There is a tide in the affairs of spacefarers ...

Fate of Worlds is at an exciting point -- it's hard to tear myself away from working on the first draft. So: to make this a quick post, I'm sticking to a couple of keen bits of space news. (In a year or so, the Known Space fans among you will thank me.)

First, NASA recently released the highest res image ever of the entire lunar far side (a small version of which is shown at left). It's a composite image assembled from thousands of detailed images captured by the Lunar Reconnaissance Orbiter -- from an altitude of only about 30 miles! Seriously cool.

And much farther from home ...

... the latest survey of the Kepler mission reports finding 54 more or less Earth-sized planets in the habitable zones of sunlike stars (that is: by virtue of these planet's orbits, liquid water can exist on the planetary surfaces). After fun with numbers, the survey suggests that across a larger sample, the prevalence of such planets around sunlike stars will turn out to be 1.4 to 2.7 percent. Multiply those numbers by estimates of the numbers of stars of various types in the Milky Way, and you get around two billion Earth-like candidates in just our galaxy. Alas, that's a prediction of only about two candidates within 100 light-years of us. Where's an FTL drive when you need one?

Of course sunlike stars (not precisely defined in the above-mentioned articles, but, presumably, yellow [G class] stars) are far from the most common stars. Red dwarfs [M class] are far more prevalent. (See here for more on stellar classification.)

The Kepler search hasn't yet checked out red dwarf stars. With good reason: red dwarfs, being dim and cool, have very small habitable zones. Any planet in such a close orbit would be tidally locked to its sun -- just as the moon is tidally locked to Earth. (See, there is some relation between parts of this post.) An atmosphere-bearing, tidally locked planet in the habitable zone of a red-dwarf star would have very tempestuous weather: extremely hot on the planet's sun-facing side and extremely cold on the planet's sun-shunning side. Great air masses would endlessly move between hemispheres, just as (but to a greater extent than) air masses circulate between Earth's tropics and polar regions. That said, such planets might have narrow liveable regions in the twilight strips near the edge of permanent darkness.  (The home of the Drar, in Destroyer of Worlds, is such a world.)

But imagine an Earth-like moon of a Jupiter-like planet, with that quasi-Jupiter in a red dwarf's habitable zone. (Artist's conception at left by Luciano Mendez, under Creative Commons license).

The planet would be tidally locked to its sun and the Earth-like moon will be tidally locked to the planet, but -- and here's the key point -- the Earth-like moon is not tidally locked to the sun. Further, tidal flexing of the moon, driven by the planet -- the mechanism that keeps water oceans liquid (beneath world-spanning icecaps) on Jupiter's moon Europa and Saturn's moon Enceladus -- can add energy (above what the star provides) to the moon's environment. In InterstellarNet: New Order, Kv'ith (home world of the Hunters, a species sometimes known to humans as the Snakes) is just such a moon.

Despite the call of Fate of Worlds, I've managed a tide-y post. (You may groan.) Now I'm back to work ...