Martin Elvis | Smithsonian Institution (original) (raw)
Papers by Martin Elvis
arXiv (Cornell University), Nov 21, 1996
New Astronomy Reviews, 2003
The Astrophysical Journal, 2012
Acta Astronautica, Sep 1, 2019
arXiv (Cornell University), Dec 2, 2016
arXiv: Earth and Planetary Astrophysics, 2019
In keeping with the Luxembourg government's initiative to support the future use of space res... more In keeping with the Luxembourg government's initiative to support the future use of space resources, ASIME 2018 was held in Belval, Luxembourg on April 16-17, 2018. The goal of ASIME 2018: Asteroid Intersections with Mine Engineering, was to focus on asteroid composition for advancing the asteroid in-space resource utilisation domain. What do we know about asteroid composition from remote-sensing observations? What are the potential caveats in the interpretation of Earth-based spectral observations? What are the next steps to improve our knowledge on asteroid composition by means of ground-based and space-based observations and asteroid rendez-vous and sample return missions? How can asteroid mining companies use this knowledge? ASIME 2018 was a two-day workshop of almost 70 scientists and engineers in the context of the engineering needs of space missions with in-space asteroid utilisation. The 21 Questions from the asteroid mining companies were sorted into the four asteroid s...
The lunar South pole likely contains significant amounts of water in the permanently shadowed cra... more The lunar South pole likely contains significant amounts of water in the permanently shadowed craters there. Extracting this water for life support at a lunar base or to make rocket fuel would take large amounts of power, of order Gigawatts. A natural place to obtain this power are the “Peaks of Eternal Light”, that lie a few kilometers away on the crater rims and ridges above the permanently shadowed craters. The amount of solar power that could be captured depends on how tall a tower can be built to support the photovoltaic panels. The low gravity, lack of atmosphere, and quiet seismic environment of the Moon suggests that towers could be built much taller than on Earth. Here we look at the limits to building tall concrete towers on the Moon. We choose concrete as the capital cost of transporting large masses of iron or carbon fiber to the Moon is presently so expensive that profitable operation of a power plant is unlikely. Concrete instead can be manufactured in situ from the lu...
The Peaks of Eternal Light (PELs), that are largely unshaded regions mostly at the lunar south po... more The Peaks of Eternal Light (PELs), that are largely unshaded regions mostly at the lunar south pole, have been suggested as a source of solar power for mining the water and other volatiles in the nearby permanently dark regions. As mining is a power-intensive activity, it is interesting to estimate the maximum solar power that could be generated at the PELs. Here we use average percentage illumination maps for a range of heights above the local topography from 2 m to 2 km to determine the total power available as a function of time of lunar day. Overshadowing of highly illuminated areas by towers placed in sunward locations (at a given time of day) limits the total power to much smaller values than the highly illuminated area would suggest. We find that for near-term realizable towers (up to 20 m), the upper limit to the time-averaged power available is ~55 MW at >70% illumination, and ~6 MW at >90% illumination. For the more distant future a maximum time-averaged power of ord...
Bulletin of the AAS, 2021
Journal of Space Safety Engineering, 2018
After two decades and more of delineating lunar geology from orbit, we now know that the Moon is ... more After two decades and more of delineating lunar geology from orbit, we now know that the Moon is far from undifferentiated magnificent desolation . Instead the maps from Clementine, LRO, Chandrayaan-1, GRAIL, and others have picked out numerous locations of especial interest. While many of these regions are widespread, other locations are quite small in area: the Peaks of Eternal Light near the poles, which are almost continuously illuminated by the Sun, cover only about 1 sq. km; the coldest of the cold traps at the poles (T \u3c 40 K), which are thought to contain volatile materials from the early solar system, cover only a few sq. km; the regions richest in thorium or in iron are also quite small. Whenever a scarce resource is found - be it a scientific resource or a commercial one - disputes will arise over how, and by whom, these resources should be exploited. Deciding how to resolve these disputes are policy questions. Once multiple players are involved they will need to be considered. The imminent prospect is for lunar landers from sovereign, philanthropic, and commercial. Hence these questions will need to be addressed soon. The goals of all these players will be diverse. They will include: lunar science, astrophysics, and commercial exploitation. Not all of these goals will be compatible. Hence an international approach to lunar regulation will be needed. We discuss the issues of justice and policy that are involved in any such regulatory framework
arXiv (Cornell University), Aug 2, 2016
Cornell University - arXiv, Feb 28, 2022
International Journal of Astrobiology, 2022
The controversial hypothesis that ‘Oumuamua (1I/2017 U1) was an alien craft dominated by a solar ... more The controversial hypothesis that ‘Oumuamua (1I/2017 U1) was an alien craft dominated by a solar sail is considered using known physics for the two possible cases: controlled and uncontrolled flight. The reliability engineering challenges for an artefact designed to operate for ~105–106 year are also considerable. All three areas generate research programmes going forward. The uncontrolled case could be either ‘anonymous METI’ (messaging extraterrestrial intelligence) or ‘inadvertent METI’. In the controlled case the nature of the origin star, trajectory guidance from the origin star to the Sun, and the identity of a destination star are all undecided. The ‘controlled’ case has more strikes against it than the ‘uncontrolled’ case, but neither suffers a knock-out blow, as yet. Some of the issues turn out not to be major obstacles to the alien craft hypothesis, but others weaken the case for it. Most, however, imply new studies. Some of these, e.g. intercept missions for new interstel...
