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When it comes to the greenhouse effect, timing is everything. The current warming of our planet is forecast to have dire effects on life. But a greenhouse effect when Earth was young may have been a boon for life.
When Earth was born, the Sun was fainter and cooler than it is today. That means Earth wouldn’t have received enough energy for liquid water to exist on its surface. Instead, any water would have been frozen solid. And without liquid water, it wouldn’t have been possible for life to take hold. Yet the geologic record of that early era suggests there was liquid water.
A recent study by researchers at the Southwest Research Institute proposed a possible solution to the problem: a steady bombardment of asteroids.
By looking at the craters on the Moon and Mercury, we know that the asteroids pounded the worlds of the inner solar system for several hundred million years. On Earth, those impacts vaporized the asteroids, spewing hot gas and rock into the atmosphere. They also created pools of molten rock on the surface.
The recent research says that the bubbling rock released a lot of carbon dioxide and other greenhouse gases into the air. That trapped more of the weak solar energy, warming the planet enough to melt the ice and create lakes and oceans. The impacts also delivered much of the chemistry of life.
So these powerful collisions might have created a powerful greenhouse effect — turning Earth into a comfortable home for life.