Data from the first and only time mankind probed Uranus appears to show two new moons hiding in the dark rings that encircle the gas giant.
Back in 1986, Voyager 2 skimmed past Uranus and found 10 new moons encircling the gas giant. Two of these, named Cordelia and Ophelia, occur on the outside of Uranus' rings, and the buffeting effect of the moons generates particular patterns in the dark particles that encircle the planet.
Now an analysis of the Voyager 2 data by Rob Chancia and Matthew Hedman at the University of Idaho appears to show similar disruptions in the inner rings around Uranus. The duo postulate that it suggests two moons might be causing the behavior, although they are likely to be very small – between two and four kilometers across.
"Our attempts to visually detect the moonlets are not exhaustive, but given the small predicted sizes of the α and β moonlets, a convincing detection may not be possible in the Voyager 2 images," they say in a paper [PDF] for The Astronomical Journal.
"Future earth-based observations may be more likely to detect these moons. Regardless of the current lack of visual detection, the identification of these periodic structures in the outer regions of the α and β rings is evidence of interactions with nearby perturbers."
The two now want to go through Hubble data to see if they can spot evidence of the two moonlets, but even that mighty telescope might not be able to spot such small, dark spots next to Uranus. Clearly a probe is needed, but NASA doesn't show much interest in Uranus compared to other planets.
Which is a pity, since Uranus is one of the oddest planets in the solar system. It's tilted around 90 degrees, so its poles are found where most planet's equators are located, and it's very cold when compared to the similarly sized Neptune.
The only planetary missions NASA has on the table are a couple of Mars missions and a possible exploration of Europa, so we'll have a to wait a while before the mystery of Uranus' tiny moons will be resolved. ®