Is There Life Beyond Earth? The Answer is in the Water

Presented here is a statistical argument that life is not unique to Earth. The conclusion that there is other life in the universe is based on two very high probabilities. The first probability is that where there is water, there is a high probability of life. The second probability is so high it is essentially a certainty: Other sources of water beyond Earth exist in the universe. These sources of water have been observed through telescopes and by probes. Tactile sensing of these water sources is not necessary; suffice it to conclude that they exist.

Some of the sources of water beyond Earth that exist include Europa, Callisto, Enceladus, asteroid 1998 KY26 and the star system NGC 1333-IRAS 4B. Further, water has been inferred (but not directly observed) based on astronomical observation of three planets orbiting the Upsilon Andromedae star and planet HD189733b in the Vulpecula constellation. Finally, it is critical to note that these sources of water have been discovered after observation of only the small patch of the Milky Way galaxy around Earth. The rest of the vast universe has not been surveyed because of limitations on current scientific instruments.

Water ice has been observed in innumerable places beyond Earth, including comets; the Moon; Mars; Europa; Callisto; Enceladus; Uranus; Miranda; Neptune; and Triton.

It would be trivial and tedious to name all of the water sources on Earth that have life. It is sufficient to consider 100 natural sources of water on a globe and note that all of them have some form of life, even if it is microbial life. (Natural sources of water that have been excessively polluted by man are excluded.)

In physics, the method is to test and observe a phenomenon 100 times, and if it occurs 100 times out of 100 times, it is accepted as a law. Gravity is an example. If it occurs only 99% of the time, a general rule and an exception to that rule are established. In either situation, the observer can conclude that in at least one of the next 100 tests of the phenomenon, the phenomenon will occur as it did in at least 99% of the previous cases.

So too with the phenomenon that life is created in water. Life can be found in 100 of 100 natural sources of water on Earth. There are hundreds of known sources of water beyond Earth, if the comets are included. A good scientist should expect to find other life in the waters beyond Earth.

The math of this argument is beyond the scope of this article - it is not intended to be a mathematical exposition on the topic.