interconnected relationship led to a trail of destruction.
When Galileo Galile turned his telescope
to Saturn in 1610, the first person in
history to do so, he was baffled. It
appeared as if the planet was sandwiched
between two very large moons. But when
he looked again 2 years later, they were
gone, only to reappear as what he
described as arms or handles another 2
years later. through his groundbreaking,
albeit crude, early telescopes, what
Galileo was actually witnessing was our
shifting perspective of Saturn's rings.
Because Saturn is tilted at 27°, its
rings angle towards Earth and then away
again as the gas giant orbits the sun.
When it appeared to Galileo that they'd
disappeared, he was viewing them
straight on. It took nearly 50 years for
telescope optics to improve enough for
astronomers to correctly identify the
strange structure. And in 1659,
Christian Huygens deduced that the arms
Galileo had described were in fact a
ring. He was also the first to identify
Titan, Saturn's largest moon. As
telescope technology continued to
improve, so did our view of the
surprisingly complex Saturnian system.
The French Italian astronomer Jean
Dominique Cassini soon discovered four
other major moons, Apotus, Ria, Tethus,
and Dioni. And in 1675, he was the first
to see a gap in Saturn's rings, now
known as the Cassini division. The next
big breakthroughs in our understanding
of the rings came in the 19th century,
including the work of James Edward
Keeler, [music]
who demonstrated that they could not be
solid uniform sheets, but were instead
composed of countless small particles,
each orbiting Saturn independently. But
it wasn't until the late 1970s that the
full intricacy and beauty of the system
[music] became clear. Pioneer 11 and the
Voyager probes changed our understanding
dramatically as with each mission came
greater resolution. By the time Voyager
2 flew past in August of 1981, it showed
for the first time that the A, B, and C
rings were actually comprised of
millions of smaller ringlets. And then
came Cassini. Orbiting Saturn for more
than a decade, it passed through the
gaps between the rings, skimmed their
edges, and for its closing act, plunged
between the [music] planet and the
innermost D-ring. The data it sent back
has revolutionized what we know of the
Saturn system. Not only painting an
extraordinarily detailed picture, but
telling a story that no one expected.
Saturn's rings are astonishingly thin,
between 10 m and 1 km thick. Yet, they
extend up to 282,000
km from the planet. Named alphabetically
in the order they were discovered. They
are called the D-ring, C-ring, B- ring,
A- ring, F- ring, G- ring, and E-ring.
And there is a final and very faint
Phoebe ring much further away in the
orbit of the moon with the same name.
The particles are kept in their orbits
by shepherd moons. Pan, Daphnes, and
Prometheus sit within the ring system
itself, while Pandora, Janice, and
Epimetheus sit just beyond the F ring.
Mimis, discovered by Hershel in 1789,
orbits further out, but exerts an
oversized level of control on the rings.
I've made another video on Mimis that
you can watch here if you want to find
out more. By the end of the Cassini
mission, Saturn's known moon count stood
at 62.
But the discoveries didn't stop there.
Advancements in groundbased telescopes
and recent surveys put the latest moon
count at a staggering 292.
and it's still rising more than any
other planet in our solar system. And as
a collection, they are extraordinarily
diverse. There are large regular moons
which orbit close to Saturn in the same
general plane and a whole host of
irregular moons that are much smaller,
more distant, and on eccentric orbits.
There are even tiny ring moons shaped
like ravioli as dust particles from the
rings accumulate around their equators.
You may wish you had a collection as
diverse and interesting as Saturn's.
This is a planet that knows how to
showcase its marbles, and you need to
bring your agame to be on its level when
it comes to home decorating. But that's
Now, [music] back to Saturn's collection. The Saturnian system is far
stranger than Galileo could have ever
imagined when he thought the planet had
handles. Cassini's measurements of the
rings also revealed what they're made
of, and that is 99.8%
water ice with particle sizes that range
from smaller than a grain of sand to as
big as a mountain. The reflectivity of
the ice crystals is what makes the rings
appear so bright, even from Earth, using
Galilean telescopes. Cassini data also
allowed scientists to calculate the mass
of the rings, around 16 quadrillion
tons. This sounds huge, but it's
actually less than 0.02%
the mass of our own moon. Combining
these two observations led to a
scientific bombshell of a question and
in turn a discovery.
Over time, micrometeorite impacts and
space dust pollute water ice and darken
it. So, why were Saturn's rings so
bright? The mass of the rings help
scientists determine how much dust would
be needed to contaminate them and thus
work out how long it would take to
darken them. The low ring mass implies
that they likely formed only 10 to 100
million years ago. That's the blink of
an eye in the 4.6 billionyear history of
the solar system and vastly different
from what was thought at the time. Until
this point, some scientists had believed
the rings were always there, that they
had formed alongside the planet.
