Tag Archives: Planetary rings

Earth might develop ‘junk’ rings — but engineers are working to prevent that

Earth may one day have its own ring system — one made from space junk.

Rendering of man-made objects in Earth’s orbit. Image via ESA.

Whenever there are humans, pollution seems to follow. Our planet’s orbit doesn’t seem to be an exception. However, not all is lost yet! Research at the University of Utah is exploring novel ideas for how to clear the build-up before it can cause more trouble for space-faring vessels and their crews.

Their idea involves using a magnetic tractor beam to capture and remove debris orbiting the Earth.

Don’t put a ring on it

“Earth is on course to have its own rings,” says University of Utah professor of mechanical engineering Jake Abbott, corresponding author of the study, for the Salt Lake Tribune. “They’ll just be made of space junk.”

The Earth is on its way to becoming the fifth planet in the Solar System to gain planetary rings. However, unlike the rock-and-ice rings of Jupiter, Saturn, Neptune, and Uranus, Earth’s rings will be made of scrap and junk. It would also be wholly human-made.

According to NASA’s Orbital Debris Program Office, there are an estimated 23,000 pieces of orbital debris larger than a softball; these are joined by a few hundreds of millions of pieces smaller than a softball. These travel at speeds of 17,500 mph (28,160 km/h), and pose an immense threat to satellites, space travel, and hamper research efforts.

Because of their high speeds, removing these pieces of space debris is very risky — and hard to pull off.

“Most of that junk is spinning,” Abbott added. “Reach out to stop it with a robotic arm, you’ll break the arm and create more debris.”

A small part of this debris — around 200 to 400 — burns out in the Earth’s atmosphere every year. However, fresh pieces make their way into orbit as the planet’s orbit is increasingly used and traversed. Plans by private entities to launch thousands of new satellites in the coming years will only make the problem worse.

Abbott’s team proposes using a magnetic device to capture or pull debris down into low orbit, where they will eventually burn up in the Earth’s atmosphere.

“We’ve basically created the world’s first tractor beam,” he told Salt Lake Tribune. “It’s just a question of engineering now. Building and launching it.”

The paper “Dexterous magnetic manipulation of conductive non-magnetic objects” has been published in the journal Nature.

The largest planetary ring system we’ve found would dominate the sky — if it was in our solar system

When talking about planetary ring systems, Saturn and Jupiter likely spring to mind — they are our closest ringed neighbors, after all. But although impressive, their rings aren’t that large, in the grand scheme of things. Jupiter’s aren’t that large even when judging only by our Solar System. Neptune and Uranus also have rings, but they’re tinier.

A picture of Saturn’s ring structure created using data from the Cassini craft on April 19 2017. Image credits Kevin Gill / Flickr.

Luckily, the Universe is a huge place, and there’s no shortage of beautiful ring systems to enjoy. There are also plenty of grand, sprawling ones to take your breath away. So, today, let’s take a look at what these ring systems actually are, how they form, and the biggest ones we’re spotted so far.

What even are planetary ring systems?

Every stellar body generates a gravitational field. Large, dense ones create a strong pull; giant, ponderous planets generate an immensely strong pull. It’s these large planets, typically gas giants, which sport planetary ring systems. It’s not all that different from how our Earth sports a Moon.

Ring systems are sprawling fields of material such as rocks, minerals, and ice. They look like wispy sheets of material, but up close, these are massive structures. They’re not particularly thick (Saturn’s rings, for example, are probably only 50 meters high) but they go all the way around a planet, most often in several different ‘rings’ each at different distances from the planet.

The exact size of the particles in a ring system is dependent on several factors: the material these particles are made of (mainly its specific strength and density), how far it is from the planet, and the strength of tidal forces at that altitude. In other words, rings are made up of particles in all kinds of shapes and sizes; the planet’s gravitational pull and rotation will try to grind them down, while a material’s toughness and its distance from the planet will help it survive in larger chunks. The materials they’re made of aren’t consistent — it’s all related to how the system and planet formed, and their history since. It’s generally gas, dust, and ice, but according to NASA, such particles can be “as large as mountains”.

