Mars is coming……….in 2018!

A map of Mars centred on the giant volcano Olympus Mons. Taken from Microsoft World Wide Telescope, credit NASA/USGS/MalinSpace Science Systems/JPL.

An email, often based on a PowerPoint presentation, has been circulating for the last six years or so and tells people that Mars is approaching in August and will be seen as big as the full Moon. To the disappointment of many of the recipients this email is a hoax. It recounts the events of August 2003 when Mars was exceptionally close to the Earth, but in a highly exaggerated fashion. Mars was not near Earth in August 2004, 2005, 2006, 2007, 2008 or 2009 and will not be near in August 2010. The next time we will have a good opportunity to view Mars will be in late July 2018.

Oppositions of Mars from 2003 to 2018. The central yellow disc represents the Sun, the next circle the path of the Earth and the outer circle or oval represents the path of Mars. Drawing Nick Lomb.

Why is Mars sometimes relatively near the Earth? Mars and the Earth both circle the Sun with Mars taking 687 days and the Earth 365 days to do so. That means Earth circling inside the path of Mars, will periodically “lap” the slower planet on the outside. On average this will happen every two years and two months with Mars being at “opposition”, that is on the opposite side of the Earth to the Sun, on those occasions. At oppositions Mars is relatively close the Earth.

To complicate matters, Mars has a much more oval-shaped path around the Sun than the Earth. As can be seen from the diagram above that means that some oppositions of Mars are more favourable, that is closer, than other ones. The one in August 2003, which triggered off the hoax email, was a favourable opposition while the next favourable opposition is the one on 31 July 2018.

Even at favourable oppositions Mars only appears like a bright red pinpoint of light to the unaided eye and certainly does not appear like the wonderful image at the top of this post. Through a telescope, like the the ones at Sydney Observatory, some detail can be discerned on the surface of the planet at those favourable oppositions. And even then the amount of surface detail is subject to the vagaries of atmospheric conditions above the telescope and on Mars itself. There have been disappointing Mars oppositions when planet-wide duststorms on Mars completely hid its surface from view.

While we wait for the opportunity that the favourable opposition of 2018 will provide to view the planet, we have unprecedented opportunities to study and become familiar with the surface of Mars on any personal computer. Numerous spacecraft have circled Mars sending back images and many are continuing to do so. Much of the mapping of Mars has been collected and is available through the Microsoft World Wide Telescope/Mars. With this web experience you can see Mars as you could during a favourable opposition or in much greater detail or in ways that are impossible from Earth such as looking down on the north or south poles of the planet.

As well as having fun with Mars on your computer, you can often see Mars in the sky with your unaided eye without having to wait for an opposition, favourable or otherwise. For example, in August 2010 Mars will be one of four planets giving a sky show by bunching up in the western sky after sunset. From 17 to 21 August it will appear close to Venus, the brightest planet.