Did Mars’s Magnetic Field Die With a Whimper or a Bang? ScienceNOW Daily News

Giant asteroids may have wiped out Mars’s magnetic field. The energy released by massive collisions upset the heat flow in the planet’s iron core that produced the magnetism, according to a new study. The finding offers a solution to the mystery of the disappearing magnetic field and sheds light on early Earth conditions.
A planet’s magnetic field results from a process called convection, Within the core, molten iron rises, cools, and sinks. The convection induces a magnetic field, in a system known as a dynamo.
Like Earth, early Mars had a magnetic field and perhaps an atmosphere conducive to liquid water. But magnetic analysis of the martian surface indicates that when Mars was a mere 500 million years old, its magnetic field withered away. Without this shield, streams of ionizing particles spewing from the sun strip away a planet’s atmosphere, killing any life that may have emerged or forcing it underground.