INTRODUCTION

Lyr's a world-model challenging exobiologists like Peter Ward Douglas ("Rare Earth"), who say complex life will only evolve on worlds almost exactly like Earth. Lyr is emphatically not Earth! Seven times as massive, in an eccentric orbit too far out from its dim little sun, with the wrong density, wrong tilt, wrong satellites, wrong geology, wrong water content... can you get wronger? Douglas says big wet worlds like Lyr will be (at best) world-seas, poor in minerals, with sparse unicellular life at most, and if it's multicellular than not intelligent, and if intelligent than not technological.

Tell that to the Lyrans.

Still, give Douglas credit for considering large planets at all. As I write (2006), we've found about 200 planets; most are Jovian. Only 4 fall in the size range between Earth and Uranus (14 earth-masses). One, around 5 masses, is probably as cold as Pluto. Another, at 7 masses, is just two million miles from its sun: probably a lava ball. The other two, each a few Earth-masses, are mere cinders orbiting a pulsar (that is, their sun went nova). Not exactly Edens! Plenty of big rocky planets surely exist, but we can only guess what this group is like--and we rarely do! Our solar system's mass-gap between gasbags and rocks has given us an imagination-gap. Even science fiction, usually quick to explore possibilities, has very few middleweight worlds: Silverberg's "Majipoor" series plus short stories like Tiptree's "With Delicate Mad Hands" or pulp tales like "We Guard the Black Planet" or "Heavy Planet". Scientifically, they range from sloppy and sketchy to downright silly. Only Poul Anderson's "The Man Who Counts" (discussed in Lyr's Evolution) details a fairly plausible middleweight world--and even it has problems.

In short: such worlds are a blind spot in the human imagination--ignored as potential biospheres. So... let's put this common planetary type center stage...

