They need our water. That’s a common explanation for why extraterrestrials invade the Earth. Roughly 70% of our planet is covered by water. Water is essential for life. If you break it into its component parts, you can use the Hydrogen atoms for fuel and breathe the Oxygen.
On the surface it seems to make some sense, or does it? Let’s accept that the aliens breathe Oxygen. While we’re at it, we’ll also ignore our understanding of physics as it relates to traveling between star systems. Water’s the key to life and Earth’s got plenty of it. So launch the invasion.
True it is essential for life, but it’s far from the only necessity. Four other elements are critical to the development of life as we know it. Carbon’s structure allows it to create complex three-dimensional molecules and structures. But Carbon can’t do it alone. It requires Nitrogen and Phosphorus to form the amino acids necessary for DNA and RNA. Finally, biochemical processes utilize Sulfur, which is the key element in hormones, vitamins, and many enzymes.
That’s all true, but that only supports the need to invade the Earth. They need it to power ships and replenish their Oxygen supply. So, as the only planet in our solar system with a surface ocean Earth’s the only viable source of water, right?
Well, as their invasion fleet approaches Earth it will pass through the Kuiper Belt. Similar to the Asteroid Belt between Mars and Jupiter, the Kuiper Belt is composed of thousands of objects. Unlike the asteroids which are made of metals and rock, belt objects are made of frozen ammonia, methane, and of course water. With ~100K objects larger than 100 Km in diameter, that should provide more than enough water for the aliens.
That requires another assumption to support the aliens need our water invasion trope. For whatever reason they’re incapable of melting ice. Despite their interstellar travel and their high-energy weapons, they need liquid water. Surely that’s a good enough set of conditions to bring their ravenous hordes to Earth, right?
It’s true that the Earth is the only planet liquid water on its surface, but it’s not the only planet with liquid H2O. In fact, the Earth represents only a small fraction of the liquid water in our solar system. Which brings us to our featured map courtesy of Yosuke Alexandre Yamashiki and his lab here’s a link to his page: Yosuke’s Website
To be fair it’s not strictly a map, but rather an infographic. The key is that while the Earth has 1.335 Billion cubic Kilometers of water, that’s only 2.72% of the estimated 64.42 Billion cubic Kilometers of water in the solar system.
Enjoy the story as the backward humans defeat the technologically superior alien invaders, but remember it’s not about the water.
As always thanks for reading and stay safe.
Armen
Note to pay the bills: The Warders series is a fantasy take on the action adventure trope. Think of it as a James Bond like thriller in a high fantasy setting. You can find a summary of the series here or find links to purchase books here.