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At least 577 records · Page 32Linked to original sources
PubMed2005

Sulfates in the north polar region of Mars detected by OMEGA/Mars Express.

The Observatoire pour la Minéralogie, l'Eau, les Glaces, et l'Activité (OMEGA) imaging spectrometer observed the northern circumpolar regions of Mars at a resolution of a few kilometers. An extended region at 240 degrees E, 85 degrees N, with an area of 60 kilometers by 200 kilometers, exhibits absorptions at wavelengths of 1.45, 1.75, 1.94, 2.22, 2.26, and 2.48 micrometers. These signatures can be unambiguously attributed to calcium-rich sulfates, most likely gypsum. This region corresponds to the dark longitudinal dunes of Olympia Planitia. These observations reveal that water alteration played a major role in the formation of the constituting minerals of northern circumpolar terrains.

Atmosphere↗
PubMed2005

Summer evolution of the north polar cap of Mars as observed by OMEGA/Mars Express.

The Observatoire pour la Minéralogie, l'Eau, les Glaces, et l'Activité (OMEGA) visible-infrared imaging spectrometer extensively observed regions of Mars with latitudes above 70 degrees N in late 2004 (heliocentric longitude from Ls 93 degrees to Ls 127 degrees ). The extent of water ice at the surface and the size of ice grains were monitored as a function of time. Bright, small-grained frost, which initially covered a large fraction of the polar cap, waned in favor of large-grained ice. In outlying regions, dominated by large-grained ice, the albedo increased over the period. Evaluating the dust content was model dependent. However, contamination of ice by dust was low.

Carbon Dioxide↗
PubMed2005

Spectral reflectance and morphologic correlations in eastern Terra Meridiani, Mars.

The Mars Express Observatoire pour la Minéralogie, l'Eau, les Glaces, et l'Activité (OMEGA) hyperspectral image data covering eastern Terra Meridiani indicate the ubiquitous presence of molecular water in etched terrain materials that disconformably overlie heavily cratered terrains and underlie the hematite-bearing plains explored by the Opportunity rover. Identification of crystalline water in kieserite (MgSO4.H2O) is linked to materials exposed in a valley and plateau to the north of hematite-bearing plains. The mineralogical similarities between the etched terrain deposits examined with OMEGA data and the layered rocks examined by Opportunity imply that the ancient aqueous environments inferred from analyses of the rover data extend over regional scales.

Extraterrestrial Environment↗
PubMed1994

Early Mars: how warm and how wet?

Early in its history, Mars underwent fluvial erosion that has been interpreted as evidence for a warmer, wetter climate. However, no atmosphere composed of only CO2 and H2O appears capable of producing mean planetary temperatures even close to 0 degrees C. Rather than by precipitation, aquifer recharge and ground water seepage may have been enabled by hydrothermal convection driven by geothermal heat and heat associated with impacts. Some climatic warming was probably necessary to allow water to flow for long distances across the surface. Modest warming could be provided by even a low-pressure CO2 atmosphere if it was supplemented with small amounts of CH4, NH3, or SO2. Episodic excursions to high obliquities may also have raised temperatures over some portions of the planet's surface.

Ammonia↗
PubMed1997

Overview of the Mars Pathfinder mission and assessment of landing site predictions.

Chemical analyses returned by Mars Pathfinder indicate that some rocks may be high in silica, implying differentiated parent materials. Rounded pebbles and cobbles and a possible conglomerate suggest fluvial processes that imply liquid water in equilibrium with the atmosphere and thus a warmer and wetter past. The moment of inertia indicates a central metallic core of 1300 to 2000 kilometers in radius. Composite airborne dust particles appear magnetized by freeze-dried maghemite stain or cement that may have been leached from crustal materials by an active hydrologic cycle. Remote-sensing data at a scale of generally greater than approximately 1 kilometer and an Earth analog correctly predicted a rocky plain safe for landing and roving with a variety of rocks deposited by catastrophic floods that are relatively dust-free.

