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Current Affairs

Moon and Earth’s common magnetic field

Date: 17 October 2020 Tags: Space

Issue

 A new study suggests that our moon once had a magnetic field that helped shield our home planet from harmful solar radiation during a critical early time.

 

Background

The shared magnetic field situation, with Earth and Moon's magnetospheres joined, could have persisted from 4.1 to 3.5 billion years ago.

 

Details

  • The Moon seems to have presented a substantial protective barrier against the solar wind for the Earth, which was critical to Earth's ability to maintain its atmosphere during this time.

  • Scientists have long known about Earth's magnetic field. Thanks to studies of samples of the lunar surface from the Apollo missions, scientists figured out that the Moon once had a magnetosphere, too.

  • The new study simulated how the magnetic fields of the Earth and Moon behaved about four billion years ago.

  • Scientists created a computer model to look at the behaviour of the magnetic fields at two positions in their respective orbits.

  • According to the model, the magnetospheres of the Moon and Earth would have been magnetically connected in the polar regions of each object.

  • Importantly for the evolution of Earth, the high-energy solar wind particles could not completely penetrate the coupled magnetic field and strip away the atmosphere.

  • The extreme ultraviolet light from the Sun would have stripped electrons from neutral particles in Earth's uppermost atmosphere, making those particles charged and enabling them to travel to the Moon along the lunar magnetic field lines.

  • This may have contributed to the Moon maintaining a thin atmosphere at that time, too. The discovery of nitrogen in lunar rock samples support the idea that Earth's atmosphere, which is dominated by nitrogen, contributed to the Moon's ancient atmosphere and its crust.

  • Understanding the history of the Moon's magnetic field helps us understand not only possible early atmospheres, but how the lunar interior evolved.

  • If our Moon played a role in shielding our planet from harmful radiation during a critical early time, then in a similar way, there may be other moons around terrestrial exo-planets in the galaxy that help preserve atmospheres for their host planets, and even contribute to habitable conditions.