ET v. Earth Pathogens

The Andromeda Strain or War of the Worlds— Will ETs Kill Us or Vice Versa?

BY TIM CALLAHAN

In H. G. Wells’ 1898 novel The War of the Worlds the seemingly invincible invading Martians are wiped out by Earth’s microbes, against which they have no immunity. In Michael Crichton’s 1969 novel The Andromeda Strain the opposite happens: the people of a small town in Arizona are annihilated by a microorganism accidentally brought to Earth in a crashed satellite. Both novels share the thesis in common that microbes from any given planet will be brutally inimical to the denizens of another planet, who have no immunity to these alien pathogens. In Gordon R. Dickson’s 1987 novel Way of the Pilgrim, the Aalaag, alien conquerors of our planet are immune to Earth’s microbes because their biochemistry is so different from that of the native pathogens. Who is right, H. G. Wells, Michael Crichton, or Gordon R. Dickson?

To some degree, each of these authors probably had a piece of the truth in their fictional works. Assuming ETs coming to Earth are carbon-based life forms that evolved in a watery medium, it seems likely that natural pre-biotic chemical reactions would produce the same basic biochemical building blocks on their home planet that gave rise to life here on Earth. This assumption is based on well known research such as the 1952 Stanley Miller and Harold Urey experiment, which produced as many as 20 different amino acids from electrical discharges into a reducing atmosphere of methane, ammonia and water vapor; the 1961 experiment by Joan Oro, which produced adenine, among other compounds, from hydrogen cyanide, and amino acids from hydrogen cyanide and ammonia;1 and the 2008 volcanic discharge experiment. 2 Beginning with the same building blocks, such as amino acids and cyclic compounds such as adenine, carbon-based life developing in water on other planets, would, given the natural chemical processes observed in these experiments, likely have generated a basic biochemistry similar to ours. That is, bodies made up of, among other things, proteins and nucleic acids. Hence, they would likely be potential food sources for Earth’s microbial pathogens.

However, there are certain factors we need to consider before making the sweeping generalization that either visiting or invading extraterrestrials would be sitting duck hosts for our microbes. Three of these are: possible differences in biochemistry between terrestrial and extraterrestrial life forms with respect to the “handedness” of their molecules, the possibly arbitrary nature of our genetic code, and the transmission of certain diseases by insect and arachnid vectors.