- 3752 - PHOBOS - exploring Mars moon? Mars Express, which is a 19-year-veteran spacecraft in orbit around Mars, came within 51.6 miles of Phobos on September 22, 2022 and was able to probe beneath the moon's surface using upgraded software on its “MARSIS” instrument (Mars Advanced Radar for Subsurface and Ionosphere Sounding).
--------------------- 3752 - PHOBOS - exploring Mars moon?
- See Review 3738 for more about moon Phobos and Review 3750 about the planet Mars.
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- Europe's “Mars Express” spacecraft has peered deeper into the subsurface of the Martian moon Phobos than ever before, finding hints of unknown structures that could be clues as to the moon's origin.
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- Understanding the interior structure of Phobos could be key in solving the mystery of its origin. We believe our Moon came from a collision between our Earth and another planetisimo. Mars’ moon Phobos was likely captured by a passer by asteroid that got locked into mar’s gravity
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- Mars has two moons, Phobos and Deimos, after the gods of 'fear' and 'panic' in Greek mythology. Unlike the major moons of our solar system, Phobos and Deimos are tiny, just 16.7 miles and 9.3 miles across, respectively. They have a similar composition to carbonaceous C-type asteroids, and are irregularly shaped like asteroids, which has led to the suspicion that they actually are rogue asteroids captured by Mars' gravity.
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- However, both Phobos and Deimos' orbits around the red planet are over Mars' equator and both orbits are extremely circular, which suggests they formed around Mars. If they had been captured, they would be expected to have more elliptical orbits in different planes.
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- Whether Mars' two small moons are captured asteroids or made of material ripped from Mars during a collision is an open question.
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- MARSIS involves a 40-meter-long antenna beaming low frequency radio waves down to the surface. Most of the radio waves are reflected directly back from the surface, but some penetrate deeper, where they encounter transitions between layers of different composition and structure, and are reflected back by these boundaries. The stronger the reflection in the resulting 'radargram', the brighter the returning radio signal.
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- A 'radargram' acquired by MARSIS during the flyby of Phobos on 23 September 2022 reveals the ‘echoes’ created when the radio signal emitted by MARSIS bounces off something and returns to the instrument. MARSIS had been designed to probe Mars' interior from an orbital distance of more than 155 miles, but the recent software upgrade allows MARSIS to operate at much closer distances, permitting its use during close fly-bys of the moons.
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- Getting even closer to Phobos will provide radargrams with even greater resolution than that achieved here. The plan over the next few years is to employ MARSIS as close as 24.9 miles to Phobos.
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- Mars Express isn't the only mission focused on Phobos. In September, 2024, the Japanese Aerospace Exploration Agency (JAXA) plans to launch the Martian Moon eXploration (MMX) spacecraft. Much like JAXA's Hayabusa2 mission to retrieve samples from the near-Earth asteroid Ryugu. MMX will capture at minimum 10 grams of regolith from Phobos' surface.
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- MMX will also deploy a small rover onto the surface, before venturing off to take a good look at Mars' second moon, Deimos, and then returning to Earth with the precious Phobos samples that will be analyzed in scientists' laboratories here on Earth.
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- November 13, 2022 PHOBOS - exploring Mars moon? 3741
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