To deal with the faint young Sun paradox, researchers are taking a fresh look at an old idea. Standard models predict that our Sun was much dimmer in its youth, but devising a way to keep the early Earth from freezing over has not been easy for climate modelers. An alternative solution is to assume our Sun started out a bit heftier (and therefore brighter) than expected.

“The faint young Sun presents us with a paradox because the predicted temperatures on Earth and Mars would have been too cold for liquid water,” explains Steinn Sigurdsson of Penn State University

Sigurdsson and his colleagues are tackling the problem anew. With funding from the NASA Astrobiology Institute, they will use improved computer models along with the most recent solar data to compare various scenarios, as well as look for possible signatures in the Sun that might reveal a “crash diet” in its past.