The “Doorway on Mars” is More Like a Dog Door

The “Doorway on Mars” is More Like a Dog Door

The Mars Curiosity rover captured this panorama of a rock cliff while traveling across Mount Sharp on Mars. The location of a so-called “Mars doorway” is circled. NASA/JPL/Mars Curiosity team

Remember all the fuss last week about the “doorway on Mars”? This week, NASA released additional information about the rock mound where the Curiosity rover photographed a fracture hole in the rock. It appears to be a door, but it is not.

Curiosity made this discovery while searching for clues to the existence of water on Mars early in its history. This odd-shaped opening turns out to be no larger than a dog door on Earth. Does this imply that canines can fit through openings 30 by 40 centimeters (12 x 16 inches) on Mars? Wouldn’t that be awesome? No, it is not. But, that knowledge is not enough to keep the “Mars aliens” enthusiasts from promoting their favorite ideas about ancient civilizations on the Red Planet.

Debunking the Doorway on Mars Idea

We pointed out in last week’s article about Curiosity’s discovery that this hole in the rocks isn’t a mysterious opening to a subterranean world on Mars. Instead, it turns out to be one of many naturally occurring rock fractures found all over the world. On Earth, we see similar types of fractures.

The break in the rocks is fairly typical of sandstones and bedrock, as seen in the main panorama posted from the rover and the Earth sandstone in the scene below. Individual layers of rock can be seen if you look closely. Anyone who has hiked in desert regions and seen desiccated sandstones or along the Front Range of the Rocky Mountains and seen layers of sandstone near the mountains will recognize the scene. When the central part of the Rocky Mountains jutted out to form the Continental Divide, sandstone layers were fractured and upended. An ancient ocean covered the region for millions of years before that. The sea bottom and shorelines were layered in fine sands, which hardened to become rock.

Earth’s view of a fractured sandstone formation. This type of rock is easily shattered by erosion or other forces. The concentric circles on the rock are “plumose” (plume-like) structures formed when the rock fractured. AWickert provided the image. CC BY-SA 3.0.

Similar rocks can be found all over the world where lakes, oceans, and riverbeds have deposited layers of sand. It can even be caused by wind-driven sand and dust. This action results in the formation of sand layers and dunes, which eventually harden into rock. Given what we know about Mars’ surface, it’s not surprising to see similar features. And, as on Earth, sandstone on Mars can erode and break pretty easily.

The existence of the shattered rock cliff region where Curiosity is exploring comes as no surprise. And we shouldn’t be surprised to see fracture “holes” where rock fragments have broken away over time. The same forces that were at work on Mars were also at work on Earth. That is why so much of Mars appears to be familiar to us.

Viewing the “Dog Doorway on Mars” in 3D

NASA released some analysis images of Curiosity’s Mastcam view of the East Cliffs region to give a good idea of the sizes of the rock layers and the “dog door.” For those of you playing along at home, the Curiosity imaging team created a 3D anaglyph (viewable with red/blue 3D glasses). Take some time to explore it; chances are you’ll find it very familiar-looking.

A 3D anaglyph (red/blue viewing) of the cliffs where Mars Curiosity is traveling. Courtesy NASA/JPL/Mars Curiosity team.

The team also focused on the “door” region and created two images from it. The first is simply a close-up in 3D anaglyph. Then they added some size and scale markings to help you understand what you’re looking at. Without a doubt, this open fracture is intriguing. It’s significant not because it’s a door to another Martian dimension, but because of what it represents. This image contains millions of years of Martian geologic history. Mars scientists are studying it closely to understand how this rock formed and what conditions were like when it did.

Zeroing in on the Dog Doorway on Mars, with scale markings to show its approximate shape and size. Courtesy NASA/JPL/Mars Curiosity team.
The same view as above, but without scale markings. Courtesy NASA/JPL/Mars Curiosity team.

Where Is Curiosity?

The spacecraft is exploring specific areas of Mars’ Gale Crater in search of evidence of Mars’ watery past. It is currently studying the chemistry of the rocks on this section of Mount Sharp from a rock mound (the shroud around Aeolis Mons, the central peak of the crater). As this is written, Curiosity’s next two days (Sols 3480-3482) will be spent checking out some “gnarly looking” rocks, analyzing what it finds, and doing a full panoramic imaging sweep specially timed for another spectacular Martian sunset view.

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