Yasiyykk
Yasiyykk
Astrographical Info
| Age | 6.1 billion years |
|---|---|
| Axial Tilt | 0.9° |
| Class | Terrestrial Exomoon |
| Diameter | 21,854 km |
| Gravity | 1.7 g (16.671305 m/s²) |
| Mass | 5.02 earths |
| Suns | 1 |
Orbital
| Galaxy | Elkska Galaxy |
|---|---|
| Orbital Period | 4.491 days |
| Rotation Period | 4.491 days |
| Semimajor Axis | 1,645,551.6 km |
| Solar Day | ∞ |
| System | Lizard-7566 system |
Atmosphere
| Atmospheric Composition | N2, O2, CO2 |
|---|---|
| Atmospheric Pressure | 1.01 atm |
| Temperature | 24 °C |
Surface
| Sea Composition | H2O |
|---|---|
| Water State | Liquid |
Yasiyykk, known to astronomers as Lizard-7566-N IV, is a large, Earth-like moon orbiting the massive gas giant Lizard-7566-N in the Lizard-7566 System. This green-and-blue super-Jovian planet, the fourth world around the G-type star Lizard-7566-A (often shortened to L7566A), dominates the sky of Yasiyykk, appearing up to eighteen degrees wide and bathing the moon in shifting emerald light.
Measuring 21,854 kilometers in diameter, Yasiyykk is noticeably bigger than Earth, with a mass five times greater. Its higher density and larger size produce a surface gravity of 1.7 times what we feel on Earth. Despite the extra weight, the moon supports a breathable atmosphere almost identical to our own—mostly nitrogen and oxygen—at a comfortable sea-level pressure of 1.01 bar. The air is a little thicker, the sky a deeper sapphire blue, and the climate pleasantly warm, with oceans and small continents keeping temperatures steady and mild nearly everywhere.
From any hillside on Yasiyykk, the view is unforgettable: sweeping cobalt seas, young mountain ranges still rising from active volcanoes, and, hanging forever overhead, the vast banded disk of Lizard-7566-N. Other moons often join the show, drifting across the sky and creating near-daily eclipses that paint racing shadows across the land. At night, brilliant auroras dance around the poles, bright enough to read by, while the giant planet's reflected glow keeps true darkness rare.
This vibrant, geologically lively world is home to the Thrids, a friendly humanoid people who stand tall with graceful blue antlers and long balancing tails perfectly suited to moving through the stronger gravity. Fluent in English and close allies of the Lizards, the Thrids welcome visitors to a moon that feels both familiar and wondrously alien—a true superhabitable paradise orbiting a colossal planet in a distant star system.
Formation
Yasiyykk did not form in the gentle accretion disk of a newborn gas giant like most moons. It was born in fire and collision 3.9 billion years ago, during the final chaotic reshuffling of the young Lizard-7566 system.
Two rogue ice-giant worlds (each the size of a small Uranus) had already been flung inward by gravitational scattering among the outer planets. One, the proto-Nuukkkyk, carried roughly 30 Earth masses of hydrogen, helium, water-ice, and rock. The other, its unnamed impactor, weighed about 25 Earth masses. Both were captured almost simultaneously by the already fully formed 8.27-Jupiter-mass super-giant Lizard-7566-N, which was still radiating enormous heat from its recent contraction.
Their orbits decayed rapidly in the dense circumplanetary environment. Within a few tens of thousands of years they collided at a shallow angle and a relative speed of 20 km/s, an impact that released more energy than a billion Chicxulub-scale strikes. The two mantles of water-ammonia ocean and silicate rock were largely vaporized; the lighter hydrogen-helium envelopes were stripped and partly re-accreted by the parent planet. A vast disk of molten silicate droplets, iron beads, and superheated steam blossomed around Lizard-7566-N, stretching from the Roche limit outward.
From the hottest, densest, most metal-rich inner portion of that disk, Yasiyykk coalesced in less than ten thousand years, sweeping up the refractory debris that had been shock-compressed and thoroughly mixed. That is why it possesses an oversized liquid iron core, a density far higher than any in-situ moon has a right to claim, and virtually no primordial hydrogen or helium envelope.
