|Source||Expedition book and Alien Planet documentary|
|Primary Terrain||Deserts and mountains, with a few areas of vegetation|
|Surface water||Small water bodies, the largest body of water is covered by a matrix of microorganisms|
|Rotation period||26.7 Earth hours|
|Orbital Period||728 Earth days|
Darwin IV is a mars-sized rocky world, the fourth planet in the Darwin Binary System formed by 6 planets, is 6.5 light years away from Earth's Solar System. With a very dense atmosphere and little gravity, it is home to a large number of complex organisms characterized by lack of eyes and rely mainly on echolocation and infrared vision, with different and aberrant forms and sizes.
Compared to Earth, the planet has far less water, and has a very dense atmosphere. The planet has lower gravity in addition to its atmosphere, allowing for organisms to get much larger than what is possible on Earth. Most of the planet's water is locked up either in the Amoebic Sea, the polar ice caps, or in the dense atmosphere of the planet. Due to its small size (it is only a few hundred kilometers smaller in diameter than Mars), it has lost most of its major oceans over the eons. The terrain around the tropics and poles in both hemispheres is predominantly a plain with some geographic features probably caused by the now extinct oceans or by the now scarce rivers and lakes, while at the equator exist a series of mountain ranges which form a mountainous belt around the planet.
Grasslands and plains
The vast majority of Darwin IV is "grassland", in the sense that large vegetation such as trees are rather sparse, due to the relative lack of surface water. Pagoda trees are the largest trees in these environments.
Forests consist mostly of plaque-bark trees, which are fed upon by trunk-suckers. In turn, the daggerwrists feed on them.
Also known as Mare Amoebicus, this territory is completely covered by a large gelatinous layer of microorganisms of about 10 meters deep which protect the last huge reserves of water, This area occupies 5 percent of the planet's surface. The fauna that lives both around and inside the sea depends mainly on this superorganism for food and shelter, including one of the largest being, the Emperor Sea Strider.
Compared to the northern pole, the southern pole is much larger. The tundras of Darwin IV are full of many strange animals, such as the tundra-plow, and the belly-thrower.
Darwin IV has a very dense atmosphere, which has given rise to creatures with wingspans as large as 300 meters.
Fauna and flora
Compared to Earth, faunal organisms here are blind, relying on other senses, due to the dense fog of the planet, preventing easy usage of eyesight, most of them tend to rely on echolocation and infrared vision to visualize their surroundings. The majority of species present a huge variety of limbs to mobilize, from monopeds, bipedals, tripods, quadrupeds, ect. Other species, mainly aereal forms have other mechanisms to mobilize, some are able to float by the use of special sacks, others by jet propulsion.
History and exploration
In this timeline the exploration of Darwin IV occurs in the "near future" where instead of humans, a series of probes with advanced artificial intelligence is sent in a trip of several decades because they travel at 20% of the speed of light.