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NASA NTRS1994

Life from the stars?

Scientists are now seriously considering the possibility that organic matter from interstellar space could have influenced, or even spurred, the origin of life on Earth. Various aspects of chemical evolution are discussed along with possible extraterrestrial sources responsible for contributing to Earth's life-producing, chemical composition. Specific topics covered include the following: interstellar matter, molecular clouds, asteroid dust, organic molecules in our solar system, interplanetary dust and comets, meteoritic composition, and organic-rich solar-system bodies.

Pendleton, Yvonne J.↗

NASA NTRS1975

The role of dust in cosmogony

A discussion is given of the production of interstellar grain cores from stellar material, the gain and loss of grain mantles in interstellar space, chemical transformations in these grains when they become part of the primitive solar nebula, and the identification of these grains with interplanetary dust derived from comets and with the matrix material in meteorites. Thus, this paper proposes a common cosmogonic framework relating studies of interstellar and interplanetary grains.

Cameron, A. G. W.↗

NASA NTRS2010

Using the Two-Burn Escape Maneuver for Fast Transfers in the Solar System and Beyond

The two-burn maneuver to escape the gravitational pull of a central body is described. The maneuver, originally suggested by Hermann Oberth, improves efficiency considerably for a wide range of missions of interest in space exploration and scientific investigation. A clear delineation of when the maneuver is more effective is given, as are methods to extract the most advantage when using the maneuver. Some examples are given of how this maneuver can enable exploration of the outer solar system, near interstellar space, and crewed missions to Mars and beyond. The maneuver has the potential to halve the required infrastructure associated with a crewed mission to Mars and achieve increased solar escape velocities with existing spacecraft technologies.

Adams, Robert B.↗

NASA NTRS2008

NASA's In Space Propulsion Technology Program Accomplishments and Lessons Learned

NASA's In-Space Propulsion Technology (ISPT) Program was managed for 5 years at the NASA MSFC and significant strides were made in the advancement of key transportation technologies that will enable or enhance future robotic science and deep space exploration missions. At the program's inception, a set of technology investment priorities were established using an NASA-wide, mission-driven prioritization process and, for the most part, these priorities changed little - thus allowing a consistent framework in which to fund and manage technology development. Technologies in the portfolio included aerocapture, advanced chemical propulsion, solar electric propulsion, solar sail propulsion, electrodynamic and momentum transfer tethers, and various very advanced propulsion technologies with significantly lower technology readiness. The program invested in technologies that have the potential to revolutionize the robotic exploration of deep space. For robotic exploration and science missions, increased efficiencies of future propulsion systems are critical to reduce overall life-cycle costs and, in some cases, enable missions previously considered impossible. Continued reliance on conventional chemical propulsion alone will not enable the robust exploration of deep space - the maximum theoretical efficiencies have almost been reached and they are insufficient to meet needs for many ambitious science missions currently being considered. By developing the capability to support mid-term robotic mission needs, the program was to lay the technological foundation for travel to nearby interstellar space. The ambitious goals of the program at its inception included supporting the development of technologies that could support all of NASA's missions, both human and robotic. As time went on and budgets were never as high as planned, the scope of the program was reduced almost every year, forcing the elimination of not only the broader goals of the initial program, but also of funding for over half of the technologies in the original portfolio. In addition, the frequency at which the application requirements for the program changed exceeded the development time required to mature technologies: forcing sometimes radical rescoping of research efforts already halfway (or more) to completion. At the end of its fifth year, both the scope and funding of the program were at a minimum despite the program successfully meeting all of it's initial high priority objectives. This paper will describe the program, its requirements, technology portfolio, and technology maturation processes. Also discussed will be the major technology milestones achieved and the lessons learned from managing a $100M+ technology program.

Johnson, Les C.↗

NASA NTRS2023

NASA’s Galactic Cosmic Ray Simulator – How we study the effects of space radiation on Earth

Earth’s atmosphere and natural magnetic field do a good job protecting us from space radiation. Space radiation is different from radiation on Earth, which mostly comes from isotopes found in rock and soil or from medical procedures like an Xray. Ionizing space radiation comes from particles ejected from the Sun, or solar particle events, and from supernovae outside our solar system making up a background of galactic cosmic radiation. These particles, representing the elements of the periodic table, have been stripped of their electrons as they are accelerated in interstellar space to almost the speed of light. One of NASA’s biggest challenges is protecting astronauts from these high energy particles of galactic cosmic radiation which can cause cancer and other diseases. To understand the biological damage imparted to living systems and to develop protective countermeasures, NASA has built a galactic cosmic ray simulator on Earth.

