weird-satellites

Here are excerpts from an article in The new York Times concerning The Two Mars satellites.

What’s all the fuss about? For many, the desire to visit Phobos and Deimos was galvanized by their deeply mysterious nature. “They’re super weird, confusing and interesting,” said Abigail Fraeman, a planetary scientist studying Mars, Phobos and Deimos at NASA’s Jet Propulsion Laboratory.

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We don’t know where the moons came from because they look like asteroids foreign to the red planet but behave like byproducts of Mars’ early, impact-laden history.

Phobos, being larger and closer to Mars, can be seen in greater detail: a misshapen mess scarred by a large crater and multiple grooves that look like they were made by a cosmic cat’s claws.

 “They check all of the boxes that are consistent with them being these captured asteroids,” said Dr. Fraeman — rubbly patchworks that drifted too close to Mars long ago and became trapped in the planet’s orbit.

But both moons orbit the equator in a neat-and-tidy circular fashion, which suggests they coalesced from a disk of debris that danced around a young Mars. It’s difficult to capture an asteroid and have it “wind up in this beautiful, symmetric, circular orbit,” said Jeffrey Plaut, the project scientist for the Mars Odyssey mission.

Mars, having a tenth of Earth’s mass, has a relatively weak gravitational pull, so it seems improbable that it would be able to capture asteroids zipping by, said Tomohiro Usui, a robotic planetary exploration expert at the Japan Aerospace Exploration Agency. But if they formed from a debris disk launched up from Mars after a colossal impact, Deimos should be orbiting closer to Mars than it is today.

Reconciling their appearances with their orbits is difficult.

“They just shouldn’t exist,” said Dr. Fraeman. “They don’t make any sense.”

A version of this article appears in print on July 28, 2020, Section D, Page 8 of the New York edition with the headline: Space Potatoes: The Fascinating And ‘Super Weird’ Moons of Mars. Order Reprints | Today’s Paper | Subscribe

 Here are further comments on the impossibility of the orbits of these satellites, taken from the book The Realm of The Terrestrial Planets, by Zdenek Kopal (Professor and Head of The Department of Astronomy at The University of Manchester), published by The Institute of Physics 1979 – pages 143 to 149:-

Here is a scan of the author’s comments on the “impossibility” of the orbits of these two satellites.