Understanding the thermal equilibrium (stability) curve may offer insights into the nature of the... more Understanding the thermal equilibrium (stability) curve may offer insights into the nature of the warm absorbers often found in active galactic nuclei. Its shape is determined by factors like the spectrum of the ionizing continuum and the chemical composition of the gas. We find that the stability curves obtained under the same set of the above mentioned physical factors, but using recently derived dielectronic recombination rates, give significantly different results, especially in the regions corresponding to warm absorbers, leading to different physical predictions. Using the current rates we find a larger probability of having thermally stable warm absorber at 10^5 than previous predictions and also a greater possibility for its multiphase nature. the results obtained with the current dielectronic recombination rate coefficients are more reliable because the warm absorber models along the stability curve have computed coefficient values, whereas previous calculations relied on g...
We have developed a consistent analytical model to describe the observed evolution of the quasar ... more We have developed a consistent analytical model to describe the observed evolution of the quasar luminosity function. Our model combines black hole mass distributions based on the Press - Schechter theory of the structure formation in the Universe with quasar luminosity functions resulting from a physics-based emission model that takes into account the time-dependent phenomena occurring in the accretion disks. Quasar evolution and CDM models are mutually constraining, therefore our model gives an estimation of the exponent, n, of the power spectrum, P(k), which is found to be -1.8 < n < -1.6. We were able to reject a generally assumed hypothesis of a constant ratio between Dark Matter Halo and the Black Hole mass, since the observed data could not be fitted under this assumption. We found that the relation between the Dark Matter Halos and Black Hole masses is better described by M_BH=M_DMH^0.668. This model provides a reasonable fit to the observed quasar luminosity function ...
The radiation from the central regions of active galactic nuclei, including that from the accreti... more The radiation from the central regions of active galactic nuclei, including that from the accretion disk surrounding the black hole, is likely to peak in the extreme ultraviolet ∼ 13 -100 eV. However, due to Galactic absorption, we are limited to constrain the physical properties, i.e. the black hole mass and the accretion rate, from what observations we have below ∼ 10 eV or above ∼ 100 eV. In this paper we predict the thermal and ionization states of warm absorbers as a function of the shape of the unobservable continuum. In particular we model an accretion disk at kT_in∼ 10 eV and a soft excess at kT_se∼ 150 eV. The warm absorber, which is the highly ionized gas along the line of sight to the continuum, shows signatures in the ∼ 0.3 - 2 keV energy range consisting of numerous absorption lines and edges of various ions, some of the prominent ones being H- and He-like oxygen, neon, magnesium and silicon. We find that the properties of the warm absorber are significantly influenced ...
