PDS_VERSION_ID         = PDS3
RECORD_TYPE            = STREAM
OBJECT                 = TEXT
  PUBLICATION_DATE     = 2006-07-27
  INTERCHANGE_FORMAT   = ASCII
  NOTE                 = "Remarks on APXS Oxide Abundance data.
          THESE NOTES CONTAIN IMPORTANT CAVEATS REGARDING 
          THE USE OF THIS DATA SET. READ THESE NOTES CAREFULLY
          TO AVOID MISINTERPRETATION OF THE DATA.
"
END_OBJECT             = TEXT
END

Remarks for Version G7 of APXS tables



Sample type
OU = outcrop undisturbed
OB = outcrop brushed
SU = soil undisturbed
SD = soil disturbed
ST = soil trench
SC = soils crest
RU = rock undisturbed
RB = rock brushed
RR = rock ratted
C   = cobbles


Information:
The oxide data were derived with the fit program, method, and calibration
parameters described in Gellert, R., et al 2006.
Periodically the local undisturbed soil was used to check for constancy of
the instrument performance and calibration as described in Ming, D.W. et al 
2008.
No degradataion or change in calibration was found.

The samples are assumed homogeneous, i.e. matrix effect corrections are 
applied assuming a homogeneous average matrix and the calibration stems from 
thick ( ~ mm ) powdered samples. This is known to be not true, especially 
in the high Silica soils.
In certain samples the results indicate that small soil grains are intermingled 
with, e.g. the Silica rich soil. As a result the low z elements of these thin 
soil grains contribute more to the signal than the high z elements, e.g. Fe.
For discussion of the effects, Squyres 2008 and Ming et al. 2008.


Caveats :
Touch and go (T&G) short spectra were taken in the morning and evening. 
In addition to the short measuring time, the temperature was also higher.
T&G are visual by the small measuring time column.
The errors for T&G are complicated ! Especially for Na,Mg,Al,P they might be
too low influenced by the overlapping peaks by degraded FWHM at higher
temperatures.


Remarks G10:
No changes in calibration.
On MERB a change in the instruments acceptance was taken into account after
sol 300.


All values are in wt % ( Ni,Zn,Br in wt percent ppm (ug/g) )
All values were assumed with Fe2+ ( even for known high Fe3+ )
All values were assumed with a homgeneous sample ! Known not to be true for
spherules !
The given errors are statistical errors of the peak areas. They represent
precision, not accuracy !
For the accuracy levels achieved during calibration, see Gellert et al. 
2006


Columns:
spectrum  Name of the summed spectrum
Type  Type of target
Name  unofficial Target name
Norm  sum of the oxide weight percent before normalization to 100 %.
Time/h  measuring time of the spectrum


References:
Gellert, R., et al. (2006), Alpha Particle X-Ray Spectrometer (APXS): Results 
from Gusev crater and calibration report, J. Geophys. Res., 111, E02S05, 
doi:10.1029/2005JE002555.

Ming, D.W. et al. (2008), Results of the Alpha Particle X-Ray Spectrometer from 
Cumberland Ridge to Home Plate, J. Geophys. Res., 113, E12S39, 
doi:10.1029/2008JE003195

Squyres, S.W. (2008), Detection of Silica-Rich Deposits on Mars,  Science,
320, 1063 - 1067, doi: 10.1126/science.1155429