MESSENGER reveals Mercury's magnetic age

Data sent from NASA's MESSENGER spacecraft is enabling scientists to piece together how Mercury's magnetic field evolved over time.

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Even though the Sun from Mercury is up to 11 times brighter than we see on Earth, with temperatures reaching 450 degrees Celsius, MESSENGER remained at room temperature during its mission due to heat-resistant ceramic cloth
Credit: NASA/John Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Mercury’s magnetic field is almost four billion years old, according to data obtained by NASA’s MESSENGER spacecraft.

MESSENGER’s magnetometer collected data on the magnetism of the rocks on Mercury’s surface, revealing the planet’s field to be between 3.7 and 3.9 billion years old.

The spacecraft obtained the data in autumn of 2014 and early 2015, before purposely crashing into Mercury in the culmination of its mission on 30 April. It had been orbiting the planet since 2011.

To collect the data, MESSENGER flew low across Mercury’s surface at about 15km; much lower than previous years, when it flew at altitudes of between 200 and 500km.

“The mission was originally planned to last one year; no one expected it to go for four,” says Catherine Johnson, a University of British Columbia planetary scientist and lead author of the study. “The science from these recent observations is really interesting, and what we’ve learned about the magnetic field is just the first part of it. If we didn’t have these recent observations, we would never have known how Mercury’s magnetic field evolved over time.”

Mercury formed about 4.5 billion years ago, around the same time as Earth, and it was already known that the planet had a magnetic field much the same as Earth’s. It is the only planet apart from Earth in the inner Solar System to have such a field, caused by the motion of liquid inside its core.
 
MESSENGER left Earth in 2004, making its first Mercury fly-by in 2008 and then orbiting the planet from 2011 until the end of its mission.

 

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