[Music] Early in its history, Mars had a
far more hospitable climate than the one that we see today, with
a thick atmosphere and abundant flowing water. So how did it
evolve from warm and wet to cold and dry? Since 2015, NASA’s
MAVEN mission has been investigating this question by
studying the red planet’s upper atmosphere. Now, it has mapped
high-altitude global wind patterns at Mars for the first
time. During the closest part of its orbit, MAVEN skims through
the upper atmosphere, ingesting air molecules and determining
their composition with an instrument called NGIMS. MAVEN
can also rotate NGIMS back and forth to measure the air’s
velocity. These measurements provide a snapshot of windspeed
and direction along a track of MAVEN’s orbit. Because the orbit
evolves over time, or precesses, the spacecraft’s closest
approach to Mars drifts across the planet, allowing it to take
snapshots at different locations. Over the past four
years, MAVEN’s tracks have added up, crisscrossing Mars at many
locations and at various seasons and times of day, wrapping the
planet in a web of observations. The measurements reveal how the
winds vary with location, and evolve throughout the Martian
year. Now, scientists have used MAVEN data to build a global map
wind currents roughly 200 kilometers above Mars: the first
time that winds have been mapped globally and at such high
altitude anywhere beyond Earth. Within the new map, scientists
discovered an unexpected feature: imprints of rugged
terrain far below. As an example, during two of its
orbits MAVEN saw winds above the Tharsis plateau diverting away
from elevated terrain, driven by giant shield volcanoes reaching
twice the height of Mount Everest. Here’s how the process
works: Down at the Martian surface, winds are forced around
and over obstacles when they encounter mountainous terrain.
Disturbances in surface-level winds also disturb the air
above, propagating up through the atmosphere as gravity waves.
When they reach the upper atmosphere, the gravity waves
block the high-altitude winds, causing them to alter course,
and allowing MAVEN to sense the presence of mountains and
valleys on the surface, while skimming the edge of space. High
above Mars, MAVEN is studying the upper atmosphere, and
reaching out to feel the breeze. It has now made the first
measurement of high-altitude, global circulation patterns,
and discovered a surprising connection to features on the
surface. These measurements also shed new light on ancient Mars,
with its thick atmosphere, and its warm, wet climate. By
revealing how the climate of Mars works today, MAVEN is
helping scientists piece together the early chapters of
its dramatic history. [Music]