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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Formation of complex impact craters - Evidence from Mars and other planets

An analysis of the depth vs diameter data of Arthur (1980), is given along with geomorphic data for 73 Martian craters. The implications for the formation of complex impact craters on solid planets is discussed. The analysis integrates detailed morphological observations on planetary craters with geologic data from terrestrial meteorite and explosion craters. The simple to complex transition for impact craters on Mars appears at diameters in the range of 3 to 8 km. Five features appear sequentially with increasing crater size, flat floors, central peaks and shallower depths, scalloped rims, and terraced walls. This order suggests that a shallow depth of excavation and a rebound mechanism have produced the central peaks, not centripetal collapse and deep sliding. Simple craters are relatively uniform in shape from planet to planet, but complex craters vary considerably. Both the average onset diameter for complex impact craters on Mars and the average depth of complex craters vary inversely with gravitational acceleration on four planets.

Pike, R. J.↗
NASA NTRS1982

Thick shell tectonics on one-plate planets - Applications to Mars

Using the zero frequency equations of a self-gravitating elastic spherical shell overlying a strengthless fluid, a theory for stress distribution in thick lithospheric shells on one-plate planets is developed. For both the compensated and flexural modes, stress distributions in lithospheres are reviewed. For compensated modes, surface stresses depend only on surface topography, whereas for flexural modes it is shown that, for long wavelengths, stress trajectories are mainly dependent on the lithospheric lateral density distribution and not on elastic properties. Computational analyses are performed for Mars, and it is found that isostatically compensated models correctly predict the graben structure in the immediate Tharsis region and a flexural loading model is satisfactory in explaining the graben in the regions surrounding Tharsis. A three-stage model for the evolution of Tharsis is hypothesized: isostasy with north-south graben formation on Tharsis, followed by flexural loading and radial graben formation on the perimeter of Tharsis, followed by a last stage of loading with little or no regional deformation.

Banerdt, W. B.↗
NASA NTRS1988

Nuclear propulsion: A vital technology for the exploration of Mars and the planets beyond

The physics and technology issues and performance potential of various direct thrust fission and fusion propulsion concepts are examined. Next to chemical propulsion the solid core fission thermal rocket (SCR) is the olny other concept to be experimentally tested at the power (approx 1.5 to 5.0 GW) and thrust levels (approx 0.33 to 1.11 MN) required for manned Mars missions. With a specific impulse of approx 850 s, the SCR can perform various near-Earth, cislunar and interplanetary missions with lower mass and cost requirements than its chemical counterpart. The gas core fission thermal rocket, with a specific power and impulse of approx 50 kW/kg and 5000 s offers the potential for quick courier trips to Mars (of about 80 days) or longer duration exploration cargo missions (lasting about 280 days) with starting masses of about 1000 m tons. Convenient transportation to the outer Solar System will require the development of magnetic and inertial fusion rockets (IFRs). Possessing specific powers and impulses of approx 100 kW/kg and 200-300 kilosecs, IFRs will usher in the era of the true Solar System class speceship. Even Pluto will be accessible with roundtrip times of less than 2 years and starting masses of about 1500 m tons.

Borowski, Stanley K.↗
NASA NTRS1989

Nuclear propulsion - A vital technology for the exploration of Mars and the planets beyond

The physics and technology issues and performance potential of various direct thrust fission and fusion propulsion concepts are examined. Next to chemical propulsion the solid core fission thermal rocket (SCR) is the only other concept to be experimentally tested at the power (approx 1.5 to 5.0 GW) and thrust levels (approx 0.33 to 1.11 MN) required for manned Mars missions. With a specific impulse of approx 850 s, the SCR can perform various near-earth, cislunar and interplanetary missions with lower mass and cost requirements than its chemical counterpart. The gas core fission thermal rocket, with a specific power and impulse of approx 50 kW/kg and 5000 s offers the potential for quick courier trips to Mars (of about 80 days) or longer duration exploration cargo missions (lasting about 280 days) with starting masses of about 1000 m tons. Convenient transportation to the outer Solar System will require the development of magnetic and inertial fusion rockets (IFRs). Possessing specific powers and impulses of approx 100 kW/kg and 200-300 kilosecs, IFRs will usher in the era of the true Solar System class spaceship. Even Pluto will be accessible with roundtrip times of less than 2 years and starting masses of about 1500 m tons.

Borowski, Stanley K.↗
NASA NTRS1991

Global hybrid simulation of unmagnetized planets - Comparison of Venus and Mars

Results from three-dimensional hybrid particle simulations of the solar wind interaction with the planets Mars and Venus are presented. The simulations produce shocks and magnetic barriers which are asymmetric. These results are qualitatively in agreement with data. In the absence of an ionosphere the subsolar shock standoff distance was found to agree with the observations if the Hall current is limited. It was also found that the solar wind interaction with Mars and Venus was substantially different. The interaction with Venus can be generally viewed as a magnetized interaction. The Mars interaction is very kinetic in nature and appears not to have a shock in the classic sense.

