Emily Lakdawalla • Jun 28, 2005
Apparently there is a bogus email circulating around the Web with the following text:
FALSE AND INCORRECT "INFORMATION" BEGINS HERE-->
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. Mars will look as large as the full moon to the naked eye. Mars will be easy to spot. At the beginning of August it will rise in the east at 10p.m. and reach its azimuth at about 3 a.m.... Share this with your children and grandchildren. NO ONE ALIVE TODAY WILL EVER SEE THIS AGAIN.
This "information" combines details that were correct about the August 2003 Mars opposition, when it was in fact closer to Earth than it had been for 60,000 years, with the completely false and inexplicable claim that it would appear "as large as the full moon." This is just not possible (as cool as it would be if it were true). I do, however, agree with the exhortation that you should go out and look at the night sky with your children and grandchildren. (Just don't promise them that Mars will look like the full Moon.)
So, if someone forwards you such a message, here is a reply you can send them, composed by The Planetary Society's Director of Projects, Bruce Betts, who also keeps his eye on the sky for the "What's Up?" segment of our weekly radio show, Planetary Radio:
Bruce Betts says
Various email circulating around the Internet says that Mars will be brighter than it has been in thousands of years and even that it will be as big as the full Moon. Neither of these statements is true. However, Mars will be very bright and easy to observe during the fall of this year (it is currently visible in the pre-dawn sky, but will get much brighter). Also, in 2003, it was closer than it had been in tens of thousands of years. Here are some of the facts about 2005
1. Mars will be closest to Earth in 2005 on October 29 or 30, depending on your time zone.
2. Because of the combination of Earth and Mars' orbital periods, Mars and Earth grow closer every 26 months. Even then, they are still many tens of millions of kilometers (or miles) away from each other.
3. Martian close approaches vary a lot in brightness because Mars' orbit is much more elliptical (less circular) than Earth's. So, sometimes we are "close" to it when it is in the part of its orbit that is nearest the Sun, and sometimes when it is farthest in its orbit from the Sun.
4. Mars was closer to Earth in the 2003 close approach than it had been in tens of thousands of years, but not by much compared to approaches that happened tens of years ago.
5. In 2005, Mars will be farther than it was in 2003, but it will still be a very good apparition. It will get brighter than the brightest star in the sky, but not nearly as bright as Venus. It will still be great to go out and see. (It will be brighter than -2 magnitudes for those who are familiar with that system of brightness.)
6. Mars never appears large enough to appear as more than a point of light to the naked eye (certainly not coming anywhere near the apparent size of the Moon in our sky).
7. Mars will be about 20 arcseconds across during this close approach, which is about 5 arcseconds smaller than in 2003. But, the disk will be quite clear in almost any small telescope. A nice amateur telescope should allow you to see at least a polar cap and some light and dark markings on the surface. It will be southern summer on Mars, however, and the south pole will be tilted towards us, so the southern polar cap will be small.
A number of sites around the Web will give more information, especially as we get closer to October. You can also listen to Planetary Radio, http://planetary.org/radio where in the last several minutes of each show we cover easy things to look for in the night sky.
Please do fight the misinformation -- but don't tell people not to look up! We shouldn't need an excuse like "closest approach for 60,000 years" to look up and see the planets. Right now, if you look to the west shortly after sunset you can see Venus looking super bright, the brightest starlike object in the sky, and much dimmer Mercury very close by. Saturn is sinking very rapidly below them. Jupiter is overhead at the same time, looking like the second brightest "star" in the sky. To see Mars, you need to get up early, before sunrise, and look east. (Thanks, Bruce, for the update.)
A coda to the information above: the actual date of Mars opposition -- the moment when Earth and Mars are at precisely the same longitude with respect to the Sun -- is November 7, 2005. But because of the non-circular shapes of Mars' and Earth's orbits, Mars gets closest to the Earth a week earlier, on October 29 or 30, 2005, depending on your time zone.
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