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Tag: Planetary science

  • Saturn’s Rings Came From a Two-Moon Collision About 100 Million Years Ago, Study Says

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    Of the solar system’s planets, Saturn piques the human imagination with its signature rings and impressive moon count of 274. But compelling new research reignites theories of an ancient collision shaping Saturn’s environment as we know it today—especially Titan, its biggest moon.

    The study, accepted for publication in the Planetary Science Journal, addresses a well-known mystery surrounding the unusually young age of Saturn’s rings as well as the oddity of Titan’s orbit. Researchers led by the SETI Institute consider the possibility that Titan was born from a two-moon collision, the impact of which subsequently led to the creation of Saturn’s younger rings. The paper is currently available as a preprint on arXiv.

    Cassini’s outstanding questions

    Humanity’s first close-up of Saturn, the sixth planet from the Sun, came from NASA’s Pioneer 11 spacecraft in 1979. Voyagers 1 and 2 then made their respective flybys a couple of years later.

    But it was Cassini that really brought Saturn into clearer focus. The spacecraft’s 13-year mission collected valuable data about Saturn, its rings, and its moons for Earthbound scientists to pick apart.

    However, some of the data Cassini sent back challenged some long-held beliefs for astronomers. For instance, several of Saturn’s many moons had odd, lopsided orbits that didn’t quite match the equations. Saturn’s rings were also a lot younger than expected.

    In addition, the planet’s internal mass was more concentrated at the center than astronomers believed, suggesting knowledge gaps in the scientific consensus surrounding Saturn’s orbital behavior.

    A daring what-if

    In 2022, one team of astronomers proposed that these discrepancies could make more sense if Saturn had lost a moon around 100 million years ago, which is when Saturn’s younger rings presumably formed. The latest study tests this hypothesis, using computer simulations to check whether an extra moon could fly close enough to Saturn to form rings.

    Of course, the effect of such a collision would have to be consistent with the distribution and characteristics of Saturn’s moons today, the team noted in the paper. Accordingly, what clued the researchers into a good starting point was a consistent anomaly in their simulations.

    “Hyperion, the smallest among Saturn’s major moons, provided us the most important clue about the history of the system,” Matija Ćuk, the study’s lead author and a researcher at the SETI Institute, said in a statement.

    Specifically, the addition of an unstable extra moon kept driving Hyperion—a moon we know is real—out of existence, which let the researchers know something was up. The team also noted that Hyperion’s orbit was locked with Titan’s, but the orbital lock of the two was also likely around a few hundred years old.

    Not one, but two

    Saturn’s moon Hyperion, captured by Cassini. Credit: NASA/JPL-Caltech/Space Science Institute

    The team finally arrived at one possible scenario. What if there were two earlier moons, not one? If a so-called “Proto-Titan” merged with a smaller “Proto-Hyperion,” it would explain the general lack of impact craters on the moon. If a smaller object tampered with Titan’s orbit pre-merger, it also made sense that Titan would have an eccentric orbit, the researchers added.

    Then the fragments near the Titan merger could have come together to form Hyperion—a lopsided, lumpy moon whose appearance perhaps befits such a wild, unusual origin story.

    As for Saturn’s rings, the researchers were surprised to find that, more often than expected, Titan’s eccentric orbit destabilizes the planet’s inner moons. This would destabilize the orbits of smaller moons, forcing them into extreme routes that ended in massive collisions, forming rings.

    All that said, the team is now counting on NASA’s Dragonfly, an upcoming mission that will reach Titan in 2034, to delve deeper into the mystery. Since the new research primarily focuses on simulations, fresher data from Dragonfly should allow them to put the hypothesis to the test, they said.

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    Gayoung Lee

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  • Parenting 101: Outschool’s free mission to Mars

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    Outschool has announced a one-of-a-kind virtual event that will allow learners around the world to communicate live with a simulated Mars mission, complete with a real Earth-to-Mars communication delay. Taking place on February 4th, the 80-minute live event will allow learning to tune in, ask questions, collaborate during the wait, and receive responses from the Mars analog crew, turning delay into discovery.

    The event is free, designed for kids ages 5-18 and will take place at 12 p.m.

    In partnership with veteran Outschool educator Tom Bickmore, who will serve as Crew Journalist during an upcoming mission at the Mars Desert Research Station (MDRS) in Utah, the event invites kids to experience what it’s truly like to talk to people on another planet.

    “When humans go to Mars, communication won’t be instant, but it can still feel human,” Bickmore said in a media release. “Kids are incredibly candid about their experiences, which makes them perfect participants in this kind of research.”

