Martian Autumn

The shortest season on Mars arrives today — autumn in the northern hemisphere, and spring in the south. The season will last just 142 Mars days. That’s 52 days shorter than northern spring.

The difference is the result of Mars’s lopsided orbit. The distance between Mars and the Sun varies by about 25 million miles. When Mars is farthest from the Sun, it moves slower than when it’s closest to the Sun. That stretches one season, and compresses another.

The differing seasons would make it hard to create a Martian calendar that’s tied to the seasons. That hasn’t stopped people from trying, though. They’ve come up with several ideas.

Some schemes divide the year into 12 equal months, like those on Earth. Others use 18 months, or even 24. And still others have tried months of different lengths.

The concept of a “month” wouldn’t be as important on Mars as it is on Earth. A month here is based on the Moon’s cycle of phases, which lasts 29 and a half days. But the two Martian moons move across the sky much faster. The tiny outer moon, Deimos, completes its cycle of phases in just five and a half days. And the bigger inner moon, Phobos, crosses the sky twice every day. So the moons probably won’t be much help in designing a calendar for the Red Planet.

And Mars is climbing into better view by the day. Right now, it’s about a third of the way up the southern sky at first light, and looks like a bright orange star.

More tomorrow.

Script by Damond Benningfield