The face that sent us back to Mars

Geologic Face on Mars Formation — NASA/JPL
Event image. The Viking frame that made this landform famous; missing-data speckles contribute to some apparent features.
NASA/JPL image-use policy · credited mission imagery, resized to WebP
· Original image source · Image licence

Follow a famous shape from a grainy Viking frame to much sharper views.

World: Mars
Case date or period: Observations · 1976–2023

Look closer

Viking’s 1976 photograph made an eroded landform look startlingly familiar. Missing-data speckles and the direction of sunlight helped shape the apparent features. Later spacecraft returned to the same place.

Follow the evidence

Compare the original image with Mars Global Surveyor’s higher-resolution observation and the wider THEMIS scene. The later views reveal slopes and ridges; the surrounding landscape contains many other eroded hills.

An independent perspective

A 2006 preprint by Vassilios S. Vassiliadis proposed looking at blurred renderings when considering possible ancient structures. This is a speculative interpretive argument, not evidence establishing construction. The original spacecraft images here let you examine how resolution, erosion assumptions and processing affect that argument.

Returning required a different view

The 2001 observation was deliberately targeted by rolling Mars Global Surveyor away from its usual straight-down orientation. NASA’s image release gives a resolution of about two metres per pixel and places the landform roughly 165 kilometres to the side of the spacecraft’s ground track. This is a new observation under a different viewing geometry, not simply a sharper enlargement of Viking’s photograph. Comparing the images therefore involves illumination and perspective as well as resolution.

A new photograph and a model answer different questions

HiRISE returned in 2023. The colour detail in this gallery comes from the November observation. The team also combined a stereo pair into a digital terrain model, then simulated how shadows would move under the lighting of the 1976 Viking encounter. Those animations explore an illumination hypothesis; they are not films taken by a spacecraft. Keep the camera observation and the rendered shadow experiment separate when comparing the familiar outline.