Longest canyon in the solar system reveals new secrets — Space photo of the week

Mars has a huge network of canyons that stretches about 2,500 miles (4,000 kilometers) across its equator. This canyon system, called Valles Marineris, is the largest in the solar system, dwarfing Earth's largest canyon, which covers 460 miles (750 km) under Greenland's ice sheet. (Condolences to the Grand Canyon and its mere 277-mile length.)

First imaged by NASA's Mariner 9 spacecraft in 1972, Valles Marineris has been captured by the HiRISE camera on NASA's Mars Reconnaissance Orbiter many times in its 19 years in orbit. However, this geological wonder still holds many secrets.

This latest photo, taken May 24 and published last week, is of the eastern side of Candor Chasma, one of the largest canyons within Valles Marineris. What it reveals could change how planetary geologists think about Mars' ancient environment.

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Using its ability to see detail down to the size of a kitchen table, HiRISE produced an image that shows layered deposits of sediment several meters thick, scientists at the Lunar and Planetary Laboratory at the University of Arizona, which developed and operates the camera, said in a description of the image. Crucially, these layers of sediment must date to after the canyon itself formed, because they appear to have been eroded, warped and bent by tectonic movements.

Related: 32 things on Mars that look like they shouldn't be there

Mars doesn't have plate tectonics like Earth does. Instead, its crust is like one giant plate, according to NASA. But faults and fractures still form in the Martian crust as it cools. Unlike Earth's Grand Canyon, which was carved by a river, Valles Marineris — including Candor Chasma — is thought to have formed by volcanic activity, with landslides, floods and erosion later sculpting it into its present form.

In 2021, the European Space Agency (ESA) revealed that the ExoMars Trace Gas Orbiter, a collaboration between ESA and the Russian space agency, had found water beneath the surface in Candor Chasma. It's thought that up to 40% of the near-surface material in Valles Marineris could be water. That would make it akin to Earth's permafrost regions in Alaska, Canada, Greenland and Siberia, where water ice permanently persists under dry soil because of the constant low temperatures.

With its steep walls and chaotic landscapes, Candor Chasma would be challenging for a Mars rover to explore. However, the German Space Agency's Valles Marineris Exploration project would study the possibility of sending a swarm of autonomous rovers, crawlers and uncrewed aerial vehicles to this treacherous terrain.

For more sublime space images, check out our Space Photo of the Week archives.