Planetary Motion

As the Earth and Mars travel around the Sun, their relative distances and positions constantly change. Use the simulation below to investigate the motion of Mars.

Heliocentric View

Wait for the applet to load and then click here to initialize the animation. You will need Netscape 3.0 or above to run this animation.

Instructions: Run the animation to see what is going on. You may start, stop, and reset at any time. Click and drag inside the animation to read the coordinates of the planet in order to obtain numerical values.

The Sun is yellow(and not to scale), the Earth is blue, and Mars is red. The time is given in days.

1. Mars is said to be in opposition when it appears opposite the Sun in the sky as seen from the Earth. This means that when looking at the sky, the Sun will appear on one horizon and you will have to turn aorund to see Mars on the other horizion. Use the Heliocentric view to answer on approximately what days are the first two occurances of opposition.
Day [0]
Day [262]

2. Mars is said to be in conjuction when it appears in the same direction as the Sun when seen from the Earth. This means that you can see both the Sun and Mars looking the same direction. Use the Heliocentric view to answer on approximately what days are the first two occurances of conjunction.
Day [127]
Day [395]

3. What is the synodic period of Mars in months based on the information in 1 and 2? (Just in case you've forgotten: the synodic period is the time for an object to complete one full orbit as seen from Earth.)
[9]Months (round to the nearest whole month)

Geocentric View

Wait for the applet to load and then click here to initialize the animation. You will need Netscape 3.0 or above to run this animation.

Instructions: Run the animation to see what is going on. You may start, stop, and reset at any time. Click and drag inside the animation to read the coordinates of the planet in order to obtain numerical values.

The Earth is blue and Mars is red.

4. (a) During the first 600 days of the animation, how many retrograde loops does Mars undergo as seen in the Geocentric view?
[2.5]

(b) Approximately what days mark the center of each retrograde loop?
Day [0], Day [258], Day [523]


(c) What relationship do the retrograde loops bear to the dates of opposition and/or conjuction?


Key: The retrograde loops occur roughly at the same time as when Mars is in opposition.

Credits

Physlet problem authored by Larry Martin and Rachel Parks, North Park University