ESA’s Mars Express has discovered a series of 'pit-chains' in the Tharsis region of Mars that could, says ESA, be tempting targets in the search for microbial life.

Sitting on the flanks of one of the largest volcanoes in the solar system, Tharsis Montes, the pit-chains are a series of circular depressions that formed along fracture points in the Martian crust.

Pit-chains, also found on the Earth and moon, are created when lava streaming from a volcano solidifies on the surface, leaving a molten tube of lava running below.

Once volcanic activity ceases, the tube empties, leaving behind an underground cavity. Eventually, the roof over the cavity can collapse, leaving circular holes.

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