Sir Patrick Moore, probably the most influential astronomer of the 20th Century, visited Worthing's Pavilion theatre last week as part of a lecture tour to mark his 80th birthday.

Sir Patrick is by his own admission no academic but his boyish enthusiasm and encyclopedic knowledge of space has rubbed off on millions of people during the past 50 years.

He once met Albert Einstein, who was unable to explain in ordinary language what infinity was and Sir Patrick appears to have learnt from that, speaking in layman's terms.

He is fortunate that his zeal for all things out of this world coincided with the space race of the late Fifties and Sixties, when the world sat glued to fuzzy-pictured black and white TV screens watching mankind take its first tentative steps to the stars.

The programme that made his name, The Sky At Night, started in 1957 and became the world's longest-running show.

Sir Patrick, complete with trademark monocle, has the look of a mad professor who was caught in the backdraft of a rocket launch.

He is renowned for his boffin-style crumpled suit, old school tie, unkempt hair and the ability to speak at the rapid-fire rate of 300 words per minute.

But the public love him, quirks and all, and respect his self-taught knowledge.

Hundreds of people gathered to hear Sir Patrick's views on the possibility of man going to Mars within the next 20 to 30 years.

He shuffled on to the stage assisted by two sticks and a stage-hand, and plonked himself in a comfy chair.

In the age of digital technology, he relied on a good old-fashioned slide projector to display photographs and drawings to illustrate his lecture.

Sir Patrick, who lives in Selsey, was greeted with generous applause as music from the Royal Scottish National Orchestra faded away and he began to talk about Mars, the Red World.

First he set the scene. The Earth, he explained, is 8,000 miles across and 93 million miles from the sun, with the moon just 250,000 miles away.

Mars is 4,000 miles across and 141 million miles from the sun, with a very thin atmosphere and a temperature range of 10C (50F) to minus 73C (minus 100F).

He said: "Our next step must be Mars, which is less unlike the Earth than any other planet and it possible we may find a certain amount of life there. We shall see."

Venus, the evening star, and about the same size of Earth, had an atmosphere dominated by carbon dioxide and clouds of sulphuric acid.

Sir Patrick said: "Go there for the weekend and you will be fried, poisoned and squashed."

On the other hand, scientists now know ice caps on Mars were very deep and made of water, which humans could harness, forming the foundation for future colonisation.

The planet's famous canals, believed in the past to be a Martian irrigation system, were simply tricks of the eye, as was a photograph taken by an early probe in 1970 which seemed to show a face on the surface.

The audience, ranging in age from six to 86, saw pictures of Mount Olympus, which is 15 miles high, and a Grand Canyon-style gorge which Sir Patrick thought would one day be a great tourist attraction.

Referring to the possibility of life, he said simple organisms could survive in the most unusual places.

He said: "There are still people who believe we are totally alone in the universe.

"I find that hard to believe. But we have no proof yet of any life beyond Earth. If we find any trace of life on Mars that could be the turning point."

Sir Patrick believed man could make the first trip to Mars in about 2020, using the sun's gravity to propel space craft towards the Red Planet, a journey that would take months.

The moons of Mars could become a staging post where bases could be established in preparation for the final push. By 2035 there might be bases on Mars itself, served by a railway network and aircraft with huge wing-spans.

Radiation was a real danger, but humans had proved they could stay in the weightlessness of space for a long time without any major ill-effects.

He thought hydroponics, the growing of plants without soil, would enable colonists to feed themselves and revealed biologists were already working on ways of growing vegetables in the open on Mars.

In the long term, terraforming could change the atmosphere so it resembled Earth, turning deserts into fields, but this was centuries in the future.

Sir Patrick wondered whether children born on Mars, where gravity was considerably weaker, would ever be able to visit the Earth.

He said: "How would you feel if your weight increased three times without an increase in heart and lung power?

"It may well be Martians won't come here and we may find two completely different branches of homosapiens developing. It is a staggering thought but not too far- fetched."

Sir Patrick concluded with a question and answer session and the words: "I wonder how right and wrong I have been this evening? Time will tell."