As everyone who reads Larry Niven knows, “Jinx” is a human colony world in his Known Space universe, and another in his long line of only-marginally-habitable locations that humans live in. For starters, it’s not even a planet: It’s a moon of a Jovian world called “Primary.” (In some stories, in others it’s called “Binary.”) Jinx - so named because they evidently lost several colony ships en rout, and found the place fairly uncomfortable when they got there, so they suspected the place was bad luck - is physically larger than earth, and quite a bit denser, with around six times the mass of our own world, and a surface gravity of 1.78 Gs. (For those not adept in such things, that means that if you’re a 100 lb girl on earth, you’d weigh 178 pounds on Jinx, and if you’re a 200 lb guy, you’d weigh in at a chart-topping 356 pounds. Yikes!)
As with every moon we actually know of, Jinx is tidally locked to Primary. That means that it’s period of rotation around it’s axis is the same as it’s period of rotation around the planet. Hence, just like our own moon, it keeps one hemisphere always pointed at the planet, and another pointed perpetually off in to deep space. But what really makes Jinx unique is it’s shape:
It’s not round, it’s shaped like a football.
Gravity, naturally pulls everything towards the center, so this means that the extreme ends of the football are actually extending out of the atmosphere and in to space. Both poles are literally in hard vacuum, so of course nothing can grow on ‘em. Picture them looking like the moon - grey and rocky. Let’s start from the North pole and head south* - after the grey moonscape of the pole, we come to a ‘temperate’ zone where there’s water, air, plants, and everything you need for human and animal life, and it’s similar to earth, though of course gravity is much higher. South of there we come to the tropics, which are as uninhabitable as the poles, though for the opposite reason: Air and water tend to pool up here in completely toxic levels, it’s super hot, uncomfortable, swampy, and awful. In addition, it’s populated with giant, occasionally crotchety Bandersnatchii, giant genetically engineered monocellular life forms who’d already been stuck on this moon for God knows how long before the humans came. At the equator is a vast toroidal ocean. The other hemisphere is a mirror image of the north, so as we continue to work our way to the other pole we encounter nasty toxic swamps, a temperate, habitable region, and, of course, the other uninhabitable pole. Consequently Niven describes it as “Looking like God’s own Easter egg,”
“How did such a thing come to be,” you ask? Good question!
We’re told that back when the Sirius system was forming, Jinx coalesced too close to Primary, and was stretched in to an oblate spheroid shape by tidal forces from the planet it orbited. Its orbit must be very close to the Roche’s limit of Primary. For our purposes, that’s the point at which tidal stresses are stronger than the strength of rock itself, and a solid object will quickly disintegrate and form a ring. When the moon cooled, it was locked in to this shape forever, six hundred miles ‘out of round‘. I’ve long wondered if Jinx is sort of Niven’s homage to Hal Clement’s planet “Mesklin” from “Mission of Gravity,” ( http://en.wikipedia.org/wiki/Mesklin ), a somewhat similarly oddball non-ball-shaped world by really the only other SF writer out there who was known for off-brand non-standardized planets. That’s not to say Mesklin and Jinx are the same, of course - Mesklin is shaped like a lens and Jinx is, as noted, a football, but from a topological viewpoint, a football can be considered the opposite of a lens.
The bottom line here, though, is that Jinx is super-cool and a very neat and unusual location in my own personal favorite fictional universe, and one that turns up again and again, worked through the woof and warp of the entire thing, and intrinsic and indispensable part of the structure of Known Space itself. I love the place.
It won’t work, though.
If we look at it closely, it doesn’t make a lick of sense. Such a thing simply can not exist within the confines of the