Brecht, Stephen H.↗
NASA NTRS2004

A New View of Mars

During the last 8 years the US has successfully sent 2 major spacecraft to Mars 1z?der= planet. The Mars Global Surveyor spacecraft (IGS), which started operating at Mars in Sept 1977 and Mars Odyssey spacecraft that started operating in Jan 2002, are both operational and collecting data, including 1.5 meter pixel imagery, them spectrometry, magnetometry, altimeter/radiometry, gamma ray and neutron counts. imaging spectrometry, and gravity. The two orbiters are conceptually similar to Earth orbiting spacecraft in that their primary purpose is to observe, monitor, and measure a variety of parameters about the planet and report any changes that might be occurring on the surfaces and in the atmosphere. As a result we now have detailed physical descriptions of the shape, topography, magnetism. surface roughness, thermal inertia, atmospheric pressure and temperature, the distribution of hydrogen in the top meter of the crust, models for the planetary interior based upon data, and an image set that portrays much of the history of the past 3 billion years. understand how the planet came to be this way.

Smith, David E.↗
NASA NTRS1991

Automated design of gravity-assist trajectories to Mars and the outer planets

In this paper, a new approach to planetary mission design is described which automates the search for gravity-assist trajectories. This method finds all conic solutions given a range of launch dates, a range of launch energies and a set of target planets. The new design tool is applied to the problems of finding multiple encounter trajectories to the outer planets and Venus gravity-assist trajectories to Mars. The last four-planet grand tour opportunity (until the year 2153) is identified. It requires an earth launch in 1996 and encounters Jupiter, Uranus, Neptune, and Pluto. Venus gravity-assist trajectories to Mars for the 30 year period 1995-2024 are examined. It is shown that in many cases these trajectories require less launch energy to reach Mars than direct ballistic trajectories.

Longuski, James M.↗
NASA NTRS1979

The distribution of lobate debris aprons and similar flows on Mars

Planet-wide mapping of lobate debris aprons and other similar flows on Mars shows a strong concentration in two latitudinal bands roughly 25 deg wide and centered at 40 deg N and 45 deg S. This distribution supports the idea that these flows form when erosional debris is transported downslope and becomes mixed with ice deposited from the atmosphere, as these latitudes should receive high seasonal H2O frost deposition relative to the rest of the planet. Flows are found in the northern hemisphere band wherever old highland surfaces occur but are found in the southern hemisphere only near the two major impact basins, Argyre and Hellas. These areas are apparently characterized by mass wasting that is rapid relative to most of the southern hemisphere highlands. The rate of mass wasting may be related to the degree of consolidation of highland material.

Squyres, S. W.↗
NASA NTRS1975

Earth-type planets (Mercury, Venus, and Mars)

Spacecraft- and Earth-based studies on the physical nature of the planets Mercury, Venus, and Mars are reported. Charts and graphs are presented on planetary surface properties, rotational parameters, atmospheric compositions, and astronomical characteristics.

Marov, M. Y.↗
NASA NTRS1977

Solar radiation incident on Mars and the outer planets - Latitudinal, seasonal, and atmospheric effects

Calculations of the daily solar radiation incident at the tops of the atmospheres of Mars and the outer planets and its variability with latitude and season are presented in a series of figures and tables. The changes in the latitudinal and seasonal distributions of daily surface insolation during the great Martian dust storm of 1971 (when Martian atmospheric optical depth increased from about tau = 0.1 to 2.0) were significant and dramatically illustrate the effect of atmospheric aerosols on surface insolation; i.e., the mean annual daily insolation at the poles decreased by more than a factor of 100 as tau increased from 0.1 to 2.0.

Levine, J. S.↗
NASA NTRS1984

On Mars: Exploration of the Red Planet, 1958 - 1978

The exploration of Mars is covered by the following topics: Mariner spacecraft and launch vehicles, search for Martian life; Voyager spacecraft; creation of Viking; Viking Orbiter and its Mariner inheritance; Viking lander; building a complex spacecraft; selecting landing sites; site certification, and data from Mars.

Ezell, E. C.↗
NASA NTRS2001

Mapping the Red Planet

Since September 1997 the Mars Global Surveyor spacecraft has been orbiting the planet Mars and acquiring new data about the red planet that is changing our view of its present state and past history. Except for a few weeks in October 1997 and a few months in the Spring/Summer of 1998 when special science operations were conducted the spacecraft spent the first 18 months if its time at Mars getting to the right orbital geometry for the mapping mission. But on March 1, 1999 the MGS spacecraft trained its instruments onto the planet to begin a full Mars year (684 Earth days) of continuous systematic mapping and observation of the planet. The camera began wide angle and high resolution mapping, the thermal emission spectrometer began sensing the atmosphere and the material properties of the surface, the magnetometer searched out regions of abnormally high magnetism, the altimeter began determining the precise shape of the planet, and the radio science experiment began determining atmospheric pressures, temperatures and mapping the planet's gravity field. In a matter of a month more data was acquired about

