Big space anniversary today which will probably go unmarked by the media, as they scrabble to fill pages and airtime with the latest Trump stories and reports of NHS misery: twelve years ago today the Huygens lander, carried to Saturn by the Cassini space probe, set down on the surface of Saturn’s largest moon, Titan.
Titan was the classic enigmatic, mysterious moon, one of the most mysterious places in the whole solar system. The size of the planet Mercury, Titan is big enough to be visible from Earth through a small telescope or even through a really good pair of binoculars, looking like a tiny “star” close to the Ringed Planet.
Photos taken by the Voyager 1 space-probe as it whooshed through the Saturn system in 1980 showed the moon’s surface was hidden beneath an opaque atmosphere of thick, orange, smoggy gas, so the Huygens team had no real idea of what Titan’s surface was like, and the probe was designed to cope with various possibilities. In the end, after floating down through Titan’s atmosphere on a parachute and sending back breathtaking images of what were obviously – and unexpectedly, the channels of rivers of some sort, and the shorelines of lakes – Huygens touched down on fairly solid ground, and before it perished in the unimagineable cold returned images from the surface showing it was surrounded by rounded pebbles of water ice, on a gritty beach-like surface.
I remember the day well. I was up in Cockermouth, visiting my mother who lived and still lives there. and I had arranged to go and give a talk on astronomy and space exploration to a class of kids at the junior school which is – literally – a stone’s throw away from my mother’s house. It was a “Tour of The Solar System”, looking at each planet and major moon in turn. I was a bit distracted during the talk, to be honest, because my head was full of thoughts of Huygens – would everything go ok? Would it take images on the way down as planned? Would it land safely? Would we get to see Titan’s surface? – but it was exciting to be able to tell the kids during the Saturn section of the talk that right then, at that very moment, a space probe was dropping down through Titan’s atmosphere and taking photos which would be on the news that evening. History in the making, as they say, because this would be the most distant landing every attempted by us. We’d landed lots of hardware on the Moon, and on Mars, but never on anything as far away as Titan…
It was a long and very frustrating wait for the images to appear online, and in those days ESA was nowhere near as generous or speedy with its image releases as it is now, so I spent a lot of time with my laptop on my knee, checking, re-checking and re-checking for images until finally, FINALLY, one appeared…
At first I wasn’t sure what I was looking at… the horizon was blurred, out of focus, and those objects in the foreground looked like stones, or rocks of some kind, but without any sense of scale, or colour, it was difficult to get too much from the image. But that didn’t matter – that was TITAN! That was the surface of Titan, the largest moon around the Ringed Planet, the moon I had seen through my own little telescope so, so many times, as a “star” close to the rings… It was a genuinely moving experience, being able to see those images as they were released. Titan would never be the same again for any of us who were “into” space or astronomy. It truly was a world, not just a moon, not just a speck of light in an eyepiece.
Later, a colour version of the image appeared, and that was when many of us fell in love with Titan…
It looked a bit like Mars, or Venus, but was obviously not either of those worlds. It was a world in its own right, a world that, from that day on, would call out to us from across the solar system like a siren.
Amazingly it was clear that night, I remember, so I got out my telescope, set it up, and looked at Saturn, which was well-placed for observation, already above the eastern horizon at sunset, and obvious to the naked eye as darkness deepened, shining not far from the stars Castor and Pollux. Lining up on Saturn with the finder scope I looked into the eyepiece.. and there it was, Titan, a speck of light close to the planet itself. And yes, it was genuinely thrilling to see it on the same day it had been “conquered” by Huygens, and looking at it I remember wondering what the little probe looked like those hours after its historic landing. Was it now covered with dust or sand, blown on the wind? Had it sank into the soft ground? We’d probably never know. But to be able to stand there and see Titan through my little telescope’s eyepiece, and look at a photo of its surface taken just hours earlier, was quite something.
Since then Cassini has revolutionised our view and understanding of Titan, using its cameras and radar instruments. We now know that Titan has huge lakes, and winding, meandering rivers – not of sparkling water, like Earth, but chemicals such as methane. We know it has vast plains of dark sand dunes, blown and sculpted by the winds, and bright clouds swirling in its atmosphere. We know that, contrary to what science fiction illustrators had imagined in the years before Huygens’ landing, the moon’s atmosphere is too thick and claggy to allow Saturn to be seen from the surface, which is shame, because that had always been one of the most thrilling and romantic views thought possible from “out there”.
Today we know that Titan is essentially a planet in its own right orbiting Saturn, and there is a huge demand from planetary scientists for a return to Titan as soon as possible, so we can properly explore its lakes – perhaps with a boat, or even a submarine – and map its surface in greater detail, studying its mountains, valleys and lake shores with a dedicated orbiter or even a balloon which would drift around the moon, carried on its winds. We will return to Titan one day, that’s for sure, it’s just a matter of when.
But today is the day to cast our minds back to events twelve years ago, when a little probe landed on the most exciting, most bizarre moon in the whole solar system. There’s a fantastic video of the landing here, made from actual images taken by Huygens as it dropped through Titan’s atmosphere and settled on the surface.
If the sky is clear before sunrise where you are tomorrow morning (in the northern hemisphere, that is), you can see Saturn for yourself, looking like a yellow-white “star” very low in the south east at around 6.30am. And if you have a telescope you’ll be able to see Titan, looking like a tiny star next to the beautiful ringed planet. If you see it, spare a thought for Huygens, and all it achieved, a dozen years ago, and marvel at the thought that we have landed one of our machines on a world so ridiculously far away that it just looks like a tiny star through a telescope.