My normally almond-brown skin is taking on a decidedly yellow tone. Some expedition members with less natural melanin are sporting an even more alarming shade of orange from their steady diet of Tangroot. Of course we could filter out the staining compounds, but it would take energy and what really would be the point? We knew this planet would change us, as we ultimately may change it to suit ourselves. Not all biospheres can support human life, and we should not invade all of those that can. In some cases we have the potential to destroy fragile ecosystems and disrupt life cycles just by our presence. It all comes down to chemistry.
The human body is host to tens of thousands of species of "friendly" bacteria. Our own body cells may be outnumbered ten to one by tiny organisms. We need them; they come with us; they are part of the package. And yet they represent billions of years of aggressive, invasive evolutionary strategies. Even otherwise benign biota in a new environment could run wild, overrunning the native species and overwhelming the entire biosphere.
Fortunately for the most part stable microbiotic systems like Sigma 957 are quite robust against invaders. The probe did extensive testing -- and we confirmed the results when we arrived -- to determine that Earth bacteria wouldn't find it easy here. Although our chemistries are similar enough that large creatures like us can eat what we find and (mostly) live, the microbial environment is mutually hostile. While this means that we're not likely to get sick on native diseases, it also means that the genetic tricks that our bacteria have evolved for living comfortably in a multicellular Earth animal will not work if they try it outside our bodies. Microbes depend on a chemical ground truth, and those differ enough to protect both sides.
We're cautious nonetheless. A cache of Earth bacteria, left carelessly, could ultimately find a way to thrive, so to reduce the chance of that we limit how much gets left about. Mostly that means we process our own wastes, recycling what we can and sterilizing anything that remains. As the old saying says, we try to leave only footprints.
For ourselves, we're soaking in it every day. This is why we all have artificial immune systems; if I didn't have one I wouldn't be here. Most likely before anything from this ecosystem could learn to pose a threat to us we'd have changed ourselves. If we stay we will, over the centuries, become native to Sigma 957.
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