The Mars Express spacecraft has delved deeper than ever before, Mars’ moon Phobos, and found hints of unknown structures that could be clues to the moon’s origin.
Mars Express, a 19-year-old veteran spacecraft in orbit around Mars, flew 51.6 miles (83 km) from Phobos on September 22, 2022, and was able to study what’s under the moon’s surface using a program. Developed on its MARSIS instrument (Mars Advanced Subsurface and Ionosphere Radar).
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Understanding the internal structure of Phobos could be a key to solving the mystery of its origin.
“We are still at an early stage in our analysis, but we have already seen potential signs of previously unknown features under the lunar surface,” Andrea Cecchetti, a member of the MARSIS science team at Italy’s National Institute of Astrophysics (INAF), said in a statement. .
In 1877, American astronomer Asaph Hall discovered two small moons orbiting Mars, which were later named “Phobos” and “Deimos”, meaning “fear” and “awe”, respectively, among the Greeks.
The recent flyby of this larger Mars moon provided the perfect opportunity to test one of the spacecraft’s earliest upgrades.
The MARSIS instrument was originally designed to study the internal structure of Mars and as a result, it is designed for use at a typical distance between the spacecraft and the planet’s surface – more than 250 km.
But it recently received a major software upgrade that allows it to be used at much closer distances that could help shed light on the mysterious origin of Phobos.
Andrea said: “During this flight, we used MARSIS to study Phobos at a close range of 83 km. The approach allows us to study its structure in more detail and identify important features that we would not have been able to see from afar. In the future, we are confident that we can use MARSIS from a distance of more than 40 km. The orbit of the Mars Express was tuned to get us as close to Phobos as possible on a few flights between 2023 and 2025, which will give us great opportunities to try.”
“We didn’t know if this was possible,” said Simon Wood, a Mars Express flight controller at the European Space Agency’s ESOC Operations Center, who oversaw the uploading of the new software to the spacecraft. The final successful modifications to the spacecraft only hours before flight.”
MARSIS is famous for its role in discovering signs of liquid water on the Red Planet, and it sends low-frequency radio waves towards Mars, or “Phobos”, using a 40-meter antenna.
Most of these waves are reflected from the surface of the object, but some travel through it and are reflected at the boundaries between the different layers of material beneath the surface.
By examining the reflected signals, scientists can map the structure below the surface and study properties such as the material’s thickness and composition.
For Mars, this can reveal different layers of ice, soil, rock, or water. But Phobos’ internal structure is more mysterious, and an upgrade to MARSIS could provide important insight.
“The question of whether the two small Mars moons were captured asteroids or were made of material torn from Mars during the collision is open,” says Colin Wilson, ESA Mars Express scientist. Two asteroids, but the way they orbit Mars could say otherwise.”
The image obtained by the MARSIS instrument, a so-called radargram (a radar image of a mineral deposit or planetary surface), was produced during the flyby of Phobos on September 23, 2022.
The continuous bright line shows the echo of the moon’s surface. The bottom reflections are either “clutter” caused by features on the Moon’s surface, or, more interestingly, signs of potential structural features below the surface.
Across the narrow path on Phobos, radargram shows a bright line divided into two parts: called AC and D-F.
The AC section was captured using the old MARSIS software, while the updated software from the tool was used to capture the DF section, which shows much more detail, according to Carlo Nina, a MARSIS software engineer at Enginium, an engineering consultancy in Milan, Italy.