Kepler-942c

The target star of this colonial mission, 41 light-years out. Every long-range observation pointed at the same conclusion: habitable. Oxygen concentration, liquid water, magnetic field strength, gravity, vegetation cover — every one of them fell inside the ideal range.

The numbers the advance team measured on the surface matched: oxygen 21, nitrogen 76, carbon dioxide lower than Earth's, temperature 22 degrees, humidity 90. The ground was wet, the texture thicker than water, drawing threads when the sampling tongs closed on it. The forest stood about 40 metres from the hatch at the landing point, the trees 5 to 12 metres tall, the leaves broad, dark green with silver in them. The surface was one unbroken run of forest, the oceans wide, the geology apparently stable. Seen from orbit, it was all but another Earth.

The first sample off the surface was that sticky layer. Under the electron microscope the microstructure was layer upon layer of extremely thin organic membrane, with a fluid between the layers that looked like cytoplasm, except that the fluid held no nuclei. The analogy the biology team offered was the surface secretion of a large multicellular organism; the closest match on Earth was amphibian skin mucus, frogs and salamanders, that family. The whole surface of the planet was covered in this layer.

Mean crustal thickness 41 kilometres. A depth of 37 kilometres fell within the lower crust, estimated to be basalt-derived rock; on that structure, a pulse at that depth should be low-frequency, non-periodic, with a single-event energy peak under 10 joules.

What the orbital geological scan could give was limited, and it had started drifting on its own. On the rescan 2.4 kilometres north of the sampling point, radius 500 metres, crustal thickness was still 31 kilometres and no known cavity was detected, but the sensor's calibration drift jumped from 0.2% on the previous pass to 0.7% — inside 24 hours, the baseline had climbed to 3.5 times what it had been. The chief of the biology team read it this way: the sensor had not aged. It was reading a signal it had not yet learned to recognize.

A planet can be correct on every single reading. After the advance team set foot on the surface, one line was added to the footnote of the first sample report:

This planet and the new Earth that most people aboard understand are not the same thing.