    On a real Mars mission, messages take approximately 10 minutes to transmit between planets due to their distance. In this event, kids will experience this same delay each way — turning this wait into a fun challenge where participants can ask questions, work together while waiting, and feel what it’s really like to chat with someone on another planet.

     – JC

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  • A Planet Inside a Planet? Traces of Pre-Moon Earth Found Deep Below

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    If proto-Earth had all its parts and chemistry replaced to become the Earth we know today, can the two still be considered the same planet? That’s the planetary version of Theseus’s Paradox, an old philosophical puzzle about identity and perception. The popular consensus until recently was that Earth’s chemistry changed completely after a giant meteorite impact, leaving nothing behind from its proto-Earth days.

    A new finding suggests that conception may be wrong. In a Nature Geoscience paper published earlier this week, researchers report detecting a chemical signature that appears to have miraculously resisted change for billions of years. Specifically, the team—an international collaboration between the U.S., China, and Switzerland—found an odd imbalance of potassium isotopes in ancient rock samples. Chemical analyses revealed the anomaly couldn’t have emerged from any known geological processes on modern Earth.

    Theseus’s planet?

    Planetary scientists have long suspected that a Mars-sized meteorite slammed into Earth some 4.5 billion years ago. The impact triggered a literal, astronomical makeover, transforming what was once a rocky, lava-filled environment into the Earth we know today.

    The general understanding was that, over time, whatever materials or processes formed proto-Earth either transformed or were replaced by ones more familiar to researchers today. It was, of course, a reasonable explanation: that the “resetting” of Earth’s chemistry miraculously created the conditions that eventually led to life.

    A potassium anomaly

    Naturally, scientists are still hoping to learn more about our planet’s earliest days. For the new paper, the authors zoomed in on potassium. On Earth, the common element normally exists in a specific combination of potassium-39 and potassium-41, with a tiny portion of potassium-40.

    Previous work by the study’s lead authors, however, showed that extraterrestrial objects—such as meteorites—have distinct potassium profiles, typically with a slightly higher proportion of potassium-40.

    Building on this knowledge, the team dug deep into the oldest available rocks on Earth, such as powdered rocks from Greenland and Canada and lava deposits in Hawaii. At the lab, they ran the samples through various techniques in analytical chemistry.

    Surprisingly, the potassium profile they ended up with was unlike anything researchers had ever seen—neither on Earth nor in cosmic objects. In fact, the “deficit” of potassium-41 was so bizarre that spotting it was “like spotting a single grain of brown sand in a bucket rather than a scoop full of yellow sand,” the researchers told MIT News.

    An ongoing mystery

    Was there really no feasible, natural way for this chemistry to have emerged? Multiple simulations and follow-up investigations of all known meteorites and geological processes seemed to point to the same answer: no. According to the paper, the most viable explanation for this material’s existence is that it was left over from proto-Earth.

    “This is maybe the first direct evidence that we’ve preserved the proto-Earth materials,” Nicole Nie, study co-lead author and a planetary scientist at MIT, explained to MIT News. “We see a piece of the very ancient Earth, even before the giant impact. This is amazing because we would expect this very early signature to be slowly erased through Earth’s evolution.”

    That said, we may as well end up finding something, like an odd meteorite, with the same potassium anomaly, in which case the signature wouldn’t necessarily be the surviving remnants of proto-Earth.

    Either way, the findings demonstrate that there’s still a lot for us to learn about our own Earth—lessons that, perhaps, may guide us away from any missteps we’re making while studying things beyond Earth.

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    Gayoung Lee

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  • The Asteroid Belt Is Vanishing

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    Between the orbits of Mars and Jupiter lies a ring-shaped region called the asteroid belt, home to the vast majority of our solar system’s space rocks. The asteroid belt is as old as the solar system itself, having formed from leftover material that failed to coalesce into a full-grown planet due to Jupiter’s gravitational influence.

    Over the past 4.6 billion years, Jupiter has continued to shape the asteroid belt through gravitational resonances—regions where an asteroid’s orbit aligns with that of Jupiter, Saturn, or Mars. This can either fling an asteroid toward the inner solar system or outward toward Jupiter’s orbit. Meanwhile, those that don’t escape constantly collide with other asteroids in the belt, gradually being pulverized into dust. As such, the asteroid belt is slowly disappearing.

    In a new study that has yet to undergo peer review, researchers led by planetary scientist Julio Fernández of Universidad de la Republica in Uruguay estimate the rate of the belt’s depletion. The findings, currently available on the preprint server arXiv, indicate that the collisionally active portion of the asteroid belt is losing about 0.0088% of its mass every million years.

