DO NOT panic. Be positive. Yes, everything on the planet looks like it's going to pot, but there's good news and quite a bit of hope – hope here on earth, and hope thousands of light years away.

Jim Al-Khalili, the broadcaster and professor of physics, dealt with the hope from a distance in an event at the book festival about the potential of life on other planets. Al-Khalili's voice you will know from Radio 4 but you may be less familiar with what he looks like. Let me explain: Patrick Moore eyes and Magnus Pyke arms. Just as it should be.

Al-Khalili's thesis is that life is likely to have existed on Mars billions of years ago because that was when conditions on the planet were most similar to conditions on earth, but he also believes that it exists right now in distant solar systems and indeed in our own solar system. It's all a lot closer than you think.

The moons of Saturn and Jupiter are the most likely locations for this alien life, says Al-Khalili, because it is there that there are magnetic fields generating heat. And where there is heat and ice, as there is on these moons, then there is likely to be water and where there is water, there is likely to be life. Tiny, microscopic life, but still: life.

The critical question then is: could Darwinian evolution take over and transform the simple, single cell life into something more complicated, something more like us and eventually something that could build a rocket and come over here and threaten us, eat us, or, as in some of the more terrible science fiction films, mate with us?

Al-Khalili thinks it unlikely and in fact he is entirely relaxed about the idea of alien visitation for a simple reason: it would be good for us. "I would like to think," he says, "that it would be very unifying for life on Earth. It might help us realise that we are, as a race, not that different from each other."

Even the search for alien life is good for us, says Al-Khalili. There was a time not so long ago, he says, when mainstream scientific thinking was that looking for life in the universe was frivolous and there are many who still think this way.

"But for me," he says, "the notion of whether we are alone is one of the most important questions human kind can ask. Finding life on another planet would be the greatest discovery since Copernicus and Galileo showed that the earth is not the centre of the planet. Finding life elsewhere would be another blow to our arrogance."

There was more hope, earthbound this time, from Christopher de Bellaigue, the historian of the Middle East during his event exploring the history of Islam.

In many ways, he said, Islam is much more closed and less enlightened than it was 100 years ago, but, here and there, there is hope that young Muslims are not necessarily consulting the old white beards anymore and are deciding for themselves what is right and wrong. Islam, said de Bellaigue, has an ocean of opportunities for the individual. It's what people have done with it that's the problem.