Atmosphere↗
PubMed1997

The Mars Pathfinder atmospheric structure investigation/meteorology (ASI/MET) experiment.

The Mars Pathfinder atmospheric structure investigation/meteorology (ASI/MET) experiment measured the vertical density, pressure, and temperature structure of the martian atmosphere from the surface to 160 km, and monitored surface meteorology and climate for 83 sols (1 sol = 1 martian day = 24.7 hours). The atmospheric structure and the weather record are similar to those observed by the Viking 1 lander (VL-1) at the same latitude, altitude, and season 21 years ago, but there are differences related to diurnal effects and the surface properties of the landing site. These include a cold nighttime upper atmosphere; atmospheric temperatures that are 10 to 12 degrees kelvin warmer near the surface; light slope-controlled winds; and dust devils, identified by their pressure, wind, and temperature signatures. The results are consistent with the warm, moderately dusty atmosphere seen by VL-1.

Atmosphere↗
PubMed1997

Results from the Mars Pathfinder camera.

Images of the martian surface returned by the Imager for Mars Pathfinder (IMP) show a complex surface of ridges and troughs covered by rocks that have been transported and modified by fluvial, aeolian, and impact processes. Analysis of the spectral signatures in the scene (at 440- to 1000-nanometer wavelength) reveal three types of rock and four classes of soil. Upward-looking IMP images of the predawn sky show thin, bluish clouds that probably represent water ice forming on local atmospheric haze (opacity approximately 0.5). Haze particles are about 1 micrometer in radius and the water vapor column abundance is about 10 precipitable micrometers.

Atmosphere↗
PubMed1998

Atmosphere-surface interactions on Mars: delta 17O measurements of carbonate from ALH 84001.

Oxygen isotope measurements of carbonate from martian meteorite ALH 84001 (delta18O = 18.3 +/- 0.4 per mil, delta17O = 10.3 +/- 0.2 per mil, and Delta17O = 0.8 +/- 0.05 per mil) are fractionated with respect to those of silicate minerals. These measurements support the existence of two oxygen isotope reservoirs (the atmosphere and the silicate planet) on Mars at the time of carbonate growth. The cause of the atmospheric oxygen isotope anomaly may be exchange between CO2 and O(1D) produced by the photodecomposition of ozone. Atmospheric oxygen isotope compositions may be transferred to carbonate minerals by CO2-H2O exchange and mineral growth. A sink of 17O-depleted oxygen, as required by mass balance, may exist in the planetary regolith.

Atmosphere↗
PubMed2000

Mars exploration. Plan for two rovers squeezes NASA budget.

NASA's decision last week to send two rovers to Mars in 2003 is being hailed by researchers as affirming the agency's commitment to exploring the Red Planet. But once the applause dies down, cash-strapped space science managers will be forced to make tough decisions about how to shoulder the added $200 million cost of a second mission, starting with $96 million that must come out of NASA's 2001 budget.

Budgets↗
PubMed2000

Planetary science. A dripping wet early Mars emerging from new pictures.

The latest images from the Red Planet, a sampling of which is shown on page 1927, are suggesting that water ponded across its equatorial region eons ago, just when life might have been emerging. Although the authors offer more than one interpretation, the one they prefer has the sediments laid down beneath broad lakes and shallow seas at a relatively clement time in the planet's history. The geologic implications of the pictures plus supportive signs from earlier missions mean that these possible lake sediments will be prime candidates for NASA missions seeking signs of past life on Mars.

Atmosphere↗
PubMed2000

Sedimentary rocks of early Mars.