Smith, David E.↗
DOE OSTI2021

National Academy of Science, Engineering, and Medicine, NASA Planetary Science and Astrobiology Decadal Survey (Chapter 3)

Our inner Solar System has the four terrestrial planets, Mercury, Venus, Earth, and Mars, along with Earth’s large Moon, two small moons of Mars, dwarf planet Ceres, numerous 100-km class asteroids, and a multitude of small bodies that populate the asteroid belt and the inner planet region. To what extent does this structure reflect a deterministic outcome of general Solar System formation processes, and how much of it is instead a consequence of stochastic events that would change in unpredictable ways if the system’s formation could be rerun? This fundamental question motivates scientific investigations of the inner Solar System, with implications not only for understanding our own planet’s origin but also for the origin of planetary systems and Earth-like planets beyond our own.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2015

Terrestrial Planet Formation Constrained By Mars and the Structure of the Asteroid Belt

Reproducing the large Earth/Mars mass ratio requires a strong mass depletion in solids within the protoplanetary disc between 1 and 3 au. The Grand Tack model invokes a specific migration history of the giant planets to remove most of the mass initially beyond 1 au and to dynamically excite the asteroid belt. However, one could also invoke a steep density gradient created by inward drift and pile-up of small particles induced by gas drag, as has been proposed to explain the formation of close-in super-Earths. Here we show that the asteroid belt’s orbital excitation provides a crucial constraint against this scenario for the Solar system. We performed a series of simulations of terrestrial planet formation and asteroid belt evolution starting from discs of planetesimals and planetary embryos with various radial density gradients and including Jupiter and Saturn on nearly circular and coplanar orbits. Discs with shallow density gradients reproduce the dynamical excitation of the asteroid belt by gravitational self-stirring but form Mars analogues significantly more massive than the real planet. In contrast, a disc with a surface density gradient proportional to r(exp −5.5) reproduces the Earth/Mars mass ratio but leaves the asteroid belt in a dynamical state that is far colder than the real belt. We conclude that no disc profile can simultaneously explain the structure of the terrestrial planets and asteroid belt. The asteroid belt must have been depleted and dynamically excited by a different mechanism such as, for instance, in the Grand Tack scenario.

Numerical methods↗
NASA NTRS1995

Mars Exobiology: The Principles Behind The Plan For Exploration

The search for evidence of life on Mars is a highly interdisciplinary enterprise which extends beyond the traditional life sciences. Mars conceivably had a pervasive ancient biosphere which may have persisted even to the present, but only in subsurface environments. Understanding the history of Mars' global environment, including its inventory of volatile elements, is a crucial part of the search strategy. Those deposits (minerals, sediments, etc.) which could have and retained a record of earlier biological activity must be identified and examined. While the importance of. seeking another biosphere has not diminished during the years since the Viking mission, the strategy for Mars exploration certainly has been modified by later discoveries. The Viking mission itself demonstrated that the present day surface environment of Mars is hostile to life as we know it. Thus, to search effectively for life on Mars, be it extant or extinct, we now must greatly improve our understanding of Mars the planet. Such an understanding will help us broaden our search beyond the Viking lander sites, both back in time to earlier epochs and elsewhere to other sites and beneath the surface. Exobiology involves much more than simply a search for extant life beyond Earth. It addresses the prospect of long-extinct biospheres and also the chemistry, organic and otherwise, which either led to life or which occurred on rocky planets that remained lifeless. Even a Mars without a biosphere would reveal much about life. How better to understand the origin and impact of a biosphere than to compare Earth with another similar but lifeless planet? Still, several relatively recent discoveries offer encouragement that a Martian biosphere indeed might have existed. The ancient Martian surface was extensively sculptured by volcanism and the activity of liquid water. Such observations invoke impressions of an ancient martian atmosphere and environment that resembled ancient Earth more than present-day Mars. Since Viking, we have learned that our own biosphere began prior to 3.5 billion years ago, during an early period when our solar system apparently was sustaining clement conditions on at least two of its planets. Also, we have found that microorganisms can survive, even flourish, in environments more extreme in temperature and water availability than had been previously recognized. The common ancestor of life on Earth probably was adapted to elevated temperatures, raising the possibility that hydrothermal systems played a central role in sustaining our early biosphere. If a biosphere ever arose on Mars, at least some of its constituents probably dwelled in the subsurface. Even today, conditions on Mars and Earth become more similar with increasing depth beneath their surfaces. For example, under the martian permafrost, the geothermal gradient very likely maintains liquid water in environments which resemble aquifers on Earth. Indigenous bacteria have recently been recovered from deep aquifers on Earth. Liquid groundwater very likely persisted throughout Mars' history. Thus, martian biota, if they ever existed, indeed might have survived in subsurface environments.

DesMarais, D. J.↗