I certainly agree with John that this is a very significant development, but I’m not sure it is quite so epic-making. For one thing, this was life created (or rather evolved) in a Petri dish. It was the ancestors of these bacteria who came from the ghastly waters of Mono Lake and had evolved there to be arsenic-tolerant. See this report in the Wall Street Journal:
The bacteria were dredged from the briny sludge of California’s Mono Lake, where the water is richly laced with arsenic and with bacteria that can survive in it. In the lab, the researchers grew the bacteria in Petri dishes in which phosphate salt normally essential for life was gradually replaced by arsenic, until the bacteria could grow without needing phosphate.
We have been finding life in places no one thought it could exist — such as hot springs in Yellowstone that sometimes exceed the boiling point of water, the tar in Pitch lake in Trinidad, and near “black smokers” many thousands of feet beneath the sea — for decades. These last organisms are completely independent of what was long thought to be another sine qua non of life: the energy of the sun, either directly, as in plants, or indirectly, as in animals. These “extremophiles” testify to the enormous power of evolution to create organisms that can exploit almost any environment.
The environmental movement has been the propaganda engine behind the ludicrous idea that life is delicate, a bunch of butterflies that can only thrive in a benign — and preferably human-free — environment. In enviro-speak, every ecosystem is a fragile one, every species threatened. In fact, of course, life is tenacious in the extreme and both can and will evolve as necessary and rebound from abuse with surprising speed.
I think the true eureka moment will come when we find an exoplanet (one that orbits a star other than the sun) that has a large percentage of molecular oxygen in its atmosphere. That moment might come soon. Before 1995, we knew of no exoplanets and could only speculate as to how many, if any, existed. Today we know of more than 500 and the number is growing rapidly. It will soon explode, thanks to the Kepler Space Telescope, designed specifically to find them. We are not yet able to analyze their atmospheres, but we will, at least in some cases, be able to soon.
And when we find one with lots of free oxygen, it will be headlines around the world. Why? Because oxygen is chemically very reactive, forming molecules with abandon. So it doesn’t hang around in the free state very long. Earth is the only place we know where there is lots of free oxygen (about 20 percent of the atmosphere). And the reason is that earth teems with plant life that absorbs carbon dioxide, uses sunlight to crack it, builds more plants with the carbon, and spits out the oxygen. We animals then exploit the oxygen (and the plants). Such a find won’t prove the existence of non-earth life, but it would be a powerful piece of evidence for the proposition, one that would cause a surge of scientific investigation such as we haven’t seen since the Manhattan Project.
And of course, finding Earth-like life won’t rule out in any way planets with utterly alien biologies, built on molecular structures we cannot even dream of. Since we don’t know their signatures (such as free oxygen), however, finding them will be a long time coming (assuming they don’t land in Central Park and ask — politely one hopes — to be taken to our leader).
My guess is that life, Earth-like or otherwise, exists wherever conditions allow it to. After all, it arose here on Earth almost as soon as things settled down enough to make it possible.