Astrophysics and planetary science are in crisis. The large missions we need for the next generat... more Astrophysics and planetary science are in crisis. The large missions we need for the next generation of observations cost too much to let us do more than one at a time. This spreads the science out onto a generational timescale, inhibiting progress in both fields. There are two escape paths. In the long run, but still well within our planning horizon, commercial space will bring mission costs down substantially allowing parallel missions at multiple wavelengths or to multiple destinations. In the short run, adopting prudent principles for designing a research program will let us maintain vitality in the field by retaining breadth at a modest cost in depth.
arXiv (Cornell University), Nov 21, 1996
New Astronomy Reviews, 2003
The Astrophysical Journal, 2012
Acta Astronautica, Sep 1, 2019
arXiv (Cornell University), Dec 2, 2016
arXiv: Earth and Planetary Astrophysics, 2019
In keeping with the Luxembourg government's initiative to support the future use of space res... more In keeping with the Luxembourg government's initiative to support the future use of space resources, ASIME 2018 was held in Belval, Luxembourg on April 16-17, 2018. The goal of ASIME 2018: Asteroid Intersections with Mine Engineering, was to focus on asteroid composition for advancing the asteroid in-space resource utilisation domain. What do we know about asteroid composition from remote-sensing observations? What are the potential caveats in the interpretation of Earth-based spectral observations? What are the next steps to improve our knowledge on asteroid composition by means of ground-based and space-based observations and asteroid rendez-vous and sample return missions? How can asteroid mining companies use this knowledge? ASIME 2018 was a two-day workshop of almost 70 scientists and engineers in the context of the engineering needs of space missions with in-space asteroid utilisation. The 21 Questions from the asteroid mining companies were sorted into the four asteroid s...
The lunar South pole likely contains significant amounts of water in the permanently shadowed cra... more The lunar South pole likely contains significant amounts of water in the permanently shadowed craters there. Extracting this water for life support at a lunar base or to make rocket fuel would take large amounts of power, of order Gigawatts. A natural place to obtain this power are the “Peaks of Eternal Light”, that lie a few kilometers away on the crater rims and ridges above the permanently shadowed craters. The amount of solar power that could be captured depends on how tall a tower can be built to support the photovoltaic panels. The low gravity, lack of atmosphere, and quiet seismic environment of the Moon suggests that towers could be built much taller than on Earth. Here we look at the limits to building tall concrete towers on the Moon. We choose concrete as the capital cost of transporting large masses of iron or carbon fiber to the Moon is presently so expensive that profitable operation of a power plant is unlikely. Concrete instead can be manufactured in situ from the lu...
The Peaks of Eternal Light (PELs), that are largely unshaded regions mostly at the lunar south po... more The Peaks of Eternal Light (PELs), that are largely unshaded regions mostly at the lunar south pole, have been suggested as a source of solar power for mining the water and other volatiles in the nearby permanently dark regions. As mining is a power-intensive activity, it is interesting to estimate the maximum solar power that could be generated at the PELs. Here we use average percentage illumination maps for a range of heights above the local topography from 2 m to 2 km to determine the total power available as a function of time of lunar day. Overshadowing of highly illuminated areas by towers placed in sunward locations (at a given time of day) limits the total power to much smaller values than the highly illuminated area would suggest. We find that for near-term realizable towers (up to 20 m), the upper limit to the time-averaged power available is ~55 MW at >70% illumination, and ~6 MW at >90% illumination. For the more distant future a maximum time-averaged power of ord...
Bulletin of the AAS, 2021
Journal of Space Safety Engineering, 2018
After two decades and more of delineating lunar geology from orbit, we now know that the Moon is ... more After two decades and more of delineating lunar geology from orbit, we now know that the Moon is far from undifferentiated magnificent desolation . Instead the maps from Clementine, LRO, Chandrayaan-1, GRAIL, and others have picked out numerous locations of especial interest. While many of these regions are widespread, other locations are quite small in area: the Peaks of Eternal Light near the poles, which are almost continuously illuminated by the Sun, cover only about 1 sq. km; the coldest of the cold traps at the poles (T \u3c 40 K), which are thought to contain volatile materials from the early solar system, cover only a few sq. km; the regions richest in thorium or in iron are also quite small. Whenever a scarce resource is found - be it a scientific resource or a commercial one - disputes will arise over how, and by whom, these resources should be exploited. Deciding how to resolve these disputes are policy questions. Once multiple players are involved they will need to be considered. The imminent prospect is for lunar landers from sovereign, philanthropic, and commercial. Hence these questions will need to be addressed soon. The goals of all these players will be diverse. They will include: lunar science, astrophysics, and commercial exploitation. Not all of these goals will be compatible. Hence an international approach to lunar regulation will be needed. We discuss the issues of justice and policy that are involved in any such regulatory framework
arXiv (Cornell University), Aug 2, 2016
Cornell University - arXiv, Feb 28, 2022
International Journal of Astrobiology, 2022
The controversial hypothesis that ‘Oumuamua (1I/2017 U1) was an alien craft dominated by a solar ... more The controversial hypothesis that ‘Oumuamua (1I/2017 U1) was an alien craft dominated by a solar sail is considered using known physics for the two possible cases: controlled and uncontrolled flight. The reliability engineering challenges for an artefact designed to operate for ~105–106 year are also considerable. All three areas generate research programmes going forward. The uncontrolled case could be either ‘anonymous METI’ (messaging extraterrestrial intelligence) or ‘inadvertent METI’. In the controlled case the nature of the origin star, trajectory guidance from the origin star to the Sun, and the identity of a destination star are all undecided. The ‘controlled’ case has more strikes against it than the ‘uncontrolled’ case, but neither suffers a knock-out blow, as yet. Some of the issues turn out not to be major obstacles to the alien craft hypothesis, but others weaken the case for it. Most, however, imply new studies. Some of these, e.g. intercept missions for new interstel...