Space Exploration Missions↗

NASA NTRS1977

An investigation of techniques for the measurement and interpretation of cosmic ray isotopic abundances

An instrument, the Caltech High Energy Isotope Spectrometer Telescope was developed to measure isotopic abundances of cosmic ray nuclei by employing an energy loss - residual energy technique. A detailed analysis was made of the mass resolution capabilities of this instrument. A formalism, based on the leaky box model of cosmic ray propagation, was developed for obtaining isotopic abundance ratios at the cosmic ray sources from abundances measured in local interstellar space for elements having three or more stable isotopes, one of which is believed to be absent at the cosmic ray sources. It was shown that the dominant sources of uncertainty in the derived source ratios are uncorrelated errors in the fragmentation cross sections and statistical uncertainties in measuring local interstellar abundances. These results were applied to estimate the extent to which uncertainties must be reduced in order to distinguish between cosmic ray production in a solar-like environment and in various environments with greater neutron enrichments.

Wiedenbeck, M. E.↗

NASA NTRS1972

Organic molecules in space.

Examination of the question of chemical evolution. Observational evidence for the occurrence of some organic compounds in space is presented, and the likely existence of more complex molecules which are as yet undetected or unidentified is pointed out. This implies that massive solid objects, i.e., planets and asteroids, were accumulated from material which already contained a variety of organic compounds. The objects or regions of the galaxy studied are comets, interstellar space, prestellar nebulae, and cool stellar atmospheres.

Donn, B.↗

NASA NTRS1972

Interstellar electron intensity

Two independent methods for measuring the electron intensity in interstellar space are proposed. The positron method involves the production of pions in proton-proton collisions, the decay of the pions into muons, and the subsequent decay of the muons into positrons. Results from detailed calculations of these processes are given in graphical form. The second method involves cosmic electron emitted synchrotron radiation in the interstellar magnetic field. These two methods are also used to analyze the spatial and temporal constancy of cosmic ray electrons in the galaxy.

Ramaty, R.↗

NASA NTRS1975

Composition and spectra of primary cosmic-ray electrons and nuclei above 10 GeV

Recent experiments have extended the knowledge of the flux and energy spectra of individual cosmic-ray components to much higher energies than had previously been accessible. Both electron and nuclear components show a behavior at high energy which is unexpected, and which carries information regarding the sources and the propagation of particles between sources and observer. Electromagnetic interactions which are suffered by the electrons in interstellar space should steepen their spectrum, a steepening that would reveal the average lifetime a cosmic-ray particle spends in the galaxy. Measurements up to 1000 GeV show no such steepening. It was discovered that the composition of the nuclear species which is now measured up to 100 GeV/nucleon changes with energy. This change indicates traversal of less interstellar matter by the high energy particles than by those of lower energy.-

Meyer, P.↗

NASA NTRS1984

Prospects for the Voyager extra-planetary and interstellar mission

An advance study has been conducted to examine the trajectory characteristics of Voyager 1 and 2 as they depart from the solar system and traverse interstellar space. A survey of the extraplanetary phase, commencing with completion of the final planetary encounters and ceasing with loss of spacecraft communication, considers the trajectory aspects attendant to a heliospheric investigation and possible sensing of a trans-Neptunian massive body. An analysis of departure telecommunications capability attempts to bound the inevitable time of communication loss. A study of the interstellar phase examines closest approaches of the spacecraft to the sun's stellar neighbours. A covariance analysis is provided to illustrate the statistical effect of stellar state uncertainties on these approaches. In addition to the Voyager spacecraft, data for Pioneers 10 and 11 are provided where appropriate.

