earth

1 - The Canadian government is fully aware of the dire need in the world for alternative energy sources, since the Earth's supply of fossil fuels is rapidly being depleted.

2 - The ozone layer is a deep layer in the stratosphere, encircling the Earth that has large amounts of ozone in it.

3 - Earth's protective ozone layer is high in the planet's atmosphere.

4 - A global network is any communication network which spans the entire Earth.

5 - Much of the renewed optimism for life on Mars comes from a wealth of data suggesting that, up to about 3.5 billion years ago, Mars was much more like Earth, with large amounts of surface water.