Sky & Telescope - February 2024 - 17

CLOUD PLUME A water-ice cloud streams some 600 km westward
of the volcano Ascraeus Mons. Before EMM, observations of these
early-morning plumes had been rare, because the ground tracks of most
Mars orbiters favor afternoon coverage. Hope, however, has seen a large
number of them.
craft came closer to Deimos was the Viking 2 orbiter in 1977.
Hope was able to map almost the whole moon with a
500 km
resolution of 10 meters per pixel. It has also given us our first
look at Deimos's farside. (Like Earth's Moon, Deimos only
points one face at its planet.) High-resolution spectroscopy
with EMUS and EMIRS revealed details of the moon's surface
composition and temperature, hinting that it's made of the
same stuff as Mars.
The origin of Mars's natural satellites - Phobos and Deidisturbed,
the solar wind interacts directly with the crustal
magnetic fields.
" It amazes me because just a different perspective can tell
you more about these phenomena in a better, informative
way that hadn't been possible before, " Al Matroushi says.
Deimos Flyby
Hope's wide orbit around Mars provided a unique opportunity
to attempt a flyby of Mars's outer moon, Deimos.
Deimos circles the Red Planet at a distance of just under
23,500 km, putting it near EMM's closest approach to Mars.
Flight engineers repositioned Hope's orbit without changing
the distance to the planet, so it could continue normal
science operations between flybys. The maneuver synchronized
the spacecraft and satellite orbits, enabling a series of
flybys approximately every two weeks. The closest approach
occurred on March 10, 2023, when the spacecraft was only
103 km away from Deimos' surface. The last time a spacemos
- has been heavily debated (S&T: Apr. 2021, p. 34). Since
both moons are extremely dark and have similar spectral
features to D-type asteroids, some researchers have argued
that they could be captured space rocks, trapped in Martian
orbit long ago.
However, it's very difficult for a captured asteroid to wind
up in a nearly perfect circular orbit like the moons both have.
Thus, scientists have imagined other theories for their origin,
most of them variations of a giant-impact scenario, in which
the impact launched enough material into space to form the
moons. While in some versions the moons coalesce directly
from the debris, in others one or several moons form first,
only to break down over time, giving birth to puny Phobos
and Deimos from their leftovers.
Hope revealed two important things about the composition
of Deimos. On one hand, the moon lacks carbon-rich
minerals, a mismatch with D-type asteroids. These asteroids
formed beyond Jupiter's orbit and are expected to be rich in
water, organics, and other volatiles. On the other hand, the
infrared spectrum of Deimos's surface seems similar to that
of basalt, a volcanic rock abundant on Mars.
sk yand tele scope .o r g * FEBRUARY 2024 17
EMIRATES MARS MISSION
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Sky & Telescope - February 2024

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