Science Opportunities - Basic Research Opportunities in Earth Science - page 76

• the evolution of the Martian crust and interior ( Figure 2.18 ). That is, the
strength and variability of magnetization demonstrate the unexpected
existence of an Earth-like planetary dynamo within the core of Mars.
Because Mars no longer has a strong magnetic field, its planetary
dynamo must have ceased to operate sometime after the formation of
the crust. These observations raise important questions about why the
Martian dynamo behaved so differently from that of the Earth. In
addition, the magnetizations have been interpreted as the equivalent of
terrestrial “seafloor stripes” that are the hallmark of plate tectonics.
Although this interpretation is controversial, the data are of first-order
importance. Further effort in understanding how planetary dynamos and
plate tectonics might work on Mars in comparison with the Earth is
critical for accurately interpreting and understanding these data.
• Another important area being explored by MGS is the climate history of
Mars. Photographic evidence has long suggested features derived from
flowing water on Mars, but recent high-resolution images show
unexpected complexity, raising questions regarding how the features
were produced. Whereas some features look like flood deposits and
channels, others look like subsurface flow. Further research using
photogeologic techniques and other methods is necessary for
understanding how flowing water under conditions very different from
those on the Earth affects the surface morphology of planets. Similarly,
recent data on surface mineralogy furnishes limited evidence for
pervasive aqueous alteration of Martian soils. This clearly has bearing on
the longevity of Martian surface waters, a key question for the history of
climate and possible life on Mars. Additional work is necessary to
understand basic soil formation and alteration processes.
1 An Integrated Strategy for the Planetary Sciences: 1995-2010. National Academy Press,
Washington, D.C., 199 pp., 1994.
2 Review of NASA's Planned Mars Program. National Academy Press, Washington, D.C.,
29pp., 1996.
Analytical Challenges
In situ planetary studies will offer great benefits for Earth and planetary
scientists, 15 but sample return offers the most promise for research funded by
EAR. Samples brought back from various solar system bodies will share a
common trait—the amount of material will be extremely small, ranging from
perhaps a kilogram of Martian soil and rock to submilligram quantities of comet
dust. In comparison, hundreds of kilograms of lunar materials were returned
during the Apollo program. The small sample sizes, coupled with the
15 A Scientific Rationale for Mobility in Planetary Environments. National Academy
Press, Washington, D.C., 56 pp., 1999.