On Saturday, August 4, 2018 the Tamworth Regional Astronomy Club (TRAC) hosted a Mars Public Viewing Night only a few days after the Red Planet had passed within 57.6 million kilometres of the Earth, the closest approach in 15 years. It displayed a disc measuring 24.3 arc seconds in diameter when viewed through a telescope. Shining at magnitude -2.8, the only objects which were brighter in the sky were Venus, the Moon and the Sun.
TRAC member, Dr Garry Bott, gave an excellent presentation at the event to the 200 strong crowd in attendance at Victoria Park and explained some interesting facts about Mars, its history and our current knowledge about this intriguing planet. Reproduced here is a summary of Garry’s presentation and follows on from the last TRAC column by Barry Gilbert about the amazing planet Mars.
At the end of July 2018, the planet Mars was the closest to the Earth it has been since 2003, some 57.6 million kilometres (36 million miles) away.
Mars appears in records dating back to Egyptian astronomers (2,000 BCE). Babylonian, and later Greek astronomers, showed interest in this perplexing “stellar” object. But more importantly, Johannes Kepler used Mars in a Sun-centred Solar System model using more correct elliptical orbits to predict Mars’ movement through the night sky. In modern history, H G Wells published War of the Worlds which was dramatised on a very famous radio program performed by Orson Wells in 1938.
Mars is approximately 53% the size of Earth, however it has the highest mountain and the deepest valley in the Solar System. Olympus Mons, a massive extinct volcano, is three times as tall as Mount Everest. The Valles Marineris system of valleys are as deep as 10 kilometres and runs east-west for 4,000 kilometres.
Mars lacks a substantial atmosphere with only an average pressure of 0.09 psi or 0.6 kilopascals, while on Earth the atmospheric pressure at sea level is 101 kilopascals. A thin atmosphere means that Ultraviolet (UV) radiation from the Sun is a problem. Any organic molecules, carbon-carbon bonds which are required for life, would be broken.
Perhaps one of the most significant differences between Earth and Mars is that Mars has no magnetic field. Earth does have a magnetic field, and this protects us from the incoming particles (electrons and protons) in the solar wind. These particles would ionise oxygen on Mars which would escape the planet along the magnetic field due to the Sun. Maven, a satellite orbiting Mars, has picked up such leakage in its spectral analysis of the space surrounding the planet.
Mars today is a planet which has very little atmosphere and no remaining surface water.
Footnote: While it’s now several weeks past the 2018 close approach of Mars to the Earth, the planet is still high overhead in the early evening hours of late September/early October, shining at around magnitude -1.4 and displaying a respectable disc of about 16 arc seconds, which is approximately the same apparent size of the disc of Saturn when viewed through a telescope. A global dust storm which enveloped much of Mars when it was at its closest has now cleared somewhat and is well worth a look through a telescope, showing the two polar caps and the various dark markings on the planet’s surface.
TRAC will be holding its next monthly Astronomy Meeting and Telescope Viewing Night on Saturday, 6 October, 2018 at the Botanic Garden’s Training Room, Victoria Park (top end of Piper Street, Tamworth) at 7pm with a talk by our visiting guest speaker, Donna Burton. Donna has worked as a support technician, telescope operator and astronomer at Siding Spring Observatory for many years, currently operates Milroy Observatory at Coonabarabran and has discovered two comets.
She will be presenting a talk about the many achievements of women in the field of astronomy and will be followed by telescope viewing (weather permitting) at around 7.30 pm. Venus, Mars, Jupiter and Saturn are all currently well placed for observation. An alternate program will be organised in the event of cloudy weather. If you are interested in attending our meeting, please send an e-mail to the Club at firstname.lastname@example.org so we have an idea of numbers. Further details about TRAC are available at our website: www.tamworthastronomy.com.au