Mars Expresss are Mysterious Martian Spiders

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The European Space Agency’s Mars Express has snapped the telltale traces of ‘spiders’ scattered across the southern polar region of Mars.
The spiders captured by TGO lie near, but outside, the region shown in this new Mars Express image.
The aforementioned dark spots can be seen all over the Mars Express image, creeping across towering hills and expansive plateaus.
More formally known as Angustus Labyrinthus, Inca City was discovered in 1972 by NASA’s Mariner 9 probe.
This new view of Inca City and its hidden arachnid residents was captured by Mars Express’s High Resolution Stereo Camera.
A Mysterious Origin We’re still not sure exactly how Inca City formed.
The ‘walls’ of Inca City appear to trace part of a large circle, 86 km in diameter.
Exploring Mars Mars Express has revealed a great deal about Mars in the last two decades and counting.


The distinctive signs of “spiders” dispersed throughout the southern polar region of Mars have been captured by the European Space Agency’s Mars Express mission.

These tiny, dark features are not spiders at all; rather, they are created when springtime sunlight strikes layers of carbon dioxide that have been accumulated over the gloomy winter months. The bottom layer of carbon dioxide ice is exposed to sunlight, which causes it to condense and release gas, which then pushes through the ice layers above it. When the gas explodes in the springtime on Mars, it breaks through layers of ice up to one meter thick and pulls dark material to the surface.

Bursting forth through ice fissures as towering fountains or geysers, the darkly dusty emerging gas descends and settles on the surface. As a result, there are dark areas that are 45 m to 1 km across. These dark areas are a warning indication that spiders may be hiding beneath because the same process also leaves distinctive “spider-shaped” patterns carved into the ice.

The ExoMars Trace Gas Orbiter (TGO), one of ESA’s other Mars explorers, has captured images of the spiders’ tendril-like patterns in particularly good detail (see below). The TGO-captured spiders are located outside, but close to, the area depicted in this latest Mars Express picture. The TGO perspective also captures the spidery, web-like channels carved into the ice below, while the Mars Express view displays the dark spots on the surface created by escaping gas and material.

The aforementioned dark patches are visible throughout the Mars Express image, scuttling across broad plateaus and tall hills. In the dark area to the left, which is located near the edge of a region of Mars known as Inca City, the majority, however, are visible as tiny spots. The network of ridges is almost geometric and linear, resembling Inca ruins, which explains why it got its name. Inca City was found in 1972 by NASA’s Mariner 9 probe. It was formerly known as Angustus Labyrinthus.

Mars Express’s High Resolution Stereo Camera captured this fresh perspective of Inca City and its secretive arachnid inhabitants. You can explore the area and learn more about the various features you can see here by clicking on the image below, which also has labels.

An Unknown Beginning.

The precise formation of Inca City is still a mystery to us. Perhaps sand dunes have eroded into stone over time. Maybe sand or magma is seeping through the cracks in the Martian rock sheets. Alternatively, the ridges might be “eskers,” which are glacier-related, winding structures.

The 86 km-diameter circle that the Inca City “walls” seem to be tracing is partially visible. Scientists therefore surmise that the “city” is located inside a sizable crater that originated when a space rock collided with the planet’s surface. The surrounding plain was probably affected by faults that rippled outward from this impact, filled with rising lava, and eventually eroded away.

The scenery slightly alters in the middle portion of the picture, where sizable oval and roundish swirls produce a marble-like effect. It is believed that layered deposits erode over time to produce this effect.

A few noticeable hills and mounds with flat tops and steep flanks that rise more than 1500 meters above the surrounding terrain can be seen in the right center of the picture. These arise when the harder material that makes up these hills is gradually left behind after softer material is worn away over time by wind, water, or ice flows.

The smooth, light-colored dust covers more and more of the ground to the right (north). Here and there on the plateaus, among the many troughs and canyons, are traces of spider activity.

Mars exploration.

In the past 20 years and counting, Mars Express has provided a wealth of information about the planet. Continued imaging of the planet’s surface, mineral mapping, investigation of the atmosphere’s composition and circulation, exploration of the planet’s subsurface, and environmental research are all being conducted by the orbiter.

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