As Nasa’s Cassini spacecraft draws ever closer to the dramatic end of its mission, it has been sending back some stunning images of Saturn.
An image taken with Cassini’s narrow-angle camera in June has been released, which shows the intricate wave structure of Saturn’s rings.
The image comes just days before Cassini begins it last orbit on September 9, with the craft finally ending its historic 13-year mission six days later with a dive directly into Saturn’s atmosphere.
This view from Cassini spacecraft shows a wave structure in Saturn’s rings known as the Janus 2:1 spiral density wave. Resulting from the same process that creates spiral galaxies, spiral density waves in Saturn’s rings are much more tightly wound. In this case, every second wave crest is the same spiral arm which has encircled the entire planet multiple times
The image was taken on June 4, and shows a wave structure in Saturn’s rings, known as the Janus 2:1 spiral density wave.
Spiral density waves result from the same process that creates spiral galaxies, but are much more tightly wound.
In this case, every second wave crest is actually the same spiral arm which has encircled Saturn multiple times.
In a post about the image, a spokesperson for Nasa said: ‘This is the only major density wave visible in Saturn’s B ring.
‘Most of the B ring is characterised by structures that dominate the areas where density waves might otherwise occur, but this innermost portion of the B ring is different.’
While the image gives the illusion that the ring plane is tilted away from the camera towards the upper-left, this is not actually the case.
The Nasa spokesperson added: ‘Because of the mechanics of how this kind of wave propagates, the wavelength decreases with distance from the resonance.
‘Thus, the upper-left of the image is just as close to the camera as the lower-right, while the wavelength of the density wave is simply shorter.’
The Janus 2:1 spiral density wave is particularly remarkable because Janus – the moon that generates it – is in a strange orbital configuration.
Both Janus and Epimetheus (another of Saturn’s moons) share almost the same orbit, and trade places every four years.
While the image gives the illusion that the ring plane is tilted away from the camera towards the upper-left, this is not actually the case. A Nasa spokesperson said: ‘Because of the mechanics of how this kind of wave propagates, the wavelength decreases with distance from the resonance. Thus, the upper-left of the image is just as close to the camera as the lower-right, while the wavelength of the density wave is simply shorter’
Each time those orbit swaps take place, the ring at this location responds, creating a new crest in the wave.
The Nasa spokesperson said: ‘The distance between any pair of crests corresponds to four years’ worth of the wave propagating downstream from the resonance, which means the wave seen here encodes many decades’ worth of the orbital history of Janus and Epimetheus.’
While Epimetheus also generates waves, these are swamped out by the waves from Janus – the larger of the two moons.
Yesterday, Nasa also released the highest-resolution colour images of any part of Saturn’s rings to date, showing a portion of the inner-central part of the planet’s B Ring.
The first image, taken on July 6, is a natural colour composite, created using images taken with red, green and blue spectral filters.
And the second is a colour-enhanced version, in which blue colours represent areas where the spectrum at visible wavelengths is less reddish, and red colours represent areas that are spectrally redder.
Analysis of additional images from this observation, taken using infrared spectral filters sensitive to absorption of light by water ice, indicates that the areas that appear more visibly reddish in the colour-enhanced version are also richer in water ice.
Earlier this week, Nasa also released a stunning ‘spacecraft’s eye’ view over Saturn’s moon Enceladus.
The video stitches together images captured by the craft’s narrow-angle camera, and offers a first-person perspective of the Aug 1 flyby, showing the relative motion of Cassini and the icy moon from about 112,000 miles (181,000 km) above.
The new view is a change from the typically static Cassini observations that have been released over the years.
It uses six images, taken with filters that allow infrared, green, and ultraviolet light, according to Nasa.
Yesterday, Nasa also released the highest-resolution colour images of any part of Saturn’s rings to date, showing a portion of the inner-central part of the planet’s B Ring. The first image is a natural colour composite, created using images taken with red, green and blue spectral filters
The second image is a colour-enhanced version, in which blue colours represent areas where the spectrum at visible wavelengths is less reddish (meaning the spectrum is flatter toward red wavelengths), and red colours represent areas that are spectrally redder (meaning the spectrum has a steeper spectrum toward red wavelengths)
These make for the red, green, and blue components in the resulting movie.
‘The heavens often seem vast and unchanging as seen from Earth, but movement in the skies is the norm,’ Nasa explains.
‘The relative motions of both Cassini and Enceladus over a 15-minute period create the movement seen in this movie sequence.’
The Cassini space probe is approaching its final orbit between Saturn and its rings before its fiery plunge into the gassy planet.
The craft is now undertaking the last of its so-called ‘Grand Finale’ orbits, each bringing the probe closer to its long-awaited death dive.
