Tarsica, Micras' satellite, is roughly the same size as Earth's moon, Luna. And they both share roughly the same daily orbit around their planet sister. The similarities between Luna and Tarsica end here however. Unlike Luna, Tarsica has a very thin atmosphere and a small amount of plantlife. Just enough to keep the atmosphere stable and self-replenishing. Due to Tarsica being both a satellite and having a thin atmosphere, the planet remains perpetually cold. Almost all water on the surface is frozen, and liquid water underground has to be reached by drilling. Hardy evergreen plants dominate the flora of Tarsica, its short Gorgon Pines seen bending against the harsh Tarsican winds through viewers telescopes on Micras. Other plants remain mostly scrub, clinging to rock crevices or near open water. Both the climate and atmosphere remain in a perpetual tundra.
The climate of Tarsica is attributed to it having a rich amount of water. Except for it being mostly frozen. The moon's core is only slightly volcanic, attributing to a number of underground water reservoirs. It does, however, remain to cold on the surface to keep water in its liquid form for very long. Only along Tarsica's equator can any liquid water be seen in amounts greater than a few square miles. The rest of the surface remains a rugged winter landscape, comparing to the higher altitudes of a mountain. Trees grow deep roots and may live to be hundreds of years old, yet grow no taller than a twelve or so feet. Thanks to the constant melting and re-freezing of water along the equator and in other "hot spots", Tarsica has plentiful snowfall. This has attributed to the common pet name of the "Christmas Moon".
Of fauna, Tarsica has little to none. Almost no birds are present except for small species similar to cardinals and chickadees which can survive the rigours of the cold and make their homes amid the small scrubbrush. All water on Tarsica is fresh rather than saline, attributing to most fauna clinging to the equatorial region. Of the largest species on Tarsica is the Polar Worm, an insect-like creature the size of a horse that prowls the wastes and eats grass and smaller insects, and the Tarsican Stone Crab, whose primary prey is the Polar Worm. Smaller species exist, such as variants of reindeer, polar bears and other life similar to that of Micras' own Arctic. However, their numbers remain relatively small due to the low oxygen content in the atmosphere. Most animal life has adapted to this situation, such as terran mountain goats or eagles did on Micras.
A map of tarisca can be found here: http://dr-spangle.com/MCS/tarsica/oldtarsica.png