Now that’s a break away gully that would be hard to backfill.

Mars has the longest valley. If you thought the Grand Canyon was big, that's nothing compared to Valles Marineris. At 2,500 miles (4,000 km) long, this immense system of Martian canyons is more than 10 times as long as the Grand Canyon on Earth. pic.twitter.com/7xAVnYX3NT

— Space Explorer Mike 🇺🇦 (@MichaelGalanin) April 1, 2020