The sad magnetic state of the solar system’s rocky worlds
PLANETARY PROTECTION Earth’s magnetic field deflects charged solar particles toward the planet’s poles, generating auroras. This photo was taken from (and shows parts of) the International Space Station.
Above: NASA; Below, from top: NASA, JHUAPL, Carnegie Inst. for Science; JPL-Caltech/NASA; NASA; JPL-Caltech/NASA
A powerful global magnetic field envelops Earth in a cozy blanket of protection against bursts of solar particles (see “The magnetic mystery at the center of the Earth“). But the solar system’s other rocky worlds aren’t so lucky.
Mercury: Paltry
The most petite planet has an appropriately puny magnetic field, just 1.1 percent as strong as Earth’s (SN Online: 5/7/15).
Venus: Zilch
Earth’s nearest neighbor doesn’t generate a planet-wide magnetic field, so the solar wind penetrates and is gradually stripping away the atmosphere.
The moon: Lost
Magnetized lunar rocks hauled back by Apollo astronauts show that, at some point, the ancient moon had a hefty magnetic field. It has since died out (SN Online: 12/4/14).
Mars: Collapsed
The Red Planet lacks a global magnetic field today, but magnetized regions of Martian crust point to an ancient magnetic field that eventually fizzled.
