Speaking at a press conference in the western German city of Cologne, Alexander Gerst said he would happily take up the challenge of flying to Mars.

The former volcanologist said he would accept whatever mission was offered to him as part of the European Space Agency (ESA) astronaut corps.

"I have nothing against that, I am an astronaut…that is my job," said Gerst. "Wherever we decide to fly, it's something interesting."

With neither ESA nor NASA possessing a launcher capable of sending humans to Mars, 38-year-old Gerst is unlikely to have to endure the possible perils a trip to the Red Planet might involve any time soon. However, he said would happily take part in future extraterrestrial missions, having left his old job in geophysics firmly behind.

"My future is certainly in space. I've given up my old job, which - to quote my former colleagues - was the second best job in the world. You can't do science part-time."

Despite his eagerness to escape the "our little blue planet," Gerst told the assembled journalists that the time he spent aboard the International Space Station (ISS) had given him a fresh perspective.

"Really, in this universe we know of no other place where we can live," he said. "It seems grotesque, seen from up there that people fight wars or pollute the environment or burn down forests."

"I don't want to be a moral apostle and to say we should do this and that. I want to get across a perspective - for people to see how it looks from outside."

"I came to think, 'If extraterrestrial beings really did come to visit us, how would we explain to them what they see?' That we burn down trees that we need to survive, that we fight wars with each other. That's something that I find hard to explain."

Soon after he landed in Kazakhstan, Gerst remarked on how good the Earth smelt. Asked if he was happy to be back, Gerst - who regularly tweeted his photographs of the "blue dot" of Earth from space - said that he was. At least for the time being.

"The grass is always greener on the other side," he said. "At the moment, I have to say I'm really happy to be back here…but certainly the time will come when I will want to go out there again."