Pioneering discovery by NASA’s MAVEN mission

NASAMAVEN’s spacecraft discovered a unique solar event that made a huge impact MarsAtmosphere, providing vital insights into the planet’s interaction with solar phenomena.

In December 2022, NASA’s MAVEN (Mars Atmosphere and Volatile Evolution) mission observed the dramatic and unexpected “disappearance” of a stream of charged particles constantly emitted from the Sun, known as the solar wind. This was caused by a special type of solar event that was so powerful, it created a vacuum in its wake as it traveled through the solar system.

As a result of this event, MAVEN measurements on Mars showed that the number of particles that make up the solar wind decreased dramatically. Without the pressure of the solar wind, the Martian atmosphere and magnetosphere expanded by thousands of kilometres. MAVEN is the only asset currently on Mars capable of simultaneously monitoring the Sun’s activity and the response of the Martian atmosphere to these solar influences.

“When we first saw the data, and how dramatically the solar wind had decreased, it was almost unbelievable,” said Jasper Halikas, a professor at the University of California, California. University of Iowa And the lead author of a new study on this event. “We formed a working group to study the event, and found that this time period was rich with amazing results.”

Learn about the “disappearance” of the solar wind on Mars witnessed by MAVEN – an event last seen nearly a quarter of a century ago on Earth. Source: NASA Goddard Space Flight Center

Understanding the disappearance of the solar wind

Mars, like all planets in our solar system, is constantly bathed in the solar wind. The solar wind exerts pressure on Mars’ magnetosphere and ionosphere, causing much of the atmosphere to escape. The December 2022 solar event was caused by fast-moving solar winds overtaking slower solar winds, which acted like a broom, sweeping up and pressing the two regions together. This interaction, called a stream interaction region, left behind a rare void of very low-density solar wind, which MAVEN observed. This “disappearance” of the solar wind led to some amazing interactions within Mars’ magnetosphere and ionosphere.

Consequences of the event

As the intensity of the solar wind decreased by a factor of 100, the pressure dropped and the planet’s magnetosphere and ionosphere were able to expand by thousands of kilometers – more than three times the typical size – and their character changed dramatically. The Sun’s magnetic field that would normally be contained within the Martian ionosphere was pushed outward, converting the ionosphere from a magnetized to a non-magnetized state. At the same time, the layer between the solar wind and the magnetosphere has become unusually quiet electromagnetically. MAVEN observations of this dramatic event and the subsequent transformation and expansion of the entire system are important for better understanding the physics that causes the loss of atmosphere and water on Mars.

“We have already been able to see how Mars responds when the solar wind is effectively removed,” Halikas added. “It represents a fascinating study of what Mars would be like if it orbited a less ‘windy’ star.”

This is an artistic rendering of NASA’s Mars Atmosphere and Volatile Evolution, or MAVEN, spacecraft orbiting Mars. Credit: NASA/GSFC

The importance of Maven notes

Disappearing solar wind events of this size are extremely rare and are produced at a time of increased solar activity, so this was the first time the MAVEN mission had the opportunity to observe such a phenomenon. While other Mars and Earth spacecraft have also observed aspects of this event, only MAVEN was able to take measurements of the Sun and the Martian atmosphere’s response to it simultaneously.

“Observing extreme conditions is always of invaluable scientific value,” said Shannon Curry, MAVEN’s principal investigator at MIT. 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.”

As the Sun moves toward solar maximum, the peak of its 11-year activity cycle, the MAVEN mission could have a greater impact on our understanding of extreme solar events.

Collaborative effort and future plans

“This really shows the cross-departmental role that MAVEN plays at Mars,” said Gina DiBraccio, MAVEN’s deputy principal investigator and deputy director of the Heliophysics Science Division at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “MAVEN not only monitors the dynamics of the Martian atmosphere, but also solar energy inputs to enhance our understanding of the Sun.”

The study is being presented at the fall meeting of the American Geophysical Union in San Francisco.

MAVEN’s principal investigator is based at the University of California, Berkeley, while NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the MAVEN mission. Lockheed Martin Space built the spacecraft and is responsible for mission operations. NASA’s Jet Propulsion Laboratory in Southern California provides navigation and deep space network support. The Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder is responsible for science operations management, public outreach, and communications. The MAVEN team is preparing to celebrate the 10th anniversary of the spacecraft’s arrival at Mars in September 2024.