Many aspects of Saturn’s rings captivate human imagination like few others can, yet astronomers are discovering that their lifespan may be shorter than previously anticipated.
Research published earlier this month in Science Advances and Icarus journals suggests that Saturn’s rings are relatively young compared to their cosmic peers; likely having existed for no more than 100 million years.
What is it?
Astronomers have long debated the age and source of Saturn’s iconic icy rings. While some think they formed through collisions between destroyed moons or comets and Saturn later on in its life cycle, others argue they formed in its original nebular material which formed it all along. Now thanks to NASA’s Cassini mission which orbited it from 2004-17 scientists have an increased understanding of when exactly these iconic icy rings formed.
Research published May 15 in Icarus Journal hints that Saturn’s rings may only be several hundred million years old by cosmic standards, with tons of mass steadily being shed each year from their orbit around Saturn. Two other recent studies published this month in Science Advances and Icarus reached similar conclusions, giving astronomers a good picture of their lifespan.
Saturn’s rings are composed of water ice particles ranging in size from microscopic dust grains to boulders several yards (meters) wide. Tiny shepherd moons orbit near the edges of Saturn’s rings to prevent them from expanding too widely or colliding with it; some energy from solar wind also provides support. These shepherd moons help maintain orbital velocity for their own purposes as well.
Micrometeoroids and solar radiation from Earth cause small disturbances that electrify and bind icy particles together into magnetic field lines in Saturn’s rings, creating spiral paths that spiral inward toward Saturn as gravity pulls on it – this process, known as ring rain, results in particles dissolving into clouds on Saturn and falling back down again as raindrops.
Scientists have observed ring rain for decades, and the Cassini mission allowed them to more closely track its effects. Cassini’s cameras captured glowing bands of ionized water crossing through Saturn’s ring plane; these so-called H3+ ions have three protons and two electrons and can easily be detected as they emit infrared light emission – making their impact visible even on dark nights on Saturn.
Scientists measured ring rain to assess how much ionized water was entering our planet from interstellar space. When they compared this figure with estimates of how much water there is within each ring, they discovered they were approximately equal; which indicates the mass loss was being evenly dispersed across them all.
Why are they losing their rings?
Saturn’s iconic rings will soon disappear from view – something which will come as quite a shock. This cosmic spectacle will occur on March 20, 2025 when Earth and Saturn align perfectly along their line of sight, lasting only weeks at most.
But that doesn’t spell doom: instead, Saturn’s rings will gradually fade as they succumb to Saturn’s gravitational pull in a process called ring erosion. Saturn’s rings consist of billions of pieces of ice and rock smaller than a grain of sand or larger than mountains that make up this system, including material escaping into Saturn’s atmosphere via Cassini; this process makes them less obvious over time but will continue as part of the cycle’s lifecycle.
Cassini scientists have successfully tracked and understood the causes of ring erosion, as well as its processes. They think the rings may be losing mass through two main mechanisms: fragmented moons falling into them; and the planet itself shedding icy debris onto their surfaces – both contributing to erosion; however, ice erosion appears to be faster and more significant.
There are various theories regarding how moons that reside within Saturn’s rings came to exist, with one popular theory suggesting a small moon got too close and was torn into pieces as it approached Saturn, then this debris eventually formed its rings systems, though how long these moons have existed remains unknown.
Astronomers have also long debated the age of Saturn’s rings, with some experts suggesting they have existed for billions of years and others citing data from Cassini that suggests otherwise. While no definitive answers exist here, it seems reasonable to assume they formed relatively recently on an intergalactic scale and thus saving humanity from having no rings whatsoever.
How long will they last?
Saturn’s rings are an exquisite tapestry of ice, rock and dust. Scientists believe their formation resulted from broken moons, comets and fragments of an once larger moon colliding into Saturn’s orbit and being pulled in. Astronomers study them as cosmic treasure troves that provide insight into how our solar system was born and why planets formed in particular places in space.
Scientists don’t yet have an exact time frame for when Saturn’s rings will disappear, though one theory indicates they might last 300 million years or less. One explanation could be due to Saturn’s rotation causing “ring rain”, draining enough water from each second that it drains to fill an Olympic swimming pool in half an hour according to NASA scientists’ new research.
Astronomers believe this ring rain, in combination with gravity, will draw Saturn’s rings into its atmosphere and cause them to combine with gas particles in its atmosphere to form H3+ ions that glow in infrared light and can cause irreparable damage and erosion to Saturn’s rings.
But the ring rain may also help slow the rate at which Saturn’s rings dissipate. Icy particles in its rings are constantly collapsing into smaller clumps that eventually combine together into larger aggregates that may withstand erosion for longer, according to research published in Science.
Saturn’s day lasts 10.7 hours, keeping its rings constantly moving; similar events occur on other planets in our solar system with shorter days; scientists hope to monitor this process with JWST and Keck telescopes, keeping track of ring rain on Saturn and other planets as well as learning more about how their rings became massive and are currently dissolving.
When will they disappear?
Saturn’s stunning rings have long held human fascination. But according to new research, their stunning beauty may no longer be with us for long.
Stargazers with basic telescopes can easily turn their devices towards Saturn to admire its breathtaking ring system composed of billions of chunks of ice and rock. But in March 2025, Saturn will move so its rings temporarily disappear from view – an event known as an equinox which occurs every 13-16 years when its orbital plane shifts such that thinnest parts are directly facing Earth.
However, this event won’t only occur every few decades; similar phenomena also take place on March, September and December of every year as well as other occasions depending on the tilt of rings’ orbital planes.
The rings resemble giant tree rings.
Saturn has an icy outer layer, protected by an outer belt of ice and rock particles held together by gravity and sunlight, but they’re not indestructible; sunlight and micrometeoroids can break them down, or they may be pulled in by its gravity into a dusty rain of ice and water that rains from above into its gravity, eventually dissipating back out to form its rings as this “ring rain” evaporates and reacts chemically with its atmosphere causing them to disintegrate and fade over time.
Sun radiation speeds the process, disrupting and electrifying icy ring particles before sending them spiralling toward Saturn’s magnetic fields, creating wakes which deposit them deep within Saturn’s atmosphere where gravity pulls them in as they evaporate away – scientists estimate this ring rain drains enough water per half hour to fill an Olympic swimming pool!
Astronomers have observed this phenomenon as an accelerator of the rings’ decline and an obstruction to observation; their brilliance diminishing and becoming harder to see from different positions, making astronomers eager to develop ways of seeing them from new vantage points. They’re working on ways of doing exactly this!