The reason for this is because women require fewer resources and are more likely to return back to Earth healthy.

A person who will travel to Mars must be in a confined space for 7 months. Apart from that he will have to go through very specific training.

Experts say women are better suited for spaceflight in almost every field.

Their bodies are smaller and lighter, meaning they need less oxygen and less food. They are also more resistant to radiation and have less chance of a heart attack.

Men need 30% more food, 60% more oxygen and 17% more water.

[Source: http://www.iflscience.com]