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Spirit acting up
Posted February 02, 2009 at 10:14 AM

A week ago last Sunday (28 January) Spirit seems to have had a "mental" hiccup. On its 1800th sol (20 times longer than it was expected to work) it reported that it had received its commands to move but chose not to. It also failed to record its activities for that day into its memory.

While it could be that Spirit is getting old and forgetful (a condition with which I can sympathize) it may be more problematic than that. When it was put through its paces to find the Sun and reorient, it worked, but the Sun was not were it was expected to be. This means the rover was not in its expected orientation. This might mean that some of its attitude sensing hardware (gyroscope and accelerometer) may be damaged.

The rover team is still working on diagnosing the problem. So far, Spirit seems to be following commands, taking pictures, saving info and downloading it. The team will test the attitude hardware and if that checks out, Spirit may resume its journey.

Methane on Mars
Posted January 22, 2009 at 10:45 AM

Big news: NASA says there's methane on Mars! Why is this big news? Well, here on Earth most of our atmospheric methane is produced by little microbes in the stomachs of ruminants (e.g. cows and caribou) which makes one wonder if the methane on Mars is also produced by living bacteria.

Back in 2003 three groups reported possible discoveries of methane using the technique of spectroscopy—you break up the light from Mars into hundreds or thousands of colors, then look for "missing" light. The missing colors were absorbed by specific compounds or materials and can be used as a fingerprint to identify them. It's really not quite this simple in practice, but with a lot of diligent effort, it really works quite well.

One group (Mumma et al.) was working from the NASA Infrared Telescope Facility, another was working from the Canda-France-Hawaii Telescope, and the last was using data from the Planetary Fourier Spectrometer on Mars Express. Since then they have all been working hard to confirm their discoveries by gathering more/better data, improving analysis techniques, and working to account for all the known variables in their models. So a few days ago, the fruits of that labor were announced by NASA.

Of course, methane can be produced non-biological means. One such method is that it could have been created during a comet-crash on Mars. One science group calculates that impacts into the Martian dust could have produced enough methane, an efficient greenhouse gas, to have helped keep Mars above freezing for quite some time. Of course, that methane would be long gone today as sunlight rapidly destroys it.

Another idea is that olivine, a mineral discovered to be in one of the methane areas can be chemically altered by water into serpentine to produce methane. This requires relatively warm, liquid water and so, if this is the mechanism, it must happen at depth and during warmer seasons. The produced methane would then seep out of cracks in the rocks and soil, also during warmer seasons when the ice in the cracks is more likely to have sublimated away into the atmosphere.

Either way, biologic or geochemical, this discovery is quite exciting! For more scientific details, you can check out Google-Scholar.

MRO Completes Primary Mission
Posted December 12, 2008 at 09:58 AM

I was just sent a press-release e-mail giving some of the details of the MRO mission now that it has completed its primary 2-year science phase. First, the good news: it has been approved for another 2-year phase for science operations. This is great as the orbiter has only sent back about 73 TB of data—yes, terabytes. As in, more data all previous Mars missions combined. One terabyte is 1,099,511,627,776 bytes (240) or the equivalent of about 132,000 introductory physics textbooks—you know, those 9"×10" jobs that are a couple inches thick. So MRO's data would fill nearly 10 million such tomes.

To quote from the release: "Since moving into position 186 miles above Mars' surface in October 2006, the orbiter also has conducted 10,000 targeted observation sequences of high-priority areas. It has imaged nearly 40 percent of the planet at a resolution that can reveal house-sized objects in detail, with one percent in enough detail to see desk-sized features. This survey has covered almost 60 percent of Mars in mineral mapping bands at stadium-size resolution. The orbiter also assembled nearly 700 daily global weather maps, dozens of atmospheric temperature profiles, and hundreds of radar profiles of the subsurface and the interior of the polar caps."

This has been a very successful mission and all I can say is congratulations to all those scientists and engineers who pulled it off. I'm looking forward to another 73 TB of data!

Mars as Art and MSL
Posted December 08, 2008 at 10:10 AM

Last Saturday I was listening to WHYY's broadcast of Studio 360 which is a great show covering the gamut of the arts. And on this particular day there was a nice piece on the rovers' PANCAM instruments—the two-eyed cameras on the "head" of Spirit and Opportunity. I have to admit that I get so buried in the science aspects of imaging that I don't always step back to just admire the view; there really is a majesty in these images. The best part is that, since the cameras are mounted at about human-eye-level, the views are very close to what you would see if you were standing there yourself.

Fortunately, we have Jim Bell in charge of the project and he sees both the science and the art. He's even published two books collecting and discussing some of the best images from the missions. Postcards From Mars that tells the story of sending the rovers and their first views, and Mars 3-D that is a collection of the stereo-images, complete with built-in red/blue glasses. Jim was interviewed for the Studio 360 piece which you can hear, and download, from their web site.

In other rover news, the next one to go, the Mars Science Laboratory has been delayed. It was intended to be launched in December 2009 but various technical difficulties have cropped up and now it is being scheduled for the next launch window in 2011. Of course, this means a tightening of the budget for other Mars missions, and a possible push-back of other 2011 probes, but as of yet nobody knows to what extent. It also means there will be no US Mars mission for the 2009 window.

Even more ice!
Posted November 25, 2008 at 04:02 PM

One of the instruments on the Mars Reconnaissance Orbiter that seems to have not garnered a lot of press is the Shallow Subsurface Radar or SHARAD. I guess that's because it doesn't return a lot of pretty pictures although the radar information it does return can be put into picture form.

SHARAD sends out a high-frequency pulse of radio waves that penetrate the surface. What happens to those waves (if they return, how they return, and how they are modified) is a complex function of what they bump into on the way down. In this way, the SHARAD team intended to look for subsurface ice layers—layers deeper than the Mars Odyssey Gamma Ray Spectrometer (GRS) could measure.

One of their prime target were these lobate debris aprons in the mid-latitudes (e.g. 35–65°). They had been first photographed by Viking orbiters and they were curious in that they appeared to have smoothed out features that one would expect of flows that were lubricated by water or ice mixed in them as opposed to just being massed of rock and boulder that had slumped.

Well, word from the SHARAD team is that in these regions, they get far more radar return than if there was just rock. The measurements they make imply a very thick layer of ice below a "thin" layer of debris (if the debris were removed, the ice would begin sublimating). Not only that, but the extent of the ice goes on for miles.

So what are buried glaciers doing so far south? It turns out that the axial tilt of Mars, currently about 25° (very similar to Earths 23.5°) wobbles significantly. The technical term for this motion is nutation and it is tied very closely to climate change.

On Earth this polar wobble is fairly small, about 2.4° but it, combined with other orbital variations, leads to a cycle of ice ages on an about 100,000 year period. Since Mars doesn't have the stabilizing effects of a large moon (due to a physics property known as conservation of angular momentum—why spinning top is harder to knock over than one that isn't) its axial tilt can swing wildly from about 15° to 35° which, combined with its significantly more elliptical orbit, can lead to great swings in climate.

Based on models and an understanding of climate at a general level, back when Mars had a much larger tilt it could have supported vast areas of glaciers down to low latitudes. If these then get covered up by dirt and debris, they could survive that way now that the axial tilt is much less. So these results appear to confirm models of early Martian climate.


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