The mystery of Mars’ moon as strange structures found on “fearful” Phobos.
The European Mars Express spacecraft has looked deeper than ever into the subsurface of the Martian moon Phobos, finding hints of unknown structures that could be clues to the moon’s origin.
Mars Expresswhich is a 19-year veteran spacecraft in orbit around Mars, came within 51.6 miles (83 kilometers) of Phobos on September 22, 2022 and was able to probe beneath the surface of the Moon using updated software in its MARSIS instrument (Mars Advanced Radar for Subsurface and Ionosphere Sounding).
Understand the inner structure of Phobos could be key to solving the mystery of its origin. “We are still in an early phase of our analysis, but we have already seen possible signs of previously unknown features beneath the surface of the Moon,” said Andrea Cicchetti, who is a member of INAF’s MARSIS scientific team, l ‘Italian National Institute of Astrophysics, in a statement (opens in a new tab).
Related: How Mars’ moon Phobos had its grooves
March has two moons, named Phobos and Deimos after the gods of “fear” and “panic” in Greek mythology. Unlike the main moons of ours solar system, Phobos, and Deimos are small, only 16.7 miles (27 kilometers) and 9.3 miles (15 kilometers) in diameter, respectively. They have a composition similar to C-type carbonaceous asteroids and are irregular in shape asteroids also, which has led to suspicion that they are actually rogue asteroids captured by the gravity of Mars. However, both the orbits of Phobos and Deimos around the red planet lie above the equator of Mars, and both orbits are extremely circular, suggesting that they formed around Mars. If they had been captured, one would expect them to have more elliptical orbits in different planes.
“Whether the two small moons of Mars are captured asteroids or are made of material torn from Mars during a collision is an open question,” said Colin Wilson, who is a scientist on the European Space Agency’s Mars Express mission. , at the same time. statement (opens in a new tab).
MARSIS involves a 40-meter-long antenna that transmits low-frequency radio waves to the surface. Most radio waves are reflected directly from the surface, but some penetrate deeper, where they encounter transitions between layers of different composition and structure, and are reflected at these boundaries. The stronger the reflection in the resulting “radargram”, the brighter the radio signal it returns.
The radargram of a narrow track on Phobos shows a bright line, bisected and labeled A–C and D–F respectively. Section A–C was captured using the old MARSIS software for comparison with D–F, which uses the new software and shows much more detail. The main bright line is the reflection of Phobos’ surface, but below it there is evidence of fainter lines that could be just interference, or “clutter”, from surface features, but could also be caused by structures beneath the surface .
MARSIS had been designed to probe the interior of Mars from an orbital distance of more than 155 miles (250 kilometers), but the recent software upgrade allows MARSIS to operate at much closer distances, allowing its use during flybys near the moons
Getting even closer to Phobos will provide radargrams with even higher resolution than what is achieved here. The plan over the next few years is to take MARSIS up to 40 kilometers (24.9 miles) to Phobos.
“Mars Express’ orbit has been fine-tuned to get us as close as possible to Phobos during a handful of flybys between 2023 and 2025,” Cicchetti said.
Mars Express is not the only mission focused on Phobos. In September 2024, the Japan Aerospace Exploration Agency (JAXA) plans to launch the Mars Moon Exploration (MMX) spaceship Very similar to JAXA Hayabusa2 mission to retrieve samples from the near-Earth asteroid Ryugu, MMX will capture at least 10 grams of regolith from the surface of Phobos. MMX will also deploy a small rover on the surface, before venturing out to get a good look at Mars’ second moon, let’sand then return to Earth with the precious samples of Phobos that will be analyzed in the laboratories of the scientists here later land.
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