On the scientific process: SAM's findings

Today's press briefing at the American Geophysical Union's Fall meeting in San Francisco was all about the SAM instrument's findings at Rocknest that, despite being not what the popular press had us believe, are nevertheless extremely interesting but before I delve into a summary of the findings, I'd like to reiterate what Grotzinger, the lead scientist for the mission who was on the panel today, said to illustrate for the over excited general public how exactly science works; repeatability is key to your results and that's why even us doctors send patients back to the labs for a second one because we HAVE TO BE ABSOLUTELY SURE about what we are seeing.

Curiosity has been busy at Rocknest, digging 6 times(NASA/JPL/MSSS)

In this case what was Curiosity's team trying to verify? Plenty it turns out. SAM has so far done 3 rounds of analysis on the sample and has a lot to show for it. Remember that SAM consists three main instruments, each of which can work on the same sample. These are the 1. Gas Chromatograph (GC), 2. a Tunable Laser Spectrometer (TLS) and 3. the Quadrupole Mass Spectrometer (QMS) which can work together with the Gas Chromatograph or as a stand alone for atmospheric analyses. For a complete SAM lecture go here. All these instruments in SAM help to further chemical analyses on Mars especially with regard to carbon-containing compounds i.e. organics.

In a nutshell, SAM found:

• A variety of gases released after heating the samples to high temperatures and pumping them to the TLS and GC for analysis. Water detected was detected which isn't unusual. The water is chemically locked into the crystal lattice of the sample grains though it was higher than expected. Carbon dioxide was formed and may have come from carbonates.

(NASA/JPL-Caltech/GSFC)

• Other gases detected include chlorine and oxygen which brought up the possibility of perchlorate (kind of like your peroxides but with chlorine instead of oxygen; highly oxidizing stuff). Perchlorate were first detected in the northern arctic regions of Mars by the Phoenix lander back in 2008 and some scientists believe that perchlorate may actually be oxidising the organics before we had a chance to detect them in previous missions. These are tentative results however. Sulphur was also found indicating the presence of sulphates or suphides in the soil.

(NASA/JPL-Caltech/GSFC)

• There were some 'carbon-containing' compounds detected. Chloromethane (methane molecule containing a chlorine atom) was found in the soil at Rocknest although the team was quick to stress that although the chlorine was decidedly Martian in nativity, the origin of the carbon is an open question and is being investigated further. The panel member for SAM, Paul Mahaffy, said that most likely the carbon in this case is simply Earth-based carbon that happened to be on the rover that recombined with the heated chlorine atoms during the experiment. Hence the team's declaration; no organic compounds have been definitively found at Rocknest. But they'll keep looking.

(NASA/JPL-Caltech/GSFC)

• Apart from the question of organics, there was an extremely interesting find of what appears to be high deuterium to hydrogen ratio (deuterium is a heavier variety or 'isotope' for hydrogen). The value is higher than that on Earth which illustrates the purpose of the ratio; its used to determine the extent of planetary atmospheric loss. The more the loss, the higher the ratio because the heavier deuterium is lost at a slower rate than the lighter hydrogen. Remember that Mars' atmosphere lacks proper protection from the solar winds erosive influence unlike on Earth where we have a powerful magnetic field that does just that.

With regard to future plans, the team said they plan to drill before the holidays at Yellowknife bay! So we have a flurry of activities to expect. Here is the latest map showing our progress up to November 30.

(NASA/JPL/ASU)

And that's your update in a nutshell. Stay curious!