The cooler outer disk condensed into the remaining 80+ moons, including the retrograde outlier Jukkysk and scores of icy worldlets. The merged, battered survivor of the collision itself settled into a closer orbit as the modern Nuukkkyk: 50.4 Earth masses, still wrapped in a deep turquoise atmosphere but forever scarred and metal-enriched by its violent rebirth.
Magnetosphere
Lizard-7566-N's Magnetosphere, driven by the planet's 8.268 Jupiter mass, 17.7-hour core rotation, and an extraordinarily conductive shell of liquid metallic hydrogen three times thicker than Jupiter's, the dynamo generates a surface equatorial field estimated at 120–160 gauss (30–40 times Jupiter's) and a dipole moment roughly 1,800 times stronger than Earth's. At the 1-bar cloud tops the field is already crushing; by the orbit of Yasiyykk, 1.2 million km out it has fallen to “only” a few hundred microtesla, yet that is still enough to dominate everything within several planetary radii.
The magnetosphere itself is a flattened, pulsating cavity extending 22.5–46.5 million km sunward and well over 200 million km down-tail, easily large enough to swallow Mercury's entire orbit around the Sun. Inside it swirls a plasma population orders of magnitude denser and more energetic than Jupiter's: peak radiation-belt fluxes exceed 100 MeV for electrons and 1 GeV for protons, delivering doses of many thousands of times deadlier than the Van Allen belts.
Yasiyykk orbits just outside the densest torus of trapped particles, but once every 41-day lap around Lizard-7566-N it swings through the night-side plasma sheet during “scourge week.” During those seven days the moon plunges directly into the heart of the radiation storm; surface doses can spike to 100–200 mSv per day even under the protection of the moon's own respectable dynamo field. When the magnetic axes of planet and moon align, flux tubes carrying 10–20 million amperes snap into existence, linking the north and south poles of both bodies. The result is planet-wide lightning storms on Yasiyykk that dwarf terrestrial superbolts and aurorae so bright they cast sharp shadows at local noon.
The interaction is mutual: Yasiyykk's own 45 µT dipole punches a noticeable “hole” in the outer magnetosphere, and the currents flowing along the flux tubes inject fresh plasma into the giant planet's auroral zones, producing ultraviolet hotspots visible even from the star's far side.
In short, the magnetosphere is less a protective bubble than an ever-changing, star-sized particle accelerator that alternately shields and scourges the moons caught in its grip, with Yasiyykk riding the razor's edge between lethal irradiation and the spectacular electromagnetic light-show that has shaped all life beneath its sky.
Interior
Like Earth, Yasiyykk posesses a large, dense metallic core composed primarily of iron and nickel (with minor sulfur and trace siderophile elements), surrounded by a thick silicate mantle exhibiting plastic, convective behavior, and capped by a relatively thin basaltic crust enriched in incompatible elements.
The planet's core occupies approximately 38 % of the total planetary radius (roughly 4,000–4,500 km in an ≈ 10,000 km radius body), meaning the core volume fraction is somewhat larger than Earth's (≈ 32 % radius). Geophysical models derived from transit timing variations, rotational flattening measurements, and moment-of-inertia constraints indicate that the core remains predominantly liquid, with at most a modest inner solid seed. Core temperatures are estimated at 5,800–6,500 K at the core–mantle boundary, sustained by a combination of three major heat sources that contribute in roughly equal thirds to the total energy budget:
- Radiogenic heating Long-lived radioactive isotopes (⁴⁰K, ²³⁵U, ²³⁸U, and ²³²Th) are present in chondritic to slightly super-chondritic abundances owing to the metal-rich environment of the ancient Lizard-7566 protoplanetary nebula. Present-day radiogenic power is ≈ 28–34 TW, comparable to or slightly exceeding modern Earth's despite the planet's younger age, because the original complement of heat-producing elements was higher.
- Tidal dissipation Yasiyykk is locked in a complex multi-body mean-motion resonance chain involving the two large inner moons Ackyym and Dakishk as well as the dominant gravitational influence of the nearby gas-giant primary Lizard-7566-N orbiting at only 1.45 AU from the host star. The resulting forced eccentricity (e ≈ 0.042–0.048) and continual librations drive intense tidal flexing throughout the mantle and especially in the deep asthenosphere. Tidal power injected into the interior is estimated at 30–38 TW, rivaling radiogenic contributions and far exceeding the ≈ 2–3 TW Earth receives from lunar and solar tides.
