Distances

Thinking Questions

Distance and Diameter of Mars: ANSWER

The radio (radar) signal took 9 minutes, 37.308 seconds to return. That is 577.308 seconds in total. However, since this is a round trip time and all we want is the one-way distance to Mars, the figure we need is 288.654.

The instantaneous distance to Mars was

288.654 times 299,792.458 km, which is 86,536,292.17 km
By the concept of significant figures, we should round this to 86,536,300 km

Using the equation given:

TD=AD*Distance/57.3º

TD=16.18" * 86,536,300 km / 57.3º (change 16.18" to degrees by dividing by 3600)

TD=0.0044944º * 86,536,300 km / 57.3º

TD = 6787.6543 km

By the concept of significant figures, we should round this to 6790 km , and the distance to 86,536,300 km.

Thus on May 1, 1999, Mars was 86,536,300 km from Earth, and its diameter is 6790 km .

Thinking Questions