In Stephen Baxter’s novel Ark (Gollancz, 2009), a starship launched by an Earth in crisis reaches a planet in the 82 Eridani system, an ‘Earth II’ that turns out to have major problems. Whereas Earth has an obliquity, or tilt relative to its orbital axis, of about 23.5 degrees, the second ‘Earth’ offers up a whopping 90 degree obliquity. Would a planet like this, given what must be extreme seasonality, be remotely habitable?
The crew discusses the problem as they watch a computerized display showing Earth II and its star. The planet’s rotation axis is depicted as a splinter pushed through its bulk, one that points almost directly at the star. But as the planet rotates, the axis keeps pointing at the same direction in space. After half a year, the planet’s north pole is in darkness, its south pole in light.
One of Baxter’s characters explains the consequences:
“Every part of the planet except an equatorial strip will suffer months of perpetual darkness, months of perpetual light. Away from the equator you’ll suffer extreme heat, aridity, followed by months of Arctic cold — we estimate the surface temperature will drop to a hundred degrees below across much of ...