Oct 25, 2012

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Four Reasons Why Earth Sustains Life

Four Reasons Why Earth Sustains Life

What are the fundamental requirements for a planet to host hardy bacteria?

And what else might be necessary for more complex life forms to exist here, on earth?

As we explain, understanding these needs will help us in the search for life elsewhere in the galaxy.



Plate tectonics and erupting volcanoes would play a key role in keeping a habitable planet’s climate stable and cosy for life. Together, they act to regulate the amount of atmospheric carbon dioxide (C02) and thus the greenhouse effect, keeping a finger on the planet’s thermostat.


Some scientists think that having a massive planet like Jupiter in the outer solar system would help nurture life on inner Earth-like worlds. The gas giant’s powerful gravitational field would pull in stray asteroids and comets that might otherwise have hit the habitable planet. Microbes living deep in a planet’s crust would be better protected, however.


One of the most important factors that determines whether life could ever develop on a world is how closely it orbits its star. Wandering too close would roast the planet’s surface and boil its oceans dry. On the other hand, shying too far away would leave the planet a frozen wasteland. The warm sweet-spot in between is called the habitable zone. Extremophiles living deep underground could possibly survive over a wider range of orbits than we once thought. It is also important, especially for complex life, for the planet’s orbit to be stable and circular.


Our habitable planet would need a magnetic field to act like a vast deflector shield, stretching far out into space. It would deflect the solar wind (a fast stream of particles from the Sun) around the planet. This wind would otherwise blow the planet’s atmosphere away. The magnetic field also protects the surface from cosmic radiation, although bacteria, such as D. radiodurans, could survive elevated radiation levels.

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