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Mars is bitterly cold. Temperatures seldom climb above freezing, and can slide far below minus-100 Fahrenheit. Yet the planet can get even colder. There’s evidence that Mars goes through periodic ice ages that can last for hundreds of thousands of years.

Ice ages can have several causes. On Mars, the most likely is a change in the planet’s tilt on its axis. Right now, the tilt is almost identical to Earth’s. That means the seasons are similar to Earth’s as well.

Over many millions of years, though, that angle can change dramatically. Mars can stand almost upright, or it can lie almost on its side. That affects how much sunlight reaches different parts of the planet, and how the Sun’s heat is distributed around it.

When Mars is on its side, the poles warm up and their ice caps vaporize. That makes the atmosphere warmer and wetter. Some of the extra water in the atmosphere may freeze around the equator, but overall, the planet is warmer than average.

Eventually, though, Mars flips upright again. The poles get colder, and the ice caps re-form. That makes Mars colder overall — perhaps triggering ice ages, with ice covering much of the planet. One recent study says this has played out many times in the past few hundred million years, giving Mars many ice ages.

Mars climbs into good view in the east-northeast by 10:30 or 11, and looks like a bright orange star. Tonight, it’s well to the upper right of the Moon.

More about Mars tomorrow.

Script by Damond Benningfield

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