The fact that many people do not learn to swim is no indication of the intrinsic lack of talent of homo sapiens in this direction, considering that some members of our species have performed amazing feats in water. The achievements of Olympic champions like Mark Spitz do make us all feel proud. Indeed most people as well as animals can swim, at least passably. Scientists are aware that the oceans are teeming with life some of which is extremely intelligent. We have come to know the dolphins, sea lions and porpoises are particularly clever. One is naturally tempted to ask as to what the chances are that there are “advanced life forms” somewhere in a liquid environment of some remote planet. When scientists refer to “advanced life forms” they are referring to “beings” who can not only communicate the way Dolphins do, but who have a real language like we have and are also capable of such activities as teaching, building and so on.
At least one prominent science fiction writer has referred in an exciting novel to the existence of one such advanced civilisation. But then we must remember that a novelist has a fertile imagination which can conjure up visions of advanced civilisation in alien worlds. For as yet we have no proof in the scientific sense that any intelligent race does inhabit a liquid environment. We would have to confess that we have no proof that life does exist, anywhere beyond the Earth. A few eminent astronomers and biologists believe that life does not exist on any other stellar body considering the enormously improbable series of events that would have had to occur for life, as we know it, to have evolved elsewhere.
Let us now examine the case of bodies with liquid environment i.e. liquid planets. One would be surprised to realise that Jupiter, the largest planet in the solar system could qualify as a liquid planet, thanks to some of its unique features. Some astronomers like to think that the solar system consists of the Sun, Jupiter and assorted debris—no doubt an extreme viewpoint reflecting their admiration for the enormous size of Jupiter as compared to other planets. Jupiter certainly deserves a special place in our solar system being more massive than all the rest of the planets put together. Its equatorial diameter alone is more than 140800 kms and its huge globe is large enough to house a thousand Earths.
The surface that we are able to see through our telescopes appears to be gaseous. We can see a dark belt where atmospheric gas comes down toward the planet’s surface; bright zones where the gas is surging upward; and such identifiable features as the Great Red Spot’s huge oval. The surface of Jupiter is always changing and, therefore, our view of it keeps altering rapidly. Jupiter spins round rather quickly. At less than ten hours, its day is the shortest in the solar system though an year in Jupiter is 11.9 times as long as an year on the Earth.
Jupiter’s mean distance from the sun is 722.8 million kilometres. It shines brightly in our skies. The Voyager probes flew past the massive planet at a respectable distance though they did not attempt to land on that planet. They sent back spectacular photographs and also plenty of information. Human beings can never go near Jupiter because the planet is surrounded by zones of lethal radiation and an immensely powerful magnetic field.
Yet, we have at last begun to know that Jupiter is really like under its upper layer of gas. For many decades astronomers had felt that it could be a miniature sun lighting and warming its moons. When this theory was disproved in the 1920s most astronomers decided there would be a rocky core surrounded by a thick layer of ice which would, in turn, be overlaid by gaseous atmosphere. Today, this last theory has also been assigned to the scrap heap of discarded astronomical ideas. We have learnt that Jupiter radiates more energy that it could if it depended entirely on the sun. Its inner temperature must be of the order of thousands of degrees. While this does not make Jupiter a miniature star it certainly rules out any thick layer of subsurface ice!
Astronomers have known for the last five decades that Jupiter’s upper gas is rich in hydrogen together with such hydrogen compounds as ammonia and methane. Lower down the situation must be different. According to one recent model Jupiter may be made up chiefly of liquid hydrogen with only a relatively small solid core. If true, this would constitute a “liquid environment” like the one we were talking about in the first paragraph. Moreover there must be a region sandwiched between the cold upper gas and the hot inner core below where the temperature is much the same as it is our oceans. It, therefore, seems likely that most of the fundamental materials needed for life exist there. This intriguingly suggests that living things may be swimming about happily in the seas of hydrogen in Jupiter.
Obviously, any such life forms would be radically different from the beings we known on Earth. Yet the conditions there may not be quite so unpromisingly hostile to life as for instance the uninhabitable surface of airless mercury or even that of the Moon, the one world we can prove is uninhabited without any doubt.
One would naturally be tempted to let one’s imagination go haywire. Would the inhabitants have fins and flippers. Do they talk in the sense that we do? What strange projections would be there from their heads or eyes or ears? What would their limbs be like! Of course, their eyesight would have to be extremely good as very little light would penetrate those murky depths. But those life forms may know nothing about the vast universe around them or alternately if their intelligence is sufficiently evolved they might have developed a technological society more advanced than ours. Unfortunately, it will be very difficult to find out whether life occupies the Jovian oceans or whether the Jovian seas are devoid of life.
Most astronomers rule out the possibility of sending a manned probe into the inhospitable domain of Jupiter, particularly since the enveloping deadly radiation insulates the planet from the rest of the solar system. The most we can hope to do is to dispatch an unmanned “entry probe” that would plunge to its destruction in the upper gas surrounding the planet, sending back information for as long as possible before the transmissions die out.
On the other hand, Jupiter has four large satellites and at least nine small ones. Of these Callisto the outermost of the large moons seems to be the most promising target for future explorers. Being over a million kilometres from Jupiter, it is safely outside the radiation zones. In the distant future, a Callisto expedition may land and its members will do all they can to go and learn whether anyone lives in the jovian seas. One wonders what they will find in the tepid oceans on that mysterious planet.