<p>Relative sizes of the 25 Solar System objects smaller than Earth. <a href="https://en.wikipedia.org/wiki/Eris_(dwarf_planet)" class="extiw" title="w:Eris (dwarf planet)">Eris</a>, <a href="https://en.wikipedia.org/wiki/Haumea_(dwarf_planet)" class="extiw" title="w:Haumea (dwarf planet)">Haumea</a>, <a href="https://en.wikipedia.org/wiki/Makemake_(dwarf_planet)" class="extiw" title="w:Makemake (dwarf planet)">Makemake</a>, <a href="https://en.wikipedia.org/wiki/90377_Sedna" class="extiw" title="w:90377 Sedna">Sedna</a>, <a href="https://en.wikipedia.org/wiki/Ceres_(dwarf_planet)" class="extiw" title="w:Ceres (dwarf planet)">Ceres</a>, <a href="https://en.wikipedia.org/wiki/(225088)_2007_OR10" class="extiw" title="w:(225088) 2007 OR10">2007 OR<sub>10</sub></a>, <a href="https://en.wikipedia.org/wiki/(84522)_2002_TC302" class="extiw" title="w:(84522) 2002 TC302">2002 TC<sub>302</sub></a>, <a href="https://en.wikipedia.org/wiki/(278361)_2007_JJ43" class="extiw" title="w:(278361) 2007 JJ43">2007 JJ<sub>43</sub></a> are missing. A number of objects (probably) smaller than <a href="https://en.wikipedia.org/wiki/Tethys_(moon)" class="extiw" title="w:Tethys (moon)">Tethys</a> but larger than <a href="https://en.wikipedia.org/wiki/Nereid_(moon)" class="extiw" title="w:Nereid (moon)">Nereid</a>, notably including <a href="https://en.wikipedia.org/wiki/4_Vesta" class="extiw" title="w:4 Vesta">Vesta</a>, <a href="https://en.wikipedia.org/wiki/2_Pallas" class="extiw" title="w:2 Pallas">Pallas</a>, <a href="https://en.wikipedia.org/wiki/50000_Quaoar" class="extiw" title="w:50000 Quaoar">Quaoar</a> and <a href="https://en.wikipedia.org/wiki/90482_Orcus" class="extiw" title="w:90482 Orcus">Orcus</a>, are also missing. <a href="https://en.wikipedia.org/wiki/Mars" class="extiw" title="w:Mars">Mars</a> is 6,792 km in diameter while <a href="https://en.wikipedia.org/wiki/Ganymede_(moon)" class="extiw" title="w:Ganymede (moon)">Ganymede</a> is only 5,268 km. <a href="https://en.wikipedia.org/wiki/Rhea_(moon)" class="extiw" title="w:Rhea (moon)">Rhea</a> and <a href="https://en.wikipedia.org/wiki/Oberon_(moon)" class="extiw" title="w:Oberon (moon)">Oberon</a> 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).
<a href="https://en.wikipedia.org/wiki/Ariel_(moon)" class="extiw" title="w:Ariel (moon)"> Ariel</a> and <a href="https://en.wikipedia.org/wiki/Umbriel_(moon)" class="extiw" title="w:Umbriel (moon)"> Umbriel</a> also share similar sizes, despite Umbriel being a bit bigger,
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Ariel's diameter is 1,158 km (719 miles) while Umbriel's is 1,170 km (727 miles).
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