it’s well-separated from our parent star, making it an easier target for direct imaging than any of the rocky planets,
• and the fact that, if viewed from afar at the right perspective, it would block more of the Sun’s light than any other planet during a transit event.

Earth may be of interest to us, since we live on it, but to an external observer, our Solar System, outside of the Sun, is dominated by Jupiter. In fact, outside of the Sun, Jupiter accounts for 250% as much mass as all other bodies in the Solar System combined. Moreover, Jupiter’s major moons contain enormous quantities of water — with three of them having more water than even Earth does — and pose fascinating possibilities in the quest for life beyond our own planet.

And yet, we’ve only just barely begun to study Jupiter. Sure, there are two fascinating missions on their way there right now, both scheduled to arrive in the early 2030s: the Europa Clipper mission and the JUpiter ICy moons Explorer (JUICE) mission. But for right now, the mission that paved their way, NASA’s Juno mission, is still operating, taking images to scout out the territory, and to teach scientists irreplaceable lessons about spacecraft survival in Jupiter’s harsh environment. The spacecraft is alive and well, capable of continuing its mission for years to come, while still teaching us valuable information about the Jovian system.

But instead of extending the mission, NASA is poised to force its termination later this month, leaving Jupiter alone and spacecraft-free for the rest of the decade. Here’s what we stand to lose.

The swirls and vortices seen in these multi-panel images of Jupiter, near Jupiter’s north polar region, showcase a variety of storms that were captured by the Juno mission’s JunoCam instrument in September of 2024. These circumpolar cyclones were identified when the spacecraft was only 6800 miles (11,000 km) above Jupiter’s atmosphere.

One of the biggest challenges in Solar System exploration is for your spacecraft — and everything on board it, including instruments and potentially (someday) living beings — to survive the harsh environment of space. Here on Earth, we have some protective effects against the greater Universe, including the magnetic field surrounding out planet and the atmosphere that acts as a filter for solar and cosmic particles. Once we depart too far from the surface of our planet, however, those effects evaporate, and we’re subject to whatever bombardment the Sun, the galaxy, and the greater Universe inflicts upon us.

But the environment around Jupiter is even harsher than deep interplanetary space in many ways. In fact, of all the planets, moons, and massive objects in our Solar System, only the Sun itself is a more copious source of radiation. Jupiter’s planetary magnetic field creates an enormous hole in the solar wind, generated by electrical currents in the planet’s core. Ejecta from its innermost large, volcano-rich moon, Io, populates this inner magnetosphere with sulfur dioxide gas, where the magnetic field forces this material to co-rotate with Jupiter itself in a torus-like shape. This combination of a gas made of heavy elements with Jupiter’s magnetic field and radiation-rich environment creates a plasma, permitting strong currents and creating permanent aurorae around Jupiter’s poles.

This Hubble Space Telescope image, acquired in ultraviolet wavelengths of light, showcases the aurorae of Jupiter. The bright streaks and dots are caused by magnetic flux tubes that connect Jupiter to its largest moons, and help one visualize the extent and power of Jupiter’s expansive surrounding magnetic field.

Another effect that arises from the interaction of material, heat, and magnetism is the creation of intense radiation belts around Jupiter, similar to (but far larger, more powerful, and more numerous than) Earth’s Van Allen belts, with the strongest, most dangerous belts being the ones that are the innermost: the ones closest to Jupiter itself. This forces any mission that wants to explore Jupiter, or any of the inner moons that are close to Jupiter (including the four large, major Galilean moons), to work within a series of very complex constraints.

• If you want to explore a world, whether it’s a planet (like Jupiter) or a moon (like Europa or Ganymede), you want to ideally do it in situ, or as close to the world itself as possible.
• From up close, you can take higher-resolution images, probe smaller features either in the atmosphere, clouds, or on the surface.
• But the more time you spend in a radiation-rich environment, the faster your spacecraft, your instruments, and any radiation-susceptible entities (including biological tissue) will degrade.
• And, perhaps most egregiously, damage is often cumulative: once you incur damage, continued exposure to these damaging effects will only worsen the situation, leading to your spacecraft (and its instruments) eventually becoming inoperable.

