A bunch of stones scoured out by the wind on Mars. We should not be surprised that some of the innumerable rocks on Mars have weird shapes, because many have been sandblasted by wind erosion for billions of years. It doesn’t take much searching on the internet to find images taken by Mars rovers that show rock formations that resemble other familiar objects, even though all are implausibly out of place. The base of an overlying bed of sandstone is the “door lintel”, and the sloping top of a bed of sandstone forms the gentle ramp that leads up to the door. The “doorway” is simply a place where the wind has been able to scour out the poorly consolidated sand and dust from the rock face a little more effectively, in an area bounded by the joints on either side. The raw image with red lines added to show some of the joints. There’s another joint that forms the right side of the feature. There is a particularly obvious joint in the left of the “door” image, but several others can be made out – including one that forms the smooth wall that lines up with the left side of the “door” itself. These are fractures that typically open up when the weight of overlying rock layers is removed by erosion. These once covered the stream and lake sediments that Curiosity examined earlier in its gradual climb up through the layers of sedimentary rock making up Mount Sharp.Ī geologist would also spot the steep and fairly straight cracks running up the rock face, and recognize these as “joints”. A geologist would note the thin and slightly sloping repeated layers of sandstone making up the whole of the rock face, and would immediately expect that they were looking at the eroded remains of hardened sand dunes. Nobody with even a little geological experience is likely to mistake the feature as a “door”. Image: NASA/JPL-Caltech/MSSS What the “door” really is The ‘door’ is circled, and is tiny and hard to see at this scale. A panorama stitched together from about 100 individual Curiosity images. So as a gateway into the hollow hills of Mars, it doesn’t lead very far. And if you boost the contrast in the dark parts of the image, the picture just about reveals a solid rock face at the back of the shadowed interior. It does look like a doorway until you realize how small it is. ![]() It is hard to spot on the panoramic image mosaic of the hillside above, but it leaps out at the eye if you see the individual frame where it occurs, seen below. ![]() ![]() Described on one website as a “ pharaonic tomb door”, because of its resemblance to some ancient Egyptian remains, it is in fact only about one foot high. Was it, some wondered, evidence that the red planet could be, or have been, inhabited by aliens? The “door” was imaged 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. Enthusiasts lit up social media recently with images of what appeared to be a “doorway” into a hillside on Mars.
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