The polar icecaps of the planet Darwin IV are similar to the icecaps of Mars. The planet's predominant color of dusky ochre is relieved by a sparse mottling of red and the two crisply defined polar caps. The northern icecap is known as Glacier Cap North, or Glacier Borealis. The southern icecap is known as Glacier Cap South, or Glacier Australis.
As there are no oceans or seas on Darwin IV, the polar caps are the largest concentrations of water, in the form of ancient ice. These glaciers recede and advance with the seasons; as with Mars, the southern cap grows larger than its northern counterpart due to the prolonged southern winter.
The sub-polar region's flora is limited by the demanding environment. Low, ground-dwelling, lichen-like plants cover the almost frozen soil in a gray-green mantle that is broken by whipweed and polardots. This is a biome in which the mechanisms of nature are at their most fragile.
Near the arctic wastes are boggy, pre-tundra moors for part of the terrain.
The flat stark tundra landscape of Darwin IV is an almost uniform olive-brown in color. Scattered patches of low-growing white and blue vegetation soften the bleak and monotonous aspect of this barren biome. Innumerable rounded boulders dot the ground in growing numbers as one approaches the vast icecap.
Both of Darwin IV's poles are covered by glaciers of immense proportions. Glacier Cap North differs from its southern counterpart by its greater thickness and by the jagged mountain peaks, B14 and B15, near its center. Glacier Cap South has no such visible peaks.
Brilliant against the gray-green clouds, the edge of a glacier appears artificial, like an improbably long, whitewashed stucco wall extending to both horizons. The polar caps extend into the distance, milky white oceans of ice shining in the suns' diminished light like a cracked and roughened lamina of ceramalloy. A dense white cloud of frozen vapor can sometimes begin to steal across the surface of the ice, obscuring the suns and the icefields from view.
The edge of a glacier has a fissured surface. Its bluish, icy face rises to varying heights, sometimes reaching thousands of meters, while other spots are no more than a few meters high. Strewn on the ground before it are fields of broken iceblocks calved off the fracturing parent glacier. These blocks, carved by wind and suns, attain the most bizarre forms. The tundra resembles a vast chessboard with hundreds of white, spired pieces slowly devolving in the thin, arctic sunslight. There can be outlet glaciers as well.
The tundra close to the glaciers stretches out like a velvet gray-green carpet, dotted with wind-carved boulders. The softening ground basks in the warmth of the newly-risen suns in the spring.
The subarctic biome presents more biological enigmas than any other region on Darwin IV.
Spring in the circumpolar tundra is a time of reawakening, when the water, trapped for months in the spongy soil above the permafrost, begins to melt and bestow its life-giving qualities. Everywhere the low, hardy tundra plants begin to show signs of life. Gently glowing buds, in unthinkable numbers, appear upon the dark ground like a carpet of stars. The melted snow and softened ground also free the vast hibernating populations of diskflyers, which take wing and ascend in swirling clouds into the air. Larger fauna, too, such as Unths, seem more alive in their warming surroundings. The suns' rays touch the arctic like a remembered caress, charging plants and animals alike with the excitement of rebirth.
During the months of Darwin IV's arctic twilight, the perpetual dusk makes spotting animals considerably easier, as the creatures' bio-lights are in constant evidence. They are, however, not the only beautiful sources of light. Often, high above the massive glacier, there can be vast, crackling auroras flickering and shimmering, providing a glorious backdrop to the crags of B14 and B15 at the great northern glacier cap that covers Darwin IV's northern pole. The wonderful play of light reflected upon the icy bank of the glaciers seems to imbue the ice with a lambent semblance of life.