- Primordial heat retention Yasiyykk formed relatively late in the history of the Lizard-7566 system, coalescing ≈ 6.1 billion years ago during a late-stage giant impact phase in a debris disk exceptionally rich in refractory metals and radionuclides. Because only ~6.1 Gyr have elapsed since accretion and core formation, a substantial fraction (≈ 25–35 %) of the original gravitational potential energy released during differentiation, plus impact heating from the final assembly stages, remains trapped within the deep interior. Secular cooling currently contributes another ≈ 30–36 TW.
The synergistic effect of these three heat engines, each delivering roughly one-third of the total ≈ 90–105 TW of internal power, produces an extraordinarily vigorous thermal state. Mantle convection is chaotic and multi-scale, with numerous small, rapidly moving cells in the upper mantle transitioning to larger, hotter plumes rising from the core–mantle boundary. True plate tectonics operates globally, but with far more numerous, narrower, and faster-moving plates than on Earth (average spreading rates 18–35 cm/yr versus Earth's 2–10 cm/yr). Subduction zones are deep, steep, and frequently experience slab break-off events, while mid-ocean ridges are broad, highly magmatic, and flanked by extensive flood-basalt provinces on the overriding plates.
Surface heat flux averages 0.42–0.55 W/m² (with local peaks > 2 W/m² above major plumes), equivalent to 6–8 times Earth's present-day value of ≈ 0.087 W/m² and comparable to Archean Earth or present-day Io. This extreme geological hyperactivity manifests in nearly continuous resurfacing: vast shield-volcano complexes, caldera systems hundreds of kilometers across, ubiquitous fissure eruptions, and episodic super-plinian events that inject ash and SO₂ into the upper atmosphere on a near-decadal basis. The resulting outgassing sustains a dense, 4.2–4.8 bar CO₂–N₂–H₂O atmosphere with frequent greenhouse excursions and a robust magnetic field generated by rapid core dynamo action protects the atmosphere from the fierce stellar wind of the young G0.7 V host star.
Atmosphere
By volume on a dry-air basis, measured at the 25-kilometer reference level, the composition is dominated by nitrogen at 80.12 percent, with oxygen contributing 19.47 percent and argon 0.371 percent. Carbon dioxide hovers between 1,180 and 1,250 parts per million (averaging 1,210 ppm), roughly 3.1 times the pre-industrial Earth value, while neon registers at 18.2 ppm, helium at 5.3 ppm, and krypton at 1.1 ppm. Methane varies seasonally between 1.4 and 2.8 ppm, kept in check yet periodically boosted by widespread biological activity. Hydrogen sulfide ranges from 0.05 to 0.45 ppm in the background but can spike above 5 ppm in plumes downwind of active volcanic centers; sulfur dioxide, carbon monoxide, and nitrous oxide are present in trace amounts, and the ozone column integrates to 285–320 Dobson units, slightly thinner than Earth's owing to enhanced shielding by CO₂ and H₂S in the ultraviolet.
Water vapor is excluded from the dry fraction and varies dramatically with latitude, season, and weather, from as low as 0.03 percent over winter polar highs to a steamy 3.2–3.8 percent in the permanently convective equatorial belt, occasionally exceeding 4 percent during monsoon maxima.
Surface pressure at the global mean datum stands at 1.012 bar, varying only ±4 millibars with topography and weather. Because the mean molar mass of the air is 29.32 g/mol (dropping to about 28.91 g/mol when humid), and surface gravity is 13.8 m/s², air density near the ground ranges between 1.36 and 1.41 kg/m³, making the lower atmosphere 15–22 percent denser than Earth's. The resulting scale height is a mere 6.88 kilometers; pressure falls to half a bar by 4.8 kilometers altitude, and the cruising altitudes familiar to terrestrial jet aircraft lie deep in Yasiyykk's stratosphere. Aerodynamic drag is correspondingly brutal—raindrops fragment before growing larger than 3–4 millimeters, skydivers reach terminal velocity stabilizes near 68 m/s, and both aircraft and flying organisms must either accept very high wing loading or remain confined to the dense air within a couple of kilometers of the surface.
