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Mars Earth Comparison

Demystifying Mars

Submitted by Anonymous on 20 August 2013

It's the tenth anniversary of the "great opposition" of Mars. Let's set the record straight.

Will Mars be as big as the Moon?

Nope. Super Mars will never be as big as the Moon.

What about the following claims?

  • Mars is the closest it has ever been to us
  • Mars will be the closest to us on August 27 (no year is designated)
  • You won't get a chance like this to see it for another 10,000 years• Mars will appear the same size as the Moon!
  • We'll have two moons in the sky!

Let's set the record straight on those dubious claims as well with some key facts about Mars.

The Numbers
Mars is the fourth planet from the Sun. We're the third rock, of course. Mars is, on average, 230,000,000 kilometres from the Sun. We're 150,000,000. One Earth year is 365 days, of course; the Martian year is 687 days.

Mars, with a diameter of 6,800 km, is smaller than our home planet (12,800) but bigger than our nearest neighbour the Moon (3,500).

The Moon orbits us at a distance of 384,000 km.

Mars could be as close to us as 80,000,000 km. Which remains 200 times further than the Moon.

In August 2013, Mars is 350 million kilometres away. But getting closer every day!

The Physics

We would have to move Mars to 2 times the lunar distance for it to appear as big as the moon in our sky. If we did that, imagine the chaos it would cause!

But Mars does get bigger every 28 months or so, before slipping away- just not "supermoon" big. These periods, as a planet grows larger, are "apparitions." When a planet is closest and largest is "opposition."

Our orbits around the Sun are not circular. The orbit of Mars is oval-shaped (or elliptical). Every 16 years or so, we get extra close. Some oppositions are better than others (August 27, ten years ago, for example).

The next opposition of Mars will be early April 2014 when Mars will be 93 million km away!

See for yourself

Follow the orange hued planet through the night sky. In August 2013, for eastern Canadians, it is visible in the early morning. Mars appears between the Sun and Jupiter before dawn. Watch the "wandering star" move through the constellations Gemini and Cancer.

With a telescope, Mars will appear as a small orange disk, not a pinpoint. Up to the 2014 opposition, it will slowly get bigger and brighter. Look for light and dark patterns on the surface and the polar ice caps.

Learn more about Mars and the solar system:

Learn about astronomical myths and mistakes:

To recap. Mars is far away, gets close every 28 months, will be quite close again in April 2014, gets really close every 16 years, but still, beside the Moon, to our eyes, is but a small orange dot. Pass it on!

Prepared by Blake Nancarrow, information technology chair for the RASC Toronto Centre.