Mars has a complex magnetic tail

Artist's concept of Mars' magnetic tail (Image Anil Rao/Univ. of Colorado/MAVEN/NASA GSFC)
Artist’s concept of Mars’ magnetic tail (Image Anil Rao/Univ. of Colorado/MAVEN/NASA GSFC)

During the 49th annual meeting of the American Astronomical Society’s Division for Planetary Sciences, the results were presented of a research that led to the discovery that the planet Mars has a magnetic tail, called magnetotail, twisted by the interaction with the solar wind. A team led by Dr. Gina DiBraccio of NASA’s Goddard Space Flight Center used data from the MAVEN space probe to discover this phenomenon that according to the researchers is linked to the process known as magnetic reconnection.

The Mars Atmosphere and Volatile EvolutioN (MAVEN) space probe reached the orbit of the planet Mars in September 2014 and during these three years has gathered data on the Martian atmosphere to understand how it got almost completely lost. According to Gina DiBraccio’s team, the process that allows part of the remaining atmosphere to get dispersed in space might be the same that’s generating a twisted magnetic tail.

This phenomenon is the consequence of the lack of a planetary magnetic field. Mars lost it a few billion years ago when its core cooled down and now there are only a few “fossil” magnetic fields left in some regions of the red planet. When these magnetic fields meet the ones brought by the solar wind and the latter are oriented in the direction opposite to the Martian magnetic fields, according to the researchers the process called magnetic reconnection happens generating the tail.

The presence of residual magnetic fields on Mars makes the planet a kind of hybrid between Earth, which has a planetary magnetic field, and Venus, which is completely devoid of magnetic field. The MAVEN space probe’s orbit changes its orientation with respect to the Sun all the time and this allows its magnetometer to conduct measurements in all regions around the red planet to build a map of its magnetic tail and its interaction with the solar wind.

The researchers built models that predicted that magnetic reconnection would cause Mars’ magnetic tail to twist 45 degrees. The data collected by the MAVEN space probe showed a good match with those models. That’s a confirmation of the magnetic reconnection as the cause of the tail’s generation but the researchers will keep on collecting the magnetometer data to see how the various magnetic fields still present on the red planet affect the tail during the planet’s rotation. This situation is very dynamic and complex also due to the continuous changes in the magnetic field transported by the solar wind.

The picture illustrates the complexity of Mars’ magnetic tail. The yellow lines represent lines of the magnetic field coming from the Sun transported by the solar wind. The blue lines represent the magnetic fields on Mars’ surface. The white “sparks” represent the magnetic reconnection activity. The red lines represent the magnetic fields derived from magnetic reconnection that connect the Martian surface to space via the magnetic tail.

Another exam that will be conducted by the researchers will be based on data collected by other instruments of the MAVEN space probe to see if the particles in the Martian atmosphere disperse in space in the same regions where magnetic reconnection processes are in progress. If that were the case, that would mean that the process contributes to the loss of the atmosphere and its contribution could be measured.

To understand the complexity of the processes around Mars, a space probe was really needed with the instruments suitable to carry out certain types of measurements. MAVEN is providing those measurements that are helping to reveal aspects of the red planet so far unknown.

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