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TONIGHT Mars is at its closest point to Earth on its 687 day per year orbit. Earth is directly between the sun and Mars. The planet stood vertically overhead shining brightly.
When Mars is behind the sun, it can be up to 400 million kilometres away, so for much of the time Mars is just a tiny dot. Tonight it has reached its closest point at 75 million kilometres, enough to produce a disk through my 500mm lens.
Mar's orbit is more elliptical than Earth's. Jupiter also alters Mars' orbit, so the distance at its closest approach every 26 months does vary a lot. Next time the planets approach each other in July 2018, the two planets will only be 57 million kilometres apart and the disk will appear to have about twice the surface area as it does tonight.
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