This is called Comparative Planetology. It may not seam like these two things go together, but they do. Mars protected those who fought for their communities, and stayed home to raise crops for food. If you weighed 70 pounds on the Earth, you would weigh about 27 pounds on Mars. Mars excites scientists because it's mild temperament is more like the Earth's than any of the other planets.
Evidence suggests that Mars once had rivers, streams, lakes, and even an ocean.
As Mars' atmosphere slowly depleted into outer space the surface water began to permanently evaporate. Today the only water on Mars is either frozen in the polar caps, or underground. Mars has much higher mountains, and far deeper canyons than the Earth. Mars' biggest canyon would stretch from New York City to Los Angeles on the Earth. That makes the Grand Canyon look tiny.