Science!: iPads and Dolphins

Lauren Admire | 7 Jun 2010 21:00

Earth's "Fractal Haze" Allowed Life to Develop

Got a few minutes? Try cracking this conundrum:

Three billion years ago, life began to arise on Earth. However, the sun was nearly 30 percent dimmer than it is today, meaning that our planet was likely covered in ice. These conditions aren't too favorable for the first signs of life to emerge, so there must have been another factor at work to make sure that life as we know it didn't freeze.

Carl Sagan tried solving this puzzle - twice, in fact. The first time, he proposed that an ammonia atmosphere could have trapped heat, only to find out later that UV radiation would have broken down ammonia. His second guess - a thick nitrogen-methane mix that also trapped heat, but blocked the UV rays - also failed, since the haze particles would have blocked visible light as well, effectively leading to a dead Earth.

Now, new scientists have stepped up to the plate and suggested a hydro-carbon haze, where particles protected potential life from harmful UV rays but also allowed visible light to come through. The result is a fractal haze, "an aerosol haze opaque enough to block the shortwave ultraviolet radiation that would have hindered or prevented life from arising," explains researcher Eric Wolf. "At the same time, it would have proven transparent enough in longer, visible wavelengths to let them keep the atmosphere warm and the planet wet enough for life to emerge. "It's surprising that molecules with complex shapes could make such a difference."

If this theory flops as well, there's another to take its place. In April, scientists suggested that Earth had fewer landmasses than previously believed. Fewer land masses means less reflected light, which means more heat absorption.

There's no reason that the two theories can't work together, though:

"Rather than being an alternate explanation to last month's theory about how Earth stayed warm under a faint young sun, the newly proposed haze layer may actually be a complement to it," says Wolf. "Researchers who conducted that study didn't include a haze layer, which probably would have helped keep their darker world warm enough to prevent water at Earth's surface from freezing. Future research could clarify the issue."

Source: Discover Magazine


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