In other words, the longer you spend in the places best suited to collecting the most useful, highest-quality data, the less capable you become of taking similar data of equal usefulness and quality in the future.

This illustration shows a general planetary magnetosphere, with this particular illustration corresponding to Earth’s. For Jupiter, the magnetic field is about 20 times as great, and the size of the magnetosphere extends for millions of kilometers in the sunward direction, while extending all the way to the orbit of Saturn on the away-facing side.

A very clever technique to combat this has been devised, fortunately, and will not only be leveraged by both the upcoming Europa Clipper mission and the JUICE mission, but is already in use by Jupiter: to have your spacecraft make wide, elliptical orbits, where the best images are acquired at or near Perijove: the periods of closest approach. Because of Kepler’s second law, we know that spacecraft that are on highly eccentric orbits — where they’re far away from the parent body they’re orbiting sometimes and very close to the parent body at other times — will spend most of their time at low-radiation/large-distance conditions, but only a little bit of time under high-radiation/short-distance conditions.

By planning your mission so that your spacecraft minimizes the time it spends under the harshest radiation conditions, it enables the ability to conduct numerous close flybys of whatever your target is over relatively long periods of time, while still maximizing the overall lifetime of your mission. This same technique was leveraged with the Parker Solar Probe, which has now taken data from points closer to the Sun than any other mission in history. For Juno, it’s meant that a mission which would have lasted merely a few months if it had entered and remained in the most radiation-rich regions around Jupiter, instead has lasted for nearly a decade, and still is capable of taking data for years to come.

This illustration shows Jupiter’s magnetosphere in the vicinity of the Galilean Satellites. Jupiter and the distances to Io, Europa, Ganymede, and Callisto are shown to scale, but the sizes of the moons themselves, as shown, are far larger than actual size. Near the orbit of Io and within, extreme radiation belts, rich in plasma, can be found.

Since it arrived at Jupiter in 2016, the Juno mission has provided an incredible amount of information about the system: information that we couldn’t have acquired from afar with remote observatories like Hubble or JWST, and has continued operating an extended mission after successfully completing its primary one. No other spacecraft has probed beneath the clouds encircling Jupiter the way that Juno has, or has imaged our Solar System’s largest planet so comprehensively and over such extended periods of time. It’s also provided a remarkable wealth of information about Jupiter’s major moons: Io, Europa, Ganymede, and Callisto, all of which are no more than 2 million kilometers distant from Jupiter itself at all times.

Some recent highlights of what Juno has found include:

It’s kind of remarkable, considering that Juno was designed to focus on Jupiter itself, including its interior, atmosphere, and auroral features.

The JunoCam instrument aboard NASA’s Juno spacecraft snapped several images of the second of Jupiter’s four large moons, Europa, during a close flyby of that world in September of 2022. It provided strong and suggestive evidence of true polar wander, supporting the notion that Europa’s surface ice sheet is a shell that floats above a worldwide liquid water ocean. Juno data also measured the smoothness of Europa’s surface, determining it to be the smoothest yet of any known major planetary body.

And yet, Juno has accomplished so much more than that. For starters, Juno collected key information that motivated the Europa Clipper mission’s existence. We’ve known for decades that Europa, the second-innermost of Jupiter’s four Galilean satellites, is covered in ice. In fact, Europa was measured, by Juno, to have the smoothest surface of any solid-surfaced world in the Solar System. But it was during three close flybys of Europa back in 2022 that Juno uncovered three key features about it:

1. It has an icy crust that migrates over time, suggesting that the crust sits atop a layer of liquid, and moves over time.
2. Features consistent with “plume stains” appeared in the Junocam data, suggesting that Europa’s subsurface ocean rises up and ruptures through the ice shell regularly.
3. And that the smooth surface could harbor either a thick ice crust and thin ocean, or a thin ice crust and a thick ocean, with either possibility admitting the existence of sub-surface hydrothermal vents. (Note: such vents are rich in life here on Earth.)

