query: How large is the Elysium Planitia region of Mars?
passage: Elysium Planitia
A 2005 photo of a locale in Elysium Planitia at 5°N, 150°E by the Mars Express spacecraft shows what may be ash-covered water ice. The volume of ice is estimated to be 800km (500mi) by 900km (560mi) in size and 45m (148ft) deep, similar in size and depth to the North Sea.[3] The ice is thought to be the remains of water floods from the Cerberus Fossae fissures about 2 to 10 million years ago. The surface of the area is broken into 'plates' like broken ice floating on a lake (see below). Impact crater counts show that the plates are up to 1 million years older than the gap material, showing that the area solidified much too slowly for the material to be basaltic lava.[4]
passage: Chryse Planitia
Chryse Planitia (Greek, ""Golden Plain"") is a smooth circular plain in the northern equatorial region of Mars close to the Tharsis region to the west, centered at . Chryse Planitia lies partially in the Lunae Palus quadrangle, partially in the Oxia Palus quadrangle, partially in the Mare Acidalium quadrangle. It is 1600 km or 994 mi in diameter and with a floor 2.5 km below the average planetary surface altitude, and is thought to be an ancient impact basin; it has several features in common with lunar maria, such as wrinkle ridges. The density of impact craters in the range is close to half the average for lunar maria.