Speaker 1: Welcome to BrainStuff, a production of iHeartRadio. Hey BrainStuff, Lauren
Speaker 1: Vogelbaum here. Earth's moon feels like an ever-present feature in
Speaker 1: our skies, even if it's really only visible from any
Speaker 1: given point on Earth about half the time. But what
Speaker 1: if you looked skyward and saw not a moon, but
Speaker 1: a ring, much like the ones that encircle our solar
Speaker 1: system's gas giants? Saturn in particular is known for its
Speaker 1: brilliant ring system, the most extensive we know of. But Jupiter, Uranus,
Speaker 1: and Neptune have rings too. Today, let's talk about planetary rings,
Speaker 1: and what it would be like if Earth boasted its own.
Speaker 1: Scientists believe Earth did have a ring once, albeit a
Speaker 1: few billion years ago. This ring would have appeared early
Speaker 1: in the formation of Earth's moon. Our best hypothesis for
Speaker 1: how the moon formed is what's called the giant impact hypothesis.
Speaker 1: The idea is that about four and a half billion
Speaker 1: years ago, while the Earth itself was still forming, a
Speaker 1: large object or fellow proto-planet about the size of Mars
Speaker 1: hit Earth at an angle. The impact threw debris into
Speaker 1: space from Earth's crust and mantle. The impactor itself, which
Speaker 1: we've named Theia, melted and merged with Earth's interior. Meanwhile,
Speaker 1: some of the hot debris got caught in Earth's orbit
Speaker 1: and eventually cooled and coalesced to form the moon. The
Speaker 1: giant impact hypothesis would explain why moon rocks have a
Speaker 1: composition similar to Earth's mantle and why they seem to
Speaker 1: have been baked, and why the moon has no iron core,
Speaker 1: because the iron in Earth's core and Theia's core remained
Speaker 1: on Earth. But while the moon was coming together... all
Speaker 1: of that debris would have been hovering in a ring
Speaker 1: in Earth's orbit. Now, planetary rings are temporary structures. We
Speaker 1: talked about this a while ago on the show, when,
Speaker 1: back in 2018, researchers found that Saturn's glorious rings have
Speaker 1: only been around for about 100 million years, and that
Speaker 1: they'll be gone, having fallen into the gassy planet, and
Speaker 1: 100 million more. So, no matter what, this early ring
Speaker 1: of Earth's wouldn't have lasted until today. But the reason
Speaker 1: that this debris became a moon and not a ring
Speaker 1: is that it existed outside of what's called the Roche limit.
Speaker 1: The Roche limit is named for the French mathematician Edouard Roche, who,
Speaker 1: in 1848, figured out that any given planet's gravitational pull
Speaker 1: on a moon will be unequal across the surface of
Speaker 1: that moon. That a planet exerts a greater gravitational force
Speaker 1: on the side of the moon closest to the planet.
Speaker 1: and a lesser gravitational force on the side facing away.
Speaker 1: This means that if a moon or other object that
Speaker 1: wanders into a planet's orbit is too close to the planet,
Speaker 1: the unequal pull of the planet's gravity could tear it apart. Essentially,
Speaker 1: the Roche limit is the minimum distance an object can
Speaker 1: be from a planet and still hold itself together by
Speaker 1: its own gravity. Inside the Roche Limit, any debris from
Speaker 1: a giant impact, or any object that the planet attracts
Speaker 1: with its gravitational pull, say smaller moons or asteroids, will
Speaker 1: get torn apart again and again, eventually ground down to water, ice,
Speaker 1: and dust particles, traveling along the planet's gravitational orbit like
Speaker 1: water running down a drain, very slowly. Researchers estimate that
Speaker 1: around Saturn, Ring material, to the amount of some 10
Speaker 1: tons or 9,000 kilos, is falling into the planet every second.
Speaker 1: Part of why our gas giants all have rings, but
Speaker 1: our rocky inner planets don't, is that the outer planets
Speaker 1: have masses large enough to attract ring material, and they
Speaker 1: orbit far away enough from the sun for water ice
Speaker 1: to stay frozen. Part of how we figured out that
Speaker 1: Saturn's rings are so young is that they're predominantly made
Speaker 1: of ice. If they were older, that ice would have
Speaker 1: gotten contaminated over time with interplanetary debris, making them dull.
