Astrobiology Top 10: Earth's Moon May Not Be Critical to Life

Astrobiology ^ | Wednesday, December 23, 2015 | Keith Cooper

[SunkenCiv]

In 1993, French astronomer Jacques Laskar ran a series of calculations indicating that the gravity of the Moon is vital to stabilizing the tilt of our planet. Earth's obliquity, as this tilt is technically known as, has huge repercussions for climate. Laskar argued that should Earth's obliquity wander over hundreds of thousands of years, it would cause environmental chaos by creating a climate too variable for complex life to develop in relative peace.

So his argument goes, we should feel remarkably lucky to have such a large moon on our doorstep, as no other terrestrial planet in our solar system has such a moon. Mars' two satellites, Phobos and Deimos, are tiny, captured asteroids that have little known effect on the Red Planet. Consequently, Mars' tilt wobbles chaotically over timescales of millions of years, with evidence for swings in its rotational axis at least as large as 45 degrees.

The stroke of good fortune that led to Earth possessing an unlikely Moon, specifically the collision 4.5 billion years ago between Earth and a Mars-sized proto-planet that produced the debris from which our Moon formed, has become one of the central tenets of the 'Rare Earth' hypothesis. Famously promoted by Peter Ward and Don Brownlee, it argues that planets where everything is just right for complex life are exceedingly rare.

[SunkenCiv]

;’)

[JimSEA]

Thanks. That’s fun.

[roadcat]

The tidal transfer of momentum relevant here is the axial rotational energy of the Sun basically pushing the Earth away.

Thanks, I get it now. The rotational spin of the Sun is flinging the Earth away. Sort of like holding the hands of a child while spinning it around, your rotational energy is imparted to the child. Poor kid, some year far in the future the Moon will be flung out of orbit from Earth.

[ShasheMac]

Maybe we could spin it so the dark side was facing us! 8D

[Mark17]

Maybe we could spin it so the dark side was facing us! 8D

Yes, we could do that. Then the moon would not be so racist.

:-)

[SunkenCiv]

• Who Needs a Moon? [2011]