Cesarone, R. J.↗

NASA NTRS1992

Research in cosmic and gamma ray astrophysics

Discussed here is research in cosmic ray and gamma ray astrophysics at the Space Radiation Laboratory (SRL) of the California Institute of Technology. The primary activities discussed involve the development of new instrumentation and techniques for future space flight. In many cases these instrumentation developments were tested in balloon flight instruments designed to conduct new investigations in cosmic ray and gamma ray astrophysics. The results of these investigations are briefly summarized. Specific topics include a quantitative investigation of the solar modulation of cosmic ray protons and helium nuclei, a study of cosmic ray positron and electron spectra in interplanetary and interstellar space, the solar modulation of cosmic rays, an investigation of techniques for the measurement and interpretation of cosmic ray isotopic abundances, and a balloon measurement of the isotopic composition of galactic cosmic ray boron, carbon, and nitrogen.

Stone, Edward C.↗

NASA NTRS1974

The origin of life

Research in the areas of precambrian paleontology, chemical evolution of genetically important monomers, prebiotic dehydration-condensation reactions, organic compounds in meteorites and interstellar space, and biological exploration of the planets is summarized. Fossils in precambrian cherts and findings of eukaryotic cells are described, and recent investigations of prebiotic conditions, energy sources, and starting materials for genetic molecules are outlined. Studies of homogeneous and heterogeneous dehydrations and of nonaqueous thermal dehydrations are described. The detection of amino acids, purines, and pyrimidines in meteorites and of biologically significant molecules in interstellar clouds is discussed, as well as the possibilities of life on Jupiter, Mars, and Titan.

Horowitz, N. H.↗

NASA NTRS1976

Interstellar molecules

Progress in the discovery and study of interstellar molecules is summarized. The 36 molecular species thus far identified in interstellar space are listed in several groups which include simple hydrides, oxides, and sulfides, various derivatives of ammonia, molecules involving linear carbon chains, cyanides, and molecules related in structure to formaldehyde, alcohols, or ethers. Several free radicals are described, the discovery of molecules in external galaxies is discussed, and possible mechanisms for molecular formation are noted. Methods for examining relative isotopic abundances by measuring molecules in interstellar clouds are outlined, mechanisms for the excitation of interstellar molecules are reviewed, and values are presented for the C-12/C-13 abundance ratio in a number of interstellar clouds. The detection of interstellar masers is discussed along with pumping mechanisms and masing transitions in H2CO, CH, OH, and SiO. The nature of dense interstellar clouds is examined in terms of several simple and complex cloud models, with emphasis on multiple condensation models.

Townes, C. H.↗

NASA NTRS2012

Origins of GEMS Grains

Interplanetary dust particles (IDPs) collected in the Earth s stratosphere contain high abundances of submicrometer amorphous silicates known as GEMS grains. From their birth as condensates in the outflows of oxygen-rich evolved stars, processing in interstellar space, and incorporation into disks around new stars, amorphous silicates predominate in most astrophysical environments. Amorphous silicates were a major building block of our Solar System and are prominent in infrared spectra of comets. Anhydrous interplanetary dust particles (IDPs) thought to derive from comets contain abundant amorphous silicates known as GEMS (glass with embedded metal and sulfides) grains. GEMS grains have been proposed to be isotopically and chemically homogenized interstellar amorphous silicate dust. We evaluated this hypothesis through coordinated chemical and isotopic analyses of GEMS grains in a suite of IDPs to constrain their origins. GEMS grains show order of magnitude variations in Mg, Fe, Ca, and S abundances. GEMS grains do not match the average element abundances inferred for ISM dust containing on average, too little Mg, Fe, and Ca, and too much S. GEMS grains have complementary compositions to the crystalline components in IDPs suggesting that they formed from the same reservoir. We did not observe any unequivocal microstructural or chemical evidence that GEMS grains experienced prolonged exposure to radiation. We identified four GEMS grains having O isotopic compositions that point to origins in red giant branch or asymptotic giant branch stars and supernovae. Based on their O isotopic compositions, we estimate that 1-6% of GEMS grains are surviving circumstellar grains. The remaining 94-99% of GEMS grains have O isotopic compositions that are indistinguishable from terrestrial materials and carbonaceous chondrites. These isotopically solar GEMS grains either formed in the Solar System or were completely homogenized in the interstellar medium (ISM). However, the chemical compositions of GEMS grains are extremely heterogeneous and seem to rule out this possibility. Based on their solar isotopic compositions and their non-solar elemental compositions we propose that most GEMS grains formed in the nebula as late-stage non-equilibrium condensates.

