28 research outputs found
Soils of eagle crater and Meridiani Planum at the Opportunity Rover landing site
No full textThe soils at the Opportunity site are fine-grained basaltic sands mixed with dust and sulfate-rich outcrop debris. Hematite is concentrated in spherules eroded from the strata. Ongoing saltation exhumes the spherules and their fragments, concentrating them at the surface. Spherules emerge from soils coated, perhaps from subsurface cementation, by salts. Two types of vesicular clasts may represent basaltic sand sources. Eolian ripples, armored by well-sorted hematite-rich grains, pervade Meridiani Planum. The thickness of the soil on the plain is estimated to be about a meter. The flatness and thin cover suggest that the plain may represent the original sedimentary surface.Additional co-authors: MP Golombek, R Greeley, JP Grotzinger, KE Herkenhoff, DJ Jerolmack, JR Johnson, B Jolliff, G Klingelhöfer, AH Knoll, ZA Learner, R Li, MC Malin, SM McLennan, HY McSween, DW Ming, RV Morris, JW Rice Jr, L Richter, R Rieder, D Rodionov, FP Seelos IV, JM Soderblom, SW Squyres, R Sullivan, WA Watters, CM Weitz, MB Wyatt, A Yen, J Zipfe
An integrated view of the chemistry and mineralogy of martian soils
No full textThe mineralogical and elemental compositions of the martian soil are indicators of chemical and physical weathering processes. Using data from the Mars Exploration Rovers, we show that bright dust deposits on opposite sides of the planet are part of a global unit and not dominated by the composition of local rocks. Dark soil deposits at both sites have similar basaltic mineralogies, and could reflect either a global component or the general similarity in the compositions of the rocks from which they were derived. Increased levels of bromine are consistent with mobilization of soluble salts by thin films of liquid water, but the presence of olivine in analysed soil samples indicates that the extent of aqueous alteration of soils has been limited. Nickel abundances are enhanced at the immediate surface and indicate that the upper few millimetres of soil could contain up to one per cent meteoritic material.Additional co-authors: Thanasis E Economou, Amitabha Ghosh, Brian C Hahn, Kenneth E Herkenhoff, Larry A Haskin, Joel A Hurowitz, Bradley L Joliff, Jeffrey R Johnson, Göstar Klingelhöfer, Morten Bo Madsen, Scott M McLennan, Harry Y McSween, Lutz Richter, Rudi Rieder, Daniel Rodionov, Larry Soderblom, Steven W Squyres, Nicholas J Tosca, Alian Wang, Michael Wyatt, Jutta Zipfe
Technique for rapid determination of relative ages of lunar areas from orbital photography
No full textPyroclastic activity at home plate in Gusev Crater, Mars
No full textHome Plate is a layered plateau in Gusev crater on Mars. It is composed of clastic rocks of moderately altered alkali basalt composition, enriched in some highly volatile elements. A coarsegrained lower unit lies under a finer-grained upper unit. Textural observations indicate that the lower strata were emplaced in an explosive event, and geochemical considerations favor an explosive volcanic origin over an impact origin. The lower unit likely represents accumulation of pyroclastic materials, whereas the upper unit may represent eolian reworking of the same pyroclastic materials.Additional co-authors: R Li, T McCoy, AS McEwen, HY McSween, DW Ming, JM Moore, RV Morris, TJ Parker, JW Rice Jr, S Ruff, M Schmidt, LA Soderblom, A Ye
Mars Surveyor Project Landing Site Activities
No full textThe Mars Surveyor Program --now a cooperative program led by NASA and CNES along with other international partners -- is underway. It has the primary science objective of furthering our understanding of the biological potential and possible biological history of Mars and has the complementary objective of improving our understanding of martian climate evolution and planetary history The missions will develop technology and acquire data necessary for eventual human Exploration. Launches of orbiters, landers and rovers will take place in 2001 and in 2003; in 2005 a complete system will be launched capable of returning samples to Earth by 2008. A key aspect of the program is the selection of landing sites. This abstract 1) reports on the status of the landing site selection process that begins with the 2001 lander mission and 2) outlines be opportunities for the Mars community to provide input into the landing site selection process
Probing the Allosteric Role of the 5 Subunit of 345 Nicotinic Acetylcholine Receptors by Functionally Selective Modulators and Ligands
