Dust in the wind

Argh! This month is the closest Mars opposition in 73,000 years (or maybe 59,604 years — I've seen both estimates), and we weren't supposed to have any dust storms this year. But early observers have been seeing some fairly major dust storm activity over Hellas, obscuring most of the detail there. Scary stuff! So far, the dust seems confined to the Hellas region and hasn't turned into a raging planetwide dust disaster like the last opposition. Maybe we'll be lucky. The peak dust storm period isn't supposed to be until after the summer solstice, in September. Cross your fingers and hope!

Mars' closest approach to the earth is on Aug. 27, 2003, at 2:51 a.m. PDT, when it will be 34,646,418 miles (55,758,006 km) from the earth, with an angular diameter of 25.1" (comparable to Jupiter). That's nearly twice as big as at it appears at unfavorable oppositions. Brightness will also be comparable to Jupiter, at magnitue -2.9. Perihelion (Mars' closest approach to the sun) occurs a few days after opposition, on the 29th. Mars lies in Aquarius, roughly 37 degrees above the horizon when it transits; not very high, but high enough (barely) that we should be able to see some good detail on reasonably steady nights. A trip south gets you a little more elevation and steadier air; it's probably worth it assuming the dust storm doesn't kill all the detail. Even the four degrees to Los Angeles can make a surprising difference, though of course if you can manage Australia then all the better!

Mars' southern hemisphere is tilted toward us now, and that hemisphere is in early summer (the solstice is on September 29), so the south polar cap (SPC) is small and continuing to shrink. Orographic clouds are possible over the Tharsis volcanoes and other mountainous areas; try blue or green filters if you have them, which may help bring out atmospheric details. (If you don't have colored filters, don't worry about it. It really doesn't make that much difference.) Look for limb haze (those filters may help again), and for bright frost spots in desert areas. Take note of the size of Syrtis Major — is it smaller than it was at the last opposition? Astronomy magazine says it should be especially narrow.

How do you know what you're looking at? Mars maps are especially hard to come by these days. Nearly everyone who used to sell them now lists them as "out of stock." Great timing, huh? But take heart! I've found a few sources (both online and off), and your estimable president has scoured the web and found some other sources as well. I've even found several fairly good options for making your own Mars globes, with labels and everything. I've collected them on the links section of my Mars page: http://www.shallowsky.com/mars.html

Of course, software is also a great option, and I have links on that same page to several programs that offer correctly positioned and labelled Mars views. But there's a warning out: a lot of you have probably used the Windows program "Mars Previewer" in the past. There's been some talk that some of the new versions of it floating around have a virus. There are virus-free versions out there, so just be careful what you download and make sure you use a virus scanner when you download Windows programs.

Oh, I suppose you want to hear about other planets too. Well, actually, there's not all that much to tell. The three outer planets — Uranus, Neptune, and Pluto — are all alive and well and observable in the nighttime sky. Mercury is observable with difficulty early in the month, very low in the evening sky and sinking fast; Saturn has moved into the morning sky and is a nice target for early risers. Jupiter and Venus are too close to the sun to be observable this month.