Solar System all have impact craters and tectonic surface features, such as rift valleys and volcanoes. The term "inner planet" should not be confused with "inferior planet", which designates those planets that are closer to the Sun than Earth is (i.e. Mercury and Venus). Asteroids except for the largest, Ceres, are classified as small Solar System bodies and are composed mainly of refractory rocky and metallic minerals, with some ice. They range from a few metres to hundreds of kilometres in size. Asteroids smaller than one meter are usually called meteoroids and micrometeoroids (grain-sized), depending on different, somewhat arbitrary definitions. The asteroid
Venus Atmospheric Maneuverable Platform of a lenticular shape which would significantly simplify packing, deployment sequence and structural mass, but it would not cruise so efficiently. The vehicle concept was also presented in May 2017 as a proof-of-concept for exploration of other planets and moons of the Solar System with an atmosphere. The 2013 preliminary concept envisions a suite of instruments NASA calls the 'Venus Flagship Design Reference Mission' for a balloon. Its mass is estimated at 20 kg and would require 50 W of electrical power to operate. The notional intuments consist on: There are ongoing discussions about possible NASA participation in Russia's Venera-D