Layered and massive outcrops on Mars, some as thick as 4 kilometers, display the geomorphic attributes and stratigraphic relations of sedimentary rock. Repeated beds in some locations imply a dynamic depositional environment during early martian history. Subaerial (such as eolian, impact, and volcaniclastic) and subaqueous processes may have contributed to the formation of the layers. Affinity for impact craters suggests dominance of lacustrine deposition; alternatively, the materials were deposited in a dry, subaerial setting in which atmospheric density, and variations thereof mimic a subaqueous depositional environment. The source regions and transport paths for the materials are not preserved.

Atmosphere↗
PubMed1995

Rapid accretion and early differentiation of Mars indicated by 142Nd/144Nd in SNC meteorites.

Small differences in the ratio of neodymium-142 to neodymium-144 in early formed mantle reservoirs in planetary bodies are the result of in situ decay of the extinct radionuclide samarium-146 and can be used to constrain early planetary differentiation and therefore the time scale of planetary accretion. The martian meteorite Nakhla (approximately 1.3 billion years old), the type sample of the nakhlite subgroup of the Shergottite-Nakhlite-Chassigny (SNC) meteorites, exhibits a 59 +/- 13 parts per million excess in the ratio of neodymium-142 to neodymium-144 relative to normal neodymium. This anomaly records differentiation in the martian mantle before 4539 million years ago and implies that Mars experienced no giant impacts at any time later than 27 million years after the origin of the solar system.

Isotopes↗
PubMed2004

Analysis of water ice and water ice/soil mixtures using laser-induced breakdown spectroscopy: application to Mars polar exploration.

Recently, laser-induced breakdown spectroscopy (LIBS) has been developed for the elemental analysis of geological samples for application to space exploration. There is also interest in using the technique for the analysis of water ice and ice/dust mixtures located at the Mars polar regions. The application is a compact instrument for a lander or rover to the Martian poles to interrogate stratified layers of ice and dusts that contain a record of past geologic history, believed to date back several million years. Here we present results of a study of the use of LIBS for the analysis of water ice and ice/dust mixtures in situ and at short stand-off distances (< 6.5 m) using experimental parameters appropriate for a compact instrument. Characteristics of LIBS spectra of water ice, ice/soil mixtures, element detection limits, and the ability to ablate through ice samples to monitor subsurface dust deposits are discussed.

Extraterrestrial Environment↗
PubMed2001

The potential impact of bystander effects on radiation risks in a Mars mission.

Densely ionizing (high-LET) galactic cosmic rays (GCR) contribute a significant component of the radiation risk in free space. Over a period of a few months-sufficient for the early stages of radiation carcinogenesis to occur-a significant proportion of cell nuclei will not be traversed. There is convincing evidence, at least in vitro, that irradiated cells can send out signals that can result in damage to nearby unirradiated cells. This observation can hold even when the unirradiated cells have been exposed to low doses of low-LET radiation. We discuss here a quantitative model based on the a formalism, an approach that incorporates radiobiological damage both from a bystander response to signals emitted by irradiated cells, and also from direct traversal of high-LET radiations through cell nuclei. The model produces results that are consistent with those of a series of studies of the bystander phenomenon using a high-LET microbeam, with the end point of in vitro oncogenic transformation. According to this picture, for exposure to high-LET particles such as galactic cosmic rays other than protons, the bystander effect is significant primarily at low fluences, i.e., exposures where there are significant numbers of untraversed cells. If the mechanisms postulated here were applicable in vivo, using a linear extrapolation of risks derived from studies using intermediate doses of high-LET radiation (where the contribution of the bystander effect may be negligible) to estimate risks at very low doses (where the bystander effect may be dominant) could underestimate the true risk from low doses of high-LET radiation. It would be highly premature simply to abandon current risk projections for high-LET, low-dose radiation; however, these considerations would suggest caution in applying results derived from experiments using high-LET radiation at fluences above approximately 1 particle per nucleus to risk estimation for a Mars mission.

Animals↗
PubMedDate not supplied

Radiation exposure predictions for short-duration stay Mars missions.

