Will Mars Look as Big as the Moon on August 27? Nope

by Fraser Cain on July 25, 2007

Mars, seen in August 2003. Image credit: HubbleEvery year around this time, an email circulates across the Internet speculating that on August 27th, Mars will look as big as the Moon in the sky. And every year, I go ahead and debunk it. Here’s a link to last year’s version. Once again, I’d like to inoculate all my Universe Today readers, to make sure you understand what’s going on, and you’re prepared to explain to your eager friends why this non-event isn’t going to happen.

Say it with me. Mars won’t look as big as the Moon on August 27th.


This strange hoax first surfaced on the Internet back in 2003. An email made the rounds with the following text:

The Red Planet is about to be spectacular! This month and next, Earth is catching up with Mars in an encounter that will culminate in the closest approach between the two planets in recorded history. The next time Mars may come this close is in 2287. Due to the way Jupiter’s gravity tugs on Mars and perturbs its orbit, astronomers can only be certain that Mars has not come this close to Earth in the Last 5,000 years, but it may be as long as 60,000 years before it happens again.

The encounter will culminate on August 27th when Mars comes to within 34,649,589 miles of Earth and will be (next to the moon) the brightest object in the night sky. It will attain a magnitude of -2.9 and will appear 25.11 arc seconds wide. At a modest 75-power magnification

Mars will look as large as the full moon to the naked eye. By the end of August when the two planets are closest, Mars will rise at nightfall and reach its highest point in the sky at 12:30 a.m. That’s pretty convenient to see something that no human being has seen in recorded history. So, mark your calendar at the beginning of August to see Mars grow progressively brighter and brighter throughout the month. Share this with your children and grandchildren. NO ONE ALIVE TODAY WILL EVER SEE THIS AGAIN

There are a few problems with this. The first problem is that the email doesn’t actually mention the date; it just says August 27th. This means it can live on for years and years, going around and around the Internet, forwarded by gullible people to their friends.

The second problem is that it’s wrong. Mars isn’t going to be making a close approach on August 27. The close approach this email is discussing happened back in 2003. It did indeed get closer than it had in at least 50,000 years, but this was a very small amount. On August 27th, 2003, Mars closed to a distance of only 55,758,006 kilometers (34,646,418 miles). The Moon, by comparison, orbits the Earth at a distance of only 385,000 km (240,000 miles). Mars was close, but it was still 144 times further away than the Moon.

Instead of appearing as a huge red orb in the sky, Mars looked like a bright red star. Observers around the world set up their telescopes, and took advantage of this close encounter. But you still needed a telescope. And if you read the email carefully again, you’ll see that it’s trying to explain that.

There’s an extra paragraph break. The last sentence of second paragraph is hanging. It says, “At a modest 75-power magnification “, but there’s no period. The next paragraph starts up with the text, “Mars will look as large as the full moon to the naked eye.” In other words, if you put one eye into the telescope and looked at Mars, and kept your other eye looking at the Moon (which isn’t actually humanly possible), the two orbs would look roughly the same size.

Mars and Earth do come together every two years, reaching the closest point on their orbits – astronomers call this “opposition”. And we’re in one of those years. But it’s not going to happen on August 27th. Instead, we’ll make our opposition on December 18th, 2007. At this point, Mars will be 88.42 million km (55 million miles) – further away than its 2003 opposition.

NASA is taking advantage of the upcoming opposition, and will launch the Phoenix Mars Lander in August. The spacecraft will make its shortest possible journey to reach Mars, arriving early next year.

And by next July, it’ll be time to write this article all over again.

About 

Fraser Cain is the publisher of Universe Today. He's also the co-host of Astronomy Cast with Dr. Pamela Gay.

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