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” Source: NASA http://www.astrobio.net/exclusive/2972/some-planets-are-better-for-life

How Earth Supports Life Proximity to Sun Atmospheric composition and layering Gravity Relationship with Moon Oceans What other conditions support life on Earth?

Proximity to Sun Earth 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% nitrogen 21% oxygen – almost all plant produced 1% 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.

Image source: http://iln. cite. hku

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

Oceans Largest source of water that supports marine plants and animals Why is water essential?

Plate Tectonics: motions of the Earth’s lithospere Helps to create magnetic fields that deflect harmful solar winds that could damage DNA Helps to replenish the essential elements for life Carbon – especially important for the carbon cycle Nitrogen Hydrogen Phosphorus Sulfur Sources: http://www.astrobio.net/pressrelease/1310/the-breathable-earth http://www.astrobio.net/exclusive/3039/plate-tectonics-could-be-essential-for-life

supports life.