Lastly, know that although we call them ‘planetary’ ring systems, they don’t only form around planets. Minor planets, moons, unignited stars (brown dwarfs) can also sport ring systems. There is even some evidence of a similar structure residing in the void between Venus and Mercury.

How do they form?

As far as we understand, there are three main ways for a planet to get the material that makes up its rings.

The first one is that they simply ‘gathered’ it in the early days of the system they inhabit — the so-called accretion stage. In this phase, a star system resembles a disk churning around its star. In time, pockets of matter come together (accrete), gaining gravitational strength, which keeps drawing more material in. This is how stars and planets form (the star just forms first and can thus grab most of the matter in the disk).

If a planet forms early and gets large enough, it can start drawing in material from around it, preventing it from accreting into the forming planets. Instead, it forms a ring system under the hosts’ tidal forces (gravitational pull + rotational movement). This is exactly the same process that builds planets around a star from the primordial dust, only at a much smaller scale.

Detail of Saturn’s shepherd moons, created using data from Cassini. Image credits NASA-JPL / Caltech.

The second way is to use your gravity to capture asteroids or moons or let some form near you and pull them inside your Roche limit. This is a theoretical boundary beyond which a planet’s tidal forces will break apart any other stellar body. Inside this range, moons and asteroids will be ground into dust. The Roche limit also dictates how far a body’s influence extends during the accretion phase — nothing can form within this boundary due to the extreme tidal forces present.

The third way generally doesn’t form very large ring systems by itself. It involves a planet capturing any material produced by asteroids crashing into its moons, or materials produced by volcanic processes that make it into space (from traditional or cryovolcanoes). Compared to the previous two, such capture processes involve minute amounts of matter.

One of the final elements that can help produce and maintain a planetary ring system is shepherd (or ‘watcher’) moons. These are larger bodies that orbit through or on the edges of rings. Their gravity pulls at particles in the ring as they orbit, which helps to maintain the shape of the rings — they ‘herd’ the ring particles, hence their names. If you see any empty strips in a ring system, it’s very likely that a shepherd moon created it.

The movements of such a moon through the ring are truly a thing of beauty. As they orbit, shepherd moons form ripples through the ring, like the wake of a boat traveling over a calm lake. This only makes the thought that such moons tend to be short-lived that much sadder. They’re generally inside their host’s Roche limit, so they will eventually be broken apart and ground down.

Now that we have a better understanding of what they are and how they form, let’s take a look at the biggest, most impressive ring system we’ve found so far.

J1407b

Artistic rendering of the exoplanet and its impressive rings. Image via Wikimedia.

Discovered way back in 2015, J1407b boasts the largest ring system we’re ever seen — around 200 times larger than Jupiter’s (the largest in our solar system). The planet that hosts it is equally immense: we don’t exactly know whether it’s a gas giant or a brown dwarf. So far, it’s been referred to as a super-Jupiter type of stellar body.

To give you an idea of just how stupidly massive this ring system is, if Saturn had the same rings, they would be many times larger in diameter than the moon in the night’s sky. It’s not only that you could see it easily with the naked eye — it would pretty much dominate the view. All in all, the exoplanet boasts some 30-odd layers of rings.

“It’d be huge. You’d see the rings and the gaps in the rings quite easily from Earth,” said Matthew Kenworthy of the Leiden Observatory in the Netherlands, one of the co-authors on the paper describing the findings, at the time. “It’d be several times the size of the full moon.”

Maybe the size of its rings helped too because J1407b was the first confirmed case of an exoplanet with a ring system. So far, it’s also the only exoplanet with rings that we’ve spotted.

Still, in cosmological terms, such lush manes of rings do not last for long. Researchers expect them to get progressively thinner and disappear in the next several million years as new moons form from the sheer quantity of material zipping and zapping through J1407b’s rings. Compared to planets in our solar system, J1407b is also very young, at only about 16 million years old. The Sun and Earth are 4.5 billion years old.

