Mars’ tiny moon Deimos might be a fractured piece of the red planet itself

Set and released in the 1950s, hot on the heels of a growing public fascination with UFOs, It Came From Outer Space explores what might happen when a small town comes face to face with alien visitors. It follows John Putnam and Ellen Fields, an amateur astronomer and a schoolteacher, respectively, as they witness the crash of a meteorite nearby. At the crash site, they find an object buried in the smoldering pit, with astounding extraterrestrial origins.

Things don’t go well for the humans or the aliens, but fortunately, little green men in advanced spaceships don’t often visit our solar system. We are visited, however, by interplanetary objects of all sizes and shapes, all of the time. And some of those objects even get captured by a planet and become moons.

For the most part, moons are believed to form in the protoplanetary disk, alongside their planets. They hang out with their planets because they came up together. This kind of simultaneous formation is believed to be the origin of most moons, with a smaller portion being captured asteroids. That was the suspected origin for the smaller of Mars’ two moons, Deimos. Now, scientists aren’t so sure, thanks to incredible new images from the United Arab Emirates’ Hope orbiter.

The Emirates Mars Mission is the nation’s first interplanetary spacecraft, and it’s sending back never-before-seen views of the red planet and its tiny entourage. Mars is a rather petite planet, having only about 15% the mass of Earth and a little more than half the diameter. Its moons are even more diminutive than our own, not even massive enough for their gravity to pull them into spheres. Instead, they are irregularly shaped, like lumpy potatoes floating through space. The larger moon, Phobos, tops out at about 17 miles across at its widest point, and Deimos is only about half that size. One thing is for sure, any Martian moon colonies will hold a few neighborhoods at most.

The small size and weird shape of Deimos led some astronomers to suggest that it might be a D-type asteroid which was captured by Mars at some point in the distant past. New data from the Hope orbiter makes that explanation unlikely.

After completing its primary mission studying the Martian atmosphere, Hope moved into an extended mission and changed its focus to Deimos. It flew to within 60 miles of the moon and snapped the highest resolution images of Deimos ever taken. In addition to taking some cosmic glamor shots, Hope used its onboard instruments to study the moon’s composition, and they found something unexpected.

See, objects in space have a signature which can tell us about where they were formed. In the same way that animals who live and eat in different environments take up different amounts of trace elements, you can read an asteroid’s origin by looking at what it’s made of. And Deimos isn’t made of the right stuff to be a D-type asteroid. In fact, its composition is startlingly similar to Mars itself, with all the right amounts of carbon and organic molecules.

That level of similarity in composition is unlikely, unless Mars and Deimos built themselves from the same material. The simplest explanation is that they are the same, because they are literally the same. Researchers for the Emirates Mars Mission now suggest that Deimos may have once been a part of the planet and was ejected from the planet and took up residence in orbit.

How and when Deimos split away from Mars isn’t clear right now, but this sort of activity is far from unheard of. Astronomers believe that our own Moon formed as a result of a collision between the Earth and a Mars-sized planet during the early period of the solar system’s formation. If it happened here and on Mars, that seems to point to planetary origin as a more common explanation for the creation of moons.

All the coolest planets keep it in the family. Catch It Came From Outer Space, available from Universal Pictures.

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