Prevalence of Earth-size planets orbiting Sun-like stars, Proceedings of the National Academy of Sciences (full article behind paywall)
"We find that 22% of Sun-like stars harbor Earth-size planets orbiting in their habitable zones. The nearest such planet may be within 12 light-years."
1 in 5 Sun-like Stars Has Earth-size Planet in Habitable Zone, UC Berkeley
"The research was funded by UC Berkeley and the National Science Foundation, with the assistance of the Keck Observatories and NASA."
NASA paywalls first papers arising from Curiosity rover, I am setting them free, Michael Eisen, UC Berkeley
"This whole situation is even more absurd, because US copyright law explicitly says that all works of the federal government - of which these surely must be included - are not subject to copyright. So, in the interests of helping NASA and Science Magazine comply with US law, I am making copies of these papers freely available here"
Keith's 5 Nov update: PNAS has finally made this paper available to the public free of charge. Its just baffling how NASA is unable to coordinate this sort of thing in advance rather than after the fact. Now, will NASA make a point of letting people know that this paper is online?