Earth is the only place in the solar system where fire occurs.
Fire seems intrinsically linked to life on Earth. The fires of the Earth’s molten core formed the land we live on, forests are at their healthiest when they burn in a controlled manner to make way for new life, and even the legendary R&B group Earth, Wind & Fire paid homage to the stuff. In fact, Earth is the only place we know of where fire occurs. That’s because fire requires three things to exist: heat, oxygen, and combustible material. This “fire triangle” is only possible on Earth, as far as we know, because of the planet’s high levels of free oxygen. Travel to other planets and moons in the solar system, and there isn’t enough (or any) oxygen for fire to exist. As for the sun, which some people imagine as a giant ball of fire, it’s actually a giant collection of gas that glows thanks to the complex nuclear fusion occurring in its core.
While fire may not exist in any other place in the solar system (as far as we’re aware), that doesn’t mean humans can’t export the stuff. NASA has experimented with fire in microgravity for more than a decade — both to discover its behavior and also design fire-resistant space material. Turns out fire in microgravity behaves much differently, appearing more sluggish (likely due to low oxygen) and forming strange, orb-like flames. So while it’s not impossible for fire to exist beyond the confines of Earth, it’ll need a lot of help from future astronauts to export it to the moon, Mars, and beyond.
Human control of fire has come a long way since its ancient origins, and today scientists are hard at work trying to recreate the very plasma that fuses at the center of the sun. Known as nuclear fusion reactors, these incredibly complex machines could help humanity kick its diet of fossil fuels while simultaneously providing nearly limitless, clean energy. Fusion reactors do this by recreating the physics at the center of stars, but because Earth isn’t nearly as dense as a star, scientists must make machines that can get really, really hot. This heat helps particles overcome their natural resistances and fuse, forming a new element while releasing lots of energy. In 2022, a fusion reactor in South Korea recorded a scorching temperature of 100 million degrees Celsius, seven times hotter than the core of the sun. This reaction lasted for only 30 seconds, but within that half-minute, that terrestrially bound mini star was the hottest place ever recorded on Earth. This is only the beginning of how hot things will get — scientists estimate that when the International Thermonuclear Experimental Reactor, the world’s largest fusion reactor, goes online in 2025, it’ll eventually reach temperatures of 150 million degrees Celsius.
