One of the Gas Giants, Neptune has a large rocky core that is surrounded by highly compressed water. The "surface" is an ocean of liquid hydrogen and helium.

Definitely not. Just like Jupiter, there's no surface to stand on... You'd have to swim around in an ocean of liquid hydrogen and helium. There's no oxygen to breathe or water to drink.

To escape Neptune's gravity and get out into space, a rocket has to travel at a speed of 52,800 mph or 23.6 km/sec. That's about 812 times faster than your parents are allowed to drive on a U.S. highway!

Triton is the only really decent sized moon. It was discovered way back in 1846. The other moons are pretty small, so no one could see them with a telescope back then.

In 1949, Nereid was discovered and it wasn't until our flying robot explorer, Voyager 2 flew by that the rest of the moons were seen for the first time!

Neptune has a pretty wild atmosphere. In 1989, one of our flying robot explorers, Voyager 2 took a close-up picture of a big storm on Neptune that we called the Great Dark Spot. (It was a lot like Jupiter's Great Red Spot.) In 1994, we took another picture on Neptune with our Hubble Space Telescope and the Great Dark Spot was GONE! (Jupiter's storm has been there for something like 300 years!)

We've also taken picture of clouds on Neptune that look similar to our cirrus clouds (like cotton stripes).

With Neptune and Uranus being so much alike, why does Neptune have storms and clouds and Uranus doesn't? Well, part of the reason is that Neptune is still contracting - this means it's getting smaller. Planets do this when they are forming. This contracting generates heat. Mixing this heat with Neptune's cold atmosphere causes all sorts of weather stuff like clouds and storms.

Here's the coolest thing: SCIENTISTS THINK THAT IT IS RAINING GIANT DIAMONDS ON NEPTUNE!! That's right - raining diamonds! A simulation of Neptune's atmosphere was recently done at University of California, Berkeley... and it produced diamond dust. So, they think with all the carbon in Neptune's atmosphere and the extreme pressure on that planet that it may be, literally, raining giant diamonds! We think that this is the absolute COOLEST thing in the entire solar system!

Sun | Mercury | Venus | Earth | Our Moon | Mars | Jupiter | Saturn | Uranus | Neptune | Pluto

Sources:
In Quest of the Universe, 2nd ed. by Karl F. Kuhn
Voyages Through the Universe, 2nd ed. by Fraknoi, Morrison and Wolff
Universe by Kaufmann
The Complete Idiot's Guide to Astronomy by Christopher De Pree and Alan Axelrod
The Astronomy Cafe by Sten Odenwald