What natural Martian features, rather than constructed networks, were revealed by high-resolution images from the Mariner missions?

Answer

valles (valleys) and chasmata (chasms)

The robotic exploration, beginning with missions like Mariner in the 1960s, revealed Mars as a heavily cratered, dry world crisscrossed by natural geological features such as *valles* and *chasmata*.

What natural Martian features, rather than constructed networks, were revealed by high-resolution images from the Mariner missions?
MarsastronomyobservationplanetCanal