I was invited out to dinner tonight and was welcomed at the door by a very enthusiastic plan to view Mars at its closest to Earth for 60,000 years. I rather too enthusiastically poo-pooed this as being a myth to a somewhat muted reception. We did go out and view Mars, which was twinkling with an orange glow to the left of a very bright full moon, and we were all moved by the enormity and majesty of space.
Mars is about half the radius of Earth and is approximately one tenth the mass. It is (on average) 249 million kilometres from the Sun and takes 1.9 years to complete its orbit. It has two moons, Deimos and Phobos, and its atmosphere is almost entirely carbon dioxide. Despite the pretty severe global warming problem you would expect it to suffer, its surface temperature never rises above -5 Celsius. NASA’s robotic explorer Rover, which has been driving around on the surface of Mars for six years is now permanently stuck so will begin to collect quite different data to its intended mission.
I think I was right that we were not particularly near to Mars. It could be seen because it was in opposition to the Earth, i.e. we were passing between Mars and the Sun so Mars appeared clearly in the night sky as it does about every 2 years and 2 months (780 days). Mars has an elliptical orbit so it is sometimes heading towards its closest point to the Sun (perihelion) and the rest of the time heading away from the Sun towards its furthest distance (aphelion). It is currently travelling away from the Sun towards its aphelion and is in fact about as far away from us as it ever gets whilst still being visible in the night sky (101 million km). Its last perihelion when it was in opposition to Earth was in 2003 at which time it was a mere 56 million km away.
There is a nice interactive solar system here courtesy of National Geographic.
Questions…
- Why does Mars appear to be reddish in colour?
- Which planet in the solar system has the most moons?
- How far is the Earth from the Sun?
- Which gas has recently been detected on Mars that has provoked renewed excitement that there may be simple life beneath its rocky surface?
Comments