Unit 3.4: Other Terrestrial Planets

• Earth has three distinct layers: the crust, the mantle, and the core. It shares similar characteristics to other planets, especially the inner or terrestrial planets
• Mercury, Venus, and Mars have similar layers with Earth.
• Mercury is the smallest terrestrial planet.
• Mercury


  Although small, it is one of the densest planets second to Earth. The planet is believed to be composed of a core, mantle, and crust
• Mercury


  The planet’s core makes up around 85% of the planet’s radius. The radius of this core is about 1 800 to 1 900 km. The core has more iron than any other planet in the solar system
• Radar images from Earth reveal that the core of Mercury is liquid. Only a thin layer covers the core.
• Mercury


  Scientists have formulated two hypotheses explaining the existence of the large core of the planet. One possible explanation is the planet’s fast formation
• Mercury may have formed quickly and the increasing temperature of the cooling sun vaporized much of the surface leaving only a thin shell
• Mercury


  Another explanation is attributed to the impacts on the planet during its early formation. The impacts may have stripped away the outer shell of the planet leaving a big core. The core generates a magnetic field about one percent as strong as that of Earth’s.
• Venus is the second planet from the Sun
• Venus


  It is believed to have compositions similar to Earth. Scientists speculate that the planet also has crust, mantle, and core.
• The crust of Venus is believed to be significantly older than Earth’s. This is due to Earth’s constantly changing surface.
• Venus' Crust

  The crust is believed to extend from 10 to 30 km from the surface.
• Venus' Mantle


  The planet’s mantle is believed to be rocky. It extends to depths of 3 000 km
• Venus' Core


  is believed to be composed of iron-nickel alloy. The core is believed to be in a liquid state.
• The slow spin of Venus compared to Earth makes scientists speculate that the planet has a weak magnetic field.
• Mars, popularly known as the red planet, is also composed of outer crust, mantle, and core
• The crust of Mars is composed mostly of dust on the surface and basaltic rocks underneath. It is believed to extend to up to 50 km.
• Mars' Crust


  The crust is believed to be ‘one piece,’ meaning, it has no mobile tectonic plates, unlike Earth. Eruptions take place at the same point for a long time building up huge volcanoes in the surface such as Olympus Mons, the Solar System’s largest mountain.
• Mars' Mantle


  The planet’s mantle is made up of silicon, oxygen, iron, and magnesium. It is believed to have a consistency similar to a rocky paste. The mantle is believed to be 5 400 to 7 200 km thick
• Mars' Core


  The core of Mars is believed to be solid. It is composed of iron, nickel, and sulfur. It is 3 000 to 4 000 km in diameter.
• Because the core is solid and does not move, Mars has no magnetic field. The absence of the magnetic field allows the bombardment of radiation making the planet not suitable for liquid water and life.