Solar Wind 'Stopped Blowing' On Mars For 2 Days
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
Credit: NASA Goddard Space Flight Center
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TechTranscript
00:00 Today, Mars is a cold desert surrounded by a thin wisp of air.
00:05 But its dry lake beds and empty river channels point to a warmer, wetter past maintained
00:11 by a thicker atmosphere.
00:13 Where did the ancient atmosphere go, and with it, the water?
00:18 To answer that question, NASA's MAVEN orbiter has been studying the upper atmosphere of
00:23 Mars since 2014.
00:25 Now, it has witnessed a rare phenomenon that was last seen more than two decades ago at
00:30 Earth.
00:32 Among MAVEN's suite of science instruments is the Solar Wind Ion Analyzer, which measures
00:37 electrically charged particles, or ions, surrounding Mars.
00:43 In this data visualization, yellow spikes indicate the velocity of charged particles
00:47 encountered by MAVEN along one of its orbital tracks.
00:51 The largest source of charged particles in the solar system is the Sun, which constantly
00:56 bombards the planets with a stream of electrons and hydrogen ions.
01:00 When this solar wind reaches Mars, it interacts with heavier ions in the planet's upper
01:05 atmosphere.
01:07 This creates a global magnetic field, or magnetosphere, that deflects the solar wind around Mars in
01:12 a bow shock.
01:14 MAVEN's science orbit is designed to probe these distinct regions in situ.
01:19 With each pass, it crosses through the magnetosphere, bow shock, and upstream solar wind, measuring
01:25 changes in ion velocity and density along the way.
01:29 On December 25, 2022, MAVEN encountered a sudden and dramatic decrease in solar wind
01:35 density.
01:36 As the pressure of the solar wind dropped, the Martian magnetosphere and bow shock ballooned
01:41 outward, engulfing MAVEN's orbit.
01:44 From the spacecraft's perspective, shielded beneath the bow shock, the solar wind had
01:48 disappeared.
01:50 In 1999, NASA's ACE satellite observed the same phenomenon at Earth.
01:56 The solar wind density dropped by more than 98%, causing our planet's magnetosphere
02:01 to expand to over five times its normal size.
02:05 These rare events occur when a fast-moving region of the solar wind overtakes a slower-moving
02:10 region, leaving a low-density void in its wake.
02:14 As quickly as the solar wind had disappeared from Mars, it returned on December 27 and
02:18 squeezed the magnetosphere and the bow shock back to their usual proportions.
02:24 MAVEN could once again feel the solar wind blowing across its instruments.
02:28 And it could continue to study how Mars had evolved from a wet, hospitable planet into
02:33 the cold, dry world we see today.
02:36 [MUSIC]