Sciency Words: The Gaia Principle

Today’s post is part of a special series that first appeared on Planet Pailly. Every Thursday, we take a look at a new and interesting scientific term to help us all expand our scientific vocabularies together. Today’s word is:

The Gaia Principle

The Gaia principle (named after the Greek word for Earth) has taken on a lot of new agey, pseudo-religious connotations. We hear about life forces, Mother Earth, and the spiritual connection we humans have (or ought to have) with our planet. That’s all very interesting, but let’s set that aside for now.

As a scientific concept, the Gaia principle or Gaia hypothesis is primarily credited to James Lovelock. In the 1960’s and 70’s, while working for NASA, Lovelock wanted to understand why Earth is so tailor-made for life while other planets, especially Mars, are not.

According to Lovelock’s hypothesis, once life takes root on a planet, it fundamentally changes the environment around it. As life evolves, so too does the planet, with the planet’s environment becoming increasingly favorable to life and life becoming increasingly well adapted to the planet’s environment.

Today, all life forms on Earth exist in a symbiotic relationship with each other and with the planet, actively (though unwittingly) maintaining the planet’s life-friendly conditions. It’s almost as though Earth has become a single organisms with countless individual “cells” working to maintain homeostasis.

A strict interpretation of the Gaia principle would tell us that if life fails to alter its environment, if it fails to spread out and establish a vast and complicated planetary biosphere, then it will wither and die.


Scientists are currently searching for evidence of life on Mars. Specifically, they’re looking for microbial life eking out an existence, perhaps only in one limited region of the planet.

Whether or not we accept the Gaia principle and how strictly we choose to interpret it has major implications for what we can expect scientists to find on Mars. Because if it’s all or nothing when it comes to life on other planets, as the Gaia principle suggests, then Mars looks pretty darn close to nothing.

So what do you think of the Gaia principle, and how likely do you think it is that we’ll find life on Mars?

Written by James Pailly.

To add more ‘Sciency Words‘ to your vocabulary, visit the Planet Pailly blog.

  • Leonardo Faria

    Next to start ExoMars mission (2016), by ESA+RosCosmos, is going to search for answers to these questions. They seem to think there is no life on Mars, but there’s been in the past, and the evidence could be actually collected by the landing rover.

    • John H Reiher Jr

      All I have to say to them is good luck. The God Mars seems to kill every other probe sent to visit him.

      • Leonardo Faria

        Well that’s true for the two Nasa’s Viking landers, but Nasa’s Pathfinder and Phoenix I think lasted both over the planned term. The God Mars was lenient. The later attempt to reactivate them failed though.

        • michael pulleine

          what about curiosity?

  • Paulo R. Mendes

    I accept the Gaia Principle – life evolves and changes the world around it. Unfortunately and thanks to random (?) events in both Mars and Venus, our world is the only one able to sustain life in the Solar System.

    • Iron Legionnaire

      Numerous moons of gas giants harbor ice and even under-surface oceans of liquid water (Europa). What would hypothetical people from Europa be called? Europeans, of course! 😛

      • Paulo R. Mendes

        It is more like Europans to me. ;D

  • Kirov

    How does the oxygen catastrophe fit in? I suppose retrospectively you could argue it fits with the Gaia principle, but at the time, wasn’t it a major change to the environment detrimental to a lot of life? Wouldn’t that have been counter to the Gaia principle?