Mars' strange magnetic tail is twisted

Magnetotail's unique orientation caused by interaction with the solar wind.
By Laurel Kornfeld | Oct 23, 2017
NASA's Mars Atmosphere and Volatile Evolution Mission (MAVEN), a probe that has been studying the Red Planet's atmosphere since 2014, discovered it has a unique, invisible magnetic tail that is twisted through interaction with the solar wind.

Gina DiBraccio of NASA's Goddard Space Flight Center in Greenbelt, Maryland, announced the finding at a press briefing held Thursday, October 19, during the 49th annual meeting of the American Astronomical Society's Division for Planetary Sciences in Provo, Utah.

MAVEN's primary goal is uncovering how the ancient planet lost most of its water and atmosphere, going from a world potentially habitable for life to the cold, dry, barren world it is today.

Mars' magnetic tail, also known as a magnetotail, is unlike those of either Venus or Earth, DiBraccio explained. Earth has a magnetic field that is generated internally, which protects the planet from the Sun's harmful radiation.

Venus has a magnetotail but no magnetic field at all. The Martian magnetotail seems to be a hybrid between those of Earth and Venus, she noted.

Based on MAVEN's observations and computer models, scientists believe Mars' magnetotail is twisted via magnetic reconnection, a process in which oppositely-directed magnetic field lines in a plasma break apart and then reconnect.

During that process, magnetic field energy is converted to plasma kinetic and thermal energy.

"Our model predicted that magnetic reconnection will cause the Martian magnetotail to twist 45 degrees from what's expected based on the direction of the magnetic field carried by the solar wind. When we compared those predictions to MAVEN data on the directions of the Martian and solar wind magnetic fields, they were in very good agreement," DiBraccio reported.

Today, Mars has only scattered remaining magnetic fields set in some of its surface regions. Scientists believe magnetic fields carried by the solar wind join these localized magnetic fields on the Martian surface to form the planet's magnetotail via magnetic reconnection.

This process may also enable charged particles or ions in Mars' upper atmosphere to flow down the magnetotail and escape into space, further depleting the planet's atmosphere.

Although magnetic fields are invisible, magnetometers like the one on MAVEN can detect their direction and strength. Because MAVEN constantly changes its orientation in relation to the Sun, it is able to measure all the regions around Mars and map its magnetotail and interaction between the magnetotail and the solar wind.


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