The Day the Solar Wind Disappeared from Mars - Earth Came Across This Rare Phenomenon 24 Years Ago

Today, Mars is a cold desert surrounded by a thin wisp of air, but its dry lakebeds and empty river channels point to a warmer, wetter past, maintained by a thicker atmosphere. Where did the ancient atmosphere go, and with it, the water? To answer that question, NASA’s MAVEN orbiter has been studying the upper atmosphere of Mars since 2014. Now, it has witnessed a rare phenomenon that was last seen more than two decades ago at Earth. . Among MAVEN’s suite of science instruments is the Solar Wind Ion Analyzer, which measures electrically charged particles, or ions, surrounding Mars. In this data visualization, yellow spikes indicate the velocity of charged particles encountered by MAVEN along one of its orbital tracks. The largest source of charged particles in the solar system is the Sun, which constantly bombards the planets with a stream of electrons and hydrogen ions. When this solar wind reaches Mars, it interacts with heavier ions in the planet’s upper atmosphere. This cr