Rendezvous Mars Science Lab Curiosity: The scoop of a lifetime

Exciting times ahead! Curiosity is hunkering down beside the sand ripple at ‘Rocknest’ for some scooping action with its CHIMRA (pronounced ‘chimera’). The aim is mainly to remove an oily film that has built up on the inner surface of the scoop during the rover’s trip from the clean rooms of Earth to the surface of Mars. The speakers today at the teleconference described it as a mouthwash kind of procedure.

Rocknest (NASA/JPL/MSSS)

Before describing the planned procedure I think now is the time to write that summary about CHIMRA that I promised so long ago now. Necessity is the mother of invention so I'll start with the single most important purpose that this (really complicated piece of) hardware serves; two instruments, the sample analysis at Mars (SAM) and the chemistry and mineralogy (CheMin) instruments are designed to take samples of Mars in for detailed, lab quality analysis. But the samples must be very fine, so fine as to easily slip through the micrometre sized sieves that guard the inlets into the instruments. CHIMRA is the one to process the sample for just that purpose.

CHIMRA is quite an instrument (one reporter at the teleconference confessed his confusion over the darn thing, I felt his pain)! Fortunately the speakers went through it with quite informative graphics.

Cutaway model of CHIMRA. The purple line shows the route samples will take. (NASA/JPL)

Basically CHIMRA consists of two parts, a motorized part with a scoop measuring 7 cm long and 4.5cm wide (coloured red in the model above) to dig in 3.5cm deep to collect soil samples and a chambered part (coloured yellow above) with chambers and passages which help to sort, sieve and portion out the samples (including core samples from the drill which won't be in use until Glenelg) for the SAM and CheMin instruments. To help the samples move along inside the CHIMRA passages and scoop, the whole thing has a vibrating mechanism that can shake the entire thing with a force of up to 8 Gs or approximately 8 kgs of force at a frequency of 70 to 85 Hz which the speakers compared to the drone you feel when your car’s engine is running neutral I presume.

That’s a whole lot of shaking and the speakers were the first to admit that they don't usually shake their hardware that much but there is a perfect reason for that. It all has to do with the last surface mission at Mars, Phoenix. This was a lander that went to the northern polar regions of Mars to sample water ice which was just underneath it. It also had a scoop but with no vibrator. So when the time came to drop the pay dirt into one of its science experiments there was no way to control the amount of material that dropped through. Sort of like the way you lightly tap your teaspoon to portion out the sugar into your morning coffee, they couldn't do that with Phoenix so they ended up flooding the instrument’s outsides with useless dirt and despite the instruments’ (weaker) vibrators, they were only lucky to get dirt in for analysis. So thanks to the lessons from Phoenix, Curiosity won’t have to suffer such setbacks thanks to its bone-shaking vibrators!

Phoenix's scoop pouring dirt in 2008 (NASA/JPL/UA)

The plan for scooping is set to commence on sol 61 which is this coming weekend. Right now as of this writing MAHLI has captured some good images of the ripple’s materials. I'll talk about that in another post when the scooping commences.

MAHLI image of scuffed ripple. Notice the fine, powdery interior and coarser ripple surface (NASA/JPL/MSSS)

Scooping and pouring is the name of the game for the coming sols with 3 procedures in total planned. Remember the mouthwash analogy, in this case they will pour the dirt right back onto the ground after each scoop. Tests done last year on the ground have shown this to be the best way of cleaning out the grime still inside CHIMRA which might screw around with SAM and CheMin’s readings. Then they will deposit some samples into these experiments. According to NASA’s press release:

Curiosity will scoop and shake a third measure of soil and place it in an observation tray for inspection by cameras mounted on the rover's mast. A portion of the third sample will be delivered to the mineral-identifying chemistry and mineralogy (CheMin) instrument inside the rover. From a fourth scoopful, samples will be delivered to both CheMin and to the sample analysis at Mars (SAM) instrument, which identifies chemical ingredients

What will Curiosity find out at Rocknest? The best answer is ‘don’t know’ but this isn’t the first time a rover has examined such a feature on Mars. The now silent rover Spirit examined a similar looking dune back in its heydays in 2004 called ‘Serpent’.

Spirit's colour view of scuffed 'Serpent'
dune (NASA/JPL/U. Cornell)

You can see that it’s similar, though it might very well be different in terms of chemical makeup, to the ripple at Rocknest.

As for the course to Glenelg, the rover is only a hundred metres away now. Once she reaches there the plan will be to scout out a place to use the percussive drill for the first time in Mars exploration! Go Curiosity!

There is a neat video if you'd like to see a demo of CHIMRA’s scoop tested out on Earth last year! Do check it out here.