Astro Blog

By Hannah Devlin , The Guardian.  Excerpt: Astronomers have discovered 128 new moons orbiting  Saturn , giving it an insurmountable lead in the running tally of moons in the solar system. Until recently, the  “moon king” title was held by Jupiter , but Saturn now has a total of 274 moons, almost twice as many as all the other planets combined....  Full article at https://www.theguardian.com/science/2025/mar/11/astronomers-discover-128-new-moons-orbiting-saturn . 

By Sarah Stanley , Eos/AGU.  Excerpt: A closer look at previously disregarded observations reveals stronger evidence that a deep ocean lies beneath Callisto’s icy surface. ... Cochrane et al.  have revisited the Galileo data in more detail. Unlike in prior studies, this team incorporated all available magnetic measurements from Galileo’s eight close flybys of Callisto. Their expanded analysis much more strongly suggests that Callisto hosts a subsurface ocean....  Full article at https://eos.org/research-spotlights/jupiters-moon-callisto-is-very-likely-an-ocean-world . 

By Kimberly M. S. Cartier , Eos/AGU.  Excerpt: Europa Clipper launched at 12:06 pm EDT on 14 October from NASA’s Kennedy Space Center in Florida. Clipper successfully deployed its solar panels and communicated with mission control once in space. ...NASA’s Europa Clipper spacecraft...will head to Jupiter’s icy moon Europa and determine whether it’s a hospitable place for life. ...There will be 49 flybys of Europa to study the moon from pole to pole ...The craft is set to  arrive  at Jupiter in April 2030. ...Europa is one of Jupiter’s four Galilean moons. Past missions to the Jovian system discovered that Europa, along with fellow icy moons Ganymede and Callisto, have vast liquid water oceans sloshing around beneath icy shells. “ Ocean worlds  have been considered potentially habitable environments for a while,” said  Monica Vidaurri , a doctoral student in planetary modeling at Stanford University in California. “This is the first time we’re really dedicating a...

https://www.mercury-messenger.org/history-culture/galileo-telescope By Shanil Virani, Astronomical Society of the Pacific - Mercury online Excerpt: Between January 7 and January 13, 1610, a series of observations was made that would forever change how we would view the cosmos. The observer detailed in this log book a discovery made using a relatively new invention at that time. The observer had discovered four small, point sources of light very close to the (giant) planet Jupiter. On January 10, one of them disappeared for a short period. The observer attributed the disappearance of the object as being hidden behind Jupiter. Given his extensive observations, he was now forced to conclude that these four points of light were orbiting Jupiter and not Earth. The observer, Galileo Galilei, and his two small pieces of glass would usher in a scientific revolution that reverberates to this day. Until this discovery, and for some 1,500 years prior to Galileo, our ancestors accepted the m...

By Katherine Kornei , Eos/AGU. Excerpt: Using data from the Cassini spacecraft, researchers studying one of the rings recently uncovered gaps just a few tens of meters wide that they believe surround unseen mini moonlets. ...In addition to capturing  more than 450,000 images  of the Saturnian system, the spacecraft inadvertently tracked distant stars poking through Saturn’s rings. ...The researchers spotted dozens of places in Saturn’s C ring— one of its innermost rings —that appeared to be 100% transparent. ...Their elongated geometry was a tip-off to their potential identity—similarly shaped structures, albeit much larger, have been  spotted in the outer regions of Saturn’s A ring . Known as propellers [resembling airplane propellers], those features are big enough to show up in Cassini imagery rather than just occultation data, Jerousek said. ...Scientists believe that propellers exist because of unseen moonlets measuring, at most, several hundred meters in d...

https://www.smithsonianmag.com/smart-news/what-does-solar-eclipse-mars-look-like-new-breathtaking-images-caught-nasa-perseverance-rover-idea-180983795/ By Carlyn Kranking , Smithsonian Magazine.  Excerpt: The robot recently observed each of the Red Planet’s moons passing across the sun in the Martian sky [see photo in this article]. 

