A planet on the sting: are Saturn’s rings older than they give the impression of being?

A debate concerning the age of Saturn’s resplendent rings has been raging for a number of a long time now, without end. A brand new examine by researchers on the Institute of Science Tokyo and the Paris Institute of Planetary Physics has recent spin to supply now that would recast the dialog.

Saturn’s rings are an arresting sight even by modest telescopes. The planet is made principally of hydrogen and helium whereas the rings are billions of items of principally bright-white water ice and rock. A few of these items are as small as a grain of salt; others are as massive as a home.

4 spacecraft have visited Saturn up to now, all launched by NASA: Pioneer 11 and the dual Voyagers 1 and a pair of flew by it whereas Cassini orbited Saturn from 2004 to 2017.

Unusually clear

Cassini specifically discovered the rings to be squeaky clear, with little or no filth. That is uncommon as a result of every thing within the Photo voltaic System, together with the earth, is consistently bombarded by darkish items of mud, every finer than a grain of sand. These particles are fragments of bigger chunks of rock in area.

Most of this particles burns up within the earth’s ambiance after they get too shut and by no means attain the floor.

Round Saturn, astronomers anticipated this darkish mud to be omnipresent within the rings, however this isn’t the case.

Based mostly on this, scientists hypothesised that Saturn’s rings are comparatively new, solely round 100 million years outdated — too younger to have gathered the mud.

This was a easy rationalization, which is sweet, however there’s a catch: scientists don’t know how the rings might have fashioned so lately.

Rings out of time

In these final 100 million years, the Photo voltaic System has been fairly calm.

“Within the very early phases of the formation of our photo voltaic system, round 4 billion years in the past, the system was chaotic and unstable,” Ryuki Hyodo, from the Institute of Science Tokyo, Chief Science Officer at Tokyo-based firm SpaceData Inc., and a coauthor of the brand new examine, mentioned. “Due to this fact there’s a higher probability of an enormous, dynamical occasion occurring then that would kind Saturn’s rings.”

“Crater measurement distribution is used to constrain the age of stable our bodies within the photo voltaic system,” Sean Hsu, a analysis scientist on the College of Colorado Boulder who wasn’t concerned within the new examine, added. “For Saturn’s rings, age dedication is much more tough — there are not any craters, and the collisional nature of ring particles erases most of its historical past. Relying on which measurements you select, it isn’t too shocking that folks find yourself with very completely different age estimates.”

“In my opinion, the ‘blind males and an elephant’ just isn’t a foul metaphor right here.”

Hold ‘em out

Within the new evaluation, Hyodo’s laptop fashions confirmed that when mud particles collided with ice in Saturn’s rings, they evaporated and dispersed into tons of of even smaller flecks, which Cassini had additionally noticed.

The fashions confirmed that these particles then smash into Saturn itself, beat the planet’s gravitational pull or are dragged into the planet’s raging ambiance. In different phrases, the pearly shine of Saturn’s rings just isn’t because of them being younger however as a result of they’ve a strategy to eject such overseas our bodies that enter their delicate world. In sum, there’s no motive for older rings to be darker (or vice versa).

In actual fact, the rings might be as outdated because the Photo voltaic System, in accordance with Hyodo.

“The fundamental assumption within the debate concerning the age of the Saturnian rings centres across the water ice composition of the ring particles,” Wing-Huen Ip, who research the origins of the Photo voltaic System and the formation of planets on the Nationwide Central College, Taiwan, and who was not part of the brand new examine, mentioned. “We really can’t be 100% positive that that is true.”

“Such an estimate is certainly questionable, as a result of we have no idea what the ring composition was when it fashioned,” Hsu mentioned.

The brand new findings had been printed within the journal Nature Geoscience in December 2024.

Europa, Enceladus, and past

Figuring out when Saturn obtained its signature rings isn’t only a matter of curiosity. “The curiosity in probing the age of Saturn’s rings is past the rings themselves — it’s concerning the implications, and there are numerous,” Hsu mentioned. “Enceladus, the geologically energetic moon of Saturn, is a top-priority goal to check habitability and astrobiology resulting from energetic plume exercise from its subsurface ocean. The evolution of Saturn’s rings has basic impacts on the evolution of Enceladus, and different icy moons of Saturn, as they’re dynamically coupled.”

Within the mid-2000s, Cassini discovered plumes considerable in water molecules leaking from Enceladus’s southern hemisphere. It additionally recorded proof of cryovolcanoes, icy promontories spewing hydrogen, salt crystals, water vapour and ice, and unstable compounds like ammonia. The vapour condenses into stable flakes, not not like snow on the earth, and drifts into certainly one of Saturn’s rings.

In 2014, NASA scientists reported discovering proof of a 10-km-thick ocean of liquid water beneath Enceladus’s south pole area in Cassini knowledge. Ip believes investigating how icy grains from the plumes of Enceladus have an effect on the ring’s composition might play a significant position in figuring out the ring’s age.

In associated information, NASA launched the Clipper mission to check Jupiter’s moon Europa, which is equally dynamically linked to Jupiter and accommodates a subsurface ocean as properly, in October 2024.

The brand new examine might additionally assist clarify why the Photo voltaic System’s 4 fuel giants have such various ring programs. Both they had been completely different by beginning or diverged as they grew. The dynamics unveiled within the examine might infuse recent perception into this debate.

“We could suggest to ship a spacecraft to Saturn’s rings to check them in additional element,” Hyodo mentioned.

Unnati Ashar is a contract science journalist.