Welcome to Lyr

LYR: BASICS
• Sun = smaller, redder, and cooler than Sol--and much commoner! Most exobiologists focus on sunlike stars. They assume viable planets around red dwarfs would have to orbit so close that solar tides would slow their spin till they're locked facing the sun--burning dayside, freezing nightside. But this overlooks four spin factors:
  1. Dumb luck. How big's a world, and what bodies formed it? What hit it later, at what angles? Jupiter and Saturn, too big to easily knock around, spin very fast indeed. They suggest most planets start fast but lose random amounts of spin to impacts. Unlucky worlds like Venus get whacked, slowed, and tidelocked. Lyr is big--and lucky.
  2. Deep time. When Luna was young and close, its tidal drag was huge. Yet Earth spins as fast as tideless Mars, despite eras of strong tidal drag! And Mercury, despite stronger solar tides, spins faster than Venus. Our sample's still too small to conclude that solar tides lock all sunhugging planets. Some, yes--but all? Serrana is a model of a viable sunhugger.
  3. Greenhouse effects. Thick air and high CO2 can warm a world enough for liquid water and life--far enough out from its sun to make solar tidelocking unlikely. "Tepid Jupiters" are common; middleweight worlds like Lyr should be too.
  4. The sun is the strongest tidal influence on sunhugging planets; but Douglas forgot moons. Their biggest tidal influence is their planet, not the sun, so they end up facing their primary--and spinning relative to their sun, even if it's close. A giant acts as spin insurance! Pegasia is a model of such a moon.
  Together, viable moons and planets with small suns probably outnumber the Earths out there. Big suns like ours are rare, but little red stars are common as dirt!
• Orbit = elliptical, from 1.1 to 1.35 AU. Why elliptical? Well, eccentric planets are commonly written off as unfriendly to life. But are they really? Don't temperature swings often help life, ensure that at least part of a year is warm enough or rainy enough?
• Total annual insolation = about 25% of Earth's (Much like our inner asteroid belt--Mars gets 44% as much sun as Earth, Jupiter only 4%). This seems fatally low, but huge Lyr is wreathed in dense greenhouse gases! See CO2 and TEMPERATURE, below. The eccentric orbit creates a short worldwide summer, then a long mild worldwide winter (the outer half of an elliptical orbit is slower--takes up more of the year).
  CONFESSION: I deliberately put Lyr in such a cold belt out of laziness. I was creating two worlds at once! This far out, Ly'rs icy moon Oisin could BE icy instead of rocky; it's like Europa, but with a thinner ice skin over its sea--so thin sunlight gets through, feeding much richer life than I expect on Europa. Any warmer, and Oisin would die; any colder, Lyr would die. If I wasn't dumber than an amoeba I'd just grant this odd couple a divorce. Lyr could orbit closer in, and Oisin could circle another gas giant further out. So if you calculate that Lyr needs more sun or Oisin less to be as I describe, don't let that convince you their TYPES aren't viable! They represent two SEPARATE scenarios for life in SEPARATE orbits, really, neither one Earthlike. They TRIPLE, not double, the number of potential lifezones.
• Axial tilt = 36 degrees. Higher than Earth's, but no Uranus.
• Surface radiation and UV levels = well below Earth's. The cooler sun produces much less, and the dense air blocks most of that. Radiation was once believed crucial to mutation, and thus to evolution itself, so cool stars might evolve complex life late or never. Today it's clear environmental stresses push evolution more than the absolute mutation rate.
• Year = about 2.5 Earth years. I'm being a bit vague because I haven't looked up the curve for light vs mass of Lyr's sun yet, and the mass determines the year-length. Just wanted some wiggle room!
• Seasons = both a planet-wide cycle, caused by the elliptical orbit, and hemispheric seasons caused by axial tilt. This means the equatorial belt isn't tropical in the seasonless year-round Terran sense. During global winter, "rainforests" are warm to mild with light rains; in the summer, hot and torrential. Quite monsoonish! The high latitudes, on the other hand, have stronger seasons than Earth in terms of light, but with milder temperature fluctuations--the thick damp air and deep seas are just too big a thermal anchor.
• Mass = 7 Earths! Why make Lyr so big? I want to show that's no problem--show how big a world can be and still have a tolerable gravity.
• Density = 3.4 gm/ml. Mars is 3.95, Earth is 5.5. Lyr has a smallish iron core for its size (most solar systems are poorer in heavy elements than ours, AND large, cool, outer planets tend to be lightly built). Though richer in silicon than iron, Lyr is still a rocky world, no gasbag like Uranus (1.25) or Saturn (0.79!)
• Diameter = 18,500 miles (29,600 km): around 2.3 Earth diameters. Circumference is about 58,000 mi (93,000 km). The map's thirty-degree lines are about 4800 mi apart (7700 km). All the land on Earth would fit into three squares! Note that Lyr's not spherical--its fast spin flattens it visibly. Lyr's diameter through the poles is only 17,500 mi (28,000 km).
• Surface area = a billion square miles (2500 M sq km): five times Earth's!