    A very slow vanishing act

    The collisionally active portion of the belt refers to asteroids that are small enough to be involved in frequent collisions and dynamical ejections—basically everything except large, primordial bodies such as Ceres, Vesta, and Pallas. A loss of 0.0088% per million years may not sound like much, but over the eons, it adds up.

    Fernández and his colleagues estimate that 3.5 billion years ago, the asteroid belt may have contained 50% more mass, with a loss rate double what it is today. That estimate correlates nicely with a more intense impact rate reflected in Earth and the Moon’s geologic records, according to the researchers.

    Where do the lost asteroids end up? Well, according to the researchers’ calculations, about 20% escape into space, occasionally crossing into Earth’s orbit and even plummeting through our atmosphere as meteors. The other 80% gets ground into meteoritic dust that filters into the zodiacal cloud—a thick, pancake-shaped dust cloud that orbits the Sun within the inner solar system.

    Will the asteroid belt completely disappear?

    Previous research has estimated that the combined mass of all the asteroids in the belt today is roughly equivalent to just 3% of the Moon’s mass. Still, it would take many, many more years for the belt to disappear completely through pulverization and dynamical ejections alone. The death of the Sun—projected to occur in about 5 billion years—will destroy it sooner than that.

    This study provides an answer to an arguably more important question: At what rate is the asteroid belt ejecting space rocks that could potentially impact Earth? Additionally, by extrapolating the rate of dynamical ejection back in time, the researchers present data that can help scientists better understand the impact history that shaped the planet’s surface.

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    Ellyn Lapointe

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  • ‘Failed Star’ Mimics a Key Sign of Life, Complicating Our Search for Aliens

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    For scientists, the urgent problem with phosphine—a molecule famously touted as a potential sign of life—isn’t so much about where it came from, but why it’s not where we think it should be. After a decade of searching, a long-awaited result has confirmed that our astronomical models aren’t a total bust. At least, for now.

    In a Science paper published today, astronomers report the first-ever detection of strong phosphine signatures on a brown dwarf—a type of planet-star hybrid more massive than planets like Jupiter but not quite big enough to sustain the hydrogen fusion that powers stars. Prominent chemical models had long predicted that cosmic entities with gassy atmospheres would be rich in phosphine, but years of searching had turned up nearly nothing. The findings thus give closure to a problem that had plagued astronomers for at least a decade.

    Just as importantly, the finding carries important implications for astrobiology. The phosphine detected on this brown dwarf, named Wolf 1130C, almost certainly formed through natural, abiotic processes. The challenge now is figuring out how an object like this could generate so much of it without life. Until researchers can explain that, any detection of phosphine—whether on a gas giant or a rocky planet like Venus—can’t be taken as a reliable sign of biology.

    “The community has been waiting for this,” said Sara Seager, an MIT astrophysicist not involved in the new work. Seager co-authored a seminal paper from 2020 on the detection of phosphine on Venus. On Earth, phosphine mainly exists as the byproduct of anaerobic life, or creatures that thrive without oxygen. Because Venus’s chemical environment isn’t conducive to the natural formation of phosphine, the 2020 paper left astronomers wondering if the phosphine could have come from a life source—a biosignature.

    “It is very refreshing—finally!” Nathalie Cabrol, research director at the SETI Institute’s Carl Sagan Center, added. Cabrol, also uninvolved in the new study, told Gizmodo in a video call that the paper presents “clear, plain” data of phosphine on the brown dwarf—just as models predicted.

    A wild phosphine chase

    Had the results come ten years ago, it wouldn’t have been this big of a deal, Adam Burgasser, study lead author and an astrophysicist at the University of California, San Diego, told Gizmodo. Chemical models had long supported the natural presence of phosphine on brown dwarfs or exoplanets with gassy atmospheres. That Jupiter and Saturn have phosphine-rich atmospheres also contributed to this assumption.

    But after a decade of finding zero (or rather, several contested) signs of phosphine where models expected it to be, astronomers started to get rather skittish, explained Burgasser. In fact, astronomers had started to seriously consider substantially revising major models to account for the lack of phosphine.

    “It’s been a real weird problem, because it’s just this one molecule that seems to be a little bit out of sync,” Burgasser said. “So, it’s actually a surprise that we have now finally detected it—in fact, detected it in abundance in this one particular brown dwarf.”

    A Webb search

    Wolf 1130C is located around 54.1 light-years from Earth. The team chose this object for its slightly unusual composition, low metallicity, and comparatively low surface temperature. The idea was to take a slightly different approach, since previous surveys had already targeted brown dwarfs with the right temperature or composition, yet astronomers hadn’t “seen the level of phosphine that we would expect,” Burgasser explained.

