Neptune is the windiest world we know, so far out that noon there is a deep dusk. Under its blue sky lies a hot, dark ocean where it may rain diamonds.
For this trip you are indestructible. Nothing can hurt you. As you fall, we will tell you what a real body would be going through.
Scroll to fall
4,800 km above the clouds
On 25 August 1989, Voyager 2 skimmed past right about here, 4,800 km above Neptune's north pole. It had been travelling for twelve years.
It is still the only visitor Neptune has ever had. Everything below you, nobody has ever seen up close.
A real body: There's almost no air. The Sun behind you is just a very bright star.
50 km above the clouds
The sky turns a deep, glowing blue. A trace of methane gas soaks up red light, so only the blue is left.
This thin layer is one of the coldest places on any planet, colder than anywhere on Earth has ever been.
A real body: Minus 218 °C. Air this cold would freeze you solid in moments.
0 km down
You fall past bright white streaks of methane ice, high clouds that cast shadows on the blue deck below.
The winds here reach about 2,000 km/h, the fastest on any planet. Voyager saw a storm as wide as Earth, the Great Dark Spot, and five years later it was gone.
A real body: Earth-normal air pressure, but at −200 °C, in a wind faster than the speed of sound.
50 km down
Below the methane lies a deck of hydrogen sulfide clouds, the gas that makes rotten eggs smell.
It was found in Uranus's clouds in 2018, and Neptune is thought to have the same.
A real body: Five times Earth's air pressure, still far below freezing, and it would smell terrible.
250 km down
The light is fading fast. Deep down here are clouds of water ice, and storms grow inside them.
As Voyager flew past, it picked up faint radio crackles that scientists think came from lightning down in these clouds.
A real body: Dozens of times Earth's air pressure, like being deep under the sea. It's almost completely dark.
5,000 km down
There's no surface to land on. The air just gets thicker and thicker until it becomes a deep, hot fluid of water, ammonia and methane.
Scientists call this layer “ice”, but it's thousands of degrees. Only the crushing pressure keeps it from boiling away. Most of Neptune is this ocean.
A real body: A hundred thousand times Earth's air pressure and about 2,000 °C, hotter than lava.
7,000 km down
Down here, the pressure may be strong enough to rip methane apart. Its carbon gets squeezed into diamond, and the diamonds sink like hail.
In 2017, scientists fired powerful lasers at plastic, squeezing it for a split second, and saw tiny diamonds form. As the diamonds fall, they may even help warm Neptune from inside.
A real body: Hundreds of thousands of times Earth's air pressure. You're falling alongside the diamonds.
12,000 km down
Halfway down, water may turn into something strange. Its oxygen locks into a solid crystal while its hydrogen flows through it like a liquid.
That flowing hydrogen carries electricity, and it may be what makes Neptune's magnetic field. The field is tipped 47° from the way Neptune spins, and its centre sits far off to one side.
A real body: Around two million times Earth's air pressure. The water around you is hot enough to glow, and it's partly solid.
24,600 km down
You've reached the bottom of the farthest planet.
At its heart is a ball of rock and metal about as heavy as the whole Earth.
Neptune still holds heat from when it formed, and gives off more than twice the warmth it gets from the Sun. That hidden heat is what drives the winds far above you.
A real body: Seven million times Earth's air pressure and about 5,100 °C, close to the temperature of the Sun's surface.
Twenty-four thousand kilometres, through blue sky, a hot ocean and diamond rain. You made it.
You would fall forever. Neptune has no ground, just a deep blue sky that thickens into a hot ocean of water, ammonia and methane.
Near the cloud tops, winds blow at about 2,000 km/h, the fastest of any planet. Below, it gets dark, then hotter than lava.
Thousands of kilometres down, carbon may be squeezed into diamonds that sink like hail. At the centre is a rocky core about as heavy as the whole Earth.
No. Neptune has no solid surface. What scientists call its "icy" layer is actually a hot, dense fluid kept from boiling away only by the crushing pressure.
Neptune still holds heat from when it formed, and gives off more than twice the warmth it gets from the Sun. That hidden heat drives winds of about 2,000 km/h.
It may. Lab experiments in 2017 squeezed plastic with lasers and made tiny diamonds, suggesting the pressure inside Neptune can turn carbon from methane into diamond hail.
Only Voyager 2, which skimmed 4,800 km above Neptune's north pole on 25 August 1989 after twelve years in space.
