The surface temperature of Venus is a sensitive function of the abundances of greenhouse gases an... more The surface temperature of Venus is a sensitive function of the abundances of greenhouse gases and also of cloud structure. In previous work we have studied the climate impact of past and continued outgassing of greenhouse and cloud-forming gases (1) and tectonic signatures that may have resulted from volcanically induced climate change (2). These studies showed that in outgassing events where large amounts of both H2O and SO2 are released, the increased albedo that arises from thickening of the clouds can, to some extent, ameliorate the greenhouse warming expected from increased abundances of these IR absorbing gases. The largest warming typically arises several hundred million years after an outgassing event when most of the excess SO2 has been removed by reaction with surface minerals, but much of the atmospheric H2O remains (because it is removed by exospheric escape on longer time scales). This combination - enhanced H2O abundance with SO2 returned to 'normal' - leads to maximum warming because the cloud thickness, and thus the albedo, is limited by the availability of SO2, whereas IR absorption in CO2 windows by enhanced H2O can cause warming on the order of 100 K. It seems likely that large comet impacts should also produce such a situation. The atmosphere of Venus currently contains 7 x 1018 grams of water, about as much as in a 25 km diameter comet. Comets may have been an important contributor to the current water inventory on Venus. Much of this may have been supplied by a few large comet impacts in the last several hundred million years (3). We will report on new runs of our Venus Evolutionary Climate Model which simulate the volatile input from large comet impacts and investigate the climate effects of these events. Calculation will be done with cometary delivery alone, and in conjunction with various outgassing scenarios. This allows us to examine how the vulnerability of the Venusian climate system to impact induced climate change is affected by the relative timing of large magmatic and impact events. (1) Bullock, M.A., and D.H. Grinspoon, J. Geophys. Res. 101, 7521-7529, 1996. (2) Solomon, S.C., M. A. Bullock, and D. H. Grinspoon, Science, 286: 87-90, 1999. (3) Grinspoon, D.H. and J.S. Lewis, Icarus, 74, 21-35, 1988.
Exploring how life is distributed in the universe is an extraordinary interdisciplinary challenge... more Exploring how life is distributed in the universe is an extraordinary interdisciplinary challenge, but increasingly subject to testable hypotheses. Biology has emerged and flourished on at least one planet, and that renders the search for life elsewhere a scientific question. We cannot hope to travel to exoplanets in pursuit of other life even if we identify convincing biosignatures, but we do have direct access to planets and moons in our solar system. It is therefore a matter of deep astrobiological interest to study their histories and environments, whether or not they harbor life, and better understand the constraints that delimit the emergence and persistence of biology in any context. In this perspective, we argue that targeted chemistry- and biology-inspired experiments are informative to the development of instruments for space missions, and essential for interpreting the data they generate. This approach is especially useful for studying Venus because if it were an exoplane...
The composition, sizes and shapes of particles in the clouds of Venus have previously been studie... more The composition, sizes and shapes of particles in the clouds of Venus have previously been studied with a variety of in situ and remote sensor measurements. A number of major questions remain unresolved, however, motivating the development of an exploratory mission that will drop a small probe, instrumented with a single-particle autofluorescence nephelometer (AFN), into Venus’s atmosphere. The AFN is specifically designed to address uncertainties associated with the asphericity and complex refractive indices of cloud particles. The AFN projects a collimated, focused, linearly polarized, 440 nm wavelength laser beam through a window of the capsule into the airstream and measures the polarized components of some of the light that is scattered by individual particles that pass through the laser beam. The AFN also measures fluorescence from those particles that contain material that fluoresce when excited at a wavelength of 440 nm and emit at 470–520 nm. Fluorescence is expected from s...
Quick, D. H. Grinspoon, S. M. Hörst, E. S. Lakdawalla, K. E. Mandt, M. Milazzo, J. Piatek, L. M. ... more Quick, D. H. Grinspoon, S. M. Hörst, E. S. Lakdawalla, K. E. Mandt, M. Milazzo, J. Piatek, L. M. Prockter, E. G. Rivera-Valentin, A. S. Rivkin, C. Thomas, M. S. Tiscareno E. P. Turtle, J. A. Vertesi, N. Zellner, Planetary Science Institute (rathbun@psi.edu), Jet Propulsion Laboratory, California Institute of Technology, Center for Earth and Planetary Studies, Smithsonian Institution, Johns Hopkins University, The Planetary Society, Johns Hopkins Applied Physics Lab, USGS, Central Connecticut State University, Lunar and Planetary Institute, Arecibo Obsevatory, SETI Institute, Princeton Universiy, Albion College.
