As darkness falls in the UK on Thursday, 18 October 2018, the waxing gibbous Moon lies just 3¼ degrees from the Red Planet, making for a nice juxtaposition in typical binoculars as depicted above. AN graphic by Ade Ashford.Anyone in Western Europe blessed with clear skies at dusk on Thursday, 18 October should cast their gaze towards the 9-day-old Moon that happens to appear close to Mars in the southern sky. Their proximity is merely a line-of-sight effect since the Moon is just 401,600 kilometres distant, whereas the Red Planet lies almost 105 million kilometres from Earth this night, hence Mars is 260 times farther away.
Mars was closest to Earth just three-and-a-half months ago when its bright ochre disc spanned an impressive 24.3 arcseconds. Now, the Red Planet’s disc measures 13.4 arcseconds – little more than half its opposition best. However, many keen Mars observers will recall the global dust storm that obliterated much of the keenly anticipated surface detail from view. Thankfully, the martian atmosphere is much clearer now, so prominent features should be easier to detect despite the planet’s shrinking apparent size.UK dusk on 18 October 2018 finds Mars almost 12 weeks past opposition, hence it’s much farther away (some 105 million kilometres) and consequently smaller. On this night the Red Planet’s disc measures just 13.4 arcseconds across and shows an appreciable phase. Magnitude -0.9 Mars is highest in the southern sky of the British Isles close to 8:30pm BST when the dark Syrtis Major feature lies north of the planet’s equator, with the brighter Hellas plain nearer the south polar cap. Users of Newtonian reflectors should invert this graphic to match their eyepiece view, while those observing with refractors and catadioptrics with a star diagonal need to mirror the illustration left-right to match what they see. AN illustration by Ade Ashford.For skywatchers in the British Isles, darkness falls around 8pm BST on 18 October 2018 and Mars is best placed for observation in the southern sky about half an hour later. Even so, the Red Planet barely attains an altitude of 17 degrees – slightly less than the span of an outstretched hand at arm’s length – as seen from the heart of the UK.
The martian longitude facing Earth at 8:30pm BST this night is 309 degrees, hence prominent features such as the dark V-shaped Syrtis Major in the planet’s northern hemisphere, the bright Hellas basin in the south (see our interactive Mars Mapper web app for annotated maps of the planet) and the shrinking martian south polar cap will be on show for those with good seeing. Note, too, that Mars now has an appreciable phase; the planet’s disc is 87 percent illuminated on the night in question.
The 12-day-old Moon lies in the same low-power binocular field as Neptune late into the evening of Thursday, 10 October 2019 when observers in the UK can find the pair highest in the southern sky against the constellation of Aquarius. The glare of the gibbous Moon will present a challenge, but well worth the attempt to find the outermost planet with modest optical aid.
For three evenings from 26–28 February 2020, observers in Western Europe including the British Isles can watch the waxing crescent Moon’s changing configuration with brightest planet Venus in the west-southwest at dusk. The pair are closest for UK-based observers on the evening of Thursday, 27 February, simultaneously visible in low-power binoculars.
Nitrogen, in the form of nitric oxide (one nitrogen atom and one oxygen atom), has been detected for the first time on the surface of Mars by a team of researchers using the Sample Analysis at Mars (SAM) instrument suite aboard NASA’s Curiosity rover, adding to the growing speculation that life could have once flourished on ancient Mars.
