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Updated 11:29 AM EDT, Tue, Jun 16, 2020

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NASA Reveals the Ancient Magnetic Field of Mercury

Goodbye, MESSENGER

(Photo : NASA) A depiction of the MESSENGER spacecraft is shown flying over Mercury’s surface above the bright orange Calvino crater.

The magnetic field of Mercury, closest planet to the sun, is almost 4 billion years old and may once have been almost as strong as Earth's, scientists say.

The data was accurately corrected by sending the Messenger in orbit in close proximity to the planet.

NASA's Messenger spacecraft discovery, which studied Mercury from orbit for four years before crashing into the planet's surface last week, will help in understanding more about how Mercury has evolved over time, they say.

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Its proof that Mercury is the only planet in the solar system other than Earth that possesses a global magnetic field generated by a shifting molten core of liquid iron, researchers say.

The new discovery has assisted scientists in combining together the history of the planet, which is situated at a distance of about 57,910,000 kilometers from the sun. Before the new discovery, scientists knew very few things about the planet.

"The mission was originally planned to last one year; no one expected it to go for four. 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,” said Catherine Johnson, a planetary scientist at University of British Columbia and lead author of the study.

The researchers have detected remnant magnetization in the crust of Mercury from orbital vector magnetic field measurements of the planet taken by NASA’s Messenger spacecraft at altitudes less than 150 km.

With the global magnetic field of Mercury, scientists were able to prove that the 2,440 km wide planet still holds a partly molten iron core that serves as a geodynamo to create the magnetic field.

Although relatively weak now, Mercury's magnetic field may have once been as much as 100 times as strong, equivalent to the Earth's magnetic field today, she says.

The slow evolution and weakening of the field can help in understanding Mercury's structure and composition and how they changed over time as the planet cooled after forming, the researchers say.

"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. This in turn helps us understand more about planetary evolution in general,” Johnson added.

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