From astrobites: “What are Mars’ moons made of?”

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Astrobites

Jul 28, 2017
Kerrin Hensley

Title: On the Impact Origin of Phobos and Deimos I: Thermodynamic and Physical Aspects
Authors: Ryuki Hyodo, Hidenori Genda, Sébastien Charnoz, and Pascal Rosenblatt
First Author’s Institution: Earth-Life Science Institute, Tokyo Institute of Technology

Status: Accepted to The Astrophysical Journal, open access

Where did Phobos and Deimos come from?

Phobos and Deimos, Mars’ two small moons, were initially believed to be the result of interplanetary kidnapping. Many moons in the Solar System appear to be captured objects, and the featureless reflectance spectra of Phobos and Deimos hint that they might be D-type asteroids. However, captured objects tend to have highly eccentric orbits, and both Phobos and Deimos orbit Mars in a nearly circular fashion. More recently, it has been proposed that both moons are the result of a massive impact 4.3 billion years ago—instead of being captured from interplanetary space, they could coalesce from the debris disk generated by the impact. Past research [Nature Geoscience] has shown that the masses and orbits of Phobos and Deimos can be explained by this method. This theory could also explain the presence of Borealis basin, an extended low-altitude region spanning Mars’ north pole, which can be seen in Figure 1.

1
Topographical map of Mars. Borealis basin is the low-lying (blue) region in the northern hemisphere. It encompasses many officially-named regions, such as Vastitas Borealis and Utopia Planitia. Adapted from this image, which is made from data from the Mars Orbiter Laser Altimeter aboard Mars Global Surveyor.

See the full article here .

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