Mars proves to be inhospitable, and they struggle to survive with their decreased water supply. Earth's correct orbital position for a return trip is one year away. While glumly celebrating their first Christmas on Mars, a sudden snowstorm blows in, allowing them to replenish their water supply. As their launch window arrives, they hear low rumbling sounds, then see rocks falling, and feel the ground shake violently. The ground level shifts during this violent marsquake. Their spaceship is now leaning at a precarious angle and cannot make an emergency blast off. To right the spaceship, the crew uses the rocket engines' powerful thrust to shift the ground under the landing legs. The attempt works and they blast off, the spaceship rising just as the Martian surface completely collapses.