A habitat is more than just a home. It's the environment that supplies everything that living things need to survive. For animals, their habitat must supply their food, water, air and space.

There are many different habitats on the Earth. These vary in the landforms, sources of water, and climate conditions. Plants and animals are specially adapted to live in their habitats. Animals suited to live in the desert (very dry, either hot or cold) would have a difficult time living in the tropical rain forest (warm and very wet).

A few living things on Earth are found in very harsh environments. We call these living things extremophiles. Some have been found in very hot or cold conditions; places where you'd never expect to find something living. One amazing example is bacteria spores that have been found in bitterly cold, dry, and airless conditions. They seem to have been able to survive for millions of years in a dormant, or "sleeping" state. Once their environmental conditions improve, they're "activated" or "brought back to life."

A new discovery found in Alaska, Carnobacterium pleistocenium, is believed to have been in ice dating back some 32,000 years. Finding and studying such extremophiles broadens scientists' understanding of possible life. And ... these finds also make scientists wonder if life can be found across the cosmos.

Could such extremophiles lie dormant in the Martian arctic? About every 100,000 years, for brief periods, liquid water may exist at the Martian poles, a region currently covered in water-ice. This may have made the soil environment habitable. Is it possible that extremophiles cycle through "active" and "dormant" states, dependent upon the changes in the Martian environment?

NASA studies these possibilities through probes and robotic missions to Mars. The Phoenix Lander will head to the Martian arctic in search of water and signs of life in 2007. It will help us evaluate the Martian polar environment, analyzing the soil for life-giving elements such as carbon, nitrogen, phosphorus, and hydrogen. Phoenix will look for chemical reactions that might indicate that the soil could sustain life. It will also measure the soil's pH and saltiness, traits that help determine habitability. In addition to looking for conditions that support life, Phoenix will also look at the soil for traits that inhibit life and growth.

Digging deep into the Martian soil, Phoenix will look for signs of life and conditions that could support life. And, perhaps evidence that extremophiles could be found there, too.

Living things adapted for Earth are not adapted for life in space. Going from Earth's environment to a space environment offers many challenges for living things. In the video, Barkley is packing for a trip to the moon. Clearly, he would need more than clean underwear and his toothbrush to survive in the moon's environment. Spacecraft create a safe environment for space travelers and space suits are designed to protect astronauts for short periods of time outside of the spacecraft.