Despite orbiting at 1.45 AU and receiving only about 940 W/m² of stellar flux—roughly 45 percent of Earth's insolation—the global mean surface temperature settles at a comfortable 22.8 °C. This mild climate is sustained by an unusually powerful suite of greenhouse mechanisms. The classical CO₂–H₂O–CH₄ greenhouse contributes roughly 24 K of warming, but the real surprises are pressure-induced absorption by N₂–N₂ and N₂–H₂ collision pairs in the deep, dense atmosphere, adding another 21–23 K, and the constant infrared glow from the nearby gas-giant primary Lizard-7566-N. When overhead, that banded ochre world subtends up to 18 degrees of sky (38 degrees across at zenith during superior conjunction—and bathes the surface in 45–85 W/m² of downward thermal radiation at an effective temperature of approximately 210 K. Together these effects produce a total greenhouse forcing of 58–62 K, nearly double Earth's, easily compensating for the distant sun.
The daytime sky is a rich cobalt that fades to pale turquoise near the horizon. At night, when the primary is above the horizon every 31.7-hour rotation, its reflected light is bright enough to read by and casts sharp shadows across the landscape in a prolonged crimson-orange “giantlight” that can persist for hours. Volcanic aerosols frequently paint the sunsets in vivid purples and bishop's rings, while high water-vapor injection and a cold mesopause keep silver-blue noctilucent clouds almost perpetually visible at high latitudes.
Land-to-Water ratio
Land covers fully 48 percent of Yasiyykk's surface— markedly more than Earth's 29 percent—yet that land is splintered into hundreds of micro-continents, elongate island arcs, and volcanic ridges, and flooded crustal fragments, none of which exceeds roughly 8 percent of the planet's total area (the largest single “continent,” the equatorial Kesharid Plate, spans only about 40 million km², comparable to Eurasia's land area but spread in a narrow, 28 000-kilometer-long ribbon). Because no substantial crustal block projects far from the global ocean, oceanic thermal moderation is extreme: even at 55° latitude, diurnal temperature swings rarely exceed 12 K and seasonal swings stay below 18 K almost everywhere except the highest topographic interiors.
The same hyperactive geology that keeps the interior molten also sculpts the surface with unrelenting violence. Hotspot chains pierce the ocean floor and micro-continents alike, producing lines of steep shield volcanoes and tablemounts that rise 7–11 km above the surrounding plains. Subduction zones generate tightly spaced arcs of stratovolcanoes whose summits often stand above 9 km; several permanently snow-free cones exceed 12 km because of continual uplift and eruption. Cryovolcanism is surprisingly common: ammonia–water slurries and CO₂ clathrate magmas erupt along extensional faults, building broad, low domes and viscous flows that freeze into brilliant white plains hundreds of kilometers across.
Many rivers begin as near-boiling artesian springs where tidal heating has raised deep aquifer temperatures above 90 °C. These thermal rivers steam violently as they descend toward the sea, depositing vast travertine terraces and silica sinter sheets that can cover thousands of square kilometers. Black-smoker communities analogous to terrestrial hydrothermal vents flourish in reverse—H₂S-rich fluids venting directly into the atmosphere—form persistent toxic plumes that drift for hundreds of kilometers downwind, creating alternating belts of verdant photosynthetic vegetation and barren, sulfur-encrusted “kill zones.”
The polar regions are almost entirely marine. Permanent continental ice caps are absent; instead, each winter the ocean freezes outward from the poles to form thick (15–40 m) seasonal sea-ice platforms. Because of the low axial tilt (11.8°) and circular orbit, these platforms retreat completely in summer, leaving only a scattering of gigantic free-floating ice shelves—some larger than Greenland—that calve from cryovolcanic islands and drift equatorward along the major gyres before disintegrating in warmer waters.
Mechanical weathering proceeds at a ferocious pace under the dense, moist atmosphere. Winds routinely loft sand and even pebble-sized grains during storms, scouring exposed bedrock into fantastical ventifact fields where every outcrop is polished, fluted, and undercut into yardangs and mushroom rocks within centuries. Erosion rates on unvegetated volcanic slopes commonly exceed 5–10 mm per year, and entire volcanic cones can be reduced to low hills in less than a million years. Only the most aggressive vegetation—dense, low, rhizomatous mats and rapidly growing pioneer forests—can stabilize soil long enough for deep regolith and eventual mature rainforest to develop.