Introduction to Life in the Solar System: Humans and our associated skin on the third rock out from the Sun are lords of life forms in the solar system. But, we’re not unique lords, just lords. Other abodes in the solar system, most probably Mars, Jupiter, Europa, and Saturn, are anywhere from possible to probably habitable homes to simple microbial life forms; perhaps something slightly above and beyond that. Taking each place in turn…


But first, a pat on the back for those terrestrial microbes; all those germs, bacteria, unicellular critters, and even viruses (though viruses, depending on your perception of their being alive as we usually define ‘alive’ might exclude them from this discussion). They are tough; I mean, they boldly go, survive, and even thrive where even angels fear to tread, far fewer humans. Microbes can live in environments where other multicellular critters also fear to tread and often can’t: from the coldest terrestrial environments, up to the near-boiling temperatures, from deep underground to the heights of the atmosphere, from inside water-cooled nuclear reactors and the interior of rocks, to intensely saline, acidic and alkaline environments, to ecosystems where the sun never shines, like the abyssal depths.

They can even survive outer space. Bacteria survived on the surface of the Moon – on Surveyor Three. This was possibly the most significant discovery of the Apollo Moon program, and it hardly even rated a mention. Astronauts from the Apollo 12 mission brought back to Earth parts of the unmanned Surveyor Three Lunar Lander. Terrestrial bacteria on those parts survived the lunar vacuum, solar radiations (UV, etc.), the massive temperature extremes, and the lack of water and nutrients. Experiments since done in low earth orbit have confirmed that given just minimal shielding, bacteria can indeed boldly go!

You’d be aware of how difficult it is to sterilize something, be it hospital equipment or a spacecraft bound for a Martian landing. They’re tough – have you ever read about a mass extinction event where a bacterial species, unlike, say, the multicellular dinosaurs, went poof? Microbes are easy to transport. They can be blasted off the surface of the Earth, shielded from radiation by the debris, and survive to land on another world and be fruitful and multiply. There’s little doubt that somewhere way out there, terrestrial bacteria have hitched a ride to the stars, bolding going where lots of microbes have gone before! Translated, I firmly expect that the universe (including our solar system) is teaming with microbial life in all sorts of places. The less-than-glamorous catch is that LGM will not stand for Little Green Men but Little Green Microbes.

On Earth, microbes rule, OK? The biomass of all those bacteria, etc., put together quickly equals the biomass of every other multicellular plant and animal added together. One could easily argue that microbes, not humans, are the jewels in God’s crown – He made so many of them and talk about being fruitful and multiplying. The number and mass of micro-organisms are many orders of magnitude greater than humanity’s numbers and collective mass. There are millions of microbes living inside you – most beneficial. It could also be argued that you are nothing more than an elaborate colony of billions of unicellular organisms – your cells that make you, you.