Cressida, one of Uranus’s moons, is on course to collide with Desdemona, another of Uranus’s moons.
According to a new study, the collision isn’t set to take place for another one million years.
Researchers say that Cressida’s gravity is causing the distortion of one of Uranus’s rings, increasing the likelihood that one of Uranus’s moons will crash into another.
Uranus is seen in this false-color view from NASA’s Hubble Space Telescope from August 2003. The brightness of the planet’s faint rings and dark moons has been enhanced for visibility. The planet’s 27 known moons are named after Shakespeare characters
NASA’s Voyager 2 spacecraft, launched in 1977, first discovered Cressida in 1986.
The moon, which measures 82 kilometers (51 miles) across, is, according to NASA, one of Uranus’s inner moons – it orbits close to Uranus.
Based on its low albedo (proportion of light reflected by a surface), its surface probably consists of dark, unprocessed, carbon-rich material.
Cressida is one of the 10 Uranian satellites discovered by the Voyager science team.
Cressida and Uranus’s other moons are the most tightly packed group of moons in the solar system, all lying within 18,000 kilometers (11,184 miles) of each other.
A new study, published online in ArXiv and conducted by researchers based at the University of Idaho, has determined Cressida’s mass, as well as the likely shape of its doomed path.
To begin with, the researchers investigated one of the planet’s rings, called Eta, finding that its orbit is slightly triangular instead of perfectly circular – which the researchers did not expect.
The researchers say that Cressida’s gravity is causing this distortion, as Eta keeps pace of Cressida’s orbit of Uranus.
By contrast, the particles inside the ring revolve faster around Uranus than Cressida does, completing three orbits within the same amount of time that Cressida takes to complete two.
Knowledge of this allowed the research team to determine Cressida’s mass, which is 1/300,000th that of Earth’s moon, and has 86 per cent of the density of water.
This makes Cressida more dense than Saturn’s small moons, which mostly consists of water ice but are also porous, making them weigh less than ice.
The researchers of this study say that Cressida is likely porous too, and these findings do not bode well for Cressida.
The image on the right, taken 90 minutes after the left-hand image by NASA’s Hubble Space Telescope’s Near Infrared Camera, shows Uranus’s rotation. Eight small Uranian satellites, which revolve around Uranus in less than a day, can be seen in both images
The denser Uranus’s neighbor moons are, the more their gravity pulls at one another, increasing the chance that one will move into the wrong path.
‘Some of these moons are probably going to crash into each other,’ Dr Matthew Hedman, a researcher at the University of Idaho and a co-author of the research, told New Scientist.
In approximately one million years, Cressida is likely to hit Desdemona, a moon that orbits 900 kilometers outside of Cressida’s path.
A collision is also set to take place Uranus’s moons Cupid and Bellinda.
Dr Robert Chancia, a researcher at the University of Idaho and the lead author of the study, says ‘there’s actually evidence of past collisions.’
Two rings near the moons may be made of debris from prior collisions.
This image, provided by NASA’s Hubble Space Telescope, is an astronomical alignment of a moon traversing the face of Uranus, and its accompanying shadow. The white dot near the center of Uranus’ blue-green disk is the icy moon Ariel