— by Cristina Deptula

Gusts of solar wind regularly flow out of the sun at nearly a million miles per hour and permeate the solar system. Earth’s magnetic field protects us from most of this radiation, but other planets with less internal magnetism, such as Mars, are much more exposed.

In Chabot’s October enrichment talk, Dr. Matt Fillingim of UC Berkeley’s Space Science Lab discussed the interrelationships among magnetism, solar wind and the evolution of planetary climate over time. Convection within Earth’s inner molten core generates our internal magnetic field, which shields us from the solar wind and generates the aurora borealis near the north and south poles. Without this protection, solar radiation would likely prove destructive to our radio and television communications, GPS systems, power grids, satellites and aircraft, as well as our atmosphere.

Earth’s atmosphere generates enough pressure for water to remain liquid on our surface, which enables life as we know it to exist. Mars currently has an atmosphere only about one percent as dense as Earth’s, but the composition of some of the planet’s rocks suggests that liquid water once flowed there. So scientists speculate that Mars once had a thicker, more insulating atmosphere. In addition, while Mars does not have a planet-wide, global magnetic field the way Earth does, researchers sometimes observe small magnetic fields in the rock near the Martian south pole. This suggests the planet used to have a stronger field and likely a hotter core.

Dr. Fillingim and other researchers suggest that a large meteorite impact jolted Mars and allowed the interior to cool, weakening the global magnetic field generated by the molten magma. Then the solar wind drove away Mars’ atmosphere, leading to a planet too cold and dry for liquid water.

Atmospheric scientists can track the loss of a planet’s atmosphere by monitoring the amount of primordial argon present. Argon is an inert gas that doesn’t combine with other elements, so the only way primordial argon can be lost is through the dissolution of the atmosphere.

Also, many researchers are currently trying to model the precise mechanisms by which Mars’ atmosphere may have disappeared. The Mars Atmosphere Volatile Evolution Mission (MAVEN), a craft the size of a school bus and the weight of a SUV, sponsored by UC Berkeley, Lockheed Martin, JPL, and other research organizations, docked at the beginning of 2014. It carries instruments that should provide insights into this matter, including a solar wind electron analyzer and an ion analyzer.

To learn more about Dr. Fillingim’s work, click here: http://sprg.ssl.berkeley.edu/matt/

To learn more about the talks at the Chabot Space and Science Center, a museum and planetarium in Oakland, CA, please visit http://www.chabotspace.org

To learn more about the solar wind’s effect on Mars and other planets, please feel free to read this article in Physics World: http://physicsworld.com/cws/article/news/2004/sep/23/mars-attacked-by-solar-wind