Elon Musk should only send one person to Mars to avoid contaminating the planet.
Elon Musk has been told to scale back his plans to conquer Mars
The billionaire SpaceX tycoon is hoping to put over a million humans on the Red Planet but a leading scientist has urged the maverick entrepreneur to scale down his ambitions.
Andrew Coates, a professor of physics at University College London (UCL) told BBC Radio 4's 'Today' programme: "One person may be okay eventually, but there are risks of contamination.
"Eventually, Elon Musk would like to be taking people to the Moon and onto Mars... I think we have to be careful on the latter one.
"The last thing we need to be doing is taking life from Earth to Mars. Robotic exploration is the way to go."
Professor Coates has no such fears about humans going to the Moon in large numbers.
He said: "The moon is absolutely no problem, we can do that.
"But I think we are going on to Mars with a lot of people and that is where we have to start worrying.
"Jumping to conclusions about colonising Mars, which is one of the stated aims, is something we would like to avoid in the future, personally."