Instead, dinosaurs had already roamed
the Earth for about 150 million years
before Saturn's rings were thought to
have formed. The question then becomes,
how did the rings get there? This
conundrum was first tackled by Edward Ro
in 1849, who explored why rings are only
found around the giant planets. He
suggested that the tidal forces between
moons and their planets, the same ones
that cause ocean tides here on Earth,
could become so strong that they could
overcome the gravity that holds a moon
together. If a moon came too close to a
planet, these forces would rip it apart,
its remnants spreading along its
original orbit to form a ring. He
calculated the minimum safe distance for
a moon's orbit as about 2.5 times the
planet's radius from its center. This is
known as the Rosh limit. For Saturn,
this is 87,000 km and aligns with the
location of the F ring. As the Cassini
data built, it became clear that
something catastrophic had happened in
the Saturnian system long after it was
formed.
In 2022, a team at MIT hypothesized that
the rings formed after the destruction
of an additional moon that orbited
between Apotus and Titan, which they
named Chrysalis. They proposed that
Chrysalis' orbit was disrupted by
Titan's gravity, causing it to be pushed
too close to Saturn. As it approached,
it was destroyed and the debris spread
to form the rings we see today. However,
when the scenario was modeled by
researchers at the SETI Institute, who
published their results in February of
2026, it was much more likely that
Chrysalis would have collided with Titan
rather than being pushed towards Saturn.
In this case, most of the debris would
have been captured by Titan's gravity or
lost from the system entirely. It
wouldn't have been able to form rings.
The team led by astrophysicist Matia
Chuk also noticed that in the Chrysalis
models, Hyperion, a small misshapen and
constantly tumbling moon, was more often
than not completely lost during the
upheaval process. But we can see
Hyperion is very much still there today.
And what's more, we know that its orbit
is locked with Titan. The Eureka moment
for Chuk was to recognize that this
Hyperion Titan relationship is
relatively young and dates to the same
period that Chrysalis would have
disappeared. Hyperion wasn't a simple
survivor of a shifting system, but a
result of it.
Chalk and his collaborators decided to
take a wider view of the Saturnian
system to explore how the rings might
have formed. This included Saturn's axle
tilt. I mentioned earlier that this is
about 27° as well as observations of its
many [music] moons. By approaching the
problem as an interconnected system
rather than looking at each phenomenon
in turn, they were able to simulate how
the events played out over hundreds of
millions of years. They concluded that
Titan likely did collide with an
additional moon, one that was four times
more massive than the proposed
chrysalis. They termed it protohyperion
since Hyperion had come out of the
event. Titan at this time was also
different, smaller and in a more
circular orbit than we observe today. In
their simulations, a protohyperion
prototitan collision occurred in 42
simulations out of 60. And in the runs
without a collision, either
Protohyperion or Apotus were ejected
from the system altogether. They
proposed that the collision happened 400
million years ago and it set in motion a
chain of events that can account for
many of our present-day observations.
So what actually happened? The team
traced the line of evidence back to a
time when Saturn slipped out of spin
orbit resonance with the other planets.
Resonance is when two orbiting bodies
fall into a repeated rhythm. They keep
meeting up in the same configuration and
over time tiny gravitational tugs from
each interaction add up amplifying their
influence over one another beyond what a
single encounter would allow. In the
case of Saturn, that small change was
enough to destabilize Protohyperion and
put it in a 21 resonance with
Prototitan, the strongest resonance
there is. For every orbit prototitan
made of Saturn, Protohyperion made two.
This caused Protohyperion to start
moving inwards quickly, not only setting
it on a collision course with
Prototitan, but yanking the orbit of
Apotus on its way and pushing Apotus
into a highly tilted orbit. Eventually,
the paths of the two proto moons crossed
and all hell broke loose.
The Titan we observe today is larger
than Mercury and is Saturn's biggest
moon. As the Cassini spacecraft passed
and delivered the aptly named Oygens's
probe to its surface, Titan was revealed
to be shrouded in a thick nitrogenrich
haze. Here, methane clouds rain down to
form flowing methane rivers. Its surface
geology also appears to be unexpectedly
young with few impact craters suggesting
it had been resurfaced in its recent
past. In Chuck's scenario, when
Prototitan cataclysmically collided with
Proto Hyperion, large portions of it
were resurfaced, smoothing over old
craters and giving it the lunar
equivalent of a facelift. A large
proportion of protohyperion merged with
Titan, but some of the remaining
fragments accreted to form Hyperion as
we know it today. The outcome for this
strange little moon in the simulations
is consistent with observations, most
strikingly that it seems to be only 400
to 500 million years old. Its irregular
shape and low density are consistent
with a body that formed from loosely
bound debris. Its chaotic rotation is a
result of the momentum of the collision.