arXiv: Instrumentation and Methods for Astrophysics, 2019
The search for life in the universe is a major theme of astronomy and astrophysics for the next d... more The search for life in the universe is a major theme of astronomy and astrophysics for the next decade. Searches for technosignatures are complementary to searches for biosignatures, in that they offer an alternative path to discovery, and address the question of whether complex (i.e. technological) life exists elsewhere in the Galaxy. This approach has been endorsed in prior Decadal Reviews and National Academies reports, and yet the field still receives almost no federal support in the US. Because of this lack of support, searches for technosignatures, precisely the part of the search of greatest public interest, suffers from a very small pool of trained practitioners. A major source of this issue is institutional inertia at NASA, which avoids the topic as a result of decades-past political grandstanding, conflation of the effort with non-scientific topics such as UFOs, and confusion regarding the scope of the term "SETI." The Astro2020 Decadal should address this issue ...
Introduction: Venus’ clouds are responsible for nearly half of the energy absorbed from the sun b... more Introduction: Venus’ clouds are responsible for nearly half of the energy absorbed from the sun by the planet at wavelengths < 600 nm [1], yet the many identities of the absorbers responsible across the solar spectrum are still unknown. While more than a dozen possible absorbers have been proposed, no individual candidate satisfactorily explains the contrasts and temporal evolution of the cloud features. Recently, the potential for bioorganic contributions to Venus’ contrasts has been discussed [2]. The possibility of life was explored earlier by Morowitz and Sagan [3] and investigated further by Cockell [4] and discussed by Grinspoon [5], Grinspoon and Bullock [6] and others [7-9] Life could have evolved on Venus independently when it had liquid water on its surface with the same life sustaining biochemistry present in Earth’s early atmosphere [10, 11]. In the lower cloud layer (47.5-50.5 km), the estimated pH of the aerosols is ~0, the atmospheric pressure is ~ 1 atm, and tempe...
The surface temperature of Venus is a sensitive function of the abundances of greenhouse gases an... more The surface temperature of Venus is a sensitive function of the abundances of greenhouse gases and also of cloud structure. In previous work we have studied the climate impact of past and continued outgassing of greenhouse and cloud-forming gases (1) and tectonic signatures that may have resulted from volcanically induced climate change (2). These studies showed that in outgassing events where large amounts of both H2O and SO2 are released, the increased albedo that arises from thickening of the clouds can, to some extent, ameliorate the greenhouse warming expected from increased abundances of these IR absorbing gases. The largest warming typically arises several hundred million years after an outgassing event when most of the excess SO2 has been removed by reaction with surface minerals, but much of the atmospheric H2O remains (because it is removed by exospheric escape on longer time scales). This combination - enhanced H2O abundance with SO2 returned to 'normal' - leads to maximum warming because the cloud thickness, and thus the albedo, is limited by the availability of SO2, whereas IR absorption in CO2 windows by enhanced H2O can cause warming on the order of 100 K. It seems likely that large comet impacts should also produce such a situation. The atmosphere of Venus currently contains 7 x 1018 grams of water, about as much as in a 25 km diameter comet. Comets may have been an important contributor to the current water inventory on Venus. Much of this may have been supplied by a few large comet impacts in the last several hundred million years (3). We will report on new runs of our Venus Evolutionary Climate Model which simulate the volatile input from large comet impacts and investigate the climate effects of these events. Calculation will be done with cometary delivery alone, and in conjunction with various outgassing scenarios. This allows us to examine how the vulnerability of the Venusian climate system to impact induced climate change is affected by the relative timing of large magmatic and impact events. (1) Bullock, M.A., and D.H. Grinspoon, J. Geophys. Res. 101, 7521-7529, 1996. (2) Solomon, S.C., M. A. Bullock, and D. H. Grinspoon, Science, 286: 87-90, 1999. (3) Grinspoon, D.H. and J.S. Lewis, Icarus, 74, 21-35, 1988.
Exploring how life is distributed in the universe is an extraordinary interdisciplinary challenge... more Exploring how life is distributed in the universe is an extraordinary interdisciplinary challenge, but increasingly subject to testable hypotheses. Biology has emerged and flourished on at least one planet, and that renders the search for life elsewhere a scientific question. We cannot hope to travel to exoplanets in pursuit of other life even if we identify convincing biosignatures, but we do have direct access to planets and moons in our solar system. It is therefore a matter of deep astrobiological interest to study their histories and environments, whether or not they harbor life, and better understand the constraints that delