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.
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),...by 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."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.
"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."
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.