Rocheworld: Weather in a Double Planet System
Physicist and Author Robert Forward Creates True Science Sci-Fi Scen
Sep 14, 2008
In addition to authoring a plausible and scientific approach to traveling to and exploring Barnard star system fictional planet Rocheworld in his book of the same name, Forward also designs a complex weather system consistent with the rotating double planet’s physical and orbital properties.
Rocheworld is actually 2 planets, Roche and Eau, orbiting each other like twin children hugging and twirling in a circle.
Bardnard's Star: Roche’s Weather
Roche is rocky and dry, dusted over by tornadoes, with many active volcanoes. A large, conical mountain formed the side closest to Eau. Other than the occasional tornado and volcanic eruption Roche remains cold and desolate for much of its orbit around Barnard.
Barnard's Star: Eau’s Weather
Though both planets technically have an atmosphere of methane and ammonia, Eau has an ammonia ocean covering most of its surface. Since liquid is much more susceptible to changes in heat and the movements of the planet, Eau has a more dynamic weather system than rocky Roche.
Ammonia Oceans and Underwater Glaciers Watery Eau
The warm crescent on Eau is close to its equator, and temperatures can reach as high as -20 degrees Celsius. Contrastingly, the polar region contains the cold crescent, where temperatures are around -40 degrees Celsius. Similar to Earth’s system, strong ocean currents develop where cold and warm crescents meet.
Since Eau’s ocean is comprised of mainly water and ammonia, the differences affect the state of these two substances the most. The top layers of the poles mainly consist of ammonia from ammonia rain. Where the ammonia content is 23% or greater, water ice formed on the top of the ocean sinks down to the bottom of the ocean, creating large underwater glaciers.
Snowing in Eau’s Ammonia Ocean
Four types of ice are possible in the Eau ocean. One type is of pure water, one of pure ammonia. The more interesting blue and white snows are a mixture of the 2 compounds. The currents and changes in temperature and ammonia content allow for situations where one type of snow may fall, while another type of snow rises. The crew of the Dragon encountered this scenario when the friendly aliens took them below the surface to protect them from the tidal forces created during periapsis.
Rocheworld “periapsis” Causes Planetary Ocean Exchange
Throughout its orbit, Eau has a large conical mountain to match Roche’s mountain where the two are closest to each other. However, Eau’s mountain is made of ocean<. During periapsis, a perfect storm of gravitational forces between Roche, Eau and Barnard, a “50-km high interplanetary waterfall” occurs.
The extra gravitational forces of Barnard as their elliptical orbit reaches it closest point cause the ocean to move toward to the water peak with humongous force. The ocean gets pulled up the water mountain in successively increasing “ring” waves, which, when the tide is strong enough, spill over to Roche in a spectacular display that only real science could dream up.
The water hits Roche in the form of thunderhead clouds and much is transformed to steam by the active volcanoes. The strong Coriolis forces in this area twirl the steam into huge tornadoes that rip across the surface of Roche. By the time this dramatic shift is over, much of Eau’s ocean has transferred to Roche.
Though Rocheworld’s ocean exchange stands out as its peak weather phenomenon, it is clear that the rest of the weather on this unique double system is also anything but ordinary. With interplanetary waterfalls, up-and-down snowstorms, and changing ocean composition and currents, Forward makes a true science setting for Rocheworld.
 |
