This entire article from Evolution News is a must-read. It talks about a recent paper by a naturalist named Robin Canup which appeared in Nature, the most prestigious peer-reviewed science journal.

So, there’s too much to quote here. I’ll grab a few snippets to give you the gist of it, then you click through and read the whole thing. 

The moon is important for the existence of a life permitting planet:

Canup knows our moon is important for life:

The Moon is more than just a familiar sight in our skies. It dictates conditions on Earth. The Moon is large enough to stabilize our planet’s rotation, holding Earth’s polar axis steady to within a few degrees. Without it, the current Earth’s tilt would vary chaotically by tens of degrees. Such large variationsmight not preclude life, but would lead to a vastly different climate.

The moon requires an improbable sequence of events:

Canup states that “No current impact model stands out as more compelling than the rest.” All are equally improbable, in other words. Indeed, they are:

It remains troubling that all of the current impact models invoke a process after the impact to effectively erase a primary outcome of the event — either by changing the disk’s composition through mixing for the canonical impact, or by changing Earth’s spin rate for the high-angular-momentum narratives.

Sequences of events do occur in nature, and yet we strive to avoid such complexity in our models. We seek the simplest possible solution, as a matter of scientific aesthetics and because simple solutions are often more probable. As the number of steps increases, the likelihood of a particular sequence decreases. Current impact models are more complex and seem less probable than the original giant-impact concept.

This is a good challenge to naturalism, but it lends support to one part of the habitability argument.

Previously, I blogged about a few of the minimum requirements that a planet must satisfy in order to support complex life.

Here they are:

• a solar system with a single massive Sun than can serve as a long-lived, stable source of energy
• a terrestrial planet (non-gaseous)
• the planet must be the right distance from the sun in order to preserve liquid water at the surface – if it’s too close, the water is burnt off in a runaway greenhouse effect, if it’s too far, the water is permanently frozen in a runaway glaciation
• the solar system must be placed at the right place in the galaxy – not too near dangerous radiation, but close enough to other stars to be able to absorb heavy elements after neighboring stars die
• a moon of sufficient mass to stabilize the tilt of the planet’s rotation
• plate tectonics
• an oxygen-rich atmosphere
• a sweeper planet to deflect comets, etc.
• planetary neighbors must have non-eccentric orbits

This is a good argument, so if you want to learn more about it, get the “The Privileged Planet” DVD, or the book of the same name.