Question

To find the speed of the X feature, you will need a distance and time. You have a value for the circumference of the GRS. By looking at the distance the X has traveled as a percentage of the GRS’s circumference (about 25% of 88,000 km), you can estimate the distance it traveled around the GRS, but you also need to know how much time it took for that partial rotation. We know there were 3, 571 hours in between images and there are 5 images total, so the total number of hours is: 3,571 hours/image x 5 images = 17,855 hours

1. Divide the distance the X traveled in kilometers by the number of total hours covered, to find the speed of the GRS at the distance of the X from its center. (Show your work.)

2. This is the approximate rotation speed. What is the rotation period, in days, at this distance from the center of the GRS? (Hint: What is the period in hours for the X feature?)

Answer 1

1)

Distance travelled by X = 0.25 * 88000 = 22000 km

Time taken to cover this distance = 17855 hours.

So the rotation speed: 22000/17855 = 1.232 km/hr.

2)

Rotation period = Circumference / Rotation Speed

Rotation Period = 88000/1.232 = 71428.57 hr.

1 Day = 24 hrs.

So, 71428.57 hrs = 2976.19 days

So, the rotation period in days = 2976.19 days