    Their hunch turned out to be correct. While studying spectral data from the James Webb Telescope’s Near-Infrared Spectrograph, the team noticed a distinct check mark in their plot—a shape characteristic of phosphine signatures. But the researchers swallowed their excitement to double- and triple-check their work.

    Comparison of JWST infrared spectral observations of Wolf 1130C (light blue line) and a typical brown dwarf (grey line). The detection of phosphine is highlighted in the zoomed-in panel at right, which compares the spectrum of Wolf 1130C (light blue line) to that of pure phosphine (green line). Credit: Adam Burgasser/UCSD

    “We were like, ‘We have to make sure this is absolutely correct,’” Burgasser recalled. Fortunately, the team included a computational modeling expert who ran week-long simulations of the dwarf’s atmosphere, along with a scientist whose career had revolved around phosphine.

    “A combination of all these things—plus the analysis we did to [describe] the abundances—made us realize that we had a very obvious and solid detection,” Burgasser said.

    No aliens here

    Again, the detection doesn’t represent a biosignature, which Burgasser, Seager, and Cabrol all emphasized. That has to do with an often glossed-over aspect of finding signs of alien life, Cabrol said. No molecule by itself is necessarily a biosignature; rather, we’re looking for the “co-evolution of life and its environment,” she said. In other words, a compound qualifies as a biosignature only if the surrounding environment suggests it couldn’t have formed through non-biological chemistry alone.

    Checking such environmental contexts would be easier for places like Venus, which is close enough for us to plan missions, Cabrol explained. “We don’t have this luxury with exoplanets. When you don’t know the environment…you cannot claim that something is a biosignature unless something is being replenished in a way that nature alone cannot explain.”

    For brown dwarfs, phosphine is not a biosignature. These stellar bodies are hot and hydrogen-rich, which is conducive to the presence of phosphine, Seager said.

    “Chemically, there’s no life involved in that,” Burgasser added.

    Homework from the universe

    That said, the team isn’t completely certain how so much phosphine ended up on Wolf 1130C, although they do explore some options. It could be due to the brown dwarf’s low metallicity, or the local environment could have been conducive to the accumulation of phosphine on Wolf 1130C. Overall, the researchers aren’t sure.

    At the same time, “the inability of models to consistently explain all these sources indicates an incomplete understanding of phosphorus chemistry in low-temperature atmospheres,” the paper noted.

    It’s as if nature came in and said, “Yeah, here’s more homework, a harder test question for you,” Burgasser joked. “We don’t even understand the natural chemistry for phosphorus—until we get that right, we can’t really rely on phosphine as a viable biosignature,” he added.

    The obvious next step would be to look for other objects with similar supplies of phosphine, which could help fill in the gaps that remain. Of course, it’s entirely possible that future discoveries may throw models into even further confusion. Either way, the findings mark a new chapter in our understanding of the cosmos.

    “But the process that will be leading to that day is beautiful in itself,” Cabrol said, “because it’s the progress of human knowledge.”

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    Gayoung Lee

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  • ‘Dead’ Star Caught Snacking on Pluto-Like Object

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    By studying the chemical composition of an odd, dying star, astronomers discovered that it had been feasting on what used to be an icy, Pluto-like object.

    Nature can get brutal. On a cosmic scale, things get even more destructive—leaving behind carnage made of stellar dust the size of an entire planet.

    Astronomers using the Hubble Space Telescope spotted a white dwarf—the remnant of a dying star’s core—enjoying a meal of some fragment researchers later identified as coming from a Pluto-like object. According to a paper on the finding published September 18 in Monthly Notices of the Royal Astronomical Society, astronomers seemingly caught the dwarf near the tail end of its meal; some time ago, the dwarf’s intense gravitational pull likely snatched an icy planet from its regular orbit.

    What’s more, further analysis of the doomed object revealed that its chemical composition included key elements such as carbon, sulfur, nitrogen, and oxygen—suggesting that, before its demise, the tiny planet may have held some water on its surface.

    A ‘cosmic crime scene’

    The atmosphere of a white dwarf typically consists of hydrogen and helium. But this particular dwarf, WD 1647+375, carried an unusual supply of volatiles, or chemical substances with low melting points. That told the researchers that something was off.

    “White dwarfs act like cosmic crime scenes,” study lead author Snehalata Sahu said in a release. “When a planetesimal [small solid objects thought to form planets] falls in, its elements leave chemical fingerprints in the star’s atmosphere, letting us reconstruct the identity of the ‘victim.’”

