The Dust Storm and the Rovers
Published on Jul 5, 2007 at 6:59 pm.
6 Comments.
Filed under Mars.
Mars is currently experiencing dust storms. Now, that is nothing really unusual for Mars. It has a lot of dust storms, and many of those storms are huge. In fact, Martian dust storms can sometimes get so active that they cover then entire planet from pole to pole. (Actually, in that case, it is usually a whole lot of smaller dust storms all over the planet that run together to look like one planet-wide dust storm). In 2001, there was such a planetary dust storm on Mars, as seen in this HST image.
Sometimes it is cool to watch these planet-wide dust storms. It is interesting if you are watching Mars slowly change day after day as the dust storm develops. Other times, however, these dust storms can be frustrating. For example, if you are trying to show Mars off to students or to the public, then it is pretty annoying if all you can see is a uniform orange ball.Â
But, right now, scientists at NASA’s Jet Propulsion Laboratory (JPL) are watching the current dust storm develop with some anxiety, because this dust storm is happening while there are space probes on the Martian surface. The Mars Exploration Rovers are still working, long past their anticipated lifetime. Sure enough, they are showing their age. Spirit has a wheel that will not turn, and Opportunity has one of its wheels that is starting to give it problems. Opportunity also has a joint on its robotic arm that is being temperamental. These Martian rovers suffer from an enormous range of temperatures each day, and that is starting to take its toll. They are becoming less and less tolerant of those temperature swings with age.
Now, we get to why the Martian dust storm begins to worry the scientists at JPL. The rovers are solar powered. They have large flat horizontal solar panels. Unfortunately, dust settles on these solar panels. The more dust that is on the solar panels, the less light gets through to make electricity. This has been a problem the entire time that the rovers have been on Mars. A dust removal system was not included in the Mars Exploration Rover design, and really wasn’t needed for the few months that the mission was supposed to last (later Mars missions will include dust removal systems). However, the rovers have been on Mars now for three and a half years. Dust keeps piling up on the solar panels, and that has cut the power available to the craft. Loss of electrical power does not just mean that the rovers will run slow or will not be able to do much (though it does mean those things). Loss of electrical power can be fatal to the rovers. If they do not get enough electricity to charge up the batteries, then they will die during the Martian night. If the electronics are not powered, the cold will kill them. So, that dust has been a worry for some time. Fortunately, Mars has an atmosphere, and the wind that deposits dust onto the solar panels also blows it off. In fact, the wind on Mars often creates dust devils. Those dust devils have been what has saved the rovers. The dust devils typically blow far more dust off of the surfaces than they deposit, so every time a dust devil blows over a rover, the solar panels are cleaned.
But, the real fear in regard to the dust storm is not so much that too much dust will settle onto the solar panels. Yes, that is happening, but there are still dust devils blowing the dust back off. The biggest concern is that too much dust kicked up into the air can cut sunlight from even reaching the surface. The current dust storm has been developing for a while, but NASA has been optimistic that they could simply operate the rovers with the lower electrical power being produced (only 31% of what it should be without the dust storm for Opportunity). If that is the worse that the dust storm does, and if the storm dissipates soon enough, then the rovers may be OK. But, if the dust storm lingers, then the combination of less light and dust accumulation on the solar panels (assuming no convenient dust devil passes by) may be a bit too much for one of the rovers. Unfortunately, planet-wide Martian dust storms sometimes last for a long time. And, there is another concern: nobody knows just how bad the dust storm will get. One of the worst dust storms was in 2001 (as shown in the HST image that I used above). Nothing like that has happened since then, and certainly nothing nearly this extreme since the rovers landed in January of 2004. There seem to be mixed signals, too, as to where this dust storm is going (kind of like weather forecasts here on Earth!). Some forecasts suggest that the dust storm has peaked and will be dissipating. But, other forecasts suggest that it will be at least a repeat of the 2001 dust storm.
So, only time will tell if the rovers will survive this dust storm. Even if they don’t, they have survived far beyond anything that was ever expected and have returned far more (and far more exciting) data than anyone had originally predicted. But, I do hope that they make it through the dust storm.
-Astroprof
Images courtesy of NASA, HST, JPL
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Ed Davies on July 6, 2007 at 5:35 am: 1
Any thoughts on whether the dust storm will cause more or fewer dust devils? My initial assumption would be that the dust devils are at least partly convective (as they are on Earth) and dust in the atmosphere would increase the heating above the ground and therefore increase the stability of the atmosphere which would presumably reduce the number and size of the dust devils.
Astroprof on July 6, 2007 at 9:13 am: 2
Martian dust devils are similar to Earth’s dust devils, so heating the ground, and the resulting localized convection plays a role in their formation. The dust storm does, indeed, warm the atmosphere. However, the dust devils are localized phenomena, so I don’t think that the broader meteorological concerns would matter with them. A bigger effect would be the lessening of sunlight making it to the ground to do the heating in the first place. That would seem to me to argue for fewer dust devils. But, Mars often acts differently than we might first suspect, so you never know. We’ve never had an operating spacecraft on the ground during a major dust storm like this, so we have no data about how the dust storm influences dust devils.
A Ler…-- Rastos de Luz on July 6, 2007 at 11:57 am: 3
[…] “The Dust Storm and the Rovers“, no Astroprof’s Page; “New Life for Stardust and Deep Impact“, no The Planetary Society Blog. Também a ler neste blog, “Ten years ago today, Pathfinder landed on Mars“. […]
A Ler…-- Rastos de Luz on July 6, 2007 at 11:57 am: 4
[…] “The Dust Storm and the Rovers“, no Astroprof’s Page; […]
dfk on July 17, 2007 at 10:54 pm: 5
It is really getting worse, as we can see now
Astroprof’s Page » 2007 Martian Dust Storm Strengthens on July 20, 2007 at 3:28 pm: 6
[…] A couple of weeks ago, I wrote about a global dust storm on Mars that was of concern to the scientists at NASA’s Jet Propulsion Laboratory. Well, the dust storm just keeps getting stronger. […]