Terrestrial Planets Earth, Mercury, Venus, Mars

1. Terrestrial PlanetsEarth, Mercury, Venus, Mars Objectives Standards (1a) Students know how the differences and similarities among the sun, the terrestrial planets, and the gas planets may have been established during the formation of the solar system • Describe the distinguishing characteristics of each terrestrial planet

2. Mercury • Innermost planet; it is hardly larger than Earth’s moon. Closest planet to the Sun and the eighth largest planet (or second smallest). • Surface Features • - Similar to the Moon in that its surface is heavily cratered (highlands), has vast smooth terrains that resemble maria, and very old.

3. Mercury • Surface Temperatures • Has the greatest temperature extremes of any planet; Temperatures vary greatly from 90 K to 700 K. • Has a very thin atmosphere consisting of atoms blasted off its surface by the solar wind.

4. Mercury • Mercury has no known satellites.

5. Venus • Venus has been known since prehistoric times. It is the brightest object in the sky except for the Sun and the Moon. • Venus is the second planet from the Sun and the sixth largest. • Venus is similar to Earth in size, density, mass (iron core), and location in the solar system. Thus, it has been referred to as “Earth’s twin.”

6. Venus • Surface Temperatures -Its surface is actually hotter than Mercury's despite being nearly twice as far from the Sun. The surface temperature of Venus reaches 475oC, and its atmosphere is 97% carbon dioxide. • Surface Features • Venus is covered in thick clouds that visible light cannot penetrate. • About 80% of Venus’s surface consists of plains covered by volcanic flow.

7. Venus • Has no satellites • It is called the "morning star" or the "evening star.”

8. Compare / Contrast Earth Venus One year is 255 Earth days Covered in thick clouds Very hot surface temperature 97% of atmosphere is CO2 Very little water vapor and nitrogen Atmospheric pressure is 90x Earth’s surface pressure • One year is 365 Earth days • Thin Atmosphere • Surface temperature allows for liquid water • Very little of the atmosphere is CO2 • Lots of water vapor and nitrogen

9. Mars • Mars is the fourth planet from the Sun and the seventh largest. • Mars has been known since prehistoric times. • Mars has the most highly varied and interesting terrain of any of the planets.

10. Mars • The Martian Atmosphere • - The Martian atmosphere has only 1 percent of the density of Earth’s. • - Although the atmosphere of Mars is very thin, extensive dust storms occur and may cause the color changes observed from Earth. • Surface Features • - Most Martian surface features are old by Earth standards. The highly cratered southern hemisphere is probably 3.5 billion to 4.5 billion years old.

11. Mars • Water on Mars • There is evidence of erosion in many places on Mars including large floods and small river systems (right). • Some areas of Mars exhibit drainage patterns similar to those created by streams on Earth. • Images from the Mars Global Surveyor indicate that groundwater has recently migrated to the surface.

12. Mars • Mars has permanent ice caps at both poles.