BellaOnline Forums Education Astronomy Mars-Moon meme makes merry-go-round of muddle

The planet Mars has twice the diameter of the Moon, so its face is four times bigger than the Moon. But the Moon is close enough that astronauts have been there. Rovers have been to Mars, but no humans - at its nearest it's 34 million miles away, over 200 times as far away as the Moon.

What do the Moon and Mars look like together in the sky? Here is a photograph taken in 2010 of a full Moon, and Mars at opposition. When Mars is at opposition, it's as close as it can get to us. But it still looks small, as things do when they're millions of miles away. If you were looking up at this without any kind of filters, Mars would look like a bright reddish star.

But it's summer and the merry-go-ground of the Mars-Moon muddle has come around again to Facebook. The third sentence is true and there's a good reason for it.

On August 27, 2003 Mars was closer to us than at any time in the previous 73,000 years. Opposition was on the following day. That's when the Sun, the Earth and Mars are in a straight line. It's called opposition because Mars is opposite the Sun in our sky.

Neither Earth nor Mars has a perfectly circular orbit, so the distance between the planets near opposition varies. You can see in this diagram how the apparent diameter of Mars changed over five oppositions. In 2003 it was, of course, noticeably larger than in the others. But it was still nearly 35 million miles away.

Wow! Very interesting. I didn't know.