With a diameter averaging about 7 miles, it's the smaller of Mars' 2 moons
In short, terrestrial planets tend to be smaller than gas giants, and gas giants ... 
Pluto has a diameter of 1,473 miles (2,370 kilometers) across,... [DOC] [TLE] Deimos (moon) - Wikipedia [PAR] Deimos (systematic designation: Mars II) is the smaller and outer of the two 
natural satellites of .... As seen from Mars, Deimos would have an angular 
diameter of no more than 2.5 ... At its brightest ("full moon") it would be about as 
bright as Venus is from Earth; ...