https://www.nytimes.com/2023/12/14/science/enceladus-moon-cyanide-life-saturn.html By Kenneth Chang , The New York Times.  Excerpt: Scientists have detected a poison among the spray of molecules emanating from a small moon of Saturn. That adds to existing intrigue about the possibility of life there. The poison is hydrogen cyanide, a colorless gas that is deadly to many Earth creatures. But it could have played a key role in chemical reactions that created the ingredients that set the stage for the advent of life. ...Mr. Peter and his collaborators, Tom Nordheim and Kevin Hand of NASA’s Jet Propulsion Laboratory in California, reported their findings in a paper published on Thursday in the journal Nature Astronomy.... 

https://skyandtelescope.org/astronomy-news/lucy-mission-flies-by-asteroid-dinkinesh-finds-a-little-surprise By EMILY LAKDAWALLA , Sky & Telescope. Excerpt: On November 1st, the Lucy mission zipped past the tiny asteroid 152830 Dinkinesh and discovered that it was actually a binary. ...While the probe caught a view of the Dinkinesh's small satellite in the one of the first images of the flyby, the mission turned as it flew by and captured another view from a different angle. That new perspective revealed that the little asteroidal moon is actually a  contact binary , meaning it's made of two objects in contact with one another. This is the first contact binary asteroid moon discovered. Read more details on  NASA's website ....

https://www.nytimes.com/2023/05/12/science/saturn-moons-jupiter.html By Jonathan O’Callaghan , The New York Times.  Excerpt: This month, the International Astronomical Union is set to recognize 62 additional  moons of Saturn  based on a batch of objects discovered by astronomers. The small objects will give Saturn 145 moons — eclipsing Jupiter’s total of 95. ...The growing number of moons also highlights potential debates over what constitutes a moon. “The simple definition of a moon is that it’s an object that orbits a planet,” Dr. Sheppard said. An object’s size, for the moment, doesn’t matter. ...In March, Dr. Sheppard was also responsible for finding  12 new moons of Jupiter , which took it temporarily above Saturn in the scuffle to be the biggest hoarder of moons. That record was short-lived, it seems....

https://skyandtelescope.org/astronomy-news/four-of-uranuss-moons-might-contain-briny-oceans/ By Emily Lakdawala, Sky & Telescope.  Excerpt: A  new paper re-analyzing Voyager observations  suggests that four of Uranus’ five icy satellites also host oceans: Ariel, Umbriel, Titania, and Oberon. (Only small Miranda, intermediate in size between Saturn’s Mimas and Enceladus, appears not to.) The oceans are desperately thin: less than 30 kilometers (20 miles) thick inside Ariel and Umbriel (both of which are about 1,000 kilometers across, similar in size to Saturn’s Tethys and Dione), and less than 50 kilometers thick within Titania and Oberon (which are larger at about 1,500 kilometers, similar to Saturn’s Rhea and Iapetus). If the oceans exist, they would be left over from much larger liquid layers that formed when the moons first formed. ...They’d be extremely briny, hyper-concentrated with whatever dissolved materials helped to lower the temperature at which water would...

https://www.nytimes.com/2023/04/25/science/mars-deimos-moon-photos.html By Jonathan O’Callaghan , The New York Times.  Excerpt: Deimos, the smaller of the two moons of Mars, might be a chip off the old block — quite literally. That’s the conclusion drawn by scientists in the United Arab Emirates, whose Hope orbiter — also called the Emirates Mars Mission and the country’s first interplanetary spacecraft — just snapped the best views of Deimos ever taken by human spacecraft. ... Mars has two irregularly shaped moons , and neither is mighty. Phobos, the larger of the two, is about 17 miles in diameter at its widest, and orbits closer to the red planet at an altitude of about 3,700 miles. Deimos is just nine miles across on its longest side, and completes an orbit of Mars every 30 hours at an altitude of 15,000 miles. The moons’ small size and quirky dimensions led to suggestions that they may be asteroids captured by Mars long ago. Not so, say researchers analyzing data recorded by H...