The human radiation environment for several short-duration stay manned Mars missions is predicted using the Mission Radiation Calculation (MIRACAL) program, which was developed at NASA Langley Research Center. This program provides dose estimates for galactic cosmic rays (GCR) and large and ordinary solar proton flare events for various amounts of effective spacecraft shielding (both operational and storm shelter thicknesses) and a given time history of the spacecraft's heliocentric position. The results of this study show that most of the missions can survive the most recent large flares (if they were to occur at the missions' perihelion) if a 25 g/cm2 storm shelter is assumed. The dose predictions show that missions during solar minima (when solar flare activity is the lowest) are not necessarily the minimum dose cases, due to increased GCR contribution during this time period. The direct transfer mission studied has slightly lower doses than the outbound Venus swingby mission [on the order of 10-20 centi-Sieverts (cSv) lower], with the greatest dose differences for the assumed worst case scenario (when the large flares occur at perihelion). The GCR dose for a mission can be reduced by having the crew spend some fraction of its day nominally in the storm shelter (other than during flare events).

Bone Marrow↗
PubMed2000

[Some medical problems of piloted mission to Mars].

Medical provisions to planetary missions take in a wide spectrum of medical, engineering and organizational issues the goal of which is to provide good living conditions for humans in space, and to ensure physical and psychic health and performance of crew members during research activities on the Martian surface and soon after return to Earth. The article carefully reviews the problems of defining conceptual approaches to medical support in a mission to Mars. These approaches are grounded on the analysis of medical experience of prolonged orbital missions and prognosis of physiological shifts due to extension of mission up to 2 to 3 years including the period of stay on the Martian surface. Special attention is given to the key medical aspects of the mission, i.e. medical monitoring, countermeasures (including utilization of a short-arm centrifuge) against the adverse effects of microgravity on crew health and keeping-up useful skills and knowledge.

Aerospace Medicine↗
PubMed2001

[Psychological aspects of training for and implementation of a piloted expedition to Mars].

Reviewed are the modern notions of the main psychological concerns regarding a mission to Mars which are maintenance of mental health, high professional reliability, and successful readaptation of the Martian crew on return to Earth. The unprecedent trail-blazing interplanetary mission distinguished by autonomy, long period, international crew and a broad range of tasks to tend will set particularly difficult requirements to the psychological support system. Among them prioritized are purposeful character building and training of future crew members already in childhood and youth. The primary goal is to bring up personality with anthropocosmic thinking as a professional quality that will eventually determine personal and professional reliability. Within the system of psychological support, the central place should be given to monitoring of crew mental heath and behavior, and preventive an corrective measures. The longer Martian day (24 hr. 36 min.) rises the issue of effective adaptation to this factor. Special simulators will be required aboard the vehicle to help the crew refresh skills in manipulation of the dynamic board systems. The program of psychological support to the Martian crew must be thoroughly tested in model studies (Antarctic field, ground-based experiments, orbital flights, Lunar base).

Adult↗
PubMed1995

Living in space: results from Biosphere 2's initial closure, an early testbed for closed ecological systems on Mars.

The following summary of results from the first 2-year closure experiment (September 26, 1991 to September 26, 1993) in Biosphere 2 is excerpted from a chapter written by William Dempster and myself for a book, Strategies for Mars, edited by Carol Stoker and Carter Emmart of NASA Ames Research Center. The book will be published later this year by Krieger Publishers. It brings together a number of the most striking initial results, including food production and nutrition; ecosystem changes; oxygen and carbon dioxide dynamics; and the human role and response to living in a small, recycling life support system. The references cited are useful as a guide to currently available articles in journals. Hopefully, the next year will see a proliferation of papers presenting more data from the first 2 years of Biosphere 2's operation. There was a wealth of data collected during the closure and by teams of researchers who had access to the facility during the 5-month transition period following the departure of the first crew and the commencement of the second closure experiment in March, 1994.

Agriculture↗