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 emanating off the Sun, known as the solar wind. This was caused by a special type of solar event that was so powerful, it created a void in its wake as it traveled through the solar system.
Learn about the “disappearance” of the solar wind
at Mars that was witnessed by MAVEN – an event last seen nearly a
quarter-century ago at Earth.
Credit: NASA’s Goddard Space Flight Center
Download high-resolution video and
images from NASA’s Scientific Visualization Studio.
Due to this event, MAVEN’s
measurements at Mars showed that the number of particles making up the solar
wind dropped significantly. Without the pressure of the solar wind, the Martian
atmosphere and magnetosphere expanded by thousands of kilometers. MAVEN is the
only asset currently at Mars able to simultaneously observe both the Sun’s
activity and the response of the Martian atmosphere to these solar influences.
“When we first saw the data, and
how dramatic the drop in the solar wind was, it was almost unbelievable,” said
Jasper Halekas, professor at the University of Iowa and the lead author on a
new study on the event. “We formed a working group to study the event, and we
have found this time period to be rich with incredible findings.”
Mars, like all the planets in our
solar system, is constantly immersed in the solar wind. The solar wind exerts
pressure on the Martian magnetosphere and ionosphere, and drives much of the
escape of the atmosphere. The solar event in December 2022 was caused by
faster-moving solar wind that overtook slower moving solar wind, which acted
like a broom, sweeping and compressing the two regions together. This
interaction, called a stream interaction region, left behind a rare void of
extremely low-density solar wind in its wake, which was observed by MAVEN. This
“disappearance” of the solar wind led to some incredible interactions within
Mars’ magnetosphere and ionosphere.
As the density of the solar wind
dropped by a factor of 100, it caused the pressure to decrease and the
magnetosphere and ionosphere of the planet were able to expand by thousands of
kilometers—more than tripled the typical size—and dramatically changed in
character. The Sun’s magnetic field that typically is embedded within the
Martian ionosphere was pushed outwards, which transformed the ionosphere from a
magnetized to unmagnetized state. At the same time, the layer between the solar
wind and the magnetosphere became unusually electromagnetically quiet. MAVEN’s
observations of this dramatic event and subsequent transformation and expansion
of the whole system is important to better understand the physics that drive
atmospheric and water loss at Mars.
“We are really getting to see how
Mars responds when the solar wind is effectively removed,” Halekas added. “It
makes for a great outlier study on what Mars would be like if it were orbiting
a less ‘windy’ star.”
Disappearing solar wind events on
this scale are extremely rare and are produced at a time of increasing solar
activity, so this was the first time the MAVEN mission had the opportunity to
observe such a phenomenon. While other spacecraft at Mars and Earth also
observed aspects of this event, only MAVEN was able to simultaneously take
measurements from both the Sun and the Martian atmosphere’s response to it.
“Observing extreme conditions is
always scientifically invaluable,” said 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.”
As the Sun moves toward solar
maximum, the peak of its 11-year activity cycle, the MAVEN mission could have
an even bigger impact on our understanding of extreme solar events.
“This really shows the
cross-divisional role that MAVEN plays at Mars,” said Gina DiBraccio, MAVEN
deputy principal investigator and deputy director of the Heliophysics Science
Division at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “MAVEN
is not only observing the dynamics of the Martian atmosphere, it is also
monitoring solar inputs to enhance our understanding of the Sun.”
The study is being presented at the
American Geophysical Union Fall Meeting 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 managing science
operations and public outreach and communications. The MAVEN team is preparing to celebrate the
spacecraft’s 10th year at Mars in September 2024.
Willow Reed
Laboratory for Atmospheric and Space Physics at the University of Colorado
Boulder
Source: NASA’s MAVEN Observes the Disappearing Solar Wind - NASA
