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En Route to Jupiter, NASA’s Europa Clipper Captures Images of Stars
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By European Space Agency
Week in images: 08-12 September 2025
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By NASA
Ames Science Directorate’s Stars of the Month: September 2025
The NASA Ames Science Directorate recognizes the outstanding contributions of (pictured left to right) Taejin Park, Lydia Schweitzer, and Rachel Morgan. Their commitment to the NASA mission represents the entrepreneurial spirit, technical expertise, and collaborative disposition needed to explore this world and beyond.
Earth Science Star: Taejin Park
Taejin Park is a NASA Earth eXchange (NEX) research scientist within the Biospheric Science Branch, for the Bay Area Environmental Research Institute (BAERI). As the Project Scientist for the Wildfire, Ecosystem Resilience, & Risk Assessment (WERK) project, he has exhibited exemplary leadership and teamwork leading to this multi-year study with the California Natural Resources Agency (CNRA) and California Air Resources Board (CARB) to develop tracking tools of statewide ecological condition, disturbance, and recovery efforts related to wildfires.
Space Science and Astrobiology Star: Lydia Schweitzer
Lydia Schweitzer is a research scientist within the Planetary Systems Branch for the Bay Area Environmental Research Institute (BAERI) as a member of the Neutron Spectrometer System (NSS) team with broad contributions in instrumentation, robotic rovers and lunar exploration. Lydia is recognized for her leadership on a collaborative project to design and build a complex interface unit that is crucial for NSS to communicate with the Japanese Space Agency’s Lunar Polar eXploration rover mission (LUPEX). In addition, she is recognized for her role as an instrument scientist for the Volatiles Investigating Polar Exploration Rover (VIPER) and MoonRanger missions.
Space Science and Astrobiology Star: Rachel Morgan
Rachel Morgan is an optical scientist in the Astrophysics Branch for the SETI Institute. As AstroPIC’s lead experimentalist and the driving force behind the recently commissioned photonic testbed at NASA Ames, this month she achieved a record 92 dB on-chip suppression on a single photonic-integrated chip (PIC) output channel. This advances critical coronagraph technology and is a significant milestone relevant to the Habitable Worlds Observatory.
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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
News Media Contacts
Calla Cofield
Jet Propulsion Laboratory, Pasadena, Calif.
626-808-2469
calla.e.cofield@jpl.nasa.gov
Christine Pulliam
Space Telescope Science Institute, Baltimore, Md.
cpulliam@stsci.edi
2025-113
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Last Updated Sep 09, 2025 Related Terms
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By European Space Agency
Week in images: 01-05 September 2025
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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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