Outer Planets
Outer Planets
1,191 articles in this category.
Outer Planets
Titan is wider than Mercury, operates a complete methane weather cycle, and contains hundreds of times more liquid hydrocarbons than all Earth’s known oil and gas reserves. It is the only known world beyond Earth where you could stand beneath clouds beside a calm lake—provided you remained sealed inside a heated, oxygenated suit.
Outer Planets
At Enceladus’s south pole, the ice above its hidden ocean may be only one to five kilometres thick, compared with Europa’s newly estimated 29 kilometres. But a spacecraft might not need to drill through it at all: Enceladus already blasts material from its ocean into space, making the lesser-known moon our most accessible alien sea.
Outer Planets
Titan is the only place besides Earth with stable liquid on its surface, a working weather cycle and complex organic chemistry — and now, according to 2025 NASA research, a plausible mechanism for building the first membrane around a primitive cell, without liquid water involved.
Outer Planets
Two of Neptune's tiny inner moons contain clay minerals that could not have formed on worlds so small and cold — suggesting they're built from the exposed interiors of much larger moons shattered when the captured Kuiper Belt world Triton tore through Neptune's original satellite system billions of years ago.
Outer Planets
JWST found water-altered clay minerals on two of Neptune's tiny inner moons and its rings that probably formed deep inside much larger icy worlds — compelling evidence that today's moons may be rubble from Neptune's original satellite system, destroyed when the captured moon Triton tore through it billions of years ago.
Outer Planets
The idea that Earth is the Solar System's ultimate water world is misleading: Europa likely holds more than twice our ocean's volume beneath a crust of ice, while Enceladus is continuously venting material from its hidden ocean directly into space.
Outer Planets
James Webb has found patches of fresh crystalline ice on Europa that should be destroyed by Jupiter’s radiation in less than 15 days — meaning parts of the moon’s frozen surface are being renewed fast enough to keep replacing it, possibly offering clues to activity beneath the ice shell.
Outer Planets
Pluto's sky is blue, chunks of its water-ice mountains float like icebergs across glaciers of frozen nitrogen, and its moon is so large that the two worlds orbit a point in empty space between them — yet Pluto still hasn't completed a single trip around the Sun since humans discovered it in 1930.
Outer Planets
Titan is the only world besides Earth with an active liquid cycle: clouds form, rain falls, rivers carve channels and seas fill and evaporate — but the rain is liquid methane and the ground beneath it is water ice frozen hard as stone.
Outer Planets
In 1989, Voyager 2 measured winds up to 2,100 kilometres an hour circling an Earth-sized storm on Neptune; by 1994, when Hubble looked again, the storm had simply vanished, unlike Jupiter's Great Red Spot, which has raged for more than a century
Outer Planets
A real group of scientists and engineers spent two days in Boulder this June asking what it would actually take to send humans to Titan, and their honest answer was that it isn't a question of physics, it's a question of time, technology and commitment
Outer Planets
Titan is never the same distance from Earth twice: the gap can run from about 1.2 billion kilometres to nearly 1.65 billion depending on where both worlds sit in their orbits, stretching a signal's one-way trip from just over an hour to past ninety minutes
Outer Planets
Voyager 2 may have caught Uranus on a freak day — a 2024 reanalysis suggests the 1986 flyby that shaped four decades of understanding arrived during a compressed state estimated to occur only about 4% of the time
Outer Planets
After twelve years and more than seven billion kilometres, Voyager 2 arrived at Neptune within 100 kilometres of where it had been aimed — a margin NASA compares to sinking a golf putt 3,630 kilometres long
Outer Planets