Before 24 Billion and Counting

Chapter 3 Part 1 Problems of publicity loom

An arrow picked up the faint image of a comet, presumably Rosetta, as it was approaching the planet from the outer reaches of space, leaving a dotted line indicating the orbit. Coming into the domain of Jupiter's moons it took a half loop around one and then appeared to take up an orbit around the planet that included three dimensional out facing loops. I could not detect a repeat in the pattern. After two complete orbits of the planet the display froze.

"Will - this is now more your country than mine - take Charles through this." 

Will's dry precise voice carried on, "What you have just seen is the comet coming towards Jupiter. Ordinarily it would just take a swing around the planet and then fly out again, away from the solar system, on a huge ellipse to return in its normal period. This one, as you saw nearly collided with Ganymede, Jupiter's largest moon. The orbit of the comet was modified to a type known as a chaotic orbit. What you saw was our best guess at its future, until we ran out of computer time. We've got NASA's computers working on the future of the orbit, but it is a calculation of extreme complexity." 

"Am I right in saying that the orbit with those out turned loops is stable but doesn't repeat?" I asked. 

"No. It is not stable. Being chaotic it is highly sensitive to other perturbations. That is why the calculations take so long - you have to account for the influence of all the moons and even the nearer planets to Jupiter, and the eccentricity in Jupiter's gravity field, and we have only an approximate data set for that." 

"So what could the outcome be?" 

"Anything from reverting to a stable Jovian or conventional cometary orbit, to falling back to Jupiter, or even diving into the solar system towards the sun." 

I protested, "Surely this can't be right - I've never heard of orbits that shape." 

Jacob intervened, "No, I'm sure Will's right. In the late nineties NASA suggested using chaotic orbits to get packages to the Moon from Earth, with a much lower energy consumption than using conventional routing. The penalties were time and an element of uncertainty. The arithmetic was easier than with the comet because the start was controlled and the only two players in the gravity dance were reasonably similar in mass. I guess we might have got the result slightly wrong for this comet because of the question over the data - but if the data is within one percent true the orbit will be very similar to what Will has put forward. Our prediction of the ultimate fate of the comet gets less accurate the longer the chaotic orbit persists." 

Will continued, "I think you have to consider that the first encounter with Ganymede is a very accurately predictable event, and it is this that leads to the chaotic orbit you have seen. It is only after the first circuit around Jupiter that I would expect deviations from my calculations to occur, because of inaccuracies in the data. In effect we have a comet in the solar system that could be launched in any direction, and I somehow doubt whether we can accurately predict what direction that will be." 

There was a silence whilst we looked at the display - Jupiter a majestic sphere, yellow with red streaks of cloud systems which we knew concealed weather of unimaginable fury, electrical storms and lightning bolts making Earth's worst thunderstorms seem puny by comparison, and a gravity field that compressed Earth gases to liquids. Attending Jupiter four of its sixteen moons, the largest of almost planetary size. 

Callisto furthest from Jupiter, has been pock marked with many collision craters. Inert and passive it orbits Jupiter slowly in nearly seventeen thousand days. 

Ganymede, the largest, a dead grey world similar to Callisto, made of rock and ice, with a surface not unlike like our own Moon but without the harsh illumination of the sun. 

Europa a sphere of slushy water ice with a small rock core, its surface comparatively smooth and shiny, sometimes described as a cracked eggshell surface. 

Io was hot and volcanic, but not with an inner energy like the Earth. It was squeezed by the intense gravity field of Jupiter into an elliptical shape which combined with the satellite's spin meant that the surface was continuously being forced in and out, and this continuous working caused the rocks under the sulphurous surface to melt, volcanoes to erupt, and lava and sulphur to flow, with sulphur dioxide gas jets and sulphur snow falling afterwards. As well as this treacherous chemical and geological activity this world was immersed in Jupiter's radiation zone, and could be the most lethal world to explore. 

And now in a mad looping tangle of an orbit, dancing unpredictably in amongst this group of spinning spheres, millions of tons of something which might go anywhere in the next ten, hundred, or a thousand years. 

Then I voiced a thought that came to me, "If someone says that the comet would hit Earth the panic would be dreadful. Just think how many people would struggle to be on the side of the world opposite impact. If someone can't come up with concrete answers the media will go mad." 

Jacob quietly replied, "That's why we thought of you. You're the nearest to a safe and trustworthy media-person we can talk to who might be able to help us tell it without precipitating - well - what'll happen could be as chaotic as this orbit." 

"I can't see NASA with their huge open publicity machine not letting the story leak if they're doing sums on it. And anyway, I know you've got a great telescope and a super computer and Will as one of the best to drive it, but it's not a unique set up. Someone else will soon find out the way you did, if they haven't already." 

Ellen nodded as I stopped, and continued my thought process. "Not only that, but if the outcome is uncertain and the arithmetic reflects that, the story that another organisation publicises could be worse than any 'cleaned up' version we put forward." 

Jacob looking straight at me asked, "Charles, are we forced to use transparent honesty, or should we try to conceal what we know?" 

"I can't see it any other way then being truthful. If you give the media a story which says we've discovered this interesting behaviour but it'll be alright because we know it will spin into a conventional safe cometary orbit in a hundred years time, someone will dig and dig and then find the truth and any one associated with the safe story will be vilified if not lynched by the mob." 

I looked at the three as I finished the sentence and they looked relieved, as though to hear some non-academic agree with the simplest course gave them comfort.