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1 - Exploration of the Martian surface: 1992–2007
- from Part I - Introduction and historical perspective
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- By L. A. Soderblom, US Geological Survey, 2255 North Gemini Drive Flagstaff, AZ 86001, USA, J. F. Bell III, Cornell University, Department of Astronomy, 402 Space Sciences Building, Ithaca, NY 14853-6801, USA
- Edited by Jim Bell, Cornell University, New York
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- Book:
- The Martian Surface
- Published online:
- 10 December 2009
- Print publication:
- 05 June 2008, pp 3-19
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Summary
ABSTRACT
Following the demise of the 1992 Mars Observer mission, NASA and the planetary science community completely redefined the Mars exploration program. “Follow the Water” became the overarching scientific theme. The history and distribution of water is fundamental to an understanding of climate history, formation of the atmosphere, geologic evolution, and Mars' modern state. The strategy was to search for past or present, surface or subsurface, environments where liquid water, the fundamental prerequisite for life, existed or exists today. During the 1996–2007 time frame, seven richly successful orbital and landed missions have explored the Martian surface, including NASA's Mars Global Surveyor (MGS), Mars Pathfinder Lander and Sojourner Rover, Mars Odyssey Orbiter, Mars Exploration Rovers (Spirit and Opportunity), Mars Reconnaissance Orbiter, and ESA's Mars Express (MEx) orbiter. “Follow the Water” has borne fruit. Although the Martian surface is largely composed of unaltered basaltic rocks and sand, the Rovers discovered water-lain sediments, some minerals only formed in water, and aqueous alteration of chemically fragile igneous minerals. The geological records of early water-rich environment have shown hints of profuse and neutral-to-alkaline water that later evolved to sulfurous acidic conditions as aqueous activity waned. We now have a global inventory of near-surface water occurring as hydrated minerals and possibly ice and liquid in equatorial and mid latitudes and as masses of water ice making up an unknown but potentially large fraction of the polar regolith. Martian meteorites have provided new insights into the early formation of Mars' core and mantle.
Mapping Mars at Global to Human Scales
- Brent A. Archinal, Randolph L. Kirk, Elpitha Howington-Kraus, Mark R. Rosiek, Laurence A. Soderblom, Ella M. Lee
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- Journal:
- Highlights of Astronomy / Volume 13 / 2005
- Published online by Cambridge University Press:
- 30 March 2016, p. 912
- Print publication:
- 2005
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- Article
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We report on current Mars mapping projects in support of NASA planetary exploration. This includes a summary of the current state and accuracy of such mapping at global, regional, and local (human) scales. The availability of Mars Orbiter Laser Altimeter data has revolutionized such mapping. Aside from its use as a global topographic dataset, images can easily be correlated to it with absolute uncertainties of ≈100 m horizontally. We are using this to create a revised version of the global Mars digital image mosaic (MDIM) that will have absolute errors of ≈231 m (one pixel) and improved cosmetic characteristics. We are undertaking stereo-topographic mapping at regional to local scales, using Viking and Mars Orbiter Camera Narrow Angle (NA) images, with horizontal resolutions of 600 to 5 m, and expected vertical precision of 200 to 1 m. Derived topography and altimetric information can also be used to calibrate shape-from-shading (photoclinometry) topographic models at down to single-pixel resolution (i.e. 1.4 m for NA images). Products of these efforts have a multitude of purposes, from assisting in large-scale geologic mapping, to characterizing the geology/safety of proposed landing sites. Plans are underway to also use THEMIS, HRSC, and HiRISE camera data in future efforts.
The Deep Space 1 Encounter With Comet 19P/Borrelly
- Diane H. Wooden, L. A. Soderblom, D. T. Britt, R. H. Brown, B. R. Sandel, R. V. Yelle, B. J. Buratti, M. D. Hicks, R. M. Nelson, M. D. Rayman, J. Oberst, N. Thomas
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- Journal:
- International Astronomical Union Colloquium/ Volume 186 /
- pp. 301-324
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NASA's Deep Space 1 (DSl) spacecraft successfully encountered comet 19P/Borrelly near perihelion and the Miniature Integrated Camera and Spectrometer (MICAS) imaging system onboard DS1 returned the first high-resolution images of a Jupiter-family comet nucleus and surrounding environment. The images span solar phase angles from 88° to 52°, providing stereoscopic coverage of the dust coma and nucleus. Numerous surface features are revealed on the 8-km long nucleus in the highest resolution images (47-58 m/pixel). A smooth, broad basin containing brighter regions and mesa-like structures is present in the central part of the nucleus that seems to be the source of jet-like dust features seen in the coma. High ridges seen along the jagged terminator lead to rugged terrain on both ends of the nucleus containing dark patches and smaller series of parallel grooves. No evidence of impact craters with diameters larger than about 200-m are present, indicating a young and active surface. The nucleus is very dark with albedo variations from 0.007 to 0.035. Short-wavelength, infrared spectra from 1.3 to 2.6 μm revealed a hot, dry surface consistent with less than about 10% actively sublimating. Two types of dust features are seen: broad fans and highly collimated “jets” in the sunward hemisphere that can be traced to the surface. The source region of the main jet feature, which resolved into at least three smaller “jets” near the surface, is consistent with an area around the rotation pole that is constantly illuminated by the sun during the encounter. Within a few nuclear radii, entrained dust is rapidly accelerated and fragmented and geometrical effects caused from extended source regions are present, as evidenced in radial intensity profiles centered on the jet features that show an increase in source strength with increasing cometocentric distance. Asymmetries in the dust from dayside to nightside are pronounced and may show evidence of lateral flow transporting dust to structures observed in the nightside coma. A summary of the initial results of the Deep Space 1 Mission is provided, highlighting the new knowledge that has been gained thus far.