Earth is the only planet we know of that has ever had a fire. While there may be volcanoes pushing out hot magma on the surface of Venus, the hottest planet in the Solar System, there has never been a fire there. Nor on Mercury, nor Jupiter, nor any of the other planets surrounding our or any other star.
In fact, for billions of years of the Earth’s history, there wasn’t any fire either. It took billions of years before the conditions for fire were possible, with the planet’s first inhabitants living in a world without fire for longer than it’s possible to imagine. While volcanos would have produced “fire fountains” like those likely produced on Io – and there may have been the odd flame from a gassy volcano belch – this is magma being forced up and sprayed out a vent, rather than actual fire.
Around 2.4 billion years ago, the Earth’s atmosphere was likely a thick haze of methane, the result of bacterial life emerging on the planet. Then the Great Oxidation Event happened, where ancient cyanobacteria began to produce energy from sunlight, releasing oxygen into the atmosphere. Here, molecular oxygen began to accumulate in the atmosphere for the first time, though still not in enough concentration for combustion to take place. The Great Oxidation Event, sometimes known as the Oxygen Catastrophe, likely plunged the Earth into a worldwide deep freeze as this oxygen destabilized methane, clearing it and collapsing its greenhouse effect. The Earth became cold, as well as fireless.
The first fossil record we have of fire comes from the Middle Ordovician period, billions of years later. In terms of fire, there is a sweet spot. Any lower than 13 percent oxygen, and plant matter will not combust. Any higher than 35 percent it will combust so well that forests would not be able to grow and sustain themselves.
In the Ordovician period 470 million years ago, the first land plants – mosses and liverworts – produced more oxygen, eventually creating enough concentration of it to inflict fires upon themselves. Eventually, around 420 million years ago, we have the first fossil evidence of fire on Earth, charcoal found in rocks from this period. However, with oxygen levels still fluctuating wildly, the first extensive wildfires didn’t take place until around 383 million years ago. And fires have been a real jerk ever since.
An earlier version of this article was published in October 2023.
Source Link: People Are Just Learning That For Billions Of Years, There Was No Fire On Earth
