Take a Trip to Mars's Largest Lake — Caralis Chaos

Mars was once home to a lake surpassing any on Earth in size, as depicted in detail by ESA's Mars Express. The regions pictured, captured by Mars Express's High Resolution Stereo Camera (HRSC), display an area known as Caralis Chaos, believed to have housed significant amounts of water, the European Space Agency writes.

In the lower-right portion of the image, the remnants of an ancient lakebed—most visible in blue tones on the provided topographic view—curve from the bottom-center upward to the top-right, encompassing a prominent central crater. This once-contained lakebed now contains numerous raised mounds formed by Martian winds depositing dust, which were then altered by water before drying and breaking apart.

Caralis Chaos is part of a larger region consisting of ancient lake basins, remnants of Lake Eridania—once spanning over a million square kilometers. Lake Eridania, holding more water than all other Martian lakes together and surpassing Earth's largest lakes, existed around 3.7 billion years ago. Initially one vast lake, it eventually dried into smaller, isolated bodies of water before disappearing entirely along with the planet's remaining water.

Cracks and Craters

Beside water features, volcanic activity leaves distinct marks on and around Caralis Chaos. Two significant cracks, called the Sirenum Fossae faults, run vertically through the image, cutting across the lakebed and surrounding terrain. These faults emerged due to stress from Mars's Tharsis region and its massive volcanoes.

Volcanic stress also explains the presence of many horizontal wrinkle ridges, common on volcanic plains where new, pliable lava sheets compressed and buckled. Additionally, various craters shaped by space rock impacts populate the region. The large central crater displays signs of material flow and valley formations, suggesting water presence even after Lake Eridania's disappearance. Nearby, a smaller crater to the south shows erosion from small gullies, and several ancient, severely eroded craters appear towards the image's right.

Exploring Mars

Mars Express has orbited Mars since 2003, mapping the surface, investigating mineral compositions, studying atmospheric conditions, probing beneath the crust, and observing environmental interactions. Over two decades, the spacecraft's HRSC has unveiled Mars's diverse terrains, including wind-shaped ridges, sinkholes by massive volcanoes, impact craters, fault lines, river channels, and ancient lava pools, contributing to an enriched, precise understanding of our neighboring planet.

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