Jim Baen's Universe

NonFiction articles

The Essay with No Title (until its end)

Written by Stephen Euin Cobb

Based on what we have seen of the rise of life on our planet, one can extrapolate that there are three basic needs for life to develop elsewhere in the universe. Only if all three of these things are present can life form, thrive and become diverse enough that it evolves to fill all the possible niches within its locally available volume.

First: an energy source. For us this is the sun. In the darkness at the bottom of the ocean this can be unstable sulfates constantly spewed from the ocean floor. In other places in the universe the energy may take a different form; but energy must be available, it must be abundant, and its availability must not be interrupted too thoroughly or for too long.

Second: complicated chemistry. There may be ways for life to form without chemistry but we have no proof of it as yet. All the life forms we have examined so far are chemical, and their chemistry is astoundingly complicated.

The third requirement is time; lots and lots of time. Time measured in many, many millions of years.

All three of these things must come together to allow for life to develop. If any one of them is lacking life is unlikely to form.

For this essay I would like to examine only one of these three. Time hardly needs any explanation; even the concept of an energy source is relatively straightforward; but complex chemistry has a billion possible permutations. Fortunately I will only talk about one: expediting it.

To expedite means to facilitate, to make something more efficient, more effective, or just plain faster. For complex chemistry solvents do exactly that. The solvent of choice on earth is of course water. The earth is positively awash in it.

But let's pause to define solvent. Solvents are liquids (usually, though sometimes they are dense gasses) which are capable of dissolving or absorbing one or more other chemical substances. To the eye, the dissolved substance magically disappears into the solvent. In reality it has been completely disassembled into its individual component molecules which are busily bouncing among the individual component molecules of the solvent.

By separating the dissolved substance into individual molecules the solvent gives the dissolved substance the opportunity for its molecules to mix and interact with the individual molecules of other dissolved substances, thus expediting their chemical reactions.

This is a powerfully useful situation, but there is no reason why the solvent must be water. Other liquids are common in this universe: ammonia, methane, hydrogen, even iron is a good solvent. It can dissolve huge quantities of carbon.

But while the solvent does not have to be water, it does have to remain liquid. If it freezes solid the substances dissolved in it are no longer free to mingle with other dissolved substances and can no longer undergo chemical reactions; in which case the expediting grinds to a halt.

In order to exist in a liquid state, a substance must be above its melting point and under enough pressure to keep it from boiling away. For most substances the amount of pressure needed for this is never zero. That is, in order to exist as a liquid, and therefore work as a solvent, the solvent must be under pressure. On earth the atmosphere provides the pressure; same on Jupiter and Saturn and the other gas giant