Hugh Pickens writes "Astrobiology Magazine reports that NASA's Spitzer Space Telescope has discovered something odd about GJ 436b, a planet about the size of Neptune located 33 light-years away, circling the star Gliese 436. The mystery? GJ 436b lacks methane, an ingredient common to many of the planets in our solar system. Methane is present on our life-bearing planet, manufactured primarily by microbes living in cows, and all of the giant planets in our solar system have methane too, despite their lack of cows. Spitzer was able to detect the faint glow of GJ 436b by watching it slip behind its star, an event called a secondary eclipse. As the planet disappears, the total light observed from the star system drops, and the diference is then measured to find the brightness of the planet at various wavelengths. Eventually, a larger space telescope could use the same kind of technique to search smaller, Earth-like worlds for methane and other chemical signs of life, such as water, oxygen and carbon dioxide. Adam Showman, a planetary scientist at the University of Arizona, says the 'provocative result' raises questions about the evolution of this planet, as well as the possibility that its atmosphere might represent an entirely new class of atmospheres that has never been explored."