https://skyandtelescope.org/astronomy-news/does-earth-have-new-quasi-moon/ By David Chandler, Sky & Telescope Magazine.  Excerpt: Recently discovered asteroid 2023 FW 13  has created a bit of a stir among asteroid watchers. It turns out to be on an orbit that is not only in a 1:1 resonance with the Earth, but follows a path that actually circles Earth — albeit on an orbit that is so eccentric that it sweeps out halfway to Mars and in halfway to Venus. There’s no formal definition for objects such as this, which are sometimes called quasi-moons or quasi-satellites. They follow a path around Earth, but usually for no more than a few decades. Perhaps the best known of these objects, known as Kamoʻoalewa, was  found in 2016 , and is considered the smallest, closest, and most stable known quasi-satellite. It has an orbit that has been in a stable resonance with Earth for almost a century, and will remain so for centuries to come, according to calculations by Paul Chodas (J...

https://www.science.org/content/article/spacecraft-explore-habitability-jupiter-s-ocean-moons By Paul Voosen, Science.  Excerpt: Ganymede, Jupiter’s largest moon, is practically a planet. Larger than Mercury, it is the only moon with its own magnetic field, produced by churning molten iron in its core. Its icy crust, more than 100 kilometers thick, ...And beneath the crust, many researchers believe, is a salty ocean, kept warm by the moon’s inner heat and Jupiter’s gravitational kneading. ...Ganymede is one of three jovian moons that may hold hidden oceans, all potential habitats for life. They are the targets of the $1.6 billion  Jupiter Icy Moons Explorer  (Juice), a European Space Agency (ESA) mission set for a 13 April launch on an Ariane 5 rocket from French Guiana. ...Juice will take 8 years to reach Jupiter. It will spend another 3 years promenading among the moons, eventually ending up in a tight orbit around Ganymede—the first time a spacecraft will orbit a moon ...

https://www.nytimes.com/2023/02/16/science/auroras-jupiter-moons.html By Robin George Andrews , The New York Times.  Excerpt: New research shows auroras can also be seen on the Galilean moons of Jupiter:  hypervolcanic Io ,  icy Europa , quirky Callisto and  gigantic Ganymede . ...other than  Ganymede , the big moons of Jupiter lack magnetic bubbles. Instead, their auroras owe their existence to Io. Its noxious atmosphere — partly supplied by the moon’s  epic volcanic eruptions  — regularly sheds into space. The castoffs mingle with sunlight and become electrically excited. Plenty gets captured by  Jupiter’s colossal magnetic bubble , but some of it slams back into Io’s atmosphere, or into the other three moons’ gassy sheaths. Those impacts are what ignite the moons’ auroral lights....

https://skyandtelescope.org/astronomy-news/astronomers-find-a-dozen-more-moons-for-jupiter/ By Jeff Hecht, Sky & Telescope.  Excerpt: The biggest planet in the solar system now has the largest family of moons. Since December 20th, the Minor Planet Center (MPC) has published orbits for 12 previously unreported moons of Jupiter. More publications are expected, says Scott Sheppard (Carnegie Institute for Science), who recently submitted observations of the Jovian system taken between 2021 and 2022. The discoveries bring the list of Jovian moons to 92, a hefty 15% increase from the previous tally of 80. ...The new finds put Jupiter’s lunar family count well ahead of Saturn’s 83 confirmed moons. However, while Jupiter may have the most moons for now, Saturn might catch up. A search for objects with sizes down to about 3 kilometers across that are moving along with the gas giants  found three times more near Saturn than near Jupiter .... 

https://www.nasa.gov/feature/goddard/2022/new-webb-image-captures-clearest-view-of-neptune-s-rings-in-decades By NASA  Laura Betz   (Goddard Space Flight Center, Greenbelt, MD), Hannah Braun and Christine Pulliam (Space Telescope Science Institute, Baltimore, MD).  Excerpt: ...Webb’s extremely stable and precise image quality permits these very faint rings to be detected so close to Neptune. ...Compared to the gas giants, Jupiter and Saturn, Neptune is much richer in elements heavier than hydrogen and helium. This is readily apparent in Neptune’s signature blue appearance in  Hubble Space Telescope images  at visible wavelengths, caused by small amounts of gaseous methane. Webb’s  Near-Infrared Camera  (NIRCam) images objects in the near-infrared range from 0.6 to 5 microns, so Neptune does not appear blue to Webb. In fact, the methane gas so strongly absorbs red and infrared light that the planet is quite dark at these near-infrared wavelengths, excep...

