Mars Will NOT Look as Big as the Full Moon, But You Can Watch it Get Closer

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For criminy’s sake, I just got one of those “Mars as big as the full Moon in August” emails. For one more time: this is completely false and it couldn’t possibly happen. Besides, in 2009 Mars is all but unobservable until the end of the year, and even next year it won’t be much better. So can we please see an end to these erroneous emails???

But Mars is coming closer to Earth (it happens like clockwork every 26 months) and the folks at Emory University have created a real-time distance calculator that shows Mars’ geocentric distance from us. It’s really fun to see how quickly Mars is coming closer to Earth (but pleeeeease it is not going to look as big the full Moon!!!) The distance is calculated in miles (sorry rest of the world) and shows up in blue when Mars is approaching and red when Mars begins to move farther from Earth. Very fun!

And if you need to know why Mars will not look as big as the full moon, see below.

Even at its closest approach, which happened back in 2003, Mars was 35 million miles (56 million km) away from Earth. You would have to magnify Mars 75 times to make it look as big as the full Moon, without a telescope. Mars won’t come this close again until 2287.

Here’s a graph from Robin Scagell at Popular Astronomy (below) which shows how the distance from Earth to Mars varies over the next few decades, shown as the size that Mars will appear in the sky. 25 arc seconds is about half the apparent size of Jupiter in the sky, which is the largest that Mars appeared in 2003.

Mars as big as the full moon just ain’t gonna happen, folks.

We’ve discussed the Mars Hoax email every years since 2003. Here are the UT articles for 2008, 2007, 2006, and 2005. And if you need more there are a few from Phil Plait the Bad Astronomer: here, here , here, and here’s the original one back in 2003.

And while I’m at it, I also recently got a “North Pole at Sunset” email. Another NOT.