It is very hard to discover moons around Uranus and Neptune compared to Jupiter and Saturn because of their extreme distances. Neptune has only 9 known outer moons while Uranus has 10 compared to Jupiter’s 87 and Saturn’s 122. It is still unknown how these outer giant planet moons formed. To better constrain the origin of the outer moons, smaller moons of Uranus must be discovered. This will allow us to compare Uranus’ moon system to the other giant planets to constrain the formation and evolution of the planets and their moons. Also, the discovery of moon dynamical families would shed light on the poorly understood collisional evolution of the systems. Using Subaru HSC in Sept 2021 two new Neptune moons and fifteen new moons of Jupiter were found. With a deep search of Saturn completed at Subaru with announced new moons of Saturn in 2019 and 2023, this leaves only Uranus without a very ultra-deep moon survey, of which only Subaru can do effectively. Very deep Uranus imaging will find for the first time moons below the collisional break, where fragments of a few km in size from past broken moons can be seen.
This document was translated from LATEX by HEVEA.