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Phoenix postponed
Posted July 31, 2007 at 06:54 PM

Just a quick note tonight: it seems as if Florida is going to be having some severe weather so the launch of the Phoenix mission (a redo with some extras of the Mars Polar Lander) is being postponed. It was originally planned to lift-off on 3 August, but there are still two more launch windows the next day. Here's hoping for clearing weather!

Rovers in the Dust
Posted July 24, 2007 at 12:22 PM

It figures, I go on vacation for a week, and that's when all the official news on the dust at the rover sites breaks! You can read the NASA PR report directly—it was updated on 23 July. In summary, it says that the dust in the area around Opportunity had thickened to the point where almost 99% of the sunlight is being blocked. It's almost as bad over at the Spirit site.

The reason this is critical is that the rovers use sunlight to charge the battery packs that run them. When the output was cut in half, the teams suspended all activity (which means Opportunity's climb down into Victoria crater is on hold). As the storm worsened, the output was cut even further so communications were even cut back. Right now, the power output is just enough to keep the batteries charged to allow the rover to stay warm enough over night to stay alive. The latest communication seems to indicate that things are getting better, but the behavior of these dust storms is very hard to predict.

For a while there, the rover had been gathering images of the local scene as the dust increased. NASA put together a composite image showing the darkening skies. Up at the top of the image you'll see the parameter τ which is the optical depth of the dust cloud and is a measure of the diminishing of the light. For the mathematically inclined, the light is dimmer by a factor of e, where e= 2.71828… is the exponential base. So, at τ=4.7, the light is at 0.62, or 62% of its nominal brightness.

Mars Odyssey is still in orbit, going strong, and the THEMIS instrument (Thermal Emission Imaging Spectrometer) is measuring the atmospheric brightness as many wavelengths. With those data the team is able to model the atmospheric temperature as well as the dust cloud thickness. These results are being put into a daily map. Although the maps claim to be of dust opacity, the numbers on the scale make me believe they are really dust cloud optical depth—opacity is a sort of light-absorbing efficiency factor for a substance and optical depth is the total opacity along a path through the substance and thus a measure of the total light blocked. The maps have also been combined as frames in a nice animation. There are some major jumps early on, but once the storm takes off, you can see it evolve almost daily.

Since we have Mars Reconnaissance Orbiter right there imaging the planet, we can see the visual effect of the storms in this mosaic. The decrease in regional contrast is stunning! This image is useful for giving you a visual reference for what those optical depth numbers "look" like.

Of course, you can also keep an eye on the dust storms yourself, either through your own observing program, if you have a telescope (and if you make images, you can submit them here) or by visiting the MarsWatch images section and seeing what our army of observers is collecting.

And let's all wish the rovers "clear skies"!

More Dust
Posted July 05, 2007 at 10:13 AM

There are more submitted images that have been posted here that show the current dust storm to be growing. It has now expanded southward to cover the south polar cap and northwest to obscure parts of Tyrrhenum and Cimmarium.

It's hard to say how this is going to affect the Rovers at this point. Meridiani, where Opportunity is poised to descend into Victoria Crater, is not visible to USA based observers—here's hoping our eastern hemisphere contributors have clear skies!

The storm is starting to close in on Spirit; if it does get there it will obscure the sunlight that is used to run and recharge the battery packs of the rover.

Opportunity APOD
Posted July 03, 2007 at 08:56 AM

So I'm checking out the Astronomy Picture of the Day (as I do every morning) and see this wonderful shot by Opportunity, one of the Mars Exploration Rovers. I thought this picture was stunning—it reminded me, somewhat, of the formations in Utah I'd visited back in 2005 right before the AAPT summer meeting (American Association of Physics Teachers). Although, the sky is just a bit too orange…

The original MER catalog image tells us that it's Cape St. Vincent, one of the many promontories at the rim of Victoria Crater. The bright band of rock just a short way down the wall marks the boundary between a relatively loose jumble of rock and older bedrock—it was the "original" surface of Mars here before the impact. There's even a nice false color image that was made to better show the transition. Now that looks more like Utah!

Opportunity has been spending some quite some time exploring the rim of Victoria Crater, a half-mile (800 m) wide impact feature. In fact, for the past 264 Sols (that's a martian day, which is about 30 minutes longer than a terrestrial day) it has traversed about a quarter of the way around, then come back. The reason: it was (in part) looking for a safe way down! That's right, the Rover team is going to send Opportunity down into Victoria crater.

The main reason for going down is that "down" equals "back in time" so the deeper it goes, the older the rocks that it will be able to investigate. This will help fill in the picture of what Mars was like (at least in this area) through time and what the water availability was at those older times. This is some exciting geology! (Hmmm—I suppose that ought to be aereology , yes?)

To get an idea of just what the rover is up against in its attempt to travel down into the crater, you can check out these 3-d images of the area it took. Since the rover cameras are about five feet above the ground, the depth perception you get from these images is about the same as you'd get if you were really standing there. You can also check out this flyover movie created by the US Geological Survey using MGS MOC images of the crater. And if you're looking for something truly spectacular, you can take a look at my favorite Victoria Crater image.

More Dust News
Posted June 28, 2007 at 08:28 AM

I got in today do review new image submissions and there was another image by Jim Melka showing dust spreading, now starting across Syrtis Major.

There was also a dust alert put out by Richard McKim, Director of the British Astronomical Association Mars section:

Dear Mars Observer

On 2007 June 25 Jim Melka (USA) informed me about a dust storm spreading west from the northern Hellas basin across Noachis. The storm over Noachis was bright yellow, and in extent is typical of one already a few days old.

Images by Ed Lomeli (USA) on June 26 showed the event to have cut across Hellespontus in two places, and to have progressed as least as far as Argyre. As of June 27 the storm also now cut across Sinus Sabaeus in Lomeli's images, spilling into Aeria-Arabia, whilst Melka's image of yesterday shows that all of Hellas is full of dust, the original core being in the NW corner, and that activity is further developing or spilling over Ausonia-Hesperia to the east.

Both the timescale and nature of this development are entirely typical for Hellas events, and the seasonal date is also normal.

Any further observations of this event - which has now become Regional in status - are requested.

2007 June 28

No word yet on what sort of images of this storm have been made by any of the current suite of orbiters, but as soon as I hear anything, I'll post it here.

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