Comet C / 2013 A1 (Siding Spring)'s close encounter with Mars in October 2014 temporarily caused strong changes in the planet's magnetic field and atmosphere. This is reported by a group of scientists from the team of the Mars satellite MAVEN (Mars Atmosphere and Volatile EvolutioN - "Evolution of the atmosphere and volatiles on Mars").
The work was published in the journal, in addition, the results of the study can be found on the NASA website.
The researchers processed data from the MAVEN satellite, which has been exploring the Martian atmosphere since September 2014. In October 2014, Comet Siding Spring passed at a distance of 140 thousand km from the surface of Mars, which is almost three times less than the average radius of the Moon's orbit around the Earth. Fearing harmful effects on electronics, scientists during the approach to the comet were forced to turn off many of the spacecraft's instruments. Some instruments, including the magnetometer, continued to collect data at the very moment when Mars and the comet came close to each other at a minimum distance.
“The comet has turned the Martian magnetic field into chaos,” commented Jared Aspley, a member of the MAVEN team at the Goddard Space Flight Center. "Such a convergence blows away part of the upper layers of the Martian atmosphere, as is usually the case during powerful solar flares." Within a few hours, Mars completely entered the cometary coma - a cloud of gas and dust surrounding the comet's nucleus. The inner region of the coma almost reached the surface of the planet, and the magnetic fields of both celestial bodies were “entangled” with each other for several hours.
Unlike Earth, Mars is not protected by a strong magnetic field. However, Mars' atmosphere offers some protection. This is because its upper layers are plasma - ionized atoms of matter. When this plasma interacts with the solar wind, a weak magnetic field appears, which slightly protects the Martian atmosphere.
The MAVEN spacecraft continues to explore the Martian atmosphere. The new data will allow us to learn about the planet's climate in the past, as well as study the impact of solar flares on the atmosphere.