The Habitable Planet

7.9: Earth and Space – The student knows components of our solar system.

7.9A: The student is expected to analyze the characteristics of the objects in our solar system that allow life to exist such as the proximity of the Sun, the presence of water, and composition of the atmosphere.

Traditional understanding of the “habitable zone”

How Earth Supports LifeProximity to SunAtmospheric composition and layeringGravityRelationship with MoonOceans

What other conditions support life on Earth?

Proximity to SunEarth is the third closest planet to the Sun,

approximately 150 million kilometers away.

Earth is just close to and far enough away from the Sun (a star) to be warm.

Earth’s Atmosphere (composition)78% nitrogen21% oxygen – almost all plant produced1% other gases (argon, carbon dioxide, trace

elements)

The atmosphere has elements essential for building the chemical compounds to support life (carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur).

Earth’s Atmosphere (layers that directly affect life)

Troposphere: lowest layer, where weather occurs, gets cooler higher up in this layer

Stratosphere: harmful UV rays absorbed (ozone layer), gets warmer the higher up in this layer

Ozone in the stratosphere absorbs most of the harmful UV rays.

Earth’s large constant mass allows for gravity which holds matter to Earth.

OceansLargest source of water that supports

marine plants and animals

Why is water essential?

Plate Tectonics: motions of the Earth’s lithospereHelps to create magnetic fields that deflect

harmful solar winds that could damage DNAHelps to replenish the essential elements for

lifeCarbon – especially important for the carbon

cycleNitrogenHydrogenPhosphorusSulfur

supports life.