Speaker 1: But they're still beautifully bright. Saturn has seven main rings,
Speaker 1: each composed of thousands of tiny ringlets. They're massively wide,
Speaker 1: extending up to 175,000 miles, or 280,000 kilometers, out into space.
Speaker 1: But they're proportionally very thin, only about 30 feet or
Speaker 1: 10 meters thick. ranging up to a little over half
Speaker 1: a mile or a kilometer at the thickest. They're made
Speaker 1: up of chunks of water ice, rock, and other materials,
Speaker 1: varying in size from specks to enormous house-sized pieces that
Speaker 1: collide constantly, shattering the larger chunks. Scientists think the rings
Speaker 1: formed when comets or asteroids collided with one or more
Speaker 1: of the planet's moons. The fragments from the collisions spread
Speaker 1: out around Saturn within the Roche limit. Saturn's two innermost
Speaker 1: rings are very transparent. The next two out are the
Speaker 1: brightest and largest. The fifth ring is very narrow and
Speaker 1: held together by two moons, Pandora and Prometheus, that sit
Speaker 1: on either side of the ring. The final two are
Speaker 1: farther out, with the farthest made up of near-microscopic ice particles,
Speaker 1: thought to have been ejected from the moon Enceladus, sprayed
Speaker 1: out of volcanic geysers near its south pole. Saturn's rings
Speaker 1: are named after the first seven letters of the alphabet,
Speaker 1: in the order that they were discovered. So, from innermost
Speaker 1: to outermost, that's D, C, B, A, F, G, and E.
Speaker 1: The rings aren't perfect circles, but instead have bends in
Speaker 1: them caused by the pull of gravity from nearby moons.
Speaker 1: There's also a mysterious phenomenon among the rings, referred to
Speaker 1: as spokes. These are features that rotate along with the rings,
Speaker 1: but appear and disappear in ways that we haven't entirely
Speaker 1: been able to explain yet. They look like spokes on
Speaker 1: the wheels of the rings, and researchers think that they
Speaker 1: may be formed by seasonal interactions between solar wind and
Speaker 1: Saturn's magnetic field, creating some kind of static electricity that
Speaker 1: pulls fine dust particles into different shapes. Saturn's rings are
Speaker 1: bright enough that Galileo observed them way back in 1610,
Speaker 1: though he didn't know what he was looking at. Their
Speaker 1: extension from the sides of Saturn reminded him of ears,
Speaker 1: and he wrote about them being two smaller stars, or
Speaker 1: perhaps two large moons. It wasn't until 1655 that Dutch
Speaker 1: scientist Christian Huygens identified them as rings. The other gas giants'
Speaker 1: rings went undetected for over 300 years. Uranuses were the
Speaker 1: first to be discovered in 1977. They run parallel to
Speaker 1: its tilted equator, which is nearly at a right angle
Speaker 1: to its orbit, so the rings appear to go up
Speaker 1: and over the planet. It has two sets, nine inner
Speaker 1: rings that are narrow and gray, and then two outer rings,
Speaker 1: one reddish and one blue. Jupiter's rings weren't discovered until
Speaker 1: Voyager 1's initial flyby in 1979. They're very faint. and
Speaker 1: they're thought to have been created by meteoroid impacts on
Speaker 1: small nearby moons. They have four components, an inner halo
Speaker 1: of dust, a bright, thin main ring, and then two wide,
Speaker 1: dim outer rings called the gossamer rings. Neptune's rings weren't
Speaker 1: definitively detected until 1989, when Voyager 2 captured images of
Speaker 1: them on its flyby. It has five main rings and
Speaker 1: four prominent ring arcs, which are smaller rings that are
Speaker 1: formed by faint, thin collections of micrometer-sized dust that's shepherded
Speaker 1: around the ring system by Neptune's four small moons. But
Speaker 1: back to Earth. It's unlikely that our planet will form
Speaker 1: its own ring system anytime soon. In order to break
Speaker 1: apart properly, an asteroid or a bunch of space rubble
Speaker 1: would need to enter our orbit at around 9,000 kilometers,
Speaker 1: which is in low-to-mid-medium Earth orbit. But what would it
Speaker 1: be like if Earth did have rings? Okay, any rings
Speaker 1: would most likely form parallel to the equator, and thus
Speaker 1: would arc across the sky from east to west. And
Speaker 1: your view of them would depend on your latitude away