Yes, there are indeed locations beneath the ices of Europa that could potentially harbor sub-surface, extremophile life. Juno set the stage for the Europa Clipper mission, which can now work to take the next scientific steps towards that goal.

Scientists are all but certain that Europa has an ocean underneath its icy surface, but they do not know how thick this ice might be. This artist concept illustrates two possible cut-away views through Europa’s ice shell. In both, heat escapes, possibly volcanically, from Europa’s rocky mantle and is carried upward by buoyant oceanic currents. If a human-size feature were to be observed from Earth, a telescope the size of Alaska would be required. Whether there is life in this subsurface ocean or not still remains to be determined.

Juno also, from a technological point of view, has taught us more than we ever could have imagined about spacecraft survival in the radiation-harsh environment around Jupiter. Juno, being “only” five times as far from the Sun as Earth is (as opposed to ten, twenty, or thirty for missions that would focus Saturn, Uranus, or Neptune, respectively), isn’t powered by a radioisotope thermoelectric generator (RTG), but instead by plain old solar panels. At such great distances, solar energy is limited. When the spacecraft flies through Jupiter’s radiation belts, the intense radiation can trigger a “something is wrong” signal, forcing the spacecraft into safe mode. This has happened four times thus far, including twice here in 2025.

As part of Juno’s design, its most sensitive instruments — and its most precious, delicate electronics — are housed inside an enormous, thick titanium vault. The thick layers of titanium act as a shield for the electronics, the same way that lead is used for shielding from X-rays and high-energy particles here on Earth. However, due to space constraints, not all instruments could fit inside the titanium vault, and the ones that couldn’t would be more susceptible to the inevitable degradation that would ensue from being exposed to this radiation-rich environment. Sooner or later, one of the spacecraft’s components would be deleteriously affected.

This image shows NASA’s Juno spacecraft, on the floor, as it was being assembled. Above the main craft, a massive, heavy titanium vault, being lowered down onto the propulsion module here, stores the most sensitive instruments and electronics, protecting them from the intense radiation environment around Jupiter.

Believe it or not, the instrument that brought us nearly all of the visually spectacular images that have been the hallmark of the Juno mission, the JunoCam instrument, isn’t classified as one of the mission’s primary science instruments. As a result, this optical imager, whose inclusion was mostly for the benefit of the general public (as opposed to scientists, although it has made important scientific contributions), isn’t inside the titanium vault. As you might have expected, that means it encounters more of these energetic charged particles that exist within Jupiter’s radiation belts, and that, in turn, means it’s going to experience degradation due to radiation exposure.

As originally reported by Universe Today’s Evan Gough, JunoCam began showing signs of degradation during its 47th orbit around Jupiter, and by the 56th orbit, practically every image that was acquired with JunoCam showed signs of corruption. In particular, the images were grainy, showing evidence of noise that appeared in horizontal streaks across the field-of-view. Areas that should have been completely dark were instead illuminated with noisy streaks; areas that should have been uniformly bright had darkened streaks streaking across them. In addition, these streams weren’t random, but appeared in clusters: bands and groups.

This image, taken of one of the circumpolar cyclones near Jupiter’s north pole, was acquired on November 22, 2023. As you can see, there are horizontal lines and graininess polluting the image: effects of the radiation damage on JunoCam. By heating up the camera, similar to the annealing process, this damage was successfully undone.

