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The steepest cliff in the solar system is Verona Rupes, on Miranda, a moon of the outer planet Uranus. Verona Rupes is a straight 12 mile (20 km) drop. For comparison, the Grand Canyon is a 1 mile cliff and Mt. Everest is five miles high. In astrogeology, a “rupes” is a long line of mountainous cliffs. Verona Rupes is a cliff named after Verona in Italy. It was named this because Verona is the setting of Shakespeare’s play Romeo & Juliet, and moons and features in the Uranian system are traditionally named after things in Shakespearean plays.
Sometimes the height of Verona Rupes is incorrectly stated as 5 km (3 miles), though its height is obviously greater than this, as a cursory look at a picture of the moon itself shows. The cliff is even more intimidating in the context of the small moon on which it is found: Miranda is only 400 km (250 mi) in diameter. Some simple arithmetic then shows that Verona Rupes is a cliff so deep it cuts 4% of the way into the moon’s surface. A similar cliff on the Earth would be 1,000 miles deep!
The tallest cliff in the solar system is not the only unusual thing to be found on the surface of Miranda. The entire surface is odd and jumbled, with so many deep scratches it looks like someone threw it in a blender. Scientists believe this pattern is due to intense tectonic activity in Miranda’s past, caused by tidal heating in its core as its orbit changed. An earlier but now largely discounted hypothesis was that at some point in Miranda’s past, it was hit by one or more asteroids so hard that the entire planet was blown apart, only to condense back together after a few years or decades. Although a fantastic-sounding hypothesis, scientists now consider it unlikely.
Many want to know: if you were to jump off the top of Verona Rupes, would you survive? The answer is possibly yes – if you included some padding or airbags. Due to the low gravity of the small moon, falling to the bottom would take about 12 minutes. The skydiver would arrive at the bottom at a speed of about 200 km/h (125 mph), about that of a very fast car. Surrounded by a large inflated ball, this would be survivable. Size would not help slow your descent: without an atmosphere, there would be no air friction.
Verona Rupes was discovered by the Voyager 2 probe during its flyby of Uranus in January 1986. This surface feature is too small and distant to be resolved with current telescopes.