Speaker 1: from the equator. Near the equator, the rings would be
Speaker 1: like thin slices of light erupting from the distant horizons
Speaker 1: and stretching up into the sky as far as the
Speaker 1: eye could see. The farther north or south you were,
Speaker 1: the more the appearance of the rings would change. They'd
Speaker 1: become markedly wider and more visible, and would, from some
Speaker 1: vantage points, appear close enough to the horizon to reach
Speaker 1: out and touch. Just as the moon currently does, the
Speaker 1: rings would reflect sunlight back to Earth and appear to glow,
Speaker 1: especially at night. Depending on exactly what they were made of,
Speaker 1: the rings could reflect so much sunlight that the planet
Speaker 1: would never fully plunge into darkness, but remain in a
Speaker 1: gentle twilight, even in the depth of night. Even daylight
Speaker 1: might be brighter because of them. Rings around Earth would
Speaker 1: have significant climatic implications. These vast sheets of debris could
Speaker 1: act as a shield in some regions, potentially preventing some
Speaker 1: of the sun's rays from reaching Earth's surface. This could
Speaker 1: lead to cooler temperatures in some areas, especially those beneath
Speaker 1: the densest parts of the ring. Conversely, the reflected sunlight
Speaker 1: from the rings could cause a warming effect in other regions.
Speaker 1: Climate models would need to account for these new variables,
Speaker 1: making our understanding of global weather patterns even more complex.
Speaker 1: Planetary rings would also pose challenges to our current satellite infrastructure.
Speaker 1: After all, we have stuff in our medium Earth orbit.
Speaker 1: Just a bit farther out than a ring would sit,
Speaker 1: we've placed a lot of telecommunications and GPS equipment, and
Speaker 1: above that, a lot of weather platforms. rings could interfere
Speaker 1: with the trajectories of nearby platforms or with communication from
Speaker 1: the ground to anything orbiting above them. The presence of
Speaker 1: a dense ring could also present navigational hazards for space
Speaker 1: missions leaving or entering Earth's atmosphere. If material from the
Speaker 1: rings should rain down onto the planet the way that
Speaker 1: Saturn's ring material does, it could also pose a hazard
Speaker 1: to the equipment in low Earth orbit, like the International
Speaker 1: Space Station. Space agencies and other satellite constructors would need
Speaker 1: to recalibrate and perhaps even redesign spacecraft to safely navigate
Speaker 1: in or through such an environment. On the flip side,
Speaker 1: falling ring material might create some spectacular meteor showers. And
Speaker 1: just think of all the new sayings we'd have to
Speaker 1: come up with. Perhaps we'd no longer shoot for the moon,
Speaker 1: but aim for the rings instead. It's not completely out
Speaker 1: of the realm of possibility. We're still learning about planetary rings.
Speaker 1: Just in 2023, an international team of astronomers published a
Speaker 1: study in the journal Nature about a new ring system
Speaker 1: they discovered in the far reaches of our solar system.
Speaker 1: The rings are around Quawar, a dwarf planet that's about
Speaker 1: as wide as Texas and orbits beyond Neptune. The rings
Speaker 1: are too faint to see directly from Earth, the team
Speaker 1: discovered them by observing an oculation, meaning that they watched
Speaker 1: the light from a background star, as Quawar blocked it
Speaker 1: by passing between us and the star during its orbit.
Speaker 1: What makes this ring system especially interesting is that it's
Speaker 1: twice as far out from the surface of the dwarf
Speaker 1: planet as scientists previously thought was possible according to the
Speaker 1: Roche limit. So who knows? Maybe rings are in Earth's
Speaker 1: future after all. Today's episode is based on the articles
Speaker 1: Does Earth Have Rings? by Laurie L. Dove and The
Speaker 1: Four Planets with Rings Might Surprise You by Mitch Ryan,
Speaker 1: both on HowStuffWorks.com. BrainStuff is a production of iHeartRadio in
Speaker 1: partnership with HowStuffWorks.com and is produced by Tyler Klang. For
Speaker 1: more shows from iHeart Podcasts, visit the iHeartRadio app, Apple Podcasts,
Speaker 1: or wherever you listen to your favorite shows.