Scientific and Technical Aerospace Reports Volume 39 April 6, 2001

An internal potential function was created using the averaged MGS vector data released by Mario Acuna for altitudes from
95 to 209 km above the Martian geoid, all longitudes, and latitudes from 87 degrees south to 78 degrees north. Even with some
gaps in coverage it is found that a consistent internal potential function can be derived up to spherical harmonic terms of n = 65
using all three components of the data. Weighting the data according to the standard errors given, the model fits to 7-8 nT rms.
The energy density spectrum of the harmonics is seen to peak near n = 39 with a value of 7 J/cu km and fall off to less than 0.5
J/cu km below n = 15 and above n = 55. Contour maps of the X (north) component drawn for 100 km altitude show the strongly
anomalous region centered at 60 degrees S latitude and 180 degrees longitude, as well as the alternating east-west trends already
observed by other groups. Maps of the other components show the anomalous region, but not the east-west trends. The dichotomy
is also maintained with much weaker anomalies bounding the northern plains. The results herein as as well as those of others is
limited by the sparse low-altitude data coverage as well as the accuracy of the observations in the face of significant spacecraft
fields. Work by Connerney and Acuna have mitigated these sources somewhat, but the design of the spacecraft did not lend itself
to accurate observations. Recent results reported by David Mitchell of the ER group have shown that the field observations are
significantly influenced by the solar wind with the possibility that the present results may only reflect that portion of the internal
field visible above 95 km altitude. Depending on the solar wind, the anomaly field may be shielded or distorted to produce spurious
results. The spectrum we have obtained so far may only see the stronger portion of the signal with a significant weaker component
hidden. Measurements of crustal anomalies versus relative ages of source bodies combined with later absolute dating of Martian
geologic units could lead to a quantitative constraint on the thermal history of the planet, i.e. the time when convective dynamo
generation ceased in the core. Determination of directions of magnetization of anomaly sources as a function of age combined
with the expectation that the Martian dynamo field was roughly aligned with the rotation axis would lead to a means of investigating
polar wandering for Mars. Preliminary analysis of two magnetic anomalies in the northern polar region has yielded paleomagnetic
pole positions near 50 N, 135 W, about 30 degrees north of Olympus Mons. This location is roughly consistent with the
orientation of the planet expected theoretically prior to the formation of the Tharsis region. In the future, more accurate observations
of the vector field at the lowest possible altitudes would significantly improve our understanding of Martian thermal history,
polar wandering, and upper crustal evolution. Mapping potential resources (e.g., iron-rich source bodies) for future practical use
would also be a side benefit. Additional information is contained in the original abstract.
Author
Mars (Planet); Magnetic Anomalies; Paleomagnetism; Planetary Magnetic Fields
20010023072 Jet Propulsion Lab., California Inst. of Tech., Pasadena, CA USA
Mars Science with Small Aircraft
Calvin, W. M., Nevada Univ., USA; Miralles, C., AeroVironment, Inc., USA; Clark, B. C., Lockheed Martin Aerospace, USA;
Wilson, G. R., Jet Propulsion Lab., California Inst. of Tech., USA; Concepts and Approaches for Mars Exploration; July 2000,
Part 1, pp. 55-56; In English; See also 20010023036; No Copyright; Avail: CASI; A01, Hardcopy; A03, Microfiche
The Mars program has articulated a strategy to answer the question ”Could Life have arisen on Mars?” by pursuing an in depth
understanding of the location, persistence and expression of water in the surface and sub-surface environments. In addition to the
need to understand the role of water in climate and climate history, detailed understanding of the surface and interior of the planet
is required as well. Return of samples from the Martian surface is expected to provide key answers and site selection to maximize
the science gleaned from samples becomes critical. Current and past orbital platforms have revealed a surface and planetary history
of surprising complexity. While these remote views significantly advance our understanding of the planet it is clear that
detailed regional surveys can both answer specific open questions as well as provide initial reconnaissance for subsequent landed
operations.
Derived from text
Mars Exploration; Aircraft; Aircraft Instruments
20010023073 Smithsonian Institution, Center for Earth and Planetary Studies, Washington, DC USA
Orbital SAR and Ground-Penetrating Radar for Mars: Complementary Tools in the Search for Water
Campbell, B. A., Smithsonian Institution, USA; Grant, J. A., State Univ. of New York, USA; Concepts and Approaches for Mars
Exploration; July 2000, Part 1, pp. 57-58; In English; See also 20010023036
Contract(s)/Grant(s): NAG5-4569; No Copyright; Avail: CASI; A01, Hardcopy; A03, Microfiche
The physical structure and compositional variability of the upper martian crust is poorly understood. Optical and infrared
measurements probe at most the top few cm of the surface layer and indicate the presence of layered volcanics and sediments,
but it is likely that permafrost, hydrothermal deposits, and transient liquid water pockets occur at depths of meters to kilometers
within the crust. An orbital synthetic aperture radar (SAR) can provide constraints on surface roughness, the depth of fine-grained
aeolian or volcanic deposits, and the presence of strongly absorbing near-surface deposits such as carbonates. This information
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