Why the ‘Super Weird’ Moons of Mars Fascinate Scientists. What’s the big deal about little Phobos and tinier Deimos?

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https://www.nytimes.com/2020/07/25/science/mars-moons-phobos-deimos.html

Source: By Robin George Andrews, The New York Times. 

Excerpt: our planetary neighbor is adorned with two moons: puny Phobos, a lumpy mass 17 miles across; and diminutive Deimos, just 9 miles long. Their names in ancient Greek may mean “fear” and “dread’, but the aesthetics of these Lilliputian space potatoes inspire anything but. ...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. ...they look like asteroids foreign to the red planet but behave like byproducts of Mars’ early, impact-laden history. And if that Japanese mission manages to grab some samples and decode the chemistry of the mangled moons, we might be able to discover their origins. In doing so, we won’t just gain a better understanding of Mars’ ancient past. We will also be able to peer back in time to the chaos that shaped the early solar system. ...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. ...“They just shouldn’t exist,” said Dr. Fraeman. “They don’t make any sense.”... 

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