Let’s Go To Mars…

As I was working out how easy it would be to control a remote vehicle on Mars, I came across this video about how long it would take to travel to Mars.

I think the young girl who said half a year should get some credit – youngest person asked but by far the closest to the correct answer.

Mars and Earth both orbit the Sun but at different distances so they are only physically near one another in space at certain times. Viewed from Earth, Mars appears to orbit in the pattern shown below. The strange pattern is why planets like Mars were known as wandering stars by our ancestors. Once it was understood that the Earth and other planets orbited the Sun and that Mars had an orbit that was elliptical, it all made sense to a clever fellow called Kepler.

Earth is a mere 150 million kilometres from the Sun whilst Mars resides at a chilly 230 million kilometres out from the Sun. Whilst a year on Earth is 365 days, Mars takes 687 (Earth) days to complete one orbit. Its axis is tilted at 25° (similar to the Earth’s 23.5°) so there are seasons on Mars too. Martian seasons are each about twice as long though since a year on Mars is nearly twice that on Earth. A day on Mars is almost the same length as on Earth because it takes 24 hours and 39 minutes to rotate once on its axis. Of course, as a result of all this it is a lot colder on Mars with a high of about 20° Celsius on the equator in summer and a low of -125° Celsius at the poles in winter. On average the temperature is -60°C so very much lower than the Earth’s average of 15°C.

The senator spoke with great certainty but was quite misinformed. It is hard to know how he could have been so wrong. One clue is the whole “you have your data, we have our data” line. His data must be wrong or misunderstood on this occcasion.

Questions…

1. What determines the length of a day on Earth?
2. What governs the length of a year on Mars?
3. Why do Mars and Earth both have seasons?
4. If you know distance and speed, how do calculate time taken?
5. How many planets are there in the Solar System?