Juice. That’s right. What has this got to do with physics? A lot. But this is not about the liquid component of fruit although, I’m sure, there is a lot of physics going on there whether in terms of molecular structure, the viscosity of the liquid, the refractive index of the juice, its heat capacity, its electrical conductivity, its mass, its colour, its acidity, etc. However exciting the physical properties of juice can be, I will not be talking about this right now but, rather, I’ll be talking about the proposed mission to study three of Jupiter’s moons, namely, Ganymede, Callisto and Europa.
Indeed, this mission currently being planned by the European Space Agency (ESA), is a little bit more exciting than juice but it is called juice, nevertheless. Juice is an acronym for JUpiter ICy moon Explorer. Not a perfect acronym but a clever one, at least. So what is Juice all about? What is it about those Jovian moons that is worth spending a billion of dollars and years of preparation on? I’ll attempt to answer that with this in mind: investing in space exploration is all about pushing our boundaries, whether physical, economical, social, political, environmental or scientific.
Jupiter is the largest by size and mass of the solar planets and is the fifth furthest from the sun. It is a big ball of gas composed mostly of hydrogen (about 90%) and helium (about 10%) and minute traces of other chemical compounds such as methane, ammonia and even water. Jupiter is so big that if it were a hollow sphere or a big empty fish bowl and if we could melt or liquefy planet Earth then we would have to pour the equivalent of 1320 Earth in it in order to fill it up! In terms of mass, it is almost 320 times more massive than our planet. What I’m trying to say here is that, for all intents and purposes, Jupiter is a huge sphere out there orbiting the Sun. We, I mean planet Earth, are not even in the same league when it comes to comparing size and mass with Jupiter.
Of the 8 planets in the solar system, four are part of the rocky or terrestrial planets and the other four are part of the gas giants. Mercury, Venus, Earth and Mars comprise the small, rocky planets. Jupiter, Saturn, Uranus and Neptune are the gas giants.
Earth has one natural satellite orbiting it every 28 days or so. It is called Moon. I know, not a very imaginative name for a… moon. Personally, I would rather refer to it as Luna or Selene. Every other moon in the solar system has a proper name. Mars, for example, has two moons and are called Phobos and Deimos. Jupiter has 66, as far as we can tell. Again, we are in no position to compete with those giants in case we become too vain about our puny planet.
Of the 66 Jovian moons, four have grabbed our attention skywards. These are Io, Europa, Ganymede and Callisto. The other 62 are not as significant in terms of mass or size. For comparison, those 62 moons put together only make up about 0.003 % of the total mass of the moons. That is to say, Io, Europa, Ganymede and Callisto put together would constitute almost 99.997% of the total mass of the 66 moons. Io and Europa are of comparable size to our Moon whereas Ganymede and Callisto are even bigger. Now, besides their size, what else could have drawn our attention to these moons?
It turns out the those four moons have very peculiar features, not so alien to our own mundane ones. For example, with more than 400 active volcanoes, Io is the most geologically active object in the solar system. Europa is covered with a solid, icy crust above a liquid ocean water. The only way to find out if this is really the case is to get up, close and personal with Europa and confirm the presence of water underneath its ice sheath. And if water is indeed on Europa then there is a good chance that its harbouring life. Be it viral or bacterial or amoeboid, it will be life. And because it would have been found on Europa then wouldn’t it be fitting to call those inhabitants, albeit simple and microscopic, Europeans?
Ganymede and Callisto are also very likely to have ice and possibly water. What we know is that Europa, Ganymede and Callisto have a rocky core surrounded by ice. There could be oceans of water, if not canals, just underneath their frozen surface. The mission planed by ESA will be about investigating those satellites and their physical and geological properties and their potential to be habitats for life. The probe which will be, well, probing those satellites will be housed in the Ariane 5 rocket that will be launched in 2022. It will take about 7.5 years for the probe to reach Jupiter and will spend another 3.5 years investigating those 3 satellites. 7.5 years is a long time, in human terms, but let’s not forget how vast the distances are between us and the satellites.
Even though we’ve sent spacecrafts even further than Jupiter, and therefore have already pushed our boundaries, this mission will be more about investigating in depth as opposed to breadth. That is, not only is it worthwhile to explore what is far away but we should also look deeper into what is relatively closer.
ESA is a collaboration of several countries, teams of scientists and people from different backgrounds. Now, if that is not an example of how we can work together regardless of political or national or social differences then I don’t know what is. Fair enough we’re spending one billion dollars, at least, on this mission but you know what, last year alone the USA spent about 66 billion dollars on the military. Could that 1 billion dollars have been better spent on other projects that would benefit the environment, the economy, the educational system? Even if we could come up with some other means to spend 1 billion dollars, I believe that the benefit of investing, for it is an investment more than a cost, the 1 billion dollars on this exploration will more than outweigh the benefits of spending that amount of money on any other sector alone.
Space exploration is not just about throwing money at the sky and hoping we hit upon some fanciful wonder of the universe and be mesmerised by its beauty. No matter how enthralling space exploration can be, no matter how amazing the solar system can be, now matter how exciting the prospects of alien life can be, the point is that space missions are very well grounded, metaphorically speaking. Rockets are not launched just on a whim. Satellites are not set into orbit for the pleasure of scientists. There are real, pragmatic and justifiable reasons to send probes to the furthest reaches of the universe. Other than expanding our knowledge, we are faced with very tangible and challenging problems way before even considering putting such a mission together.
By pushing our boundaries of space exploration we are also pushing our understanding in other scientific fields. We have to overcome mechanical challenges, we have to think about more resistant materials, we have to have biologists and chemists involve if we’re seeking out new lifeforms, we need computer scientists and engineers to navigate the spacecraft remotely, we need to bring in a whole hosts of different technicians to be able to meet and overcome the challenges posed by such a mission.
I will not enumerate the different technological advancement that are directly or indirectly linked to space exploration. There are just too many and the point here is to realise that we should be ready to push our boundaries further, work through our political, social and economic differences and invest in the pursuit of knowledge. Science for the sake of science is reason enough to be involved in such endeavours. Justifying those missions are far easier than having to justify spending 66 billions dollars on military.
So we have to wait until 2030 until we can receive some more information about those satellites. And who knows, that may be the year we make first contact with an extraterrestrial entity. It might not have eyes like we do, it might not fly like the birds we know, it might not have fins like the fish in our oceans, it might not even resemble anything we’ve seen before, but what would be definite is that its discovery will give us a glimpse of what we might encounter if we are to go even further in our exploration and seek new worlds, light years beyond our solar system. Until then, we need to appreciate the fact that, of all lifeforms here on Earth, we are fortunate enough to be able to gaze towards the stars, leave the confinement of our planet for the and cruise the interstellar vastness of the cosmos in search of new life, new worlds, new dreams. And you cannot put a price on that.