NASA’s MESSENGER reveals Mercury’s ancient ‘Electromagnetic Field’

The four-year mission of Messenger at Mercury came to an abrupt end when last week when the NASA spacecraft had deliberately crashed on the surface of the planet. The enormous amount of data gathered by the spacecraft before its end is now helping scientists with answering questions about the solar system’s innermost planet in extraordinary details.

Scientists have been able to discover that Mercury, located 36 miles from the sun now possess a magnetic field dating back to almost four billion years, on the basis of magnetic field measurements taken by the Messenger at an altitude as low as 9 miles. The planet had been just 700 million years of age at that time, according to scientists. The findings have been published in the journal Science earlier this week.

The lead author of the study, Catherine Johnson, a planetary scientist at the University of British Columbia in Vancouver said in a statement, that, “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.”

Mercury’s magnetic field, similar to the one of Earth’s is considered to be generated as a result of the “dynamo effect,” that is caused by the circulation of liquid iron deep inside its core. Besides Earth, Mercury is the only planet to have such a magnetic field in the inner solar system.

For a long time now, scientists have known that the magnetic field of Mercury is similar to the Earth’s one although Mercury’s one is much weaker, but they had no idea how old this field was. The Messenger’s magnetometer had been able to detect trace signals of the magnetization in the crust when it flew close to the planet.

The scientists have been able to estimate the planet’s magnetic field to be very ancient, at least 3.7 billion go 3.9 billion years old by examining the number of impact craters for calculating the age of these regions on the surface.

Johnson said, “The strength of Mercury’s magnetic field may have ranged anywhere from its strength today to something about 100 times stronger, comparable to the strength of Earth’s magnetic field at Earth’s surface today.” The present-day magnetic field of Mercury is extremely weak, about 1 % the strength of Earth’s field.

Johnson concluded, “Being able to pin down how long Mercury has had a magnetic field helps us narrow down scenarios for the early history of Mercury and how it has changed over time.”