Evrim Yazgin
Cosmos science journalist
NASA’s Mars Atmosphere and Volatile EvolutioN (MAVEN) mission observed a sudden disappearance of solar wind while in orbit around the Red Planet. The solar wind then resumed as normal 2 days later.
Solar wind is a constant stream of charged particles emanating from the Sun. The solar wind interacts with particles in the upper atmosphere and magnetosphere of planets like Earth and Mars.
On December 25, 2022, MAVEN’s measurements showed the number of charged particles in the solar wind dropped unexpectedly by a factor of 100. Without the pressure of the solar wind, Mars’s atmosphere and magnetosphere ballooned by thousands of kilometres.
Two days after Christmas, the solar wind returned to normal.
The last time such a phenomenon was observed was in 1999. While in orbit around Earth, NASA’s ACE satellite noticed a 98% drop in solar wind which lasted 3 days.
Such events occur when a faster-moving solar wind explodes out of the Sun, overtaking the slower moving wind. Acting like a broom, the faster wind sweeps and compresses the two regions together. In its wake, is a void of extremely low density solar wind.The latest NASA observations are the subject of a study being presented at the American Geophysical Union Fall Meeting in San Francisco this week.
“When we first saw the data, and how dramatic the drop in the solar wind was, it was almost unbelievable,” says lead author Jasper Halekas, professor at the University of Iowa. “We formed a working group to study the event, and we have found this time period to be rich with incredible findings.”
MAVEN is uniquely capable of observing both solar activity and the Martian atmosphere simultaneously.
“Observing extreme conditions is always scientifically invaluable,” says Shannon Curry, principal investigator for MAVEN at the University of California, Berkeley. “MAVEN was designed to observe these types of interactions between the Sun and the Martian atmosphere, and the spacecraft provided exceptional data during this truly anomalous solar event.”
MAVEN’s primary mission is to help scientists understand why Mars is dry and desolate.
Observations from Earth and on the Martian surface carried out by rovers suggests that the Red Planet was once wet, warm and had the building blocks of life. Along with Earth, it potentially had the right conditions to be a viable candidate for the evolution of life billions of years ago.
