Science News Roundup: Did asteroid that hit Australia help thaw ancient 'snowball Earth'?

Following is a summary of current science news briefs.

Hairy situation: Scientists explain how stress-related graying occurs

Marie Antoinette's hair turned white overnight, according to folklore, before she was executed by guillotine in 1793 during the French Revolution. The ill-fated queen embodied an extreme example of the phenomenon of stress-induced graying of the hair. The biological mechanism behind such graying had long remained a mystery. But researchers said on Wednesday they have figured out how it happens: it is driven by the body's "fight-or-flight" response to danger.

Did asteroid that hit Australia help thaw ancient 'snowball Earth'?

Scientists have identified Earth's oldest-known impact crater, and in doing so may have solved a mystery about how our planet emerged from one of its most dire periods. Researchers have determined that the 45-mile-wide (70-km-wide) Yarrabubba crater in Australia formed when an asteroid struck Earth just over 2.2 billion years ago. The collision occurred at a time when the planet was believed to have been encased in ice and the impact may have driven climate warming that led to a global thaw.