Titania (moon) an extended mission. Another mission concept proposed was the Uranus orbiter and probe concept, evaluated around 2010. Uranus was also examined as part of one trajectory for a precursor interstellar probe concept, Innovative Interstellar Explorer. A Uranus orbiter was listed as the third priority for a NASA Flagship mission by the NASA Planetary Science Decadal Survey, and conceptual designs for such a mission are currently being analyzed. Titania (moon) Titania is the largest of the moons of Uranus and the eighth largest moon in the Solar System at a diameter of . Discovered by William Herschel in 1787, Titania is
Solar System moons. The centaurs and many short-period comets also orbit in this region. Due to their greater distance from the Sun, the solid objects in the outer Solar System contain a higher proportion of volatiles, such as water, ammonia, and methane than those of the inner Solar System because the lower temperatures allow these compounds to remain solid. The four outer planets, or giant planets (sometimes called Jovian planets), collectively make up 99% of the mass known to orbit the Sun. Jupiter and Saturn are together more than 400 times the mass of Earth and consist overwhelmingly of hydrogen and helium.