Astrobiology includes the study of ways that astronomical events can influence the evolution of life on Earth. Alex Pavlov of the NAI University of Colorado team reports in two papers how passage of the solar system through dense cool clouds of dust and gas (called molecular clouds by astronomers) could influence the climate, producing extinctions and perhaps triggering the state known as “snowball Earth”. Much of this research was performed while Pavlov was a NAI postdoctoral fellow.