MARS SEASON HAS ARRIVED

With Mars at opposition this December - and a rare lunar occultation expected too - now's the time to start observing and tracking its changing features, writes Paul G Abel

On 8 December 2022, Mars reaches opposition. It's going to be a splendid telescopic target, well-placed for observation in the Northern Hemisphere and well worth observing in the dark winter months. And as an added bonus, on the same night as opposition the Moon will appear to pass in front of Mars in an event known as a lunar occultation. December is set to be the month of Mars. But before then, Mars will be growing steadily larger and brighter, meaning there's plenty to see in the run-up. Here we'll explore the exciting phenomena we can observe before and after opposition.

Opposition occurs when an outer planet is opposite the Sun in the sky. Sun, Earth and planet all lie in a straight line, with Earth in the middle, and at this time the planet is due south at midnight and visible all night. We don't get a Mars opposition every year, nor are they all favourable for UK observers. This is due to the shape of the Martian orbit. All planetary Perihelic orbits are slightly elliptical, but the Martian one is more so than Jupiter's and Saturn's. As a result, Mars comes to opposition once every two years.

▲ At perihelion, Mars is at the closest point to us in its elliptical orbit. Aphelion is the opposite

The position of Mars in its orbit dictates its altitude in our skies at opposition. In a perihelic opposition, Mars is at (or near) perihelion (its closest point to the Sun). The planet is large and bright, but low down for Northern Hemisphere observers. In aphelic oppositions, Mars is at its furthest point from the Sun and has a small apparent diameter, but is high in UK skies. December's opposition is a transitional one: moving from perihelic to aphelic. In my opinion, these are the best: Mars reaches a good size and is fairly well placed.

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