How strong is Mercury’s magnetic field compared with Earth’s?

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Messenger: Mercury — Mercury Mercury as seen by the Messenger probe, January 14, 2008. This image shows half of the hemisphere missed by Mariner 10 in 1974–75 and was snapped by Messenger's Wide Angle Camera when it was about 27,000 km (17,000 miles) from the planet.

Mercury’s magnetic field is significantly weaker than that of Earth, measuring only 1 percent as strong.1

Despite this difference in intensity, the two fields share structural similarities; both are roughly dipolar and aligned with their respective planet's axis of rotation. Most researchers believe Mercury's field is generated by a magnetohydrodynamic dynamo theory mechanism, similar to Earth's, involving fluid motions within the planet's iron-sulfur core.1

Because of its lower strength, Mercury's magnetosphere is much smaller than Earth's. Its sunward extent reaches only about 5 percent of the distance of Earth’s magnetosphere, and the solar wind can occasionally compress this boundary to the planet's surface.1