Posted by: T. Boyd | August 11, 2011

The Annual “Mars as Big as the Moon” Hoax

Every year since 2003, in August, an e-mail hoax has been released upon the public saying that on August 27 Mars will appear to be as large as the full moon.  It will claim that Mars is at a record setting minimum distance from Earth on that date, and to be sure to not miss this once-in-a-lifetime chance to see this wonderful phenomenon.

This is not true.  And the claim about the size comparison with the moon is also false.  Here is a brief history of this story.

On August 27, 2003, Mars did get a tiny bit closer to the earth than usual. The 2 planets are on the same side of the sun every 780 days or so, and that year it was the smallest distance that it has been in thousands of years. How much closer? And when were the other close times in recent years? Here is a table showing how much bigger Mars appeared to be in 2003 compared to other years when it was close or will be close.

Year Month 2003 was this much larger
1956 Sep 1.41%
1971 Aug 0.80%
1986 Jul 8.19%
1988 Sep 5.37%
2018 Jul 3.29%

So you can see that, even though it was unusually close in 2003, it was not something all that rare.

The other misleading statement is about the size compared to the moon.  The original story said that if you looked through a telescope at 50 power, Mars would appear in the telescope to be about the same size as the full moon appears to the naked eye.  That is quite a different story.

By the way, the next “closest distance” will be next spring, on March 3, 2012.  The last previous time was January 10, 2010.


  1. A prize for the first person to announce they have received this hoax via e-mail this year!

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