The first space age began on October 4, 1957, with the launch of the Russian satellite Sputnik 1. It will end in 2010 with the last space-shuttle flight. The second space age began in December 2004, when Nasa published its “mission architecture” to set up a moon base and then fly to Mars. If all goes well, man will once again walk on the moon in 2020 and, for the first time, walk on Mars in 2037.

It will have taken 80 years to get from Sputnik to Mars, decades longer than anybody expected. For the truth is that Space Age 1 was a great disappointment. The beautiful white Saturn V rockets that powered America’s dash to the moon in the 1960s gave way to the shuttle – a clumsy, dangerous truck that barely staggered into Earth orbit – and to the International Space Station, a pale shadow of the grand multipurpose space lab of the scientists’ dreams. Nobody has stepped on the moon since December 14, 1972, when the Apollo 17 mission blasted off the lunar surface.

Two things were wrong with Space Age 1. First, it began as a war effort. After Sputnik, the Americans had to chase the Russians into space, and the Apollo programme was dominated by global strategy, not science. Nasa didn’t even send a geologist to the moon until Harrison Schmitt flew with Apollo 17. The shuttle was largely built as military hardware. Secondly, as the Russian programme faltered, and then as the cold war ended, space became a Nasa monopoly. Innovation was stifled as money was poured into the increasingly hopeless shuttle programme.

Space Age 2 will, everybody hopes, be different. The moon-Mars hop is not a mission in time of war. Science will come first. Furthermore, Nasa will have to compete. Dozens of private-enterprise schemes like Virgin Galactic are finding cheap and cheerful ways of getting into space. And, more importantly, Europe, Russia, Japan, China, India are all joining in the second space race. Even Britain’s Beagle lander, which vanished from the Martian surface, is to be resurrected as a water-detecting lunar probe. The hope is that, this time, space will be a co-operative, global effort – an act of peace, not war.

It will also, primarily, be a human rather than a robotic programme. After the endless problems with the shuttle, many began to think that putting humans in space was just too costly and clumsy. Indeed, until recent rethinks, the entire space policy of the British government centred on a refusal to back any manned programme.

Few people think like this now. The reason is that robots are, in fact, not very effective. After its launch in 1990, for example, the Hubble Space Telescope was found to have serious optical flaws. These had to be corrected by astronauts; and the life of the Hubble has been extended by human maintenance programmes. Humans are also quicker than robots. In its first 330 days on the Martian surface, the Nasa rover Spirit covered 3.9 kilometres. In three days on the lunar surface, Apollo 17 astronauts covered 35 kilometres in their lunar roving vehicle. And they were able to think on their feet. In space, therefore, the next 50 years should prove a lot more exciting than the past 50. So what will happen?

Well, we may find we’re not alone. The search for aliens has, so far, not gone well. Vast sweeps of the sky have produced no “Hi, guys!” moment and, until the 1990s, the idea of finding life on other planets had come to seem laughable. Then everything began to change. Hubble confirmed there were, indeed, planets circling stars other than our sun. More importantly, our ideas about life began to change as a result of our discovery of some very strange creatures here on Earth.

Known as extremophiles, they live in conditions previously thought utterly inimical to life. Whole ecologies were discovered living by super-hot vents on the ocean floor, and anaerobic bacteria were found that eat rocks. Best of all were the tardigrades, or water bears. Found on the highest mountains and in the deepest oceans, they can survive huge doses of radiation and temperatures from almost absolute zero to over 150C. So life can exist almost anywhere. Aliens are no longer a laughing stock.

The key question we need to and can answer in Space Age 2 is: how likely is it that life will get started? We know life established itself on Earth pretty quickly – within a couple of hundred million years of the end of an intense meteorite bombardment that would have sterilised the planet for its first, say, 500m to 700m years. But this speed may be dumb luck. The best way to find out is by planting boots on the moon, then Mars. On the moon because we should be able to find bits of early Earth blasted there by meteorite impacts. Very early Earth has been lost to us owing to geological activity, but nothing much ever happens on the moon, so 4-billion-year-old chunks of our planet should be just lying around. Mars is even better. Four billion or so years ago it was a much more peaceful place than Earth, a much better place for life to get started. Indeed, it may have started there and arrived on Earth as a water bear on a meteorite. So if we prove there has been – or is – life on Mars, then we’ll know we’re not just a fluke, and the universe is not a desert but a jungle.

But even without aliens, Space Age 2 will teach us a lot more about ourselves. The most profound impact of Space Age 1 on the human imagination was not a scientific discovery, it was the sight of our planet from space. In theory, we’d known for centuries we were just clinging onto a rather small rock hurtling through a very unfriendly void. But seeing it changed everything. It fired the environmental movement and made us all feel more fragile.

The big question that will be answered in Space Age 2 is: can we ever hope to get off this appallingly vulnerable pebble? Of course, we have already made it to the moon and stayed for months in Earth orbit. But it remains unclear whether we can sustain truly long-term off-Earth habitation. A simple round trip to Mars will take three years – far longer than any astronaut has yet stayed in space. The problems are huge. Radiation from a single solar flare while astronauts are in transit to Mars could kill them all. Low or zero gravity causes the body to waste away, and degrades the immune system. Very long-term effects of exposure are unknown but likely to be serious. Disease processes in space are not understood. Very recent findings from a shuttle mission showed that salmonella bacteria grown in space were much more virulent. This is bad enough in itself. But, in addition, the bacteria became more virulent because the behaviour of their genes changed. The same thing has been shown to happen in human kidneys. The long-term effects of such changes are unknown.

On the upside, because space flight means we must study the human body in these conditions and find solutions, medical science will advance. Increasingly, scientists are finding out what goes on in the body by watching its reaction to extreme conditions. The way the body adapts to low gravity and higher radiation levels will reveal how it works in ways we cannot begin to imagine.

Astronomy is certain to be transformed by Space Age 2. The Hubble is nearing the end of its life. Its successor is the James Webb Space Telescope, which should be launched in 2013. This will not orbit but float at L2, a position 1.5m kilometres from Earth, where the sun’s and the Earth’s gravity cancel each other out. That, along with telescopes on the dark side of the moon, will hugely multiply our astronomical capability.

Will it all pay? To the scientists, of course, this is irrelevant. We explore space to discover and to satisfy the human hunger for adventure. But the human hunger for profit is equally strong.

Space tourism is an obvious earner, but, within the next 50 years it is only likely to be a niche market for the very rich. Mining the moon for titanium is possible. The moon is full of it and its high value could justify the cost of shifting it back to Earth. There are also strong scientific reasons for landing on asteroids, and these could yield much easier commercial mining benefits. For a few years there has been excitement about the large amounts of helium-3 on the moon. This, it is thought, could be used to create fusion energy on Earth, a technology that still seems to be at least 30 years away. But the value of helium-3 now seems to have been discounted.

Who knows? The one certainty about Space Age 2 is uncertainty. For a start, it might not happen. Nasa will struggle to finance a Mars mission on its own – even its ability to fund its next moon mission is in doubt – and some degree of international co-operation is essential. With global tensions heightening, the competing nations might decide to go it alone. In addition, all the technology has to be cutting edge. We know in theory how to get to Mars, but not in practice. On top of that, after the two shuttle disasters, Nasa is very risk-averse, so any mission budget will be loaded with safety demands.

But if it does happen, wonders undoubtedly await us. Space Age 1 opened a door only to reveal another door. Beyond that next door, we will see something entirely new and different. We may see a jungle, a cosmos that must, logically, be teeming with life, instead of the desert to which we have grown accustomed. Or we may just see ourselves. Again. Either way, space is, once again, the next big thing.