Not long after its creation, it was
captured by Titan and the two are now in
a 43 resonance. As for Titan, the force
of the collision pushed it into a highly
elliptical orbit, a process that had
started as soon as it became resonant
with Proto Hyperion and accelerated
after the collision. As with our own
moon and Earth, tidal interactions are
pushing Titan away from Saturn. But
here's another twist. Cassini data
revealed this outward journey is
happening much faster than predicted at
a rate of approximately 11 cm a year. A
large collision as modeled by Chuck can
account for this. And the impact of the
newly enlarged Titan goes even further.
As its orbit changed shape and grew, it
swept through the Saturnian system,
wreaking gravitational havoc even on the
giant Saturn itself. As we've explored,
resonances between objects are hugely
important in space. And they don't just
occur when orbits align. They can also
link the orbit of one body to the spin
of another. Planets aren't perfect
spheres. The influence of the sun and
their moons flatten them into oblate
spheroids. This also causes them to
wobble as they spin on their axis like a
child's spinning top. This wobble is
called procession. Following the
collision, Titan's rapidly enlarging
orbit changed Saturn's procession,
causing it to wobble faster and faster.
This pushed Saturn's axle spin into
resonance with Neptune's orbit. The only
way that this lock could be maintained
as Titan continued to pull away was for
Saturn to tilt onto its side. Due to
their formation process, giant planets
are expected to have close to zero tilt.
So Saturn's 27°
has been a puzzling anomaly for some
time. This scenario modeled by the SETI
team is one of the most convincing to
date to explain it.
For around 200 million years or so, the
Saturnian system stabilized. But as
Titan's inexorable pull away continued,
it wasn't long before it caused more
damage. About 100 million years ago, its
orbit became locked into a 4-1 resonance
with one of two inner moons. This
relationship tilted Titan and shifted
the orbits of the inner moon pair,
leading to their collision. The force of
the crash and the tidal influence of
Saturn tore the inner moons apart,
producing vast amounts of debris. Over
time, some material accreted into new
moons, some was lost, and the rest
spread into the thin orbiting disc we
recognize as Saturn's iconic rings. That
is how they came to be, and that is why
they are so young.
And as this story comes full circle,
let's take stock. The tilted orbit of
Ipotus, the unusual age and shape of
Hyperion, Titan's thick atmosphere,
youthful surface, and its expanding
elliptical orbit, Saturn's tilt and the
way it wobbles on its axis, and of
course, the stunning rings. All part of
the same violent story, all driven by
Titan.
This model is the first to bring
together so many anomalous observations
of Saturn into a single scenario. It's a
bold idea, and what comes next is
whether it can be confirmed.
Thankfully, a new mission to the
Saturnian system is already in the
works. NASA's Dragonfly mission plans to
send a nuclearpowered car-sized rotor
craft to Titan. It will have the ability
to fly and land on the moon's surface,
collecting and analyzing samples from
multiple locations. Kitted out with an
array of onboard instruments to test
Titan's surface and atmospheric
chemistry, it has the potential to
provide evidence of historical
resurfacing. Scheduled to launch in
2028, it will reach Titan in late 2034.
Chuk and his co-authors concluded their
astonishing paper with a nod to this
future mission. They note that even if
the specific sequence of events they lay
out is not confirmed, they think their
work can frame new hypothesis about the
evolution of Saturn's complex satellite
system. To me, that underlines something
central to the scientific process. None
of the underlying physics in this
remarkable study is new. Resonance,
procession, and tidal forces are all
very well understood. But what the team
have done is show us how elegantly
interconnected these processes can be.
As for Saturn's rings, Cassini's last
act was to dive repeatedly through the
gap between its clouds and inner rings
before finally plunging into the planet
itself. These observations revealed that
the rings are constantly [music]
changing. Individual particles jostle
one another and many fall into Saturn's
atmosphere as a steady rain of ice up to
40 tons every second. The constant loss
of material implies that the rings may
only last for a few hundred million
years more. The Saturnian system has
been dubbed a dynamicist paradise and
its interconnected evolution continues
to play out. What might it look like in
another 100 million years? As it turns
out, we're quite lucky to be here at the
right time to see its rings at all.
daily life while supporting future
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