https://eos.org/articles/to-make-a-big-moon-start-with-a-small-planet By Kimberly M. S. Cartier , Eos/AGU.  Excerpt: In a contest of which planet in the solar system has the most relatively massive moon, Earth takes the prize. The Moon is roughly 1% of Earth’s mass, whereas the moons of all the remaining moon-bearing planets—that’s all of them save for Mercury and Venus—are less than one ten thousandth their planets’ masses. ...“We think that a giant impact is a very efficient way to form fractionally large moons,” said  Miki Nakajima , a planetary scientist at the University of Rochester in New York. Large collisions are thought to be a common occurrence in the chaos of a still-forming solar system, but if all giant impacts formed fractionally large moons, our solar system would be rife with them. ...Using computer simulations, Nakajima and her colleagues explored what happens when rocky or icy would-be planets of various sizes collide. The researchers found that after such a...

https://www.nytimes.com/2020/07/25/science/mars-moons-phobos-deimos.html Source:   By Robin George Andrews, The New York Times.  Excerpt: our planetary neighbor is adorned with two moons: puny Phobos, a lumpy mass 17 miles across; and diminutive Deimos, just 9 miles long. Their names in ancient Greek may mean “fear” and “dread’, but the aesthetics of these Lilliputian space potatoes inspire anything but. ...the desire to visit Phobos and Deimos was galvanized by their deeply mysterious nature. “They’re super weird, confusing and interesting,” said Abigail Fraeman, a planetary scientist studying Mars, Phobos and Deimos at NASA’s Jet Propulsion Laboratory. ...they look like asteroids foreign to the red planet but behave like byproducts of Mars’ early, impact-laden history. And if that Japanese mission manages to grab some samples and decode the chemistry of the mangled moons, we might be able to discover their origins. In doing so, we won’t just gain a better understanding of ...

https://www.sciencemag.org/news/2019/11/how-enceladus-got-its-water-spewing-tiger-stripes Source:   By Adam Mann, Science Magazine. Excerpt: Researchers say they have solved a long-standing mystery about Saturn’s tiny, frozen moon Enceladus: why its south pole features long, water-spewing geysers known as tiger stripes. The study could also help explain why these unique formations aren’t seen on any other satellite in the solar system. Enceladus became a star attraction in 2005, when NASA’s Cassini mission photographed enormous jets of water ice and vapor emanating from four parallel slashes near its south pole. Since then, researchers have detected organic molecules and hydrogen in the jets—potential food for microbes—making Enceladus one of the top destinations in the search for life elsewhere in the Solar System. ...As it orbits around Saturn, Enceladus experiences gravitational tidal forces that squeeze and heat it. ...According to the new study, led by Douglas Hemingway of...

http://science.sciencemag.org/content/359/6375/503 Source:   By Pallava Bagla, Science. Summary: Sometime this summer, an Indian spacecraft orbiting over the moon's far side will release a lander. The craft will ease to a soft landing just after lunar sunrise on an ancient, table-flat plain about 600 kilometers from the south pole. There, it will unleash a rover into territory never before explored at the surface. That's the ambitious vision for India's second voyage to the moon in a decade, due to launch in the coming weeks. If Chandrayaan-2 is successful, it will pave the way for even more ambitious Indian missions, such as landings on Mars and an asteroid, as well as a Venus probe. Lunar scientists have much at stake, too. Chandrayaan-2 will collect data on the moon's thin envelope of plasma, as well as isotopes such as helium-3, a potential fuel for future fusion energy reactors. And it will follow up on a stunning discovery by India's first lunar foray, whi...