Understanding the thermal equilibrium (stability) curve may offer insights into the nature of the... more Understanding the thermal equilibrium (stability) curve may offer insights into the nature of the warm absorbers often found in active galactic nuclei. Its shape is determined by factors like the spectrum of the ionizing continuum and the chemical composition of the gas. We find that the stability curves obtained under the same set of the above mentioned physical factors, but using recently derived dielectronic recombination rates, give significantly different results, especially in the regions corresponding to warm absorbers, leading to different physical predictions. Using the current rates we find a larger probability of having thermally stable warm absorber at 10^5 than previous predictions and also a greater possibility for its multiphase nature. the results obtained with the current dielectronic recombination rate coefficients are more reliable because the warm absorber models along the stability curve have computed coefficient values, whereas previous calculations relied on g...
We have developed a consistent analytical model to describe the observed evolution of the quasar ... more We have developed a consistent analytical model to describe the observed evolution of the quasar luminosity function. Our model combines black hole mass distributions based on the Press - Schechter theory of the structure formation in the Universe with quasar luminosity functions resulting from a physics-based emission model that takes into account the time-dependent phenomena occurring in the accretion disks. Quasar evolution and CDM models are mutually constraining, therefore our model gives an estimation of the exponent, n, of the power spectrum, P(k), which is found to be -1.8 < n < -1.6. We were able to reject a generally assumed hypothesis of a constant ratio between Dark Matter Halo and the Black Hole mass, since the observed data could not be fitted under this assumption. We found that the relation between the Dark Matter Halos and Black Hole masses is better described by M_BH=M_DMH^0.668. This model provides a reasonable fit to the observed quasar luminosity function ...
The radiation from the central regions of active galactic nuclei, including that from the accreti... more The radiation from the central regions of active galactic nuclei, including that from the accretion disk surrounding the black hole, is likely to peak in the extreme ultraviolet ∼ 13 -100 eV. However, due to Galactic absorption, we are limited to constrain the physical properties, i.e. the black hole mass and the accretion rate, from what observations we have below ∼ 10 eV or above ∼ 100 eV. In this paper we predict the thermal and ionization states of warm absorbers as a function of the shape of the unobservable continuum. In particular we model an accretion disk at kT_in∼ 10 eV and a soft excess at kT_se∼ 150 eV. The warm absorber, which is the highly ionized gas along the line of sight to the continuum, shows signatures in the ∼ 0.3 - 2 keV energy range consisting of numerous absorption lines and edges of various ions, some of the prominent ones being H- and He-like oxygen, neon, magnesium and silicon. We find that the properties of the warm absorber are significantly influenced ...
Astrophysics and planetary science are in crisis. The large missions we need for the next generat... more Astrophysics and planetary science are in crisis. The large missions we need for the next generation of observations cost too much to let us do more than one at a time. This spreads the science out onto a generational timescale, inhibiting progress in both fields. There are two escape paths. In the long run, but still well within our planning horizon, commercial space will bring mission costs down substantially allowing parallel missions at multiple wavelengths or to multiple destinations. In the short run, adopting prudent principles for designing a research program will let us maintain vitality in the field by retaining breadth at a modest cost in depth.