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By NASA
6 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
This artist’s concept shows a brown dwarf — an object larger than a planet but not massive enough to kickstart fusion in its core like a star. Brown dwarfs are hot when they form and may glow like this one, but over time they get closer in temperature to gas giant planets like Jupiter. NOIRLab/NSF/AURA/R. Proctor An unusual cosmic object is helping scientists better understand the chemistry hidden deep in Jupiter and Saturn’s atmospheres — and potentially those of exoplanets.
Why has silicon, one of the most common elements in the universe, gone largely undetected in the atmospheres of Jupiter, Saturn, and gas planets like them orbiting other stars? A new study using observations from NASA’s James Webb Space Telescope sheds light on this question by focusing on a peculiar object that astronomers discovered by chance in 2020 and called “The Accident.”
The results were published on Sept. 4 in the journal Nature.
As shown in this graphic, brown dwarfs can be far more massive than even large gas planets like Jupiter and Saturn. However, they tend to lack the mass that kickstarts nuclear fusion in the cores of stars, causing them to shine. NASA/JPL-Caltech The Accident is a brown dwarf, a ball of gas that’s not quite a planet and not quite a star. Even among its already hard-to-classify peers, The Accident has a perplexing mix of physical features, some of which have been previously seen in only young brown dwarfs and others seen only in ancient ones. Because of those features, it slipped past typical detection methods before being discovered five years ago by a citizen scientist participating in Backyard Worlds: Planet 9. The program lets people around the globe look for new discoveries in data from NASA’s now-retired NEOWISE (Near-Earth Object Wide-field Infrared Survey Explorer), which was managed by NASA’s Jet Propulsion Laboratory in Southern California.
The brown dwarf nicknamed “The Accident” can be seen moving in the bottom left corner of this video, which shows data from NASA’s now-retired NEOWISE (Near-Earth Object Wide-Field Infrared Survey Explorer), launched in 2009 with the moniker WISE. NASA/JPL-Caltech/Dan Caselden The Accident is so faint and odd that researchers needed NASA’s most powerful space observatory, Webb, to study its atmosphere. Among several surprises, they found evidence of a molecule they couldn’t initially identify. It turned out to be a simple silicon molecule called silane (SiH4). Researchers have long expected — but been unable — to find silane not only in our solar system’s gas giants, but also in the thousands of atmospheres belonging to brown dwarfs and to the gas giants orbiting other stars. The Accident is the first such object where this molecule has been identified.
Scientists are fairly confident that silicon exists in Jupiter and Saturn’s atmospheres but that it is hidden. Bound to oxygen, silicon forms oxides such as quartz that can seed clouds on hot gas giants, bearing a resemblance to dust storms on Earth. On cooler gas giants like Jupiter and Saturn, these types of clouds would sink far beneath lighter layers of water vapor and ammonia clouds, until any silicon-containing molecules are deep in the atmosphere, invisible even to the spacecraft that have studied those two planets up close.
Some researchers have also posited that lighter molecules of silicon, like silane, should be found higher up in these atmospheric layers, left behind like traces of flour on a baker’s table. That such molecules haven’t appeared anywhere except in a single, peculiar brown dwarf suggests something about the chemistry occurring in these environments.
“Sometimes it’s the extreme objects that help us understand what’s happening in the average ones,” said Faherty, a researcher at the American Museum of Natural History in New York City, and lead author on the new study.
Happy accident
Located about 50 light-years from Earth, The Accident likely formed 10 billion to 12 billion years ago, making it one of the oldest brown dwarfs ever discovered. The universe is about 14 billion years old, and at the time that The Accident developed, the cosmos contained mostly hydrogen and helium, with trace amounts of other elements, including silicon. Over eons, elements like carbon, nitrogen, and oxygen forged in the cores of stars, so planets and stars that formed more recently possess more of those elements.
Webb’s observations of The Accident confirm that silane can form in brown dwarf and planetary atmospheres. The fact that silane seems to be missing in other brown dwarfs and gas giant planets suggests that when oxygen is available, it bonds with silicon at such a high rate and so easily, virtually no silicon is left over to bond with hydrogen and form silane.