No full textUSGS High-Resolution Topomapping of Mars with Mars Orbiter Camera Narrow-Aangle Images
No full textWe describe our initial experiences producing controlled digital elevation models (DEMs) of Mars with horizontal resolutions of ≤10 m and vertical precisions of ≤2 m. Such models are of intense interest at all phases of Mars exploration and scientific investigation, from the selection of safe landing sites to the quantitative analysis of the morphologic record of surface processes. Topomapping with a resolution adequate to address many of these issues has only become possible with the success of the Mars Global Surveyor (MGS) mission. The Mars Orbiter Laser Altimeter (MOLA) on MGS mapped the planet globally with absolute accuracies <10 m vertically and ~100 m horizontally but relatively sparse sampling (300 m along track, with gaps of>1 km between tracks common at low latitudes). We rely on the MOLA data as the best available source of control and process images from the narrow-angle Mars Orbiter Camera (MOC-NA) with stereo and photoclinometric (shape-from-shading) techniques to produce DEMs with significantly better horizontal resolution. The techniques described here enable mapping not only with MOC but also with the high-resolution cameras (Mars Express HRSC, Mars Reconnaissance Orbiter HiRISE) that will orbit Mars in the next several years. * Correspondence author
Evidence for recent volcanism on Mars from crater counts
No full textImpact craters help characterize the age of a planetary surface, because they accumulate with time. They also provide useful constraints on the importance of surface erosion, as such processes will preferentially remove the smaller craters. Earlier studies of martian crater populations revealed that erosion and dust deposition are important processes on Mars. They disagreed, however, on the age of the youngest volcanism. These earlier studies were limited by image resolution to craters larger than a few hundred metres in diameter. Here we report an analysis, using new images obtained by the Mars Global Surveyor spacecraft, of crater populations that extend the size distribution down to about 16 m. Our results indicate a wide range of surface ages, with one region—lava flows within the Arsia Mons caldera—that we estimate to be no older than 40–100 million years. We suggest that volcanism is a continuing process on Mars
Overview of the Opportunity Mars Exploration Rover mission to Meridiani Planum: Eagle crater to Purgatory ripple
No full textThe Mars Exploration Rover Opportunity touched down at Meridiani Planum in January 2004 and since then has been conducting observations with the Athena science payload. The rover has traversed more than 5 km, carrying out the first outcrop-scale investigation of sedimentary rocks on Mars. The rocks of Meridiani Planum are sandstones formed by eolian and aqueous reworking of sand grains that are composed of mixed fine-grained siliciclastics and sulfates. The siliciclastic fraction was produced by chemical alteration of a precursor basalt. The sulfates are dominantly Mg-sulfates and also include Ca-sulfates and jarosite. The stratigraphic section observed to date is dominated by eolian bedforms, with subaqueous current ripples exposed near the top of the section. After deposition, interaction with groundwater produced a range of diagenetic features, notably the hematite-rich concretions known as ‘‘blueberries.’’ The bedrock at Meridiani is highly friable and has undergone substantial erosion by wind-transported basaltic sand. This sand, along with concretions and concretion fragments eroded from the rock, makes up a soil cover that thinly and discontinuously buries the bedrock. The soil surface exhibits both ancient and active wind ripples that record past and present wind directions. Loose rocks on the soil surface are rare and include both impact ejecta and meteorites. While Opportunity’s results show that liquid water was once present at Meridiani Planum below and occasionally at the surface, the environmental conditions recorded were dominantly arid, acidic, and oxidizing and would have posed some significant challenges to the origin of life.Additional co-authors: J Farmer, WH Farrand, W Folkner, R Gellert, TD Glotch, M Golombek, S Gorevan, JA Grant, R Greeley, J Grotzinger, KE Herkenhoff, S Hviid, JR Johnson, G Klingelhöfer, AH Knoll, G Landis, M Lemmon, R Li, MB Madsen, MC Malin, SM McLennan, HY McSween, DW Ming, J Moersch, RV Morris, T Parker, JW Rice Jr, L Richter, R Rieder, M Sims, M Smith, P Smith, LA Soderblom, R Sullivan, NJ Tosca, H Wnke, T Wdowiak, M Wolff, A Ye
