QUESTION:
What are the properties and percentages of the soil?

ANSWER from Jeff Plescia on November 16, 1998:
The chemical composition of Martian soil was determined by the two
Viking Landers and by the Pathfinder rover.

The soil has the following composition, average of about 5 sites
at the Pathfinder landing site (see Science, volume 278, December 5,
1997) for the Pathfinder papers:

These are expressed as oxides in weight percent:

Na2O:	2.3 (range 1.3-3,8)
MgO:	7.7 (range 7.1-8.3)
Al2O3:	8.5 (range 7.4-9.1)
SiO2:	49.5 (range 47.9-51.0)
SO3:	5.5 (range 4.0-6.5)
Cl:	0.6 (range 0.5-0.7)
K2O:	0.3 (range 0.2-0.5)
CaO:	6.5 (range 5.6-7.3)
TiO2:	1.2 (range 0.9-1.4)
FeO:	16.0 (range 13.4-17.4)

These add up to 98%. They do not add to 100% because of averaging.
Also, there may also be elements in the rock that were not measured
which could account for many percent.  But this is a good average.

Some of the material is magnetic as it adhered to the magnets.

The size of the particles ranges from microns (dust) to millimeters
to meters.  The exact size-frequency distribution has not been measured
for the soil particles. 16% of the surface around the lander is covered
with rocks. Rocks > 0.5 m cover only 1.5%