So why is silane in The Accident? The study authors surmise it is because far less oxygen was present in the universe when the ancient brown dwarf formed, resulting in less oxygen in its atmosphere to gobble up all the silicon. The available silicon would have bonded with hydrogen instead, resulting in silane.
“We weren’t looking to solve a mystery about Jupiter and Saturn with these observations,” said JPL’s Peter Eisenhardt, project scientist for the WISE (Wide-field Infrared Survey Explorer) mission, which was later repurposed as NEOWISE. “A brown dwarf is a ball of gas like a star, but without an internal fusion reactor, it gets cooler and cooler, with an atmosphere like that of gas giant planets. We wanted to see why this brown dwarf is so odd, but we weren’t expecting silane. The universe continues to surprise us.”
Brown dwarfs are often easier to study than gas giant exoplanets because the light from a faraway planet is typically drowned out by the star it orbits, while brown dwarfs generally fly solo. And the lessons learned from these objects extend to all kinds of planets, including ones outside our solar system that might feature potential signs of habitability.
“To be clear, we’re not finding life on brown dwarfs,” said Faherty. “But at a high level, by studying all of this variety and complexity in planetary atmospheres, we’re setting up the scientists who are one day going to have to do this kind of chemical analysis for rocky, potentially Earth-like planets. It might not specifically involve silicon, but they’re going to get data that is complicated and confusing and doesn’t fit their models, just like we are. They’ll have to parse all those complexities if they want to answer those big questions.”
More about WISE, Webb
A division of Caltech, JPL managed and operated WISE for NASA’s Science Mission Directorate. The mission was selected competitively under NASA’s Explorers Program managed by the agency’s Goddard Space Flight Center in Greenbelt, Maryland. The NEOWISE mission was a project of JPL and the University of Arizona in Tucson, supported by NASA’s Planetary Defense Coordination Office.
For more information about WISE, go to:
https://www.nasa.gov/mission_pages/WISE/main/index.html
The James Webb Space Telescope is the world’s premier space science observatory, and an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).
To learn more about Webb, visit:
https://science.nasa.gov/webb
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Space Telescope Science Institute, Baltimore, Md.
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Last Updated Sep 09, 2025 Related Terms
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By NASA
Explore This Section Overview Science Science Findings Juno’s Orbits Spacecraft People Stories Multimedia JunoCam Images Jupiter hosts the brightest and most spectacular auroras in the Solar System. Near its poles, these shimmering lights offer a glimpse into how the planet interacts with the solar wind and moons swept by Jupiter’s magnetic field. Unlike Earth’s northern lights, the largest moons of Jupiter create their own auroral signatures in the planet’s atmosphere — a phenomenon that Earth’s Moon does not produce. These moon-induced auroras, known as “satellite footprints,” reveal how each moon interacts with its local space environment.
Juno capturing the marks on Jupiter of all four Galilean moons. The auroras related to each are labeled Io, Eur (for Europa), Gan (for Ganymede), and Cal (for Callisto). NASA/JPL-Caltech/SwRI/UVS team/MSSS/Gill/Jónsson/Perry/Hue/Rabia Before NASA’s Juno mission, three of Jupiter’s four largest moons, known as Galilean moons — Io, Europa, and Ganymede — were shown to produce these distinct auroral signatures. But Callisto, the most distant of the Galilean moons, remained a mystery. Despite multiple attempts using NASA’s Hubble Space Telescope, Callisto’s footprint had proven elusive, both because it is faint and because it most often lies atop the brighter main auroral oval, the region where auroras are displayed.
NASA’s Juno mission, orbiting Jupiter since 2016, offers unprecedented close-up views of these polar light shows. But to image Callisto’s footprint, the main auroral oval needs to move aside while the polar region is being imaged. And to bring to bear Juno’s arsenal of instruments studying fields and particles, the spacecraft’s trajectory must carry it across the magnetic field line linking Callisto and Jupiter.
