The discovery of Makemake's little moon increases the parallels between Pluto and Makemake. This is because both of the small icy worlds are already known to be well-coated in a frozen shell of methane. Furthermore, additional observations of the little moon will readily reveal the density of Makemake--an important result that will indicate if the bulk compositions of Pluto and Makemake are similar. "This new discovery opens a new chapter in comparative planetology in the outer Solar System," Dr. Marc Buie commented in the April 26, 2016 Hubble Press Release. Dr. Buie, the team leader, is also of the Southwest Research Institute.
When the American astronomer James Christy discovered Pluto's largest moon Charon back in 1978, astronomers were quick to calculate the mass of the system. Pluto's mass was hundreds of times smaller than the mass originally estimated for it when it was first discovered in 1930. With Charon's discovery, astronomers suddenly acquired a new understanding that something was fundamentally different about Pluto.
As of December 2015, confirmed liquid water in our own Solar System--excluding Earth--accounts for about 25 to 50 times the volume of our planet's water. The moons of our Sun's family thought to possess liquid water are: