http://www.spaceflightnow.com/news/n0706/19planetlife/ This is something i actualy thought about, before i heard astronomers were pondering it. Looking at spectra from reflected light on extra solar planets to see if we can find absorption lines that relate to life. It could well be our first evidence of extra terestrial life comes hundreds of years before we ever see it with our own eyes. If we do find evidence of likely life its going to send speculation through the roof