The fact that we failed to notice 99.999% of life on Earth until a few years ago is unsettling

From Why Not Mars by Idle Words.

But the really exciting news for Mars was the discovery of unexpected life on Earth. Microbiologists had long suspected that the 12,000 or so known species of microbes were just a fraction of the total, with perhaps another hundred thousand “unculturable” species left to discover. But when new sequencing technology became available at the turn of the century, it showed the number of species might be as high as one trillion. In the genomic gold rush that followed, researchers discovered not just dozens of unsuspected microbial phyla, but two entire new branches of life.

These new techniques confirmed that earth’s crust is inhabited to a depth of kilometers by a ‘deep biosphere’ of slow-living microbes nourished by geochemical processes and radioactive decay. One group of microbes was discovered still living their best lives 100 million years after being sealed in sedimentary rock. Another was found enjoying a rewarding, long-term relationship with fungal partners deep beneath the seafloor. This underground ecology, which we have barely started to explore, might account for a third of the biomass on earth.

At this point, it is hard to not find life on Earth. Microbes have been discovered living in cloud tops, inside nuclear reactor cores, and in aerosols high in the stratosphere. Bacteria not only stay viable for years on the space station hull, but sometimes do better out there than inside the spacecraft. Environments long thought to be sterile, like anoxic brines at the bottom of the Mediterranean sea, are in fact as rich in microbial life as a gas station hot dog. Even microbes trapped for millions of years in salt crystals or Antarctic ice have shown they can wake up and get back to metabolizing without so much as a cup of coffee.

The fact that we failed to notice 99.999% of life on Earth until a few years ago is unsettling and has implications for Mars.