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Selfsim
2012-Feb-17, 08:57 AM
Hi All;

So, recently in the news ...
Microbial oasis discovered beneath the Atacama Desert: (http://www.physorg.com/news/2012-02-microbial-oasis-beneath-atacama.html)

Whilst the main story is interesting, this part caught my eye:


To carry out this investigation, scientists used an instrument called SOLID (Signs of Life Detector), which was developed by the research team with the aim of using it for future missions on Mars.

The core of SOLID is a biochip –called LDChip– which includes up to 450 antibodies to identify biological material, such as sugar, DNA and protein. Samples can be taken, incubated and processed automatically and the results can be observed in an image with shiny points that show the presence of certain compounds and microorganisms.

Using this technique, the researchers in collaboration with Catholic University of the North in Chile have confirmed the presence of underground archaea and bacteria in the desert.
Does anyone know, (in a little more detail), how this chip actually works ?

Should we expect it to successfully detect 'life' on Mars (if it was present) ? Why ?
(I'm kind interested to understand whether the life components its designed to detect, could exist, given Mars' soil chemistry .. ie: perchlorates, etc).

Would it violate the 'planetary protection policy' ?

Regards

Selfsim
2012-Feb-18, 01:03 AM
Its interesting … (This snip from Wiki (http://en.wikipedia.org/wiki/Atacama_Desert#Comparison_to_Mars)) …

In 2003, a team of researchers published a report in the journal Science titled "Mars-like Soils in the Atacama Desert, Chile, and the Dry Limit of Microbial Life" in which they duplicated the tests used by the Viking 1 and Viking 2 Mars landers to detect life, and were unable to detect any signs in Atacama Desert soil.
The region may be unique on Earth in this regard and is being used by NASA to test instruments for future Mars missions. The team duplicated the Viking tests in Mars-like Earth environments and found that they missed present signs of life in soil samples from Antarctic dry valleys, the Atacama Desert of Chile and Peru, and other locales.
So, it looks like its taken about 9 years to develop robotics-useful, (biochip based), life detection technology for detecting life in the Atacama desert.

Interesting.

Regards

Selfsim
2012-Feb-18, 01:46 AM
Hmm ..

It seems that this kind of technology has been in use for a while ... (from Wiki):

with purposes ranging from testing public water systems for disease agents to screening airline cargo for explosives.
and they make use of surface plasmon resonance, flourescence and chemiluminescence.

DNA, RNA, various proteins, and even living cells are used as the sensing mediators.

It looks like the anti-body-antigen chip variants, rely on binding between antigens and antibodies which produces a chemiluminescence reaction, which then produces light. Detection is via a CCD.

In the case of an anti-body microarray (http://en.wikipedia.org/wiki/Antibody_microarray) (which would seem to be of the same type as mentioned in my OP):

a collection of capture antibodies are spotted and fixed on a solid surface such as glass, plastic or silicon chip, for the purpose of detecting antigens. Antibody microarray is often used for detecting protein expressions from cell lysates in general research and special biomarkers from serum or urine for diagnostic applications.
...
The end result is that a flourescent ‘spot’ indicates that the antigen has bound to the antibodies at that spot . The identity of the antigen is then inferred form the knowledge of the specificity of the antibodies at that spot.

So, it seems like the design of these chips is reliant on prior knowledge of the anti-body/antigen reaction, which occurs in our own version of ‘life’.

Once again, very customised technology, and very specific to the type of terrestrial life one is looking for.

In the case of the announcement of Atacama life, they must have designed the array specifically looking for archaea, and some other bacteria types (?)

I think MSL/Curiosity should also be capable of detecting archaea, from its onboard isotope mass spectrometer (from memory) .. ie: C12/C13 isotope ratios.

Very interesting.

Regards