For decades, astronomers assumed that Mars was geodynamically dead — a planet without rumbling earthquakes and erupting volcanoes. Though remnants of towering volcanoes exist on the surface of the Red Planet today, these colossal structures have been dormant for millions of years. With little to no heat firing the planet's engine, scientists reasoned, Mars became dormant long ago. However, over the last five years, this assumption has been proven wrong. NASA's InSight mission has detected quakes and even evidence of recent volcanism around one Martian region, known as Elysium Planitia. And now, they think they know why this activity is...