NASA release stunning new image of Saturn
Sen—The imaging wizards working on the Cassini mission have delivered a Christmas gift to space fans in the shape of this astonishing new view of planet Saturn.
It looks unusual because the giant world and its spectacular rings were backlit with the Sun behind them while the NASA probe was in Saturn's shadow.
That is a line-up that happens rarely for the orbiter which has been studying the planet and its retinue of moons since 2004. The last time it delivered such a view was in September 2006 with a picture that was named In Saturn's Shadow.
The two bright dots resembling stars below the rings to the left of the planet are actually two of Saturn's many moons - Enceladus which spouts salty jets from an underground sea, and Tethys.
Cassini took the photo on 17 October from a position about 19 degrees below the ring plane and looking towards their non-illuminated side. Separate images taken with infrared, red and violet spectral filters were combined to produce an enhanced colour view.
As well as being a work of beauty, the picture also helps the Cassini team with their science because it allows them to examine ring and atmospheric phenomena that are not easily seen from other angles.
The picture, with its impressive light, shade and colours appears quite different from that take in 2006 which was a mosaic of 165 separate shots taken over three hours. It was processed to look like natural colour and, with enhanced contrast, took on an aethaerial glow.
In Saturn's Shadow: The 2006 image of Saturn showing Earth as a dot between the rings. Credit: NASA/JPL/Space Science Institute
The planet's dark side, away from the Sun, was illuminated by sunlight reflected from the rings. The observations allowed the discovery of two previously unknown rings in the Saturnian system. The outermost ring is the already known E ring which is fed by those geysers from Enceladus.
Perhaps the most amazing part of the picture is something that is not immediately obvious, a speck that is visible in a gap between the rings to the left of Saturn. That was the distant Earth, viewed from a distance of well over a billion kilometres, and looking remote and vulnerable.
That image of Earth as a few pixels was itself reminiscent of a previous, similar view in which leading Cassini scientist Carolyn Porco also played a major role.
As a young planetary scientist she suggested to mission managers at NASA's Jet Propulsion Laboratory (JPL) that they turn the Voyager 1 probe round as it headed out of the Solar System to look back at the planets.
There was initial opposition, but legendary space populariser Carl Sagan came up with the same idea and, thanks to his campaigning, the manoeuvre was carried out with great success. It led to a remarkable image of Earth as a tiny speck.
The Earth is ringed in this image of the "Pale Blue Dot" from Voyager 1. Credit: NASA/JPL
Carolyn told Sen: "I came up with the idea independently to take an image of the Earth (and all the other planets) with Voyager. And I did meet resistance. But in the end, it was Carl who did the political maneuvering and I assisted. He obviously had more cache and political muscle than I did, and he did all the final convincing, needing to enlist the support of the NASA Administrator."
Sagan dubbed it the Pale Blue Dot and wrote: "That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives."
Remembering how she proposed the Voyager 1 photo, Carolyn told me: "The mission managers at JPL looked at me like I was crazy because there was clearly no 'science' in doing so.
"In hindsight, I laugh to think about how resistant, and also unimaginative, the folks at JPL were to it all, when in fact, it is probably the most famous image Voyager ever took."
Of the 2006 image, Carolyn said: "I'm very proud that on Cassini, we trumped the Pale Blue Dot picture, with our own version showing our blue-ocean planet through the rings of Saturn during an event never before captured - a total solar eclipse by Saturn. Glorious!"
• Update: Cassini will be looking back at Venus today as the planet makes a rare transit across the face of the Sun. The team will use an infrared spectrometer called VIMS to try to measure the chemical signature of the planet's atmosphere to test a process that can be used to examine the transiting exoplanets of other stars.