• Gravity = 1.33 G--but it varies! Lyr spins so fast it's oblate (flattened like Saturn), so polar gravity is 1.4 (close to the center of mass), while it drops to only 1.23 G in the tropics (the swollen equator's further from the core, AND centrifugal force lightens you). Lyr's as heavy as seven Earths, yet you could walk! Surprised? Gravity rises only as the cube root of mass. Also, big worlds aren't as dense, since they can hang on to more light matter--hydrogen, helium, ice, carbon, quartz. The result? Similar gravities. Saturn's mass is 110 times Venus's--and their gravities are both Earthlike! Alien biospheres may roast, freeze, drown, or poison you--but not flatten you.
• Moons = six. Four are just rocks under 1000 km wide, but one's 2100 km (1300 mi) across--let's stick with our Celtic sea-motif and call it Manannan. The sixth is as big as Titan: 5000 km/3100 mi. We'll call it Oisin ("o-SHEEN") after that legendary mariner. Oisin orbits 300,000 miles out, further than Luna, but it's so big its tidal pull is over 50% stronger. Lyr is too massive for that to have slowed its spin much, but the tidal stress explains Lyr's hyperactive tectonics. Oisin's a world in its own right--a world with life.
• Moonlight = bright. Oisin looks big--nearly 20% wider than Luna, taking up 40% more sky--and its icy skin is brilliant. A full Oisin is nearly four times as bright as our full moon. Planetary nightlight! The other five moons are small, but at least one is nearly always up, so it's rarely dark on Lyr.
• Rings = one, from 12-30,000 km above the surface; rarely visible in daylight but fairly impressive on dark nights--a bronze arch (it's mostly rock, not ice like Saturn's rings).
• Internal heat and volcanic potential = large. Tidal stress from the large moon and the swift spin add to Lyr's own huge internal heat reservoir.
• Day = only 12 Earth hours! Oisin's tidal drag can't slow massive Lyr much. Lyr's fast spin drives strong currents and winds. The short day evens daily temperature swings a lot.
• Water = 13 times Earth's, by volume. Why so much? Well, exobiologists write off planets like Lyr as world-seas: no land, no weathering, few minerals in the sea, impoverished life (and even if intelligent life did evolve, no opportunity for technology to develop in a deep-sea environment). Lyr's meant to show that even a big wet world can have enough land to develop civilization. Lyr has 200 times the water of Serrana, a dry world-model that's still a healthy biosphere. And I suspect the range from the wettest to driest sapiogenic worlds is really more like 10,000 than 200! (Sapiogenic = not merely viable but generating intelligent species).
  Now, some of you aren't thinking "Why so much water?" but "Why so little?" Cool worlds collect ice, after all--Europa and Callisto may have seas up to 100 km deep. But the data's mixed--Jupiter's surprisingly dry. So I was cautious on Lyr--wet, but not drenched.
• Sea = 95% of surface area, and it averages 7 km deep, compared to 4 for Earth's seas. Salinity is only 1.5%, about half Earth's.
• Land = only 4.5% of Lyr's surface. But that's 45 million square miles (115 M sq km)--three-fourths as much land as Earth! Another 3% of the surface is continental shelves, and mid-ocean shallows, reefs and seamounts are another 2%. Total highlands: 9-10%. Compare this to Earth, 30% highlands; Venus, 8%; Mars, 50%. Lyr's tectonics create light continental rock a bit faster than Earth, over an area as big as 5 Earths, and over 7 billion years (these rocks increase over time; even a billion years ago Earth had less land). Today, Lyr has 12 times Earth's continental rock. Wherever it breaks the surface, erosion shapes the rock into narrower, taller platforms then Earth's (for continental shelves follow sea level, whether it's high or low). Lyr's abyssal creep is faster than Earth's, but the seas are so wide that islands and proto-continents are slow to accrete into Earthlike continents. So Lyr's lands are scattered, spidery and small--but not just peaks poking above the sea.
• Tectonic activity = higher than Earth. Fewer heavy elements means less radioactive heating, but a big world holds heat better, and tidal stress from the huge moon Oisin stokes the inner fires. The heat's dispersed both by volcanoes and many active spreading zones. Without its sea, Lyr looks more like Venus than Earth--a chaos of rifts and fractured, flexing platelets. (Some experts deny Venus any plates at all, but not me. They're just small and rubbery--so hot they bend, not break.)
• Relief = Earthlike. Lyr's vigorous spreading zones push up many Andes-like ranges at plate boundaries, and huge volcanoes rise over hot spots. Most peaks never break the surface, but the highest rise 5.1 km above sea level (Earth: 8.85); the deepest ocean trench is 19 km (Earth: 11).
• Atmosphere = nitrogen 66%, neon 14%, oxygen 12%, argon 6%, helium 2%. It's no coincidence the air is fairly Earthlike, on a living world. Photosynthesis does that! I'm not pushing an extreme Gaia hypothesis, in which life deliberately generates an optimal envelope for itself (Earth's isn't optimal, after all--we have big dead zones.)
• Air pressure at sea level = about 6 Earth atmospheres. The partial pressure of oxygen is 3.5 times Earth's. Quite breathable short-term, but harsh on Terran lungs over time. And you might feel mild nitrogen narcosis at first--partial pressure at sea level on Lir is like 100 feet down (30 m) on Earth. Rapture of the Surface! Would you adjust over time? No one's done long-term studies on rapture--too risky! Certainly you'd be near the limit of Terran tolerance--though mountain air would bring relief. Native life, of course, is comfortable at sea level--indeed, takes advantage of the tripled oxygen. Fliers on Lyr, supercharged, can lift more weight per kilo of muscle, and the dense air encourages wings. Living in a sea of almost waterlike air, everyone flies!
