Mars approaches (question for astronomers)

I received this chain e-mail today, together with some vivid photographs of Mars:

Is this correct? I find it hard to imagine that Mars would ever appear as large as the Moon in the night sky.

If it is true, will I be able to see it from Perth Western Australia? (Antipodean constellations, for example, are quite different from the northern hemispheric view, for those who don’t know.)

The close approach of Mars occurred on August 2003. Here’s a cite:

This E-Mail story gets circulated each year and in late July, 2007, I’m sure someone will ask about it then too.

Mars never appeared to the naked eye to be the size of the full Moon by the way.

…and it would REALLY suck if it ever did.

Oh well there goes my perfectly good excuse to buy a telescope.

Thanks all.

I’ve gotten this one too. I believe there was a nugget of truth in it at one time: Mars, as viewed through a decently sized telescope, would have been as large as the full moon is to the naked eye. Or something to that effect. There are several big images in the middle of the email which break up the sentences in an awkward way. After many forwards, cutting and pasting, it gets further and further from the truth. (Not to say this was completely true to begin with- like most things, I think it started with a bit of truth, some good intentions, and a lot of stupid.)

Mars is quite interesting though a telescope, regardless of its size. . . You can note the growing and shrinking of the polar ice caps, see global dust storms (in the dulling of the planet), and see albedo differences over the mid-lattitude areas. It takes some getting used to; the more you look at the planet through a telescope the more details you can discern.

Here’s the Snopes write up about the email.

The line break makes it less clear that the writer is saying:

emphasis mine

Which is a pretty useless and confusing comparison anyway. The point of using a comparison is to put it into terms of what the reader can visualize. Would the average reader know how much magnification that is? Would they have a sense of how big Mars normally looks at 75 power magnification? Of course not.

The closest in 60,000 years is misleading too. He makes it sound like it’s going to be a hundred times closer than on a normal pass when it was really only a few percent closer than normal.

If Mars and the Moon have an equal apparent diameter you can work it out with equal angles.

Rad[sub]moon[/sub]/D[sub]moon[/sub] = Rad[sub]mars[/sub]/D[sub]mars[/sub]

So Rad[sub]mars[/sub] = D[sub]mars[/sub]/D[sub]moon[/sub]*Rad[sub]moon[/sub]

which at closest approach works out to Mars having a radius about 6 times that of Jupiter.

Mars’ diameter is about 4,200 miles.
The Moon’s angular size is about 30 minutes of arc.
For Mars to have this same angular size, its distance would have to be about 480,000 miles. :eek: Wow that was a close call. I’m glad that won’t happen again for another 60,000 years.

The sorority house up the hill isn’t excuse enough? :wink: