Starwatch: Mars and the Moon on show

Starwatch chart 7 Jan 2019

This coming weekend, keep a look out for the Moon as it slides past the red planet Mars. The chart shows the view looking south at 18:00 GMT on 12 January. The view will be similar on the days either side of this. Mars is about twice the physical diameter of the Moon but appears so much smaller in the sky because it is so much further away. Whereas the Moon orbits the Earth, and on 12 January will be around 396 thousand kilometres away, Mars is in an orbit that carries it around the Sun. On 12 January, it will be 203 million kilometres away from Earth. In many ways, Mars is intermediate in character between Earth and the Moon. Whereas the Moon is airless and the Earth has a full atmosphere, Mars has a tenuous atmosphere. Whereas the Moon is arid and Earth boasts an abundance of water, Mars shows evidence that water once flowed there but no longer. During 2019, Mars will travel behind the Sun from our perspective. Having been visible since 2017, it will be lost from view in July and return to the dawn sky in October.