• CO2 = only 150 ppm at present, but Lyr's dense air gives that real punch--equivalent to 900 ppm on Earth, 2-3 times our current level. It fluctuates, of course, but Lyr is always a strong greenhouse (and with its dim sun, it needs to be!) Lyran volcanoes belch far more CO2 than Earth's, though the huge seas absorb it quickly: ash and rising CO2 make the nutrient-starved deepsea plankton bloom, sucking up CO2 again. The land surface is proportionately so small that rock-weathering, important on Earth, has little effect on CO2. In any case, Lyr's greenhouse is double-glazed--six atmospheres of damp sea air make excellent insulation on their own. CO2 isn't as crucial as on Earth.
• Temperature = Around 6 C warmer than Earth's global average. But the warmth is more evenly distributed by the dense air and world-sea, so the tropics are slightly cooler than Earth's, while the poles are much warmer--the icepack melts each summer.
• Sky color = variable. The sun looks red-orange, but the dense air scatters not just blue but green and even yellow; over land the noon sky is pale cream, tinting to light turquoise over seas. Sunsets are spectacular, as high-floating clouds often glow ruby-red, lit from the underside by refracted rays. Since the sun's image refracts several degrees around the planet in the dense air, daylight lasts half an hour longer than you'd expect. At night, the main light is a firelike glow from the moons, particularly huge Oisin, and the rings; few stars can pierce the thick cloudy air.
• Cloud cover = Denser than Earth's on average, comparable to our tropics. Deserts are rare on Lyr.
• Albedo (reflectivity) = More clouds, but the deep sea reflects less than Earth's extensive deserts, steppes and ice caps. These factors roughly cancel out... in visible light. But in the infrared, Lyr looks dark: a strong greenhouse effect.
• Polar caps = winter ice-shelves only. They were permanent in ancient times, but now they break up in summer. Glaciation's confined to high-latitude mountains.
• Climate belts = Lyr's dense air and fast spin creates five Hadley cells, not Earth's familiar three (tropic, temperate, and polar). These five convection cells create a torrid zone at the equator, a warm dry zone around 18 degrees north and south, a temperate wet zone around 36, a cool dry zone near 54, a cold wet zone around 72, and a cold dry polar zone. See climate zones.
• Air loss over time = negligible. That's a problem, not a virtue! In Lyr's early days, when its sun was dimmer (most stars slowly brighten with age) the world-sea was cold at the surface, with wide ice shelves at the poles. There was little land yet, and all of it was ice-capped. Life began in the deep rifts, more extensive and active than Earth's, and crept up slowly into the dim, cold, unpromising light. The land took an extra billion years to conquer. But then, Lyr has time: its sun will outlast Sol by 5-10 billion years!
• Age = 7 billion Earth years.
• Biomass = 250% of Earth's (but average density = 50% of Earth's).
  • Land = Twice Earth's density (so many jungles, so few deserts) but only 1.5 times Earth's total land biomass (Lyr has less land)
  • Sea = only 40% of Earth's planktonic density (fewer nutrients), but 2.8 times Earth's oceanic biomass (Lyr's seas are seven times as big!)
• Habitat diversity = low. Most land is forest or rainforest. Mixed savanna, grasslands and rainshadow deserts are fairly small. The deep seas have proportionately less shallow water and coral reefs than Earth, though more in absolute terms. They're lush but not quite as exuberant as Earth's best--less insolation, less minerals. The deep seas are biological deserts, for plankton here is limited by mineral shortages--there aren't many deserts and glaciers to fertilize them with dust and silt.
• Biodiversity = high! That sounds wrong, given the narrower range of habitats, but every continent is fertile--most have rainforest, the habitat richest in species. More important, they're so isolated they could be different planets. Every land holds Australian surprises. Even though animals here evolve flight early on, few will cross such wide seas. Most intelligent species will fly too, so they'll lack incentives to build deep-sea ships; whole civilizations may flower in ignorance of each other.
• Intelligent life = 16 species on land alone! Winged, diving fishers; fructivorous and omnivorous arboreals and nut-cracking fliers in the rainforests; grazers and predators on the prairies. There may be amphibious reef dwellers and quasi-cetaceans offshore, too. See Peoples and Evolution.
• Nomenclature = "Lyr" is a Celtic sea-god. Regional names, though, are based on works by world-builder Poul Anderson: "The Queen of Air and Darkness" in the far north, "The Man Who Counts" in the equatorial west, "The People of the Wind" in the north-central continental cluster, and so on.

TOUR LYR! Climb volcanoes, swim seas, meet weird creatures. First: survival tips! Then, pick a region:
Ythri -- Polesotechnic Chain -- Troisleons -- Roland -- Oronesia -- Gaiila -- Flandry -- Diomedes -- Ak'hai'i -- Averorn

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