Expert: Courtney Seligman - 4/26/2009

Question
Hello, I have recently recieved an email saying that mars will appear as big as the moon this year on august 27th. Is this true?

thank you!

Answer
This is a misconception or hoax that has cropped up every couple of years since 2003. Below, I've copied a note from my website about the 2005 opposition. I think you'll find this an adequate answer, but if you'd like a more detailed discussion, just let me know.

MATERIAL COPIED FROM MY WEBSITE (http://cseligman.com/questions.htm):

Mars will be the closest to us in 66000 years, and look as large as the Moon -- hoax
    Mars will be relatively close to the Earth in October and November (of 2005), with the closest approach on October 30, at a distance of 43 million miles. However, even at that distance Mars' apparent diameter will 80 times smaller than the Moon's, and the planet will only appear as a bright dot, without a telescope. At the closest recent approach, in August of 2003 (see The Oppositions of Mars), Mars was still almost 35 million miles away, appeared 70 times smaller than the Moon, and was still just a bright dot without optical aids. That close approach, or opposition, was the closest one in 60,000 years, by a few hundred miles; but there will be other very slightly closer approaches over the next few centuries, and when Mars' eccentricity reaches its greatest possible value a little over 200,000 years from now, it could be as close as 30 million miles -- but even then, it would still appear 60 times smaller than the Moon, and be only a bright dot in our sky. In other words, Mars can never appear anywhere near the size of the Moon, and its upcoming close approach, although considerably closer than normal ("normal" is about 49 million miles), is not nearly as close as just a couple of years ago.

ADDITIONAL COMMENTS:

If you check the page/diagram at http://cseligman.com/text/planets/marsoppositions.htm you'll see that the August 27 date is only correct for the 2003 opposition, and that Mars won't even be at opposition this year. Also, at its next opposition (in 2010), it will almost as far from us as it can possibly be at opposition, and will be over 100 times smaller than the Moon. If you looked at it through a telescope, using a magnification or power of 100 or so, its telescopic image would be about the same size as the Moon looks without magnification. However, the tremendous brightness of the Moon, and something called the Moon illusion, would still make Mars look smaller in the telescope than the Moon does in the sky.

Courtney Seligman