    So the team embarked on some detective work. One thing that stood out to them was the abundance of nitrogen in WD 1647+375, which the researchers explained was a “particularly important chemical fingerprint of icy worlds.” The dwarf’s oxygen gain was also much higher than it would have been had the victim been a rocky object.

    “We know that Pluto’s surface is covered with nitrogen ices,” Sahu added in a Hubble statement. “We think that the white dwarf accreted fragments of the crust and mantle of a dwarf planet.”

    From Hubble’s ultraviolet signals, the team was able to deduce that the star’s meal had been ongoing for at least the last 13 years, consuming the object at a rate of around 440,925 pounds (200,000 kilograms) per second. If so, the victim at its prime would have had a minimum diameter of about 3 miles (5 kilometers).

    All the evidence suggested that WD 1647+375 was snacking at an object that was once an icy planetesimal floating around the local version of the Kuiper Belt, an icy ring of debris around our solar system.

    A peek into the past and future

    This discovery offers a surprising window into both the past and future of cosmic systems, the researchers explained.

    For instance, comets and icy planetesimals like WD 1647+375’s giant snack “deliver water and other volatiles to terrestrial planets in extrasolar systems—a prerequisite for the development of life in other worlds,” according to the paper. Now that we know such icy planetesimals do exist, this theory could be tested further with other objects, namely the recent interstellar comet visitor, 3I/ATLAS.

    But WD 1647+375 itself offers a sneak peek of what’s to come for our own solar system, Sahu added. Our Sun will eventually burn out and collapse into a white dwarf like WD 1647+375. When that happens, the planets in our solar system may encounter a similar fate as this icy planetesimal.

    “If an alien observer looks into our solar system in the far future,” Sahu said, “they might see the same kind of remains we see today around this white dwarf.”

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    Gayoung Lee

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  • Starfield Doesn’t Require Fast Travel After All…Sort Of

    Starfield Doesn’t Require Fast Travel After All…Sort Of

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    Pluto isn’t a planet. That really shouldn’t be a controversial statement any more, but it regains new contentiousness with the release of epic space RPG, Starfield. Developer and streamer Alanah Pearce wanted to find out if Bethesda’s epic space RPG really does require fast travel for all interplanetary travel, by setting off on the seven hour trip from Earth to the dwarf planet.

    This Narrative Adventure About Doomed Teenage Dinosaurs Feels Too Real

    Starfield intends players to use fast travel to move between planets and solar systems. Disappointing many, who had hoped for a more natural ability to fly from orb to orb, it was widely speculated that the game was instead beaming players into bordered skyboxes within a solar system, with the uninhabited planets just decorations on the walls. Brave explorer, podcaster, and Santo Monica Studios writer, Alanah Pearce, decided to find out the truth.

    Screenshot: Alanah Pearce / Bethesda / Twitch / Kotaku

    Pearce’s plan was to fly within the familiar trails of the Milky Way to discover if those extra worlds could be reached under a player’s own space-steam. To do this, the plan was to point toward a location, then leave the game running while she slept. However, Pearce’s first problem was where to head. Initially trying to aim for Earth, it turned out that the game’s ultra-realistic planetary orbits would have made it unrealistic to accurately aim before heading to bed. Instead, after much deliberation, the decision was made to point the ship to the right of Pluto.

    Read More: 17 Things I Wish I Knew Before I Started Playing Starfield

    It turns out it’s not that simple. It’s never that simple. Every time Pearce’s Xbox controller fell asleep, the game paused, meaning there were stretches of the night where no progress was made until the streamer woke up to hit A, then went back to sleep.

    On waking seven hours later, what Pearce unequivocally proved is that the game isn’t using skyboxes. The solar systems depicted in the enormous space map are for real, and like the real thing, mostly made of terrifyingly vast stretches of absolutely nothing. And now she was 47 kilometers from the dwarf body.

    By this point, the textures were heavily blurred, suggesting Bethesda had not intended anyone to do this. Rather confirming that, on actually reaching the non-planet, Pearce flew straight through the skin of Pluto’s surface, on some level going “inside” it, whereupon the trans-Neptunian object became invisible showing the rest of space around her ship.

    Getting out the other side proved somewhat trickier. Because, even though Pluto is endlessly demeaned for its diminutive size, it still has a diameter of 2,376km. And travelling at these subspace speeds meant that would take hours itself. So, you know, Alanah Pearce went back to bed.

    After another five hours, the ship was outside of the planet again. Astonishingly, in the process, Pearce reports that she was so tired that she’d fainted on her return to bed and smacked her head. But it was for Science.

     

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    John Walker

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