Cassini’s last orbit begins this week on September 9. On September 14, the probe will take its final images of Saturn, snapping images of the gas giant’s hexagon-shaped vortex at its north pole as well as its moons Titan and Enceladus
This view of Saturn, taken by the Cassini probe, shows the planet’s northern hemisphere in 2016. The craft is now undertaking the last of its so-called ‘Grand Finale’ orbits, each bringing the probe closer to its long-awaited death dive
Cassini’s last orbit begins this week on Saturday September 9, with the craft finally ending its historic 13-year mission six days later with a dive directly into Saturn’s atmosphere.
Saturday’s orbit will send the craft through the outermost layers of the planet’s atmosphere, passing just 1,680 kilometres (1,043 miles) above the clouds.
Two days later Cassini will make a final, 119,049-kilometre (73,973-mile) flyby of Saturn’s largest moon Titan, causing the craft to slow down and re-position its orbit for its death dive.
Cassini has been probing Saturn, the sixth planet from the sun, and its entourage of 62 known moons since July 2004, providing enough data for almost 4,000 scientific papers. Pictured are the number of orbits and flybys the craft has performed over the past 13 years of research
This image of Saturn’s rings was taken in visible light with the Cassini spacecraft narrow-angle camera on Jan 28, 2016. Cassini’s final dive will end a mission that provided groundbreaking discoveries that included seasonal changes on Saturn, the moon Titan’s resemblance to a primordial Earth, and a global ocean on the moon Enceladus with ice plumes spouting from its surface
On September 14, the probe will take its final images of Saturn, snapping images of the gas giant’s hexagon-shaped vortex at its north pole as well as its moons Titan and Enceladus.
The probe will then turn its antennae toward Earth, transmitting data until the final moment before it burns up as it heads straight into the gas giant’s crushing atmosphere on September 15.
Cassini’s final dive will end a mission that provided groundbreaking discoveries that included seasonal changes on Saturn, the moon Titan’s resemblance to a primordial Earth, and a global ocean on the moon Enceladus with ice plumes spouting from its surface.
‘The mission has been insanely, wildly, beautifully successful, and it’s coming to an end in about two weeks,’ Dr Curt Niebur, Cassini program scientist, said on a telephone conference call with reporters last week.
Last week, Nasa shared a stunning new view of Saturn’s turbulent clouds, captured the day Cassini first began its Grand Finale. The breathtaking photo shows the swirling clouds ‘on top of the world’ at the ringed planet just weeks before Saturn’s northern summer solstice
Cassini’s final photo as it heads into Saturn’s atmosphere will likely be of propellers, or gaps in the rings caused by moonlets, said project scientist Dr Linda Spilker.
The spacecraft will provide near real-time data on the atmosphere until it loses contact with Earth at 7:54 am ET (12:54 am BST) on September 15, Nasa said.
Dr Spilker said Cassini’s latest data on the rings had shown they had a lighter mass than forecast.
That suggests they are younger than expected, at about 120 million years, and thus were created after the birth of the solar system, she said.
During its final orbits between the atmosphere and the rings, Cassini also studied Saturn’s atmosphere and took measurements to determine the size of the planet’s rocky core.
Cassini has been probing Saturn, the sixth planet from the sun, and its entourage of 62 known moons since July 2004, providing enough data for almost 4,000 scientific papers.
Since the craft is running low on fuel, Nasa is crashing it into Saturn to avoid any chance Cassini could someday collide with Titan, Enceladus or any other moon that has the potential to support indigenous microbial life.
By destroying the spacecraft, Nasa will ensure that any hitchhiking Earth microbes still alive on Cassini will not contaminate the moons for future study.
Last week, Nasa shared a stunning new view of Saturn’s turbulent clouds, captured the day Cassini first began its Grand Finale.
In a movie stitching together 21 images taken with Cassini’s wide-angle camera, Nasa reveals a look at the entirety of the main rings. The images were taken over a period of roughly four minutes on August 20, 2017
The breathtaking photo shows the swirling clouds ‘on top of the world’ at the ringed planet just weeks before Saturn’s northern summer solstice – a period soon to be followed by years of darkness.
Cassini began the first of its final five orbits mid-August, bringing it closer to Saturn than ever before.
Images from its August 20 dive now offer a mesmerising ‘inside out’ perspective from the gap between the planet and its rings.
In a strikingly dynamic photo captured on April 26, 2017 – the day it approached Saturn for its first dive – Cassini observed the planet’s north pole as it remained bathed in sunlight, from about 166,000 miles away.
But soon, the region will be enveloped in darkness.
Nasa’s Cassini space probe (artist’s impression) is approaching its final orbit between Saturn and its rings before its fiery plunge into the gassy planet. The craft is now undertaking the last of its so-called ‘Grand Finale’ orbits, each bringing the craft closer to its long-awaited death dive
‘Although the pole is still bathed in sunlight at present, northern summer solstice on Saturn occurred on May 24, 2017, bringing the maximum solar illumination to the north polar region,’ Nasa said.
‘Now the sun begins its slow descent in the northern sky, which eventually will plunge the north pole into Earth-years of darkness.
‘Cassini’s long mission at Saturn enabled the spacecraft to see the sun rise over the north, revealing that region in great detail for the first time.’