Brimstone — Charles G. Dyer

Helen Rogers is a brilliant geologist. Her paper about an imminent disastrous asteroid impact is laughed out of an international seminar. She lobbies rich people to sponsor an escape to Mars. Then the difficult tasks of managing people and organising the building of a suitable spacecraft begin.
As the asteroid approaches, the spacecraft is prepared for launch from orbit with nearly two dozen carefully selected people. On the ground, governments can no longer hide the threat and widespread panic ensues.
The one-way voyage through space is long and dangerous.
Mars has a hostile environment that does not easily support life. No provisions are made for a return to Earth. The pioneers have to adapt quickly or die. Read on to see how they manage