Solar Wind 'Stopped Blowing' On Mars For 2 Days

Space.com

For two days in the December the solar wind suddenly stop on Mars and its atmosphere on the sun-facing side swelled "by nearly four times its usual size — from its usual 497 miles (800 km) to over 1,864 miles (3,000 km)".  Credit: NASA Goddard Space Flight Center

Transcript

00:00Today, Mars is a cold desert surrounded by a thin wisp of air.

00:05But its dry lake beds and empty river channels point to a warmer, wetter past maintained

00:11by a thicker atmosphere.

00:14Where did the ancient atmosphere go, and with it, the water?

00:18To answer that question, NASA's MAVEN orbiter has been studying the upper atmosphere of

00:23Mars since 2014.

00:25Now, it has witnessed a rare phenomenon that was last seen more than two decades ago at

00:30Earth.

00:32Among MAVEN's suite of science instruments is the Solar Wind Ion Analyzer, which measures

00:37electrically charged particles, or ions, surrounding Mars.

00:43In this data visualization, yellow spikes indicate the velocity of charged particles

00:47encountered by MAVEN along one of its orbital tracks.

00:51The largest source of charged particles in the solar system is the Sun, which constantly

00:56bombards the planets with a stream of electrons and hydrogen ions.

01:00When this solar wind reaches Mars, it interacts with heavier ions in the planet's upper

01:05atmosphere.

01:07This creates a global magnetic field, or magnetosphere, that deflects the solar wind around Mars in

01:12a bow shock.

01:14MAVEN's science orbit is designed to probe these distinct regions in situ.

01:19With each pass, it crosses through the magnetosphere, bow shock, and upstream solar wind, measuring

01:25changes in ion velocity and density along the way.

01:29On December 25, 2022, MAVEN encountered a sudden and dramatic decrease in solar wind

01:35density.

01:36As the pressure of the solar wind dropped, the Martian magnetosphere and bow shock ballooned

01:41outward, engulfing MAVEN's orbit.

01:44From the spacecraft's perspective, shielded beneath the bow shock, the solar wind had

01:48disappeared.

01:50In 1999, NASA's ACE satellite observed the same phenomenon at Earth.

01:56The solar wind density dropped by more than 98%, causing our planet's magnetosphere to

02:01expand to over five times its normal size.

02:05These rare events occur when a fast-moving region of the solar wind overtakes a slower-moving

02:10region, leaving a low-density void in its wake.

02:14As quickly as the solar wind had disappeared from Mars, it returned on December 27 and

02:18squeezed the magnetosphere and the bow shock back to their usual proportions.

02:24MAVEN could once again feel the solar wind blowing across its instruments.

02:28And it could continue to study how Mars had evolved from a wet, hospitable planet into

02:33the cold, dry world we see today.

02:40NASA Jet Propulsion Laboratory, California Institute of Technology

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