Astronomers use spacecraft to weigh one of Saturn's rings
A team of astronomers has succeeded in weighing the core of Saturn's brightest ring, known as the B ring, for the first time. The discovery, which made use of data collected by NASA's Cassini spacecraft, may lead to numerous insights regarding the age and formation of the ring system.
The ring's mass was discovered using Cassini's visible and infrared mapping spectrometer, which observed fine-scale ring features known as spiral density waves by analyzing the light from a number of bright, distant stars as it passed through Saturn's B ring.
The team noted that even though the opacity of the ring varied greatly from region to region, the mass of the ring was relatively unchanged leaving scientists uncertain as to what may be causing the disparate levels of opacity and reflectiveness.
"Appearances can be deceiving," states co-author of the study Phil Nicholson of Cornell University, Ithaca, New York. "A good analogy is how a foggy meadow is much more opaque than a swimming pool, even though the pool is denser and contains a lot more water."
According to the researchers, it is possible that the high levels of opacity in Saturn's B ring could result from a population of large particles, or possibly an as-of-yet unknown aspect regarding the structure of the ring.
The results of the study may inform the prevailing theories regarding the formation of Saturn's iconic ring system, as well as its age. For example, whilst the density of B ring's mass did not vary much from area to area, the overall mass was markedly lower than had been predicted.
As a ring develops, it accrues a significant amount of dust from meteorites and other sources,which acts to darken the ring and increase its mass. Therefore, since Saturn's B ring has a lower-than-expected mass, it is possible that it is much younger than had previously been believed. The researchers estimate that the ring may only be a few hundred million years of age rather than the few billion years that had previously been theorized.
Whilst Cassini is entering the twilight of its career, the probe is far from done with uncovering the mysteries of the ringed giant. As part of its grand finale, the probe is set to perform the most accurate measurement to date of the mass of the planet minus its ring system, allowing scientists a rare opportunity to gain an accurate reading of the mass of Saturn's rings.
A paper on the findings has been published online in the journal Icarus.