Goarthech (Cherith Beacons): At first glance, and even second and third glances, Goarthech is all that one might want in a garden world for a prospective colony. Moderate gravity, close to standard. A warm, mid-range yellow sun, a conveniently located moon. An oxygen atmosphere with enough to breathe, but not enough to set everything on fire.
And to add to those practical requirements, Goarthech is a beautiful world, one that had development corporations drooling over the images the far horizon probe sent back: majestic purple mountains, burnt orange seas under a sky just the purplish side of blue, with tumbling arcs of tropical islands to watch the sunsets from. A little chilly (planetary average temperature of 242 K) for many races, but nothing that couldn’t be handled.
That is what the first-in survey team thought until they discovered the planet’s secret. The fortunate ones discovered it when they read the chemical analysis of the planetary atmosphere, while those less fortunate discovered it through choking, gagging, retching, and carrying their colleagues with insufficiently sturdy constitutions back to the nearest evacuation shuttle. Evacuation shuttles which, in the fullness of time, would be jettisoned back into the planetary atmosphere along with anything else it had touched.
Goarthech, it turns out, has considerable geothermal activity going on in its extensive shallow seabeds, and this activity in turn supports a large and rather well-developed ecology of sulphoxy-metabolism bacteria – and while some of their metabolic byproducts contribute to giving the planetary oceans their lovely burnt-orange hue, one in particular bubbles to the surface in quantities sufficient to make it a constant low-level presence in the atmosphere.
That product? Thioacetone, a chemical notorious even in minuscule quantities for irritating beyond measure the chemoceptors of virtually every known race to have chemoceptors, and by so doing induce some of the most remarkably appalling olfactory qualia translatable across species.
Perhaps one day a race will join the Worlds whose members find thioacetone a pleasant experience, or who are, at the least, anosmic, and who care nothing for driving away any potential visitors to their colony, and on that day, Goarthech will at last live up to its potential.
But for now, the “Stinking Vale” remains on the Commission for Colonization’s open list, tempting and tantalizing the hard of sniff.