Earth's collision with a Mars-sized body may have given it its life-essential volatile elements. Pictured: In this NASA handout, the umbra, or moon's shadow, passes over Earth during the total eclipse Monday, August 21, 2017. Viewing the eclipse from orbit were NASA's Randy Bresnik, Jack Fischer and Peggy Whitson, ESA (European Space Agency's) Paolo Nespoli, and Roscosmos Commander Fyodor Yurchikhin and Sergey Ryazanskiy. 

Photo: Getty Images/NASA