Document ETH-074: Climate and Geography

The planet of Eth mirrors Old Earth in many ways regarding composition. Most of the rock is silicon dioxide, with lighter elements remaining near the crust while heavier elements likely linger near the liquid nickel-iron core. The only difference to note is the high concentrations of calcium in the crust and the low concentration of nitrogen and carbon. Unlike Old Earth, there exists no plates nor plate tectonics, minimizing the geologic activity. Bizarrely, there is much less activity than is predicted by models, suggesting an additional force at work. This leaves the terrain very flat, assisted by the frequent flash floods. These floods also give rise to shallow temporary seas, covering only a small portion of land.

Climate
Despite being the most inner planet in the system, the temperature of Eth is rather cold, averaging around 10 o  on the equator and -30 O  at the poles. This is due to the fact that Eth orbits a red dwarf star, just large enough so that the distance between the star and Eth prevents Eth from becoming tidally locked. The low abundance of the greenhouse gas CO 2  also contributes to the cold weather Because Eth’s minute axial tilt is all but negligible on climate, the planet lacks seasons. This has lead to a very sharp boundary between the northern and southern latitudes where the ground turns white due to ice and the grey equatorial region that rarely dips below freezing, despite being so close to it. The stability is also assisted by the winds, that almost always blow east-west, preventing polar air from mixing with equatorial air.

Atmosphere
The atmosphere is strikingly similar to Old Earth because of the presence of life with similar metabolisms, composed of nitrogen, oxygen and carbon dioxide. The atmosphere contains a large amount of calcium dust (most commonly in the form calcium chloride) that is maintained by the waste products of heterotrophs and the near-constant wind. This makes habitability dubious, as protective suits are necessary since CaCl 2  is a skin and respiratory irritant, especially in sustained contact (see Document ETH-344 for a review on Eth habilitbiblity). The dust also reduces visibility, although it is likely that the native fauna view a different section of the electromagnetic spectrum, that is likely unimpeded by the dust.