Sky & Telescope - February 2024 - 15

Since Mars rotates slightly faster than Hope, the craft's
instruments can watch global weather patterns as they
evolve. This information helps paint a complete picture of
the Martian atmosphere, complementing the more granular
views collected by closer-in satellites, such as ESA's ExoMars
Trace Gas Orbiter and NASA's MAVEN.
EMM also adds an unprecedented perspective to the
temporal dimension. Most missions around Mars have localtime-locked
orbits, passing above the same locations at the
same local time every orbit. " If you only had a weather satellite
on Earth that looked at 3 a.m. and 3 p.m., it'd be pretty
hard to tell you what was going on in the middle of the day, "
Edwards says. EMM can look at things like how water vapor,
dust, and water ice vary on a daily and seasonal basis. " That's
something that we haven't really had before. "
On the Shoulders of Giants
If going to Mars wasn't already an ambitious goal, Emirati
bigwigs imposed a stringent timeframe: The spacecraft had
to reach Mars before the country's 50th anniversary in 2021.
That gave the team a total of six years to plan, build, and
launch the mission, not including the nearly seven-month
cruise to Mars.
To save time and minimize risks, Emirati scientists decided
to play it safe and stick to what had worked in the past. They
established collaborations with international knowledge transfer
partners, as they call them, who could teach them how to
do new things. This strategy had served them before when
they launched a series of three Earth-observing satellites
between 2009 and 2018: The first two were co-built, then the
third was built domestically.
For EMM, the UAE Space Agency partnered with the
University of Colorado, Boulder; Arizona State University;
and the University of California, Berkeley, to develop the
spacecraft and its instruments, including many U.S.-based
researchers on the mission's science team (such as Edwards).
Also, rather than new instruments developed from scratch,
the observing tools onboard Hope are updated versions of
previous instruments successfully used in other space missions.
EMIRS is based on the Thermal Emission Spectrometer
(TES) included in the Mars Global Surveyor spacecraft and,
more recently, as the OSIRIS-REX Thermal Emission Spectrometer
(OTES). The Emirates Mars Ultraviolet Spectrometer
(EMUS) is a new riff on a two-element imaging spectrograph,
similar to previous instruments such as Cassini's UVIS but
updated to be the most sensitive ultraviolet spectrometer ever
sent to Mars.
Lastly, the Emirates Exploration Imager (EXI) is Hope's
visible-light and near-ultraviolet camera. It can capture highresolution
images and even 4K-quality video. Its design is similar
to other imaging systems, such as the Mars Color Imager
(MARCI) onboard NASA's Mars Reconnaissance Orbiter.
" EMM is standing on the shoulders of giants but looking
farther than anybody's seen before, " says Justin Deighan
(University of Colorado, Boulder), EMUS instrument lead
scientist and EMM's deputy science lead. " [It's] really pushing
the limits of what we know in a lot of areas and painting in
that coverage that we had just little glimpses of in the past. "
A Dynamic Atmosphere
EMM completed its first Martian year of science observations
in April 2023, and scientists have yet to distill all the results
from its seasonal coverage. However, it has already provided
new insights into the workings of the Martian atmosphere.
Specifically, it has improved our understanding of weather
circulation in the lower atmosphere, the mechanisms that
drive the upward transport of energy and particles, and the
subsequent escape of these atmospheric particles to space.
Solar radiation helps drive loss from the upper atmosphere.
It breaks down H2O and CO2 molecules, freeing oxygen and
hydrogen atoms, which sometimes shoot off to space, never
to come back. EMUS can see these atoms and how they are
spread throughout the extended corona around the planet.
Meanwhile, EMM provides a global view of the distribution
of dust, clouds, and water vapor across all times of day
and all seasons, and it does so simultaneously for the upper
and lower atmosphere, which is important for understanding
how these layers are coupled. This is particularly critical
for understanding how water from the lower atmosphere is
transported to the upper atmosphere, where it may break up
and escape.
" We are learning how these energetic atoms are made,
and how they get out of the thermosphere and into space, "
Deighan says. " A lot of the earlier missions, they're deeply
embedded in this corona - it doesn't matter where you look,
you're just seeing what's right in front of your face. "
Emirati scientists presented several findings related to
Martian weather at the 2023 EGU meeting in Vienna. Khalid
Badri (Mohammed Bin Rashid Space Centre), for example,
showed Hope data taken while monitoring several weekslong,
regional dust storms. The global coverage, combined
with hourly observations, enabled researchers to track the
amount of dust the storms mobilized and its distribution
to all longitudes, increasing the dust load over most of the
planet. These observations can be useful for understanding
the behavior of dust in the atmosphere, which is one of the
main drivers of atmospheric dynamics on Mars.
Meanwhile, Hope researchers are using the EXI instrument
to look at the cloud patterns across Mars during the
day, almost like a weather satellite. They have observed that
ice clouds tend to form early in the morning at low latitudes,
gradually dissipating by midday. Maryam Yousuf (Mohammed
Bin Rashid Space Centre) showed the seasonal and daily
variations of orographic clouds in the Tharsis Montes region.
Even on Mars, clouds can greatly influence ground temperatures
by reducing the amount of heat lost to space. Current
climate models, however, aren't very good at accounting for
clouds' effects. Researchers hope the new data will help them
improve those models.
While other missions have observed these processes before,
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Sky & Telescope - February 2024

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