Messenger, S.↗

NASA NTRS1976

Radical formation, chemical processing, and explosion of interstellar grains

The ultraviolet radiation in interstellar space is shown to create a sufficient steady-state density of free radicals in the grain mantle material consisting of oxygen, carbon, nitrogen, and hydrogen to satisfy the critical condition for initiation of chain reactions. The criterion for minimum critical particle size for maintaining the chain reaction is of the order of the larger grain sizes in a distribution satisfying the average extinction and polarization measures. The triggering of the explosion of interstellar grains leading to the ejection of complex interstellar molecules is shown to be most probable where the grains are largest and where radiation is suddenly introduced; i.e., in regions of new star formation. Similar conditions prevail at the boundaries between very dark clouds and H II regions. When the energy released by the chemical activity of the free radicals is inadequate to explode the grain, the resulting mantle material must consist of extremely large organic molecules which are much more resistant to the hostile environment of H II regions than the classical dirty-ice mantles made up of water, methane, and ammonia.

Greenberg, J. M.↗

NASA NTRS1995

Where Are the Interstellar Comets?

The existing theories of comet dynamics held that large numbers of comets are ejected to interstellar space and that other stellar systems would do the same; however, no comet on a hyperbolic orbit has ever been observed. Calculations developed by Duncan et al. are used to show that most comets thought to be ejected would actually be captured by the Oort Cloud.

comets interstellar comets Oort Cloud orbital dyna↗

NASA NTRS2001

Water Ice and Life's Roots in Space

Nearly three decades ago as Voyager 2 spacecraft raced out of the Solar System. NASA engineers turned its camera arm around (at the request of the American astronomer Carl Sagan) to take a parting snapshot of Earth. Earth's image was a single pale blue pixel, its color caused by the Rayleigh scattering of sunlight in the water of our oceans. Earth is a water planet, and this is the color of life. No matter how far we travel on our planet, no matter how high or deep, if we find liquid water, we find some form of life that manages to survive there. And yet there is a cruel irony. Water in its solid crystalline form is hostile to life. Organisms can roost in geysers, wallow in brine and gulp down acid, but they cowered from ice. The rigid ordering of water molecules in ice crystals expels impurities and tears organic tissue beyond repair. In fact, about the only good thing you can say about ice is that it gets out of the way: Its low density ensures that it floats and leaves the water dwelling creatures in peace. Recent discoveries have caused us to rethink this basic premise. New lines of evidence both observational and experimental - suggest that prebiotic organic compounds are not only comfortable in, but in fact had their origin in a peculiar form of solid water ice that is ubiquitous in interstellar space, but completely absent from Earth. Only recently have we been able to create even submicroscopic quantities of this ice in terrestrial laboratories, yet it constitutes the most abundant form of water in the universe. Interstellar ice is a far cry from the ice we are so familiar with on Earth. This interstellar ice has no crystalline structure, and despite the fact that its temperature is a scant few degrees above absolute zero (where all molecular motion ceases), it is highly reactive and can flow like water when exposed to radiation. It is in fact this ice's similarity to liquid water that allows it to participate in the creation of the very first organic compounds.

Blake, David↗

NASA NTRS1981

Voyager at Saturn

The spacecraft design and operations and mission results of the Voyager Project are reviewed with particular emphasis on the results of the Saturn encounters. The mission was undertaken by two spacecraft: Voyager 2, launched first on August 20, 1977 on a lower energy trajectory to Jupiter, Saturn, Uranus and Neptune; and Voyager 1, launched on September 5, 1977 on a higher energy trajectory to closer flybys of Jupiter and Saturn. The Voyager spacecraft make use of earlier Mariner and Viking Orbiter design concepts, with additional capabilities for solar independent power, long-range communications and autonomy as well as equipment for the 11 science investigations. The Voyager operations system consists of a ground data system, missions operations system, and support by the Mission Control and Computer Center and Deep Space Network. Among the results of the Jupiter encounter are data concerning the magnetospheric structure and atmospheric dynamics of the planet and the surface features of the Galilean satellites. The encounters with Saturn produced scientific data concerning wind speeds, auroral emissions, and radio emissions from the planet, the fine structure of the previously known and newly discovered rings, the surface features of the satellites and the atmospheric composition and conditions of Titan. Voyager 1 is presently making field and particle measurements on its flight into interstellar space, while Voyager 2 is headed for an encounter with Uranus in January 1986 and Neptune in August 1989.

Heacock, R. L.↗