Earth’s final growth spurt
What led to water on the interior of the Moon or the formation of the Borealis basin that covers 40 percent of the surface of Mars? And what caused at least some of Earth’s tilt — without which there would be no change of seasons?New research from NASA’s Lunar Science Institute points to the same culprit: rocky bodies known as planetesimals that populated the solar system billions of years ago and eventually clumped together to form planets. As the planets and the Moon (which was created by a massive impact between a Mars-sized body and the young Earth) continued to cool several hundred million years after their formation, planetary scientists believe that planetesimals struck them again. Now scientists are one step closer to pinpointing the size of those rocky bodies that hit at the end of planet formation, a process known as accretion. Knowing this detail is important for understanding...