Alan Boyle writes:NASA's secret is finally out: Researchers say they've forced microbes from a gnarly California lake to become arsenic-gobbling aliens. It may not be as thrilling as discovering life on Titan, but the claim is so radical that some chemists aren't yet ready to believe it. If the claim holds up, it would lend weight to the idea that life as we know it isn't the only way life could develop. Organisms with truly alien biochemistry could conceivably arise on a faraway exoplanet, or on the Saturnian moon Titan, or even here on Earth. "Our findings are a reminder...