Humans need to settle on Mars as a "plan B" – or we risk going the way of the dinosaurs.

That's the belief of top theoretical physicist Michio Kaku, who said Mars is one of our best hopes of avoiding "extinction".

According to the American science titan, "99.9% of all life forms" become fossils – and "disappear off the face of the Earth".

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Humanity risks the same fate if we don't invest in space travel, and find a way to settle on Mars.

"Look at the dinosaurs," Kaku said, speaking on ABC's Late Night Live.

"The dinosaurs did not have a space program, and that's why they are not here today to talk about it."

It's easy for humans to think we'll buck the trend and survive through any cataclysmic event.

But Kaku is concerned that the only real way to avoid the total wipe-out of humanity is to colonize Mars.

"Extinction is the norm," he explained.

"We think of Mother Nature as being warm and cuddly, which is partly true.

"But nature is merciless when it comes to wiping out inefficient life forms."

Kaku is one of many scientists who back a process called terraforming.

This hypothetical process involves changing the surface and climate of Mars, to make it hospitable for humans.

There are lots of theories about how this could work, including melting the polar ice caps to heat the planet up.

This could be done using "solar satellites" that beam sunlight onto the caps, kickstarting the process.

"Once you can raise the temperature of Mars by six degrees, it takes off all by itself," said Kaku.

"All of a sudden you get a runaway greenhouse effect, and Mars basically terraforms itself."

Professor Kaku was keen to point out that humans shouldn't abandon Earth completely.

Mars could simply be a useful alternative – if only temporary – to avoid a destructive event on our home planet.

The red planet could work like a space bunker, keeping humans safe from mega-tsunamis or disastrous climate events.

"No one is talking about leaving the Earth and going to Mars," said Kaku.

"We're talking about a settlement, a self-sustaining settlement on Mars, that's not going to drain resources of the planet Earth but will give us an insurance policy, a plan B."

Space won't simply be an evacuation point, however.

Kaku believes that out "grandkids will have the ability to honeymoon on the Moon".

He said it's "only three days away", and added that it's "an easy target."

This story originally appeared in The Sun.