A new image captured by the Cassini space probe, which orbits Saturn, revealed a hole blown in the planet's outermost ring. A collision event with the ring has produced a temporary effect known as a “jet”.
The new image captures an event that is thought to have happened “relatively recently,” and was caused by a rogue body from within Saturn’s F ring itself, not from anything colliding with it from deep space. But how recent is “relatively” on these timescales and distances? (Saturn is 746 million miles away from us, and the Cassini is 1.4 million miles from Saturn.)
Turns out, very.
“Well, the collision itself happened within a day or so of when this image was taken,” on April 8, explained John Weiss, a ring scientist in Washington State, speaking over the phone.
“You get to expecting in planetary science for things to have happened millions of years ago and you don’t think to ever get to observe things actively happening," said Weiss. "But that’s the kind of funky thing with Saturn’s rings. You can actually see evidence of things that happened yesterday, or the day before.”
Cassini has been able to observe a regular number of these kinds of events, which is what makes Saturn an usual site of observation in our part of the universe. Weiss says that it happens to be observed "at least several times a year."
"There’s good evidence that there’s a lot of these sized bodies in the core of the ring itself, but you can’t normally see them because they’re covered by the dust cloud around them," he says. "But they’re in there, and every so often move across the ring space and blow a bunch of those dust particles out. This one was traveling faster than one meter per second."
Weiss says the cause of this particular collision was likely the gravitational effects of Saturn's potato-shaped moon, Prometheus.
"And maybe also Pandora. They stir up some of these bigger bodies so when they come by their orbit, the moons’ gravity give them little nudges and randomizes their speed and they come crashing through the ring. It’s a slow, cumulative effect that over time the moons will stir things up in the outer rings."
How and when Saturn’s rings formed is a point of intense conjecture among the planetary scientists who study them. They are known to be made up of trillions of particles, mostly consisting of water and ice mixed with some denser rock materials. They vary in size from tiny (micrometer scale) dust motes to pieces the size of houses. They are traveling around the planet at enormous speeds of thousands of miles per hour, differing depending on how close or far they are from the planet’s surface.
The rings are likely the result of a major collision event, or series of events, where comets or a long destroyed moon, or moons, of Saturn were violently torn apart and eventually settled into their now stable orbits around the planet in the configuration which is famed for its staggering beauty. While vast in their distances across (174,000 miles), the rings are only about 30 feet tall.
Theories point to their formation being a relatively recent event in cosmic time, because had the rings formed at the same time as the planets did in the early days of the solar system billions of years ago, they would have long been absorbed into Saturn’s mass by its immense gravity, burned up on their way down to its surface, and we would not be able to see them now. This would suggest that Saturn’s rings are instead only hundreds of millions of years old, making them young on a timescale stretching back to the dawn of the universe.
So had life evolved on Earth in a different time, human beings might never have seen Saturn’s ring at all, least of all developed the Cassini spacecraft with which to observe them.
When considering these mind-bending timescales, think of one of the most famous and beautiful images of deep space ever captured: the Pillars of Creation of the Eagle Nebula, 7000 light years from Earth. First photographed by the Hubble Space Telescope in 1995, they no longer exist, the image having been captured by peering into what is now the distant past. But if you want to see Saturn’s rings for yourself while they are still there to be seen, you can, even the most modest telescope in the right conditions will let you take a close up look at one of the most mysterious and stunning objects in our solar system.
Elmo is a writer with Real Future.