Show of hands: Who here was taught in school that the thing that differentiates Earth from every other body in our solar system is that it contains life?
How is that possible? Because: water!
And not just water, but LIQUID water!
We were taught that Earth was the only place in our solar system that could possibly have liquid water because of our atmosphere and the fact that we were the exact right distance from the sun. Any closer and the water would all evaporate in the extreme heat. Any farther and the water would all freeze in the extreme cold.
Fast-forward to modern day, where NASA can’t seem to stop finding water in our solar system!
For example, we’ve now determined there is water in the form of ice on the moon! How much? We’re not quite sure yet, but the two most likely answers are:
1.) Less than you’d find in a desert on Earth
OR
2.) Millions of tons
Those of you who are good at math may notice that there’s kind of a big disparity there. The problem is we just don’t know what’s lurking in the shadows of the moon on the surface, or in lava tubes.
It would be great if it was in the millions of tons because NASA is planning to make the moon a jumping-off point for longer missions, to Mars and beyond. NASA is even looking at constructing permanent structures on the moon. If liquid water and oxygen could be harvested out of ice already on the moon, that would make a sustainable presence there so much easier.
But the water doesn’t end with the moon! Name a planet in our solar system and the odds are good it has water!
Unless you picked Venus.
(Sorry, Venus, but you’re the odd planet out!)
Mercury may be the closest planet to the sun, but it is not the hottest planet. Venus holds that title, since its atmosphere traps a lot of heat, whereas Mercury’s thin atmosphere lets much of the heat dissipate. But Mercury’s north and south poles never face towards the sun, and so ice deposits have formed there, and NASA is pretty sure the deposits are frozen water. Now, these deposits aren’t anywhere as big as on Earth’s poles, but small deposits in shadowed areas of craters.
Because of its thin atmosphere, the surface of Mars also doesn’t retain much heat. It tends to be pretty cold, keeping any water on or near the surface of Mars frozen. However, we're pretty sure now that there are lava tubes on Mars, which could be a game changer! If the lava tubes run deep enough underground, they could hold liquid water, as there is the potential for warmer temperatures below the surface.
Moving on to Jupiter, an estimated 0.25% of Jupiter’s gaseous atmosphere is water molecules. Interestingly enough, Jupiter’s atmosphere does not appear to be an even mixture, so at certain spots, the water concentration could be higher than that.
Saturn doesn’t just have ice in its rings. There is also water in Saturn’s upper atmosphere. But here’s the crazy part: this water comes from a moon! One of Saturn’s known moons, Enceladus, shoots geysers of water vapor into space so far, that the some of the water actually ends up in Saturn’s atmosphere!
The biggest geysers on Earth are in Yellowstone, shooting up between 300-400 feet. Enceladus has geysers that reach more than 62 miles high (that’s 327,360 feet).
Here's an actual picture of Enceladus and it's geysers, taken by NASA's Cassini orbiter in 2017:
I've got to say it: That's no moon! It's a rocket-powered planet! (<- That's a Star Wars joke.)
Moving on!
Uranus is the least dense planet in the solar system, which might be because it is full of water! Between the icy surface and the rocky core, Uranus could be 80% or more liquid, with a mix of water, methane, and ammonia.
Neptune has water in its upper atmosphere, but we don’t know what’s down below. On Neptune, the temperature increases the further down you go in the atmosphere, possibly because it’s retaining heat from planetary formation. Some scientists believe Neptune’s surface could be an entire liquid ocean of water, despite being 30 times farther away from the Sun than Earth is.
And last, but not least, Pluto, which will always be a planet in my heart! We really don’t know much about Pluto because it is so far away from Earth. Here’s what we do know:
1. Discovered in 1930, Pluto hasn’t even completed one full orbit around the sun since we learned of it's existence, and it won’t in our lifetimes. It takes 248 years to complete a single loop. Could Pluto have seasons as it moves closer and further from the sun? We’re not sure!
2. It has mountains that are about as tall as the Rocky Mountains. How did they form? No one knows!
3. It got its name when an 11-year-old girl suggested naming it after the Roman god of the underworld. What the heck was wrong with that kid? I don’t know!
Some scientists believe that below the frozen surface of methane and nitrogen, Pluto could have an entire underground ocean of liquid water. This would be possible if, when the surface froze, it trapped gasses which now serve as insulation to keep the ocean from freezing.
And that's just planets! With over 200 moons in our solar system, how much more water is out there?
So much of this is still theory and conjecture, but every day we’re learning more and more about our neighboring planets and what we're discovering is even more incredible than we could have hoped!