Mars Will Not Kill You This August!


A recent reader’s letter started like this: ” Hi Dave, Is this information about Mars being as big as the full moon genuine? if so it will be amazing.” Oh give me a break!!! Every year this rumour returns.

For the 12th year in a row, a message about the Red Planet is infecting worldwide email boxes. It instructs readers to go outside after dark on August 27th and behold the sky. “Mars will look as large as the full moon,” it says. “No one alive today will ever see this again.” Don’t believe it. The closest Mars could get to earth was about 50 million kilometres, but to the naked eye it would still only look marginally brighter and bigger than a star.


Have you seen this email? Are you puzzled by it too?

Here’s a copy of part of the message:

“Planet Mars will be the brightest in the night sky starting August. It will look as large as the full moon to the naked eye. This will cultimate on Aug. 27 when Mars comes within 34.65M miles of Earth. Be sure to watch the sky on Aug. 27 12:30 am. It will look like The Earth has 2 Moons. Don’t Miss it….. The next time Mars may come this close is in 2287. NOTE: Share this with ur friends as NO ONE ALIVE TODAY will ever see it again.”

The Mars Hoax got its start in 2003 when Earth and Mars really did have a close encounter. On Aug. 27th of that year, Mars was only 56 million km away, a 60,000-year record for Martian close approaches to Earth. Someone sent an email alerting friends to the event. The message contained some misunderstandings and omissions—but what email doesn’t? A piece of advanced technology called the “forward button” did the rest.

At the NMC’s Rogers Observatory – the Mars opposition in August 2003, when crowds lined up to see the red planet make its closest approach to Earth in nearly 60,000 years.

Tolerant readers may say that the Mars Hoax is not really a hoax, because it is not an intentional trick. The composer probably believed everything he or she wrote in the message. If that’s true, a better name might be the “Mars Misunderstanding.”

Another aspect of the Mars Hoax: It says “Mars will look as large as the full Moon if you magnify it 75x using a backyard telescope.” The italicized text is usually omitted from verbal and written summaries of the Hoax. (For example, see the beginning of this story.) Does this fine print make the Mars Hoax true? After all, if you magnify the tiny disk of Mars 75x, it does subtend an angle about the same as the Moon.

No. Even with magnification, Mars does not look the same as a full Moon.

Photoshop image of Mars appearing as large as a full Moon

Only in Photoshop does Mars appear as large as a full Moon

This has more to do with the mysterious inner workings of the human brain than cold, hard physics. Looking at Mars magnified 75x through a slender black tube (the eyepiece of a telescope) and looking at the full Moon shining unfettered in the open sky are two very different experiences.

A good reference is the Moon Illusion. Moons on the horizon look huge; Moons directly overhead look smaller. In both cases, it is the same Moon, but the human mind perceives the size of the Moon differently depending on its surroundings.

Likewise, your perception of Mars is affected by the planet’s surroundings. Locate the planet at the end of a little dark tunnel, and it is going to look tiny regardless of magnification.

Bummer! To see Mars as big as a full Moon, you’ll need a rocket ship, and that may take some time. Meanwhile, beware the Mars Hoax.

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