2005: IVA-1A
2010: 3
Priority: Low
Characterize the particulates that could be transported to hardware and infrastructure through the air (including both natural aeolian dust and other materials that could be raised from the Martian regolith by ground operations), and that could affect engineering performance and in situ lifetime. Analytic fidelity sufficient to establish credible engineering simulation labs and/or performance prediction/design codes on Earth is required.
Measurements
a. A complete analysis, consisting of shape
and size distribution, mineralogy, electrical and thermal conductivity,
triboelectric and photoemission properties, and chemistry (especially chemistry
of relevance to predicting corrosion effects), of samples of regolith from a
depth as large as might be affected by human surface operations.
Note #1:
For sites where air-borne dust naturally settles, a bulk regolith sample would
be sufficient—analysis of a separate sample of dust filtered from the atmosphere
is desirable, but not required.
Note #2: Obtaining a broad range of
measurements on the same sample would be considerably more valuable than a few
measurements on each of several samples (this naturally lends itself to sample
return).
Note #3: There is not consensus on adding magnetic
properties to the list of measurements.
b. Characterize at least one
regolith deposit with fidelity sufficient to establish credible engineering
simulation labs and/or software codes on Earth to solve engineering problems
related to differential settlement of the regolith, and plume/regolith
interactions (see Note #4).
For one site on Mars (see Note
#5), measure the following properties of the regolith as a function of depth to
1 meter:
Particle shape and size distribution
Ice content and composition
to within 5% by mass
Regolith density to within 0.1 g/cm3
Gas permeability
in the range 1 to 300 Darcy with a factor of three accuracy
Presence of
significant heterogeneities or subsurface features of layering
An index of
shear strength
Flow Rate Index test or other standard flow index measurement
Repeat the above measurements at a second site in different geologic
terrane.
c. The same measurements as above on a sample of air-borne dust
collected during a major dust storm.
d. Subsets of the complete analysis
described above, and measured at different locations on Mars (see Note #2). For
individual measurements, priorities are:
shape and size distribution and
mineralogy
electrical
chemistry
Note #4. Because
there is a large engineering lead-time required to solve the geotechnical
problems, these data must be obtained early in the precursor
program.
Note #5. These measurements should be made
in a competent regolith deposit as opposed to loose drift material (cohesionless
sand dunes), as landing is expected to attempt to avoid the looser material.
Also, if mission planners would select high latitude polar deposits for a human
landing site, geotechnical data would be required from a representative location
of those deposits. These measurements should include polarity and magnitude of
charge on individual dust particles suspended in the atmosphere and
concentration of free atmospheric ions with positive and negative polarities.
Measurement should be taken during the day in calm conditions representative of
nominal Extra Vehicular Activity (EVA) excursions.
Source:
MEPAG (2008), Mars Scientific Goals,
Objectives, Investigations, and Priorities: 2008, J.R. Johnson, ed., 37 p. white
paper posted September, 2008 by the Mars Exploration Program Analysis Group
(MEPAG) at http://mepag.jpl.nasa.gov/reports/index.html.