From here:
http://www.astronomy.com/Content/Dynamic/Articles/000/000/001/611spati.asp
"While Earth’s axial tilt has only varied between 22 to 24.5 degrees in the past 10 million years, Mars has experienced a more extreme wobble, ranging from 14 to 48 degrees."
Another interesting read:
http://www.rps.psu.edu/jan97/planets.html
"The obliquity of a planet is the angle of its spin axis -- that imaginary rod that skewers a planet through the poles -- in relation to the plane of its orbit. In Earth's case, this angle is a modest -- and reasonably steady -- 23.5 degrees, enough of a tilt to account for our seasons. Because of Earth's obliquity, in the northern hemisphere the winter sun stays low in the sky, casting its rays obliquely across the landscape. In summer it climbs to more nearly overhead, an angle much better for warming."
---snip---
"Mars, Laskar showed, still does, its obliquity varying chaotically between 0 and 60 [Note: I did notice there was a difference in the numbers] degrees. The only thing that saved Earth from a fate worse than Mars', he says, was hooking up with the moon.
A little orbital mechanics may be in order here. Earth is a body in complex motion. It rotates, of course, once every 24 hours. At the same time, on a different time scale, it revolves around the sun. But there are other, subtler, motions which must also be accounted for. Earth's imperfection as a sphere, for one thing, adds a motion called precession, akin to the wobbling of a spinning top. Earth wobbles, as noted above, only slightly and in very slow motion, its obliquity oscillating from 22 to 24 degrees every 40,000 years.
Meanwhile, however, the gravitational pull of the other planets in the solar system, especially the giants Jupiter and Saturn, causes a different kind of precession: a wobble in the plane of Earth's orbit. Imagine the orbital plane as a solid object, a spinning frisbee or a dinner plate, with the sun a dollop of mashed potatoes in its center, and Earth a wad of chewing gum stuck to its outer rim. The insistent tug of these outer, larger planets against the sun's stronger pull causes the plate to wobble as it spins.
The real action, in terms of shifting obliquity, comes when these two types of wobble -- the planetary and the planar -- stumble onto the same frequency. Then you get what's known as a spin-orbit resonance: in synch, the two motions combine their energy, creating a much larger force. It's not unlike the kind of timing it takes to keep a hula-hoop spinning around your hips, or to successfully push a child's swing. For a planet, however, resonance means chaos, as two small competing wobbles become one huge concerted one.
What saves Earth from falling into a spin-orbit resonance, Laskar says, is the moon. Because of its size and proximity, the moon exerts a strong gravitational pull of its own on our home planet -- a pull which turns out to be a stabilizing influence. The lunar effect acts to accelerate Earth's global precession, maintaining it at a steady frequency well higher than the torpid wobbling of the orbital plane. Take the moon away, Laskar says, and keep things otherwise the same -- give Earth the same mass, orbital position, rotation rate, etc. -- and Earth's obliquity would fluctuate between 0 and 85 degrees."
and it would mean a much lower value of the Drake Equation variables Ne and Fl: a lower probability of extraterrestrial life.
That I am not sure of. Life may be just as likely, but adapted to those environments. I just dont know. Life sure seems to be able to live in the extremes on this planet.
I don't like it. No wonder things are all messed up. Can't you fancy-pants pointy-headed intellectuals do something about all this bobbing and weaving around? It's bad for the digestion.
One of these days you'll admit that the Fermi Paradox keeps looking better and better.