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Who knew? Earth is unavoidably dirty. It doesn't matter what we do. Consider a NASA clean room. I reckon it would be far cleaner than any operating theater that I have ever occupied, that is to say, as clean as humanly possible. But even in Earthbound places like that, an oily film of life on Earth settles on the surfaces of the instruments humanity would send to explore the other planets.

Good scientists know things like this, and they work with engineers to devise procedures to eliminate all realistic threat of cross-planetary contamination in this kind of research. BTW, that they must do so is a tribute to the sensitivity and sophistication of the instruments of the Mars Science Laboratory. Curiosity's instruments are so sensitive, measuring parts per billion and less, that all possibility of terrestrial contamination must be eliminated. So, NASA employs procedures so that the findings returned by their instruments on Mars are defensible as pure Mars findings.

Come out into the tall grass if you would like to know more about how NASA solved this problem.


I mentioned in one of my earlier Mars diaries that NASA's Dr. John Grotsinger had announced in a NASA press conference that the rover would be looking for sand to run through the CheMin and SAM instruments, described, respectively, here and here.  

Large (i.e. scoop-able by the robotic arm) deposits of sand aren't sitting around just everywhere on the surface of Mars in general or the Gale Crater in particular. In this image at a location NASA has named Rocknest, small dunes have formed in the lee of larger, scattered rocks upwind.

Here is how NASA intends to use this sand to assure the decontamination of the rover's instruments. The sand appears in the upper right quadrant of the image.According to NASA engineer, Daniel Limonadi:

"Even though we make this hardware super squeaky clean when it's delivered and assembled at the Jet Propulsion (Laboratory), virtue of its just being on Earth you get a kind of residual oily film that is impossible to avoid," said Daniel Limonadi, a sampling system engineer at JPL. "And the Sample Analysis at Mars instrument is so sensitive we really have to scrub away this layer of oils that accumulates on Earth."

"What we're doing at the site is we take the sand sample, this fine-grained material, and we effectively use it to rinse our mouth three times and then kind of spit out," Limonadi said. "We will take a scoop, we will vibrate that sand on all the different surfaces to effectively sandblast those surfaces, then we dump that material out and we rinse and repeat three times to finish cleaning everything out.... Our Earth-based testing has found that to be super effective at cleaning."

The Mars Science Laboratory employs tools, receptacles and various test chambers to analyze the materials encountered on Mars, or what I like to call "the dishes". These must be cleaned before their first use and also thereafter between uses to avoid cross contamination between different samples. It's long, but a great video about how they will be doing that is in this earlier Mars diary.

Here are my previous diaries in this series inspired by NASA's new roving science lab on Mars, listed in the order I have posted them.

Mars Curiosity Rover -- Meet the ChemCam

Ray Bradbury is Honored Today on Mars

What Curiosity Can Do, Part 2.

What Curiosity Can Do on Mars and in this Election

Will Curiosity Mission Finally Vindicate the Life Science Results from the 1976 Viking Lander?

From Mars: SAM Takes a Deep Breath and Flexes his Arm

From Mars: Here's Looking At You, Kid.

On Mars: Super Rover has X-ray Vision

On Mars: Let the Science Begin

On Mars: We have found an Interesting Rock

On Mars: Obama and Biden Campaign This Week

On Mars: Curiosity Does Contact Science

On Mars: A River Ran Through It

On Mars: Sol 52 Update

On Mars: 2000 AD Space Robot Held Together with 2000 BC Technology

Originally posted to Astro Kos on Thu Oct 04, 2012 at 06:03 PM PDT.

Also republished by SciTech, Kossacks on Mars, and Community Spotlight.

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