A human-operated spaceship reaches the moon in 3 days. The moon is about 386,400 km from Earth. Mars, our closest planetary neighbor, is, at its closest, about 140 times farther away from us than the moon if Mars stays in place. Assuming a very simple model of the solar system, about how long would it take that same spaceship to reach Mars?
A:about 7.5 years
B:about 22.5 years
C:about 1 year
D:about 2.5 years
If the spaceship takes 3 days to reach the moon, and the moon is about 386,400 km away, then the spaceship travels at a speed of approximately 386,400 km / 3 days = 128,800 km/day.
Since Mars is about 140 times farther away from Earth than the moon, the distance to Mars is 140 * 386,400 km = 54,096,000 km.
Using the speed of the spaceship calculated earlier, to travel a distance of 54,096,000 km, it would take approximately 54,096,000 km / 128,800 km/day ≈ 420.5 days.
Therefore, it would take the same spaceship about 420.5 days to reach Mars, which is approximately equivalent to 1.15 years.
Therefore, the correct answer is C: about 1 year.