Earth's perilous journey through the Milky Way's spiral may shape the planet's geology
As Earth passes through the primary spiral arms of the Milky Way, thick interstellar clouds may hammer the planet with comets that have helped create the continental crust.
TroibNews 
As Earth passes through the primary spiral arms of the Milky Way, thick interstellar clouds may hammer the planet with comets that have helped create the continental crust.
