Old rocks hold on to their secrets. Now, a geophysicist at Michigan Technological University has unlocked clues trapped in the magnetic signatures of mineral grains in those rocks. These clues will help clear up the murky history of the Earth's early core.

The journal Earth and Planetary Science Letters published a paper on the subject earlier this year. Aleksey Smirnov, an associate professor of geophysics and adjunct associate professor of physics at Michigan Tech, led the study.

The work took him Down Under, where he drilled into rock outcrops in Australia's Widgiemooltha dike swarm that are more than two billion years old. Studying rocks this old--and extracting data from them--is tricky but helps unravel the core's mysteries.

However, Smirnov's findings created their own mystery: the magnetic readings were significantly larger than anticipated. This could have implications for early life on earth.