Mars' apparent retrograde motion
![Mars' apparent retrograde motion](https://planetary.s3.amazonaws.com/web/assets/pictures/_1200x777_crop_center-center_82_line/mars-retrograde.jpg 1200w, https://planetary.s3.amazonaws.com/web/assets/pictures/_768x497_crop_center-center_82_line/mars-retrograde.jpg 768w, https://planetary.s3.amazonaws.com/web/assets/pictures/_576x373_crop_center-center_82_line/mars-retrograde.jpg 576w)
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