This Week’s Night Sky: Watch Mars Reverse Its Tracks

The red planet will be in retrograde starting on Saturday, a cosmic illusion that lasts for a few months every two years.

With nothing more than your unaided eyes, you should be able to see six dark patches on the lunar surface. These are known as mare, or seas, but they are actually ancient lava plains. When giant asteroids impacted the moon billions of years ago, lava welled up through the resulting cracks and oozed out over the surface, creating the collection of smooth plains.

At the same time, the open cluster Messier 44 (M44), which sits 610 light-years away, will be to the upper left of the moon, forming a neat triangle with M67. Known as the Beehive, M44 is close enough and bright enough to be just visible to the naked eye as a fuzzy spot in the dark sky. Binoculars

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