These two events serendipitously occurred during Juno’s 22nd orbit of the giant planet, in September 2019, revealing Callisto’s auroral footprint and providing a sample of the particle population, electromagnetic waves, and magnetic fields associated with the interaction.
Jupiter’s magnetic field extends far beyond its major moons, carving out a vast region (magnetosphere) enveloped by, and buffeted by, the solar wind streaming from our Sun. Just as solar storms on Earth push the northern lights to more southern latitudes, Jupiter’s auroras are also affected by our Sun’s activity. In September 2019, a massive, high-density solar stream buffeted Jupiter’s magnetosphere, briefly revealing — as the auroral oval moved toward Jupiter’s equator — a faint but distinct signature associated with Callisto. This discovery finally confirms that all four Galilean moons leave their mark on Jupiter’s atmosphere, and that Callisto’s footprints are sustained much like those of its siblings, completing the family portrait of the Galilean moon auroral signatures.
An international team of scientists led by Jonas Rabia of the Institut de Recherche en Astrophysique et Planétologie (IRAP), CNRS, CNES, in Toulouse, France, published their paper on the discovery, “In situ and remote observations of the ultraviolet footprint of the moon Callisto by the Juno spacecraft,” in the journal Nature Communications on Sept. 1, 2025.
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Last Updated Sep 02, 2025 Related Terms
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By NASA
5 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
The north polar region of Jupiter’s volcanic moon Io was captured by the JunoCam imager aboard NASA’s Juno during the spacecraft’s 57th close pass of the gas giant on Dec. 30, 2023. A technique called annealing was used to help repair radiation damage to the camera in time to capture this image. Image data: NASA/JPL-Caltech/SwRI/MSSS Image processing by Gerald Eichstädt An experimental technique rescued a camera aboard the agency’s Juno spacecraft, offering lessons that will benefit other space systems that experience high radiation.
The mission team of NASA’s Jupiter-orbiting Juno spacecraft executed a deep-space move in December 2023 to repair its JunoCam imager to capture photos of the Jovian moon Io. Results from the long-distance save were presented during a technical session on July 16 at the Institute of Electrical and Electronics Engineers Nuclear & Space Radiation Effects Conference in Nashville.
JunoCam is a color, visible-light camera. The optical unit for the camera is located outside a titanium-walled radiation vault, which protects sensitive electronic components for many of Juno’s engineering and science instruments.
This is a challenging location because Juno’s travels carry it through the most intense planetary radiation fields in the solar system. While mission designers were confident JunoCam could operate through the first eight orbits of Jupiter, no one knew how long the instrument would last after that.
Throughout Juno’s first 34 orbits (its prime mission), JunoCam operated normally, returning images the team routinely incorporated into the mission’s science papers. Then, during its 47th orbit, the imager began showing hints of radiation damage. By orbit 56, nearly all the images were corrupted.
The graininess and horizontal lines seen in this JunoCam image show evidence that the camera aboard NASA’s Juno mission suffered radiation damage. The image, which captures one of the circumpolar cyclones on Jupiter’s north pole, was taken Nov. 22, 2023. NASA/JPL-Caltech/SwRI/MSSS Long Distance Microscopic Repair
While the team knew the issue may be tied to radiation, pinpointing what, specifically, was damaged within JunoCam was difficult from hundreds of millions of miles away. Clues pointed to a damaged voltage regulator that is vital to JunoCam’s power supply. With few options for recovery, the team turned to a process called annealing, where a material is heated for a specified period before slowly cooling. Although the process is not well understood, the idea is that the heating can reduce defects in the material.
“We knew annealing can sometimes alter a material like silicon at a microscopic level but didn’t know if this would fix the damage,” said JunoCam imaging engineer Jacob Schaffner of Malin Space Science Systems in San Diego, which designed and developed JunoCam and is part of the team that operates it. “We commanded JunoCam’s one heater to raise the camera’s temperature to 77 degrees Fahrenheit — much warmer than typical for JunoCam — and waited with bated breath to see the results.”
