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The Solar System. The Inner Planets. The Solar System Overview Terrestrial Planets. Lecture 33. Chapter 16.1  16.8. The Big Bang – beginning of the Universe 12-16 billion years ago. Galaxies are flying away from each other No expansion within galaxies. Our Cosmic Origins.

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Lecture 33

The Solar System. The Inner Planets.

The Solar System Overview

Terrestrial Planets

Lecture 33

Chapter 16.1  16.8

Our cosmic origins

The Big Bang – beginning of the Universe

12-16 billion years ago

Galaxies are flying away from each other

No expansion within galaxies

Our Cosmic Origins

  • Only hydrogen and helium in the early Universe

  • All other chemical elements were created inside stars

  • We are all created from the stars’ stuff

  • Current composition of the Sun: 70%H, 28%He, 2%others

Images of time

Speed of light: c = 300,000 kilometers per second

Light year – distance which light travels in 1 year

From the Sun to Earth - 8 minutes

From the Sun to Pluto - 5 ½ hours

To the closest star - 4 years

Through the Milky Way - 100,000 years

To the closest galaxy - 2,500,000 years

Images of Time

  • The farther away the object, the further back we look in time

The solar system


Sun (the only star)

9 planets

Nearly 100 moons



Free-flying gas and ‘dusty’ particles

The Solar System

Solar system

APOD: 2002 April 29 - Dusk of the Planets


Solar System

The sun

Temperature (at surface) - 6000 degrees Kelvin (K)

Size (diameter) - 1,392,500 kilometers (km)

Mass – 1.86 1030 kilograms (kg) or 98% of the total mass of the Solar system

Energy production rate – 4 million tons of mass (E=mc2)

Age – 4.6 billion years

Total stable life time - ~10 billion years

The Sun

Our very own star

APOD: 2003 May 17 - Dark Sky, Bright Sun

APOD: 2003 March 24 - A Digital Sunset Over Europe and Africa

APOD: 2002 July 29 - A Setting Sun Trail

Our very own star

Inside the terrestrial worlds
Inside the Terrestrial Worlds

Two families of planets in the Solar system: terrestrial (Earth-like) and Jovian (Jupiter-like)

The terrestrial planets are relatively small and almost spherical

The Earth has a radius of 6,378 km and an obliquity of 1/298

They are mostly made of rocky materials that can deform and flow

Every object exceeding ~500 km in diameter can become spherical under the influence of gravity

Lithospheres of the terrestrial planets
Lithospheres of the Terrestrial Planets

Planetary surfaces are all warmed by sunlight, but the high temperatures inside the planets today are due to radioactive heating.

Mercury and moon
Mercury and Moon

The 2 smallest terrestrial worlds covered with lots of impact craters.

They have volcanic activity in the past (example - lunar maria).

Mercury has a 88-day orbit and a 59-day rotation.

Temperature is up to 425oC on the day side and down to 150oC on the night side.

It has many craters, but also traces of geological activity.


Venus is the third brightest object in the sky after the Sun and the Moon.

Venus has very similar parameters to those of the Earth.

However, it spins backwards (clockwise if looking from its north pole).

Its atmosphere has 96% CO2, surface temperature 400740 K, surface pressure is 90 times the Earth’s one.

It has volcanic activity, but probably no tectonic activity.

The Soviet spacecraft Venera 9 landed on Venus and send a panoramic view of its surface.

The US Magellan spacecraft transmitted radio images.

Lecture 33 1348515

This is an intermediate-size planet and the most distant of the terrestrial planets from the Sun.

It has polar caps made of frozen CO2, many deserts, and volcanoes.

There is no liquid water on Mars today, but rather traces of past water flows.

The surface is different in the northern (low plains) and southern (highlands).

Only 13 missions to Mars out of 23 were successful.

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Terrestrial planets are small and rocky

Only a handful geological processes shape the terrestrial planets

Every terrestrial world was heavily cratered long ago. Most of the craters are erased now.

Understanding of planetary geology might help us learn about planets of other star systems