CONDITIONS FOR LIFE IN THE SOLAR SYSTEM UNIT

CONDITIONS FOR LIFE IN THE SOLAR SYSTEM UNIT 5

TEKS: 7. 9 A • Analyze the characteristics of objects in our solar system that allow life to exist such as proximity to the sun, presences of water, and composition of the atmosphere.

KEY CONCEPTS • What conditions on Earth enable life to exist? • What conditions on other bodies in the solar system might enable life to exist? • Where might life possibly exist beyond Earth?

CONDITONS FOR LIFE ON • Despite. EARTH the extreme conditions in which some organisms live, all of Earth’s life-forms need the same basic things to survive: • • A source of energy Protective atmosphere Liquid water Nourishment

ENERGY FROM THE SUN • The Sun is the source of most energy on Earth. • Sunlight provides light and thermal energy. • A small percentage of organisms on Earth receive energy from chemicals or from Earth itself.

PROTECTION BY THE ATMOSPHERE Earth’s atmosphere: • absorbs sunlight during the day and keeps thermal energy from escaping into space at night. • absorbs most of the Sun’s ultraviolet light, as well as X-rays and other potentially harmful light from the Sun. • also protects Earth’s surface from meteoroids.

LIQUID WATER • Liquid water is necessary for all life on Earth. • Depending on temperature and pressure on Earth, water is solid, liquid, or gas. • Water changes from a liquid to a gas or to a solid as its temperature and pressure change.

NOURISHME NT • Living things are nourished by nutrients they take from the air, water, and land around them. • All molecules that provide nourishment for life on Earth contain carbon. • Organic refers to a class of chemical compounds in living organisms that are based on carbon.

LOOKING FOR LIFE ELSEWHERE • Though it is possible that inorganic life could exist elsewhere, astrobiologists are most interested in places beyond Earth where water is liquid and carbon is plentiful. • Because liquid water is essential for life on Earth, scientists look for places in our solar system, on the Moon, and beyond where liquid water might exist or might have existed in the past.

MAR S • Other than Earth, Mars is the planet scientists think is most likely to have liquid water. • There is abundant evidence for water vapor and water ice on the Martian surface, and photographs show surface features on Mars that appear to have been carved by moving water.

NATURAL SATELLITES • Several moons in the outer solar system, such as Jupiter’s moon Europa, have surface features that indicate the presence of liquid water not far below. • Several other moons in the outer solar system, including Triton, a moon of Saturn, and Enceladus, a moon of Neptune, show evidence of geysers. • A geyser is a warm spring that sometimes ejects a jet of liquid water or water vapor into the air.