WEBVTT FILE

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Today, Mars is a cold, dry world

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with a tenuous atmosphere
only 1% as thick as Earth's.

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But in the ancient past, water flowed
freely across the Martian surface,

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maintained by a thick, early atmosphere.

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Since it first arrived at the Red Planet
in September 2014,

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NASA's MAVEN spacecraft has been studying
how that atmosphere was lost to space -

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and with it, the water. Now, as MAVEN
continues its mission, we can look back on

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its many remarkable discoveries
during its first ten years

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at Mars.

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[Music]

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In 2015,

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MAVEN observed the solar wind
eroding the Martian atmosphere.

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The solar wind is a stream of electrically
charged particles blowing from the sun.

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MAVEN watched as ions from the Mars
upper atmosphere

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were accelerated by the solar wind’s,
magnetic field and driven into space,

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confirming that this process
has deeply eroded the Martian atmosphere.

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In 2017, MAVEN showed that a
process called

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“sputtering” has had an even greater effect
on the atmosphere.

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When ions from Mars get picked up
by the solar wind’s magnetic field,

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they can crash into neutral atoms
at the top of the atmosphere,

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sputtering them into space.

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MAVEN measured

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present-day isotopes of argon,
which can be removed only by sputtering,

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to determine that 65% of the noble
gas has been lost over time.

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This allowed scientists
to estimate the escape of other gases

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and determine that sputtering has been

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the primary mechanism
driving the atmosphere into space.

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Later in 2017, MAVEN revealed

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a twist in Mars's invisible magnetic tail.

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When the sun's magnetic fields reach Mars,
they pile up and wrap around the planet,

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creating an induced magnetic field
that is drawn out behind Mars

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like a comet's tail.

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The Martian crust also contains
small pockets of its own

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early magnetic field,
which rotate along with the planet.

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MAVEN discovered
that when these two fields interact,

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they put a twist in the magnetotail,
confirming model predictions.

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In 2018, a runaway series of dust storms

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created a dust cloud
so large that it enveloped the planet.

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During this global dust storm,
MAVEN observed an abrupt, unexpected spike

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in the amount of water
in the upper atmosphere.

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It discovered that heating from dust
storms can loft

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water molecules
far higher into the atmosphere than usual,

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leading to a sudden surge
in water lost to space.

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Later in 2018, MAVEN

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announced the discovery
of a new type of aurora at Mars.

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The mission had previously observed
auroras during solar storms

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after electrons from the sun struck
the upper atmosphere,

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causing it to glow with ultraviolet light.

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MAVEN's 2018 discovery was the first
observation of a Mars proton aurora.

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When protons from the solar wind
pick up electrons

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from the Martian ionosphere,
they can slip through the planet's

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bow shock and plunge into its upper
atmosphere, causing widespread auroras.

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On Earth, proton auroras are isolated
near the poles,

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but on Mars they can bathe the dayside
in ultraviolet radiation.

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In 2019,

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MAVEN produced the first map of wind
currents in the Martian thermosphere,

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revealing disturbances in
high-altitude winds

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caused by terrain features
on the surface.

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MAVEN sensed these disturbances
as it skimmed through

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the upper atmosphere,

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feeling the imprint of mountains
and valleys far below.

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In 2020, data from MAVEN
led to the creation of another new map

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showing the Martian atmosphere's electric
current systems for the first time.

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MAVEN detected these currents
indirectly,

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by observing the solar wind’s magnetic
field lines drape around the planet.

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Mapping the electric current systems
can help scientists

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to better understand
the forces that drive atmospheric escape.

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In 2022, MAVEN watched

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as the solar wind unexpectedly
disappeared from Mars.

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The event occurred
when a fast-moving patch of the solar wind

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overtook a slower-moving region,
leaving a void in its wake.

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In response, the Martian magnetosphere
ballooned

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outward by thousands of kilometers,
engulfing MAVEN's orbit

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and causing the solar wind
to temporarily disappear from view.

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In 2022 and 2023,
MAVEN captured stunning ultraviolet

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images of Mars when the planet was near
opposite ends of its elliptical orbit.

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The first image was taken
when the southern hemisphere

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was in summer, which coincides with Mars's
closest approach to the sun.

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Canyons and basins are covered
with a thin haze

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of ozone, indicated by a tinge of pink.

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The second image was taken
during northern spring,

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after Mars had passed its furthest point
from the sun.

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White clouds hint at rapidly
changing conditions in the northern polar

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regions, while deep magenta signals a
buildup of ozone during the frigid winter.

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In 2024, MAVEN

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observed the aftermath of an X-class
solar flare,

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the strongest type of eruption
from the sun.

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The flare was quickly followed by a burst
of charged particles crashing into Mars,

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leaving black and white streaks on images
taken by NASA's Curiosity rover.

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MAVEN watched from above as auroras
lit up the planet

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in a brilliant display
of celestial fireworks.

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[Music]

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In its first decade
at Mars, MAVEN has vastly expanded

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our understanding of the Red Planet
and its climate history.

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Today, it continues to be a
critical member

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of NASA's fleet of robotic explorers,
observing

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the interaction between the solar wind
and the Martian atmosphere

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and providing a window
into the ongoing evolution of Mars.

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[Music]