Tracing path of carbon, scientists rewrite picture of early planet formation When people think about the most important ingredient for life on other planets, they usually talk about water. But there’s another element that makes our existence possible. “We’re carbon-based life forms,” said University of Chicago geophysical scientist Fred Ciesla, “and carbon is an important part of keeping a mild climate.” It can also be used as forensic tool to piece together how the earth and solar system must have formed. In twopapers, Ciesla and colleagues at California Institute of Technology, the University of Michigan and the University of Minnesota laid out a history of carbon in the formation of the solar system.