Monday, August 2, 2010

Mars is normal right now

My mom sent me a hilarious email recently, asking if it was a joke or not. Unfortunately it's not, but very wrong nonetheless. As much as I'd love to see what new insane features this rumor acquires as it mutates through time**, this has gone on long enough...

"Two moons on August 27" was the tagline. "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 culminate on Aug. 27 when Mars comes within 34.65M miles off earth. Be sure to watch the sky on Aug. 27 12:30 am. It will look like the earth has 2 moons. The next time Mars may come this close is in 2287."

The best part though, is the picture showing what it allegedly will look like:

To any astronomy buff, this should of course be instantly recognizable as a photo taken by the Cassini spacecraft as it orbits Saturn, of two of Saturns moons hovering over the rings. I can't find the exact image attributed to Cassini, but here's a similar example, showing Dione (the larger moon) and Mimas in crescent phase over the rings (Dione is additionally lit up on the 'dark side' by Saturn off to the right. Mimas is much farther forward, on the near side of Saturn, so it's not):

Pretty, huh? But no matter how close any other planet gets to Earth, we're never going to see "two moons" in our sky. You'll have to fly to Mars for that. Sorry.

Anyway, as already documented on all those websites like snopes, this email has been going around since 2003 when Mars did indeed come closer to the Earth on August 27th than it had in over 60,000 years - all of human history. But even then, to the naked eye it only looked like a very bright orange dot. You'd need a telescope to appreciate the increase in angular size of the disc.

So if you get an email like this, please tell them it is both grossly incorrect and seven years out of date, and instead tell them that Jupiter is reaching opposition on September 21, and this is when it will be the closest to us in 12 years, since Jupiter is nearing perihelion (which occurs in March 2011). That is, when Jupiter is closest to the sun (perihelion), which happens once every Jupiter-year or once ever 11.8 Earth-years, we can get as close as possible to Jupiter by being directly between it and the sun (opposition). We are directly between Jupiter and the sun once every 1.1 Earth-years (a little more than a year because Jupiter orbits in the same direction as us, so we have to catch up a bit after going back to the same point in the solar system that we were in during opposition the year before), so every 12 oppositions is a particularly good one. That's this September. Make sure you get a look at it through a telescope at high magnification. Pretty spectacular.

**Natural selection depends on two things: a source of mutation, and replication. I understand the replication of these emails. Gullible preteens forwarding every email they get to all of their friends, a fad that has recently been transferred to middle-aged women as well... but where is the mutation? Who decided to add a picture of Saturn? Who changes the year of the alleged event every year? Is there some secret club of astronomers who are giggling as they see how many new ludicrous details they can get to catch on??

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