Blimp

The blimps are an ancient and long-lived alien race that took up residence on Jupiter in the distant past. They protect their new home by directing comets into other planets, which eventually led them into conflict with Earth.

Anatomy & Physiology
Blimps, despite their name, more closely resemble hot air balloons. The upper body consists of a balloon filled with heated hydrogen, ringed with six pairs of eyes around the equator. Below this a trunk with a mouth on each side. These mouths are only for producing sound and cannot consume food. The trunk splits into six tentacles, which then split into six "hands" that themselves split into six "fingers." At the center of each tentacle is a mouth used for feeding. No size or weight are ever given for blimps, but their descriptions indicate that they are larger than humans, although not drastically so.

As creatures from Jupiter, blimps have an extremely low body temperature, far below the freezing point of water. Because of this, humans and blimps can only touch each other for a few seconds without protection before the temperature difference injures them both. They are also anaerobes, and unlike all Earth life they do not make any use of water. Instead, they appear to breathe hydrogen and use ammonia as a solvent.

Diet
Blimps can eat food in solid, liquid, or gaseous form. They are primarily shown eating aeroplankton, which they often prepare as cuisine.

Reproduction & Life Cycle
Blimps reproduce by excreting nanogametes into the atmosphere, where they sink about 2,000 miles down to the area of Jupiter's atmosphere where gaseous hydrogen transitions to liquid. At the "surface" of this ocean, the nanogametes aggregate into masses that eventually form juveniles, which make their way up to the upper atmosphere. Once a juvenile reaches a blimp city, a new adult is carved out of its mass.

Blimps live extremely long lives. A blimp not yet a million years old is considered young, and some of the oldest blimps remember their migration to Jupiter 330 million years ago.

History
The blimps evolved on a Jovian planet they called Firsthome. For at least a billion years, they protected their planet from "snowstrikes" (cometary impacts) by directing incoming comets into their sun, which eventually aroused the ire of the star's native plasmoids. The plasmoids, refusing to destroy the blimps outright, responded with a series of targeted solar eruptions, driving the blimps from their homeworld. The evicted blimps tamed giant spaceborne aliens called magnetotorii and attached their moons to them, embarking on an an interstellar journey.

The blimps arrived on Jupiter around 330 million years ago, during Earth's Carboniferous period. They quickly settled the planet, which already had a thriving ecosystem similar to their own. They installed their moons in the planet's orbit as Jupiter's innermost four moons, and used the Galilean moons to deflect comets. The blimps learned from their earlier mistake, and instead bombarded other planets in the solar system. One such comet struck the Earth at the end of the Cretaceous period, wiping out the dinosaurs. The blimps would later direct another comet at Earth in the early 23rd century, unaware that the planet was inhabited.

Technology
Blimps primarily use biotechnology. Their cities, for instance, are enormous organisms the size of small nations, which blimps inhabit by the millions. The cities are colonies of trillions of gas-filled creatures that form agglomerations not unlike coral. The blimps are able to biochemically guide their precise growth.

Uniquely, blimp biotechnology incorporates metal and robotics, as they are innately able to excrete waste metals into a complicated machine called a symbiaut. Symbiauts are essentially robots, controlled and programmed by the blimp that created them, made for specific functions. They generally have wheels, and were thus called "wheelers" by humans, but many are also able to move using blimp gravity technology.

Blimps have highly advanced gravitic technology that generates an antigravity force to manipulate objects. This force has a short range, forcing the blimps to maneuver Jupiter's moons in order to affect objects that are further away.