Did Snowball Earth's Melting Let Oxygen Fuel Life?

New Scientist ^ | 11-27-2006 | Jeff Hecht

[blam]

Did snowball Earth's melting let oxygen fuel life?

22:00 27 November 2006
NewScientist.com news service
Jeff Hecht

We may owe our green Earth to a big freeze that covered the entire planet in thick sheets of ice 2.3 billion years ago, researchers say.

As this “snowball” Earth thawed, the new theory goes, it released strong oxidants into the oceans and atmosphere for the first time, setting off the chain of events that led to oxygen-tolerant marine organisms and photosynthesis as we know it today.

The evolution of efficient, oxygen-based photosynthesis has been hard to explain. Primitive life forms garnered energy from sunlight, using it to free electrons from sulphur and iron in an oxygen-free environment.

Oxygenic photosynthesis, which involves freeing electrons from water to produce oxygen, requires more energy. But oxygen was deadly to most primitive life on Earth. “The first organisms to do this would die,” says Hyman Hartman at MIT in Boston, US.

Glacial surfaces

So how did organisms evolve oxygen tolerance? Hartman and colleagues decided to focus on the role of hydrogen peroxide (H2O2). Ultraviolet light from the Sun produces H2O2 when it hits water molecules.

Today, sunlight destroys the peroxide as it forms. However, if UV light penetrated the surface of a glacier, small amounts of peroxide would have been trapped in the glacial ice for long periods, they say.

Indeed, H2O2 has been spotted on Jupiter’s icy moon Europa. The surface of a terrestrial ice sheet would have been very similar on a primitive Earth that lacked an oxygen-rich atmosphere and a protective ozone layer.

Primitive organisms

A thaw would have dissolved the peroxide into the oceans and atmosphere,

[thatolkevin]

The evolution of efficient, oxygen-based photosynthesis has been hard to explain.

Indeed.

[the final gentleman]

Maybeso.

But I thought that Snowball Earth was a billion year frozen condition that covered the Earth until the end of the Precambrian - our first and biggest and best episode of worldwide Global Warming.

I could be wrong.

But, hey, so could they.

[mountainlyons]

Hey, that is not what science channel said. I wish they would get it straight.

[nonsporting]

The evolution of [efficient, oxygen-based] photosynthesis has been hard to explain.

Stop the presses.