File:Relative satellite sizes.jpg

Relative sizes of the 25 Solar System objects smaller than Earth. Eris, Haumea, Makemake, Sedna, Ceres, 2007 OR₁₀, 2002 TC₃₀₂, 2007 JJ₄₃ are missing. A number of objects (probably) smaller than Tethys but larger than Nereid, notably including Vesta, Pallas, Quaoar and Orcus, are also missing. Mars is 6,792 km in diameter while Ganymede is only 5,268 km. Rhea and Oberon are nearly the same size to within uncertainty, though Rhea is suspected to be the bigger one. Oberon has a diameter of 1,522 km (946 miles). It is slightly narrower than Rhea's 1,528 km (949 miles). Ariel and Umbriel also share similar sizes, despite Umbriel being a bit bigger,