18 Miles From Deimos . ... Credit Copyright: The Viking Project , NASA Explanation: Diminutive Deimos is the smallest of the two tiny Moons of Mars. Potato shaped and barely 6 miles wide this asteroid-like body was visited by the Viking 2 orbiter in 1977. This image was made when the spacecraft approached to within 18 miles of Deimos' surface. ... Craters and large chunks of rock are seen scattered on the surface. ... NASA Web Site Statements, Warnings, and Disclaimers . ...