NASA Mars Illusions Show How Rover Images Become Real Geology
Mars imagery tends to short-circuit the human mind, making objects such as rocks, hills, or ridges appear as open books, a teddy bear’s face, a door, a symbol, or the famous Viking “Face” image. However, the lesson from the imagery here is not that Mars has been hiding various man-made artifacts all along. The lesson is that rover cameras and orbiter imaging systems generate patterns that make our pattern recognition minds recognize certain shapes, but the actual science is done using geometry, lighting, mineral context, and repeated measures.
This detail is essential since any alien life has not yet been found on Mars and much of the strange-looking formations found there represent pareidolia when people see recognizable shapes in random patterns. This tendency, however, is very relevant to Mars exploration engineers develop imaging equipment to document the landscape, navigate, and provide context while geologists then need to differentiate between visual resemblance and evidence.
A “small rock that looks like an open book” discovered by the Curiosity rover in Gediz Vallis in April 2023 provides an interesting example. Despite looking like a man-made artifact thanks to its layered pattern, Mars rocks tend to be fractured, wind-worked, and eroded. An interesting shape captured in one image may very well be genuine without being anything extraordinary. Similarly, the 2022 “doorway” formation seen by Curiosity is just a particular case of an eroded rock formation that has been seen at the right angle.
The same applies to orbital imaging of large-scale patterns. A formation captured by NASA’s Mars Reconnaissance Orbiter and published by the University of Arizona in January 2023 has reminded many of the face of a teddy bear. However, the geological truth is rather less exciting but informative it is likely a hill fractured into pieces that lies in the center of an ancient crater. The Viking “face” follows the same pattern from decades back later observations proved that its peculiar appearance was dependent on lighting and viewing angle.
When appearance is connected with process, things start getting interesting. Curiosity’s flower-like mineral deposit discovered in February 2022 was unusual enough for the team to notice it, but the analysis didn’t stop with visual assessment. Mineral deposits like that are associated with ancient water interacting with rocks. In other words, while the image itself draws attention, geological value lies in what the deposit is and what conditions led to its formation.
The same thing holds true for some of the greatest findings on Mars in the last two decades. Opportunity’s iron-rich spherical formations known as “blueberries,” discovered in 2004, weren’t important because they looked different. Their importance came from their interpretation as formations smoothed by a lot of water billions of years ago, making them one of the first discoveries proving that Mars had been a very watery planet in its distant past. Curiosity’s polygonal mud cracks in Mount Sharp dated to roughly 3.8 billion to 3.6 billion years ago look like a tile floor, but their geological importance is related to the cycle of repeated drying and moistening and, correspondingly, rising and falling water levels in Gale Crater.
Features that remain unclear can also be rich with scientific insight. Near the south pole, black “spiders” formations seen during the Martian spring are neither animals nor plants but formations resulting from the release of the springtime sublimation of the carbon dioxide underground ice that breaks through the surface ice, lifting the dark dust up. According to ESA, these formations can vary in size from 150 feet to 3,300 feet in diameter. “Inca City,” another orbital favorite, looks like ruins but may, in fact, be composed of elevated sand dunes turned to stone; the nature of these formations is still uncertain with the scientists suspecting them to be part of a larger impact crater. And this is how Mars geology usually operates resemblance may happen accidentally while the question is what processes would explain the landscape.
Rovers provide an additional level of discipline since they do more than taking images. The Perseverance rover’s analysis of an unusually white rock called Atoko Point in Jezero Crater showed that it consisted of pyroxene and feldspar with possible transport from the crater rim or ancient rivers. In other places of Jezero, Perseverance has used instrument context beyond imaging to analyze the ancient terrain and the rocks’ composition. The point is clear a Mars feature that looks interesting on the picture won’t turn into scientific data until it is related to mineralogy and setting.
The same applies to organics. The Perseverance rover’s SHERLOC instrument combines context imaging with deep-UV Raman spectroscopy allowing scientists to map organics and minerals in Jezero Crater mudstones. Technically speaking, while imaging can reveal the texture and color, spectroscopy allows analyzing the material. Even at that, however, the interpretation will be done with care the in situ Raman analyses can’t establish whether the organics detected are abiotic or biotic. Which is a good reminder for every image of Mars that becomes viral for the wrong reasons.
For the reader, the point is quite obvious on Mars, the visually appealing shape is not a conclusion but the starting point for the proper scientific investigation. Cameras on Curiosity, Perseverance, Viking, and Mars orbiter missions are especially great at generating patterns, but the real task and, accordingly, the more crucial one is to turn these patterns into the scientific data. In other words, Mars becomes a real place not when it shows us illusions but reveals the history of its water, climate changes, impacts, and past habitability.
By David Whitaker – Associate editor for AMI’s aerospace and drone systems desk, translating flight systems, aircraft programs, spaceflight, and UAV developments into accessible technical stories.