Soon after the annealing process finished, JunoCam began cranking out crisp images for the next several orbits. But Juno was flying deeper and deeper into the heart of Jupiter’s radiation fields with each pass. By orbit 55, the imagery had again begun showing problems.
“After orbit 55, our images were full of streaks and noise,” said JunoCam instrument lead Michael Ravine of Malin Space Science Systems. “We tried different schemes for processing the images to improve the quality, but nothing worked. With the close encounter of Io bearing down on us in a few weeks, it was Hail Mary time: The only thing left we hadn’t tried was to crank JunoCam’s heater all the way up and see if more extreme annealing would save us.”
Test images sent back to Earth during the annealing showed little improvement the first week. Then, with the close approach of Io only days away, the images began to improve dramatically. By the time Juno came within 930 miles (1,500 kilometers) of the volcanic moon’s surface on Dec. 30, 2023, the images were almost as good as the day the camera launched, capturing detailed views of Io’s north polar region that revealed mountain blocks covered in sulfur dioxide frosts rising sharply from the plains and previously uncharted volcanos with extensive flow fields of lava.
Testing Limits
To date, the solar-powered spacecraft has orbited Jupiter 74 times. Recently, the image noise returned during Juno’s 74th orbit.
Since first experimenting with JunoCam, the Juno team has applied derivations of this annealing technique on several Juno instruments and engineering subsystems.
“Juno is teaching us how to create and maintain spacecraft tolerant to radiation, providing insights that will benefit satellites in orbit around Earth,” said Scott Bolton, Juno’s principal investigator from the Southwest Research Institute in San Antonio. “I expect the lessons learned from Juno will be applicable to both defense and commercial satellites as well as other NASA missions.”
More About Juno
NASA’s Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the Juno mission for the principal investigator, Scott Bolton, of the Southwest Research Institute in San Antonio. Juno is part of NASA’s New Frontiers Program, which is managed at NASA’s Marshall Space Flight Center in Huntsville, Alabama, for the agency’s Science Mission Directorate in Washington. The Italian Space Agency, Agenzia Spaziale Italiana, funded the Jovian InfraRed Auroral Mapper. Lockheed Martin Space in Denver built and operates the spacecraft. Various other institutions around the U.S. provided several of the other scientific instruments on Juno.
More information about Juno is at:
https://www.nasa.gov/juno
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Last Updated Jul 21, 2025 Related Terms
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By NASA
4 Min Read Stay Cool: NASA Tests Innovative Technique for Super Cold Fuel Storage
The tank for NASA’s two-stage cooling tests is lowered into a vacuum chamber in Test Stand 300 at NASA’s Marshall Space Flight Center in Huntsville, Alabama. Credits: NASA/Kathy Henkel In the vacuum of space, where temperatures can plunge to minus 455 degrees Fahrenheit, it might seem like keeping things cold would be easy. But the reality is more complex for preserving ultra-cold fluid propellants – or fuel – that can easily overheat from onboard systems, solar radiation, and spacecraft exhaust. The solution is a method called cryogenic fluid management, a suite of technologies that stores, transfers, and measures super cold fluids for the surface of the Moon, Mars, and future long-duration spaceflight missions.
Super cold, or cryogenic, fluids like liquid hydrogen and liquid oxygen are the most common propellants for space exploration. Despite its chilling environment, space has a “hot” effect on these propellants because of their low boiling points – about minus 424 degrees Fahrenheit for liquid hydrogen and about minus 298 for liquid oxygen – putting them at risk of boiloff.
In a first-of-its-kind demonstration, teams at NASA’s Marshall Space Flight Center in Huntsville, Alabama, are testing an innovative approach to achieve zero boiloff storage of liquid hydrogen using two stages of active cooling which could prevent the loss of valuable propellant.
“Technologies for reducing propellant loss must be implemented for successful long-duration missions to deep space like the Moon and Mars,” said Kathy Henkel, acting manager of NASA’s Cryogenic Fluid Management Portfolio Project, based at NASA Marshall. “Two-stage cooling prevents propellant loss and successfully allows for long-term storage of propellants whether in transit or on the surface of a planetary body.”
