Red Planet

Programme Outline

Mars is introduced as a planet similar to Earth in that it has an atmosphere, a tilted axis, seasons, and a day of just over 24 hours. But there are crucial differences between the two planets. Mars has a sub-zero climate, experiences global dust storms, and has an atmosphere 150 times more rarefied than Earth's.

Space missions are shown to have improved our knowledge of Mars enormously. The Viking orbiters took images of the planet's surface topography, and the Viking landers searched unsuccessfully for life in the red soil of the planet. Viewers are taken on a guided tour of Mars, including Mariner Valley, the 4000-kilometre rift cutting across the planet's equatorial regions, and the great shield volcanoes, such as Olympus Mons, the tallest volcanic peak in the Solar System.

Volcanic activity may once have been important not only in triggering massive flash floods, but in giving Mars a more substantial atmosphere and a warmer surface. But after the volcanic activity ceased, there were no eruptions to replenish the atmosphere, which leaked into space because of the weak Martian gravity.

Results of recent missions to Mars are summarised, including the Mars Pathfinder landing and Mars Global Surveyor's evidence for ancient Martian oceans and a weak magnetic field. Planned future expeditions to Mars are discussed. The search for microbial life will continue.

00.10 - 00.53 Introduction

• Mars as the 'dusty red planet'.
• The relevance of Martian exploration.
• The planet's similarities to Earth.

00.53 - 02.30 Moons and seasons

• Mars's bitterly cold temperatures are explained by its distance from the Sun.
• Its two tiny moons are introduced.
• The effects of Mars's tilted axis and elliptical orbit on its seasons, and the seasonal differences between the northern and southern hemispheres.
• The seasonal variation in extent of the polar ice caps.

02.30 - 03.22 Dust storms

• The first pictures of Mars, acquired by the early Mariner spacecraft, leading to a growth in our knowledge of the planet's surface.
• Introduction to the dust storms that can envelop the entire planet.

03.22 - 04.26 Water

• The Viking orbiters revolutionised our understanding of Mars. Their pictures hinted at the presence of water in the form of sub-surface ice and suggested the occurrence in the past of flash floods.
• Frosts and early morning fog.
• Touchdown of the two Viking landers which dug for signs of life.

04.26 - 06.00 Rifts and volcanoes

• To give an idea of scale, North America is superimposed on Mars.
• As we 'fly' over the Martian surface, we see major surface features, including Mariner Valley (the longest rift), and the great volcanic peaks, including Olympus Mons, the tallest volcano in the Solar System.

06.00 - 06.51 Ancient oceans

• The theory of ocean formation on Mars is introduced.
• The reasons why life has not formed on Mars are explained in terms of its great volcanic activity and climatic instabilities.
• Cessation of volcanic activity is suggested as the main cause of Mars's very thin atmosphere today.

06.51 - 08.22 Robots on Mars

• The touchdown of Mars Pathfinder, and the work of its six-wheeled rover Sojourner in analysing the composition of Martian rocks - with results that may support the existence of oceans in the past.
• Supporting evidence comes from Mars Global Surveyor in orbit, which finds a huge flat region.
• Surveyor also measures the weak Martian magnetic field.

08.22 - 09.50 Future exploration

• With the success of Pathfinder and Surveyor, further missions are planned, each with a lander and an orbiter.
• The main aim of the Mars Surveyor programme is to understand the history of water on Mars; meanwhile landers will continue to search for signs of life.