On Dr. Laurel Kirkland's web page, she gives a link to a preprint of a report accepted for publication to the Journal of Geophysical Research discussing her teams examination of the accuracy of infrared spectrometers for detecting minerals in real world samples.
She states that her experiments show that simple surface roughness can obscure mineral signatures that one might assume would be there based on laboratory measurements of sensitivity.
She states this has been well known from reports dating back to 1961.

Laurel Kirkland
Infrared Remote Sensing of Mars and Earth.
http://www.lpi.usra.edu/science/kirkland/

With the publication of this report, I think Christensen et.al. will be forced to prove their TES instrument really does have the sensitivity they claim to detect carbonates on real world samples, not just laboratory samples as has been done so far.

Bob Clark