The new technique, known as “tube on tank” cooling, integrates two cryocoolers, or cooling devices, to keep propellant cold and thwart multiple heat sources. Helium, chilled to about minus 424 degrees Fahrenheit, circulates through tubes attached to the outer wall of the propellant tank.
NASA’s two-stage cooling testing setup sits in a vacuum chamber in Test Stand 300 at NASA’s Marshall Space Flight Center in Huntsville, Alabama. NASA/Tom Perrin The tank for NASA’s two-stage cooling tests is lowered into a vacuum chamber in Test Stand 300 at NASA’s Marshall Space Flight Center in Huntsville, Alabama.NASA/Kathy Henkel The tank for NASA’s two-stage cooling tests is lowered into a vacuum chamber in Test Stand 300 at NASA’s Marshall Space Flight Center in Huntsville, Alabama. NASA/Kathy Henkel The tank for NASA’s two-stage cooling tests is lowered into a vacuum chamber in Test Stand 300 at NASA’s Marshall Space Flight Center in Huntsville, Alabama. NASA/Kathy Henkel Teams installed the propellant tank in a test stand at NASA Marshall in early June, and the 90-day test campaign is scheduled to conclude in September. The tank is wrapped in a multi-layer insulation blanket that includes a thin aluminum heat shield fitted between layers. A second set of tubes, carrying helium at about minus 298 Fahrenheit, is integrated into the shield. This intermediate cooling layer intercepts and rejects incoming heat before it reaches the tank, easing the heat load on the tube-on-tank system.
To prevent dangerous pressure buildup in the propellant tank in current spaceflight systems, boiloff vapors must be vented, resulting in the loss of valuable fuel. Eliminating such propellant losses is crucial to the success of NASA’s most ambitious missions, including future crewed journeys to Mars, which will require storing large amounts of cryogenic propellant in space for months or even years. So far, cryogenic fuels have only been used for missions lasting less than a week.
“To go to Mars and have a sustainable presence, you need to preserve cryogens for use as rocket or lander return propellant,” Henkel said. “Rockets currently control their propellant through margin, where larger tanks are designed to hold more propellant than what is needed for a mission. Propellant loss isn’t an issue with short trips because the loss is factored into this margin. But, human exploration missions to Mars or longer stays at the Moon will require a different approach because of the very large tanks that would be needed.”
The Cryogenic Fluid Management Portfolio Project is a cross-agency team based at NASA Marshall and the agency’s Glenn Research Center in Cleveland. The cryogenic portfolio’s work is under NASA’s Technology Demonstration Missions Program, part of NASA’s Space Technology Mission Directorate, and is comprised of more than 20 individual technology development activities.
Learn more about cryogenic fluid management:
https://go.nasa.gov/cfm
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Last Updated Jul 18, 2025 EditorLee MohonContactCorinne M. Beckingercorinne.m.beckinger@nasa.govLocationMarshall Space Flight Center Related Terms
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By NASA
Image data: NASA/JPL-Caltech/SwRI/MSSS; Image processing: Jackie Branc (CC BY) JunoCam, the visible light imager aboard NASA’s Juno spacecraft, captured this view of Jupiter’s northern high latitudes during the spacecraft’s 69th flyby of the giant planet on Jan. 28, 2025. Jupiter’s belts and zones stand out in this enhanced color rendition, along with the turbulence along their edges caused by winds going in different directions.
The original JunoCam data used to produce this view was taken from an altitude of about 36,000 miles (58,000 kilometers) above Jupiter’s cloud tops. JunoCam’s raw images are available for the public to peruse and process into image products. Citizen scientist Jackie Branc processed the image.
Since Juno arrived at Jupiter in 2016, it has been probing beneath the dense, forbidding clouds encircling the giant planet – the first orbiter to peer so closely. It seeks answers to questions about the origin and evolution of Jupiter, our solar system, and giant planets across the cosmos.
Learn more about NASA citizen science.
Image credit: Image data: NASA/JPL-Caltech/SwRI/MSSS; Image processing: Jackie Branc (CC BY)
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