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[Music]

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Early in its history, Mars had a
far more hospitable climate than

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the one that we see today, with
a thick atmosphere and abundant

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flowing water. So how did it
evolve from warm and wet to cold

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and dry? Since 2015, NASA's
MAVEN mission has been

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investigating this question by
studying the red planet’s upper

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atmosphere. Now, it has mapped
high-altitude global wind

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patterns at Mars for the first
time. During the closest part of

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its orbit, MAVEN skims through
the upper atmosphere, ingesting

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air molecules and determining
their composition with an

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instrument called NGIMS. MAVEN
can also rotate NGIMS back and

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forth to measure the air’s
velocity. These measurements

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provide a snapshot of windspeed
and direction along a track of

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MAVEN’s orbit. Because the orbit
evolves over time, or precesses,

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the spacecraft’s closest
approach to Mars drifts across

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the planet, allowing it to take
snapshots at different

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locations. Over the past four
years, MAVEN’s tracks have added

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up, crisscrossing Mars at many
locations and at various seasons

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and times of day, wrapping the
planet in a web of observations.

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The measurements reveal how the
winds vary with location, and

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evolve throughout the Martian
year. Now, scientists have used

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MAVEN data to build a global map
wind currents roughly 200

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kilometers above Mars: the first
time that winds have been mapped

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globally and at such high
altitude anywhere beyond Earth.

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Within the new map, scientists
discovered an unexpected

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feature: imprints of rugged
terrain far below. As an

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example, during two of its
orbits MAVEN saw winds above the

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Tharsis plateau diverting away
from elevated terrain, driven by

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giant shield volcanoes reaching
twice the height of Mount

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Everest. Here’s how the process
works: Down at the Martian

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surface, winds are forced around
and over obstacles when they

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encounter mountainous terrain.
Disturbances in surface-level

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winds also disturb the air
above, propagating up through

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the atmosphere as gravity waves.
When they reach the upper

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atmosphere, the gravity waves
block the high-altitude winds,

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causing them to alter course,
and allowing MAVEN to sense the

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presence of mountains and
valleys on the surface, while

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skimming the edge of space. High
above Mars, MAVEN is studying

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the upper atmosphere, and
reaching out to feel the breeze.

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It has now made the first
measurement of high-altitude,

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global circulation patterns,
and discovered a surprising

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connection to features on the
surface. These measurements also

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shed new light on ancient Mars,
with its thick atmosphere, and

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its warm, wet climate. By
revealing how the climate of

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Mars works today, MAVEN is
helping scientists piece

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together the early chapters of
its dramatic history.

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[Music]