This type of damage was consistent with the type of degradation you’d expect from radiation acting on a digital camera: a camera powered by charge-coupled devices, or CCDs. CCDs work by detecting photons, and then converting those photons into electrical signals that get recorded by the internal electronics within the camera. With extra radiation, of course there are going to be extra, unwanted electrical signals within the camera, but what’s more troubling is the features that persist even when there’s no longer active radiation affecting the camera. Over time, cumulative damage from radiation will damage the internal structure, made largely of silicon crystal, which can (for example) cause electrons to be kicked into the conduction band, which results in the dark streaks you see across Jupiter, above.

There are approximately 200 people, including technicians, engineers, and scientists, who work on Juno at any given time. (And most only do it part-time, working on other missions and endeavors as well.) You might think that prospects for repairing a radiation-damaged digital camera, from hundreds of millions of kilometers away, would be out of the realm of possibility. But the clues as to what was happening were written on the images, allowing mission personnel to experiment on a clone of the camera, in a laboratory setting. At last, they figured it out: there must have been a malfunctioning voltage regulator in the power supply that was powering the camera.

This color-balanced image of Jupiter’s moon Io, taken with NASA’s Juno spacecraft, shows the moon in close to true color, with volcanically active mountains, calderas, and features resembling lava flows all visible. Toward the lower-right of the image, just past the shadow line marking the day/night boundary, an erupting volcanic plume can be seen. This JunoCam composite was designed to show Io in as close to true color as possible.

There aren’t very many tools on board the spacecraft, but one thing that JunoCam was equipped with was an on-board heater. Thinking that if they heated up the camera, it might serve the same function as the annealing process common to metalworking scenarios, thye gave it a shot: commanding JunoCam’s lone heater to raise the temperature to 77 °F (25 °C), or some 243 °F (135 °C) hotter than ambient temperatures. It worked, and when the degradation reappeared, they turned the heater up even higher and it worked again. It was only by:

• extending the mission,
• identifying the problems that arose,
• and using what tools were available to solve them,

that enabled scientists to discover a method for healing the radiation damage to Juno’s main imaging camera.

Today, Juno scientists are looking forward to the possibility of investigating previously unexplored regions of the Jovian system, including several moons that have never had a close flyby performed of them. In addition to Amalthea, the moons Thebe, Adrastea, and Metis are all targeted for future flybys if an extended mission gets approved. And the lessons from Juno go beyond its scientific lessons as well. As the mission’s principal investigator, Dr. Scott Bolton, also noted, “In addition to scientific exploration, Juno is providing critical new information directly relevant to national security by teaching us how space systems can survive and even reverse degradation from exposure to intense radiation.”

This image shows the JunoCam imager, which was marketed as the Juno mission’s outreach camera. JunoCam, although it also had science goals related to properties of and weather within Jupiter’s cloudtops, has provided a wealth of information through its images, and continues to do so here in September of 2025, for now.

Due to the quality at which Juno is operating, today, planetary scientists are seeking a further 3 year extension of Juno, leaving only a tiny gap during which Jupiter will be devoid of having an operational scientific spacecraft orbiting it. For a mission whose initial costs exceeded a total of $1 billion, and that maybe are approaching $1.5 billion total, it’s kind of amazing that for just a few tens of millions of dollars, we could keep it operating for several years more, squeezing more science, more technology lessons, and more information out of a spacecraft that’s already exceeded expectations and enabled its already-on-the-way successors.

Too bad that, here in 2025, the mission has already been zeroed out for funding by the current administration. It doesn’t need to die just yet, and there are still many lessons that Juno will be uniquely poised to teach us in the coming months and years. But if no additional funding comes by the end of September, its fate is sealed: it’s going to be directed into Jupiter itself. Just as Cassini was sent into Saturn at the end of its mission to avoid contaminating Saturn’s moons with any stowaway organics brought from Earth, so too will Juno be brought to an end by forcing it to plunge into a gas giant world. It doesn’t have to end this way, of course, but unless something drastic changes in the next few weeks, Juno will die an unnecessarily premature death, like so much of NASA science here in 2025.