Astronomers have discovered 12 new moons orbiting Jupiter, bringing the total to 79.
Eleven are "normal" outer moons, but the 12th, thought to be less than 1km in diameter, has been termed an "oddball" due to its curious orbit.
The tiny moon's orbit takes it both inside and outside of where the other new moons orbit, putting it at a high risk of colliding with them.
"This is an unstable situation," said Dr Scott Sheppard from the Carnegie Institution for Science team.
"Head-on collisions would quickly break apart and grind the objects down to dust."
Jupiter's 79 moons make it the most orbited planet in the Solar System.
Its four biggest moons – Io, Europa, Ganymede, and Callisto – are known as the Galilean moons because they were first spotted by Galileo Galilei in 1610.
Europa is believed to have a vast liquid ocean beneath its icy surface and is among the likely habitable places in the Solar System beyond our own Earth.
Jupiter's biggest moon, Ganymede, also has an underground salt ocean – although this ocean may be too salty to be habitable.
:: NASA discovers Jupiter's atmosphere moves like Earth's
The Carnegie team led by Dr Sheppard first spotted the moons last year while they were searching for a giant planet orbiting the sun beyond Pluto.
"Jupiter just happened to be in the sky near the search fields where we were looking for extremely distant Solar System objects," he explained.
"So we were serendipitously able to look for new moons around Jupiter while at the same time looking for planets at the fringes of our Solar System," Dr Sheppard added.
"It takes several observations to confirm an object actually orbits around Jupiter, so the whole process took a year," said Gareth Williams, of the International Astronomical Union.
Nine of the new moons are part of a distant swarm of moons that orbit Jupiter in the opposite direction of its spin rotation.
Astrophysicists believe that these small moons, which are clustered in three bands, are the remnants of three massive moons which were broken apart by collisions with other bodies in space.
Two of them are much close to Jupiter and orbit the gas giant in the same direction as the planet's rotation, and are also believed to be part of a larger moon which had broken apart.
But the "oddball" moon has really excited the astronomers.
:: NASA solves mystery of Jupiter's lightning
"Our other discovery is a real oddball and has an orbit like no other known Jovian moon," Dr Sheppard explained.
More from Science & Tech
"It's also likely Jupiter's smallest known moon, being less than one kilometre in diameter".
The team believes the "oddball" was probably part of a larger moon, and have suggested naming it Valetudo, after the Roman god Jupiter's great-granddaughter, the goddess of health and hygiene.
[contf] [contfnew] 
Sky News
[contfnewc] [contfnewc]
