SpaceX CEO Elon Musk has repeatedly stated that he plans to establish a permanent settlement on Mars with a population of at least one million by 2050. However, this ambitious and risky plan may be doomed to failure from the very beginning. At least that’s what biologist and author Kelly Weinersmith thinks.

In a new interview CNN Kelly and her husband, cartoonist Zach Weinersmith, have spoken at length about their skepticism about colonizing the Red Planet.

“It is impossible to increase the population of Mars to one million people without a catastrophe,” warned Weinersmith.

According to the biologist, women on the Red Planet will most likely not be able to conceive and give birth to children due to gravity problems (the gravitational force near the surface of Mars is about 2.5 times weaker than on Earth). Also, there is no liquid water, it is very cold and the whole planet is a huge desert.

Still, Weinersmith reminded that the Red Planet could be a great place for research in the short term.

These fears largely echo those of other experts critical of Musk’s plans to colonize Mars. Besides the political, technological and ethical issues, this project could be prohibitively expensive even for the richest man in the world.