So it might be just youthful energy that makes large ring systems possible. Right now, we simply don’t know. The methods we use to spot exoplanets (planets outside our solar system) aren’t very good at all at picking up ring systems — they can do it, but there’s a lot of luck involved.

For now, our best knowledge of planetary ring systems come from our neighboring planets. There may well be larger rings than those boasted by J1407b out there, but until we can get a better view into deep space — or, even better, make our way there — they will likely remain undiscovered.

Saturn.

Planetary rings are surprisingly chemically-rich, paper reports

Saturn’s rings are very chemically complex, new research shows, and actively change the makeup of the planet’s atmosphere.

Saturn.

Titan in front of Saturn and its rings.
Image credits NASA / JPL-Caltech / Space Science Institute.

Data beamed back from the Cassini spacecraft during its final descent into the depths of Saturn shows that the giant’s rings are more chemically complex than we’ve believed.

If you like it, study the rings on it

“This is a new element of how our solar system works,” said Thomas Cravens, professor of physics & astronomy at the University of Kansas and a co-author of the new paper.

Cravens is a member of Cassini’s Ion and Neutral Mass Spectrometer (INMS) team. Back in 2017, as Cassini plunged into Saturn’s upper atmosphere, it sampled the chemical makeup of points at various altitudes between Saturn’s rings and atmosphere using its onboard mass spectrometer.

The paper reports finding a surprising chemical complexity in the planet’s rings. This challenges the current view, based on past observations, that the rings “would be almost entirely water”, Cravens explains.

“Two things surprised me. One is the chemical complexity of what was coming off the rings — we thought it would be almost entirely water based on what we saw in the past. The second thing is the sheer quantity of it — a lot more than we originally expected.”

“the mass spectrometer saw methane — no one expected that. Also, it saw some carbon dioxide, which was unexpected,” Cravens explains. “The rings were thought to be entirely water. But the innermost rings are fairly contaminated, as it turns out, with organic material caught up in ice.”

The INMS-readings were performed in the gap between the inner ring and upper atmosphere. They uncovered the presence of water, methane, ammonia, carbon monoxide, molecular nitrogen, and carbon dioxide in the rings.

Dust grains from Saturn’s D (innermost) ring constantly rain down into the planet’s upper atmosphere, carrying a coating of this ‘chemical cocktail’. This process takes place at an extraordinary rate, the team adds — 10 times faster than previously estimated. This process is powered by the different spin rates of the planet and its rings (the rings spin faster than the planet’s atmosphere). Over time, this process likely changed the carbon and oxygen content of Saturn’s atmosphere.

“We saw it was happening even though it’s not fully understood,” Cravens adds. “What we saw is this material, including some benzine, was altering the uppermost atmosphere of Saturn in the equatorial region. There were both grains and dust that were contaminated.”

The findings not only shed light on the chemical complexity of planetary rings, but also raise important questions pertaining to their formation, lifespan, and interaction with the host planet.

For example, given the very high rate of material transfer to the atmosphere, it may be safe to assume that planetary rings are much more short-lived than previously estimated. In the absence of a source of fresh material to make up for this particle flow, rings may simply drain away into nothingness. One possibility that derives from these findings is that Jupiter likely also had its own set of fully-fleshed out rings, which gradually drained into the wispy trail that surrounds the gas giant today.

The origin of these complex materials is also of interest to astronomers; “[is material in the rings] left over from the formation of our solar system? Does it date back to proto pre-solar nebula, the nebula that collapsed out of interstellar media that formed the sun and planets?”

Finally, the team reports that this influx of matter also impacts the planet’s ionosphere by converting hydrogen ions and triatomic hydrogen ions into heavier molecular ions — thereby depleting the ionosphere of charged particles.

But Cravens’ main contribution involved interpreting that data with a focus on how materials from the rings are altering Saturn’s ionosphere.

“My interest was in the ionosphere, the charged-particle environment, and that’s what I focused on,” Cravens said. “This gunk coming in chews up a lot of the ionosphere, affects its composition and causes observable effects — that’s what we’re trying to understand now. The data are clear, but explanations are still being modeled and that will take a while.”

The paper has been published in the journal Science.