The “door” on Mars? Planetary scientist explains what you really see

Enthusiasts lit up Social media recently posted photos of what appeared to be an “entrance” to a hillside on Mars. And some wondered, was this evidence that the Red Planet could be inhabited or was inhabited by extraterrestrials?

‘The Door’ was photographed by NASA’s Curiosity rover on May 7 on the slopes of Mount Sharp, the central massif within Gale crater, where it landed in 2012. It was described on a website as a ‘Pharaonic tomb door’ due to its resemblance to some ancient Egyptian remains. In fact, it is only about one foot high.

The mosaic of the hillside panorama above is hard to spot, but it jumps out if you see the single frame where it’s happening, as shown below. It looks like a hallway until you realize how small it is. And if you enhance the contrast in the darker parts of the image, the image reveals a solid rock face in the back of the darkened interior. So, as a gateway to the hollow hills of Mars, it doesn’t drive very far.

A Raw Curiosity camera image centered on “The Door”.NASA / JPL-Caltech / MSSS

What made the ‘door’ on Mars?

No one with even a little geological experience is likely to mistake the feature as a “door”. The geologist was noting the thin, slightly sloping layers of sandstone that make up the entire rocky face and immediately expected that they were looking at the eroded remains of the hard sand dunes. These once covered stream and lake sediments that Curiosity examined earlier as it gradually ascended through the layers of sedimentary rock that make up Mount Sharp.

The geologist will also discover the steep, straight fissures that ascend the surface of the rock and identify them as “knuckles.” These are fractures that usually open up when the weight of the rock layers that cover them are removed by erosion.

There is a particularly obvious hinge to the left of the ‘door’ picture, but many other connections can be made – including the hinge that forms the smooth wall that lines up with the left side of the ‘door’ itself. There is another hinge that forms the right side of the feature.

Raw image with red lines added to show some joints.NASA/JPL-Caltech/MSSS

Entire hills eroded again. An “entrance” is simply a place where the wind has been able to more effectively clean loose sand and dust from the surface of the rocks in an area bounded by joints on both sides. The base of the top layer of sandstone is the ‘door sill’, and the sloping top of a sandstone bed forms the gentle slope that leads to the door.

Artifacts on Mars?

It doesn’t take much searching on the Internet to find images taken by Mars rovers that show rock formations that look like other familiar objects, even though they are all unreasonably out of place. It should not be surprising that some of the countless rocks on Mars have strange shapes because many have been subjected to sand eruptions caused by wind erosion for billions of years.

A handful of stones swept away by the wind on the surface of Mars. The one in the middle looks like a femur from this angle.NASA/JPL-Caltech/MSSS

Apart from “doors” and “hardware” pieces ranging from wrecked “spaceships” and “jet engine” to individual items of “tableware”, “pyramids” and various “human heads” and “dinosaurs” were also photographed, “bones” and even “squirrel”.

Only a few of these weird things are real, and these are all junk that humans put out there. Others lose their visual distinction if they are seen from a closer distance or from a different perspective.

A true alien artifact on Mars: the back cover of the Persevere Lander, discarded prior to landing.NASA/JPL-Caltech

Why do we see familiar things in space?

“Seeing” the familiar even when there is no phenomenon called pareidolia. This refers to what happens when you see faces in the random pattern of your wallpaper, peeking out from the grain of wood floors or in the clouds.

The latter, for example, is what makes Jupiter look angry in the image below.

Jupiter looking angry, photographed by NASA’s JunoCam on May 19, 2017.NASAJPL-Caltech / SwRI / MSSS / Jason Major

Mysterious things don’t just appear on Mars. In December 2021, China’s Chang’e 4 rover — which is still doing great things on the far side of the moon more than three years after its landing — spotted a shack-shaped object 80 meters away.

I duly darted towards it and revealed that it was just a boulder, presumably coming out of a nearby impact crater. Some say it looks like a crouching rabbit, but I doubt anyone claims it was carved by extraterrestrials.

A far view from the Chang’e 4 rover shows a hut-like boulder 80 meters away, as well as a close-up view of when I got there.CNSA / CLEP

One of the most famous and largest examples of pareidolia is the Horsehead Nebula. This is a vast cosmic cloud of gas and dust within which entire star systems are formed. The image collected in the right part of the spectrum with the appropriate exposure time shows a shape that most people recognize as a horse’s head. Change the wavelengths (which we can do) or look at them from a different direction (which we cannot do), and the recognizable form will fade away.

The Orion’s Horsehead Nebula is depicted in the visible part of the spectrum.ESO

Back on land, climbers often look up at the Great Gable, a mountain in Cumbria, UK, for Cat Rock, also known as Sphinx Rock. From below, this looks like a seated cat, seen from the side, resembling the head of a sphinx. As far as I know, everyone accepts this as a fluke, and no one claims to be evidence that aliens have left landscape clues for their visits to Earth. It’s amazing why people insist on making such claims about the Floki rock formations on Mars.

In the end, although you can generally believe your eyes, you must be careful to believe your brain’s interpretation of what your eyes see.

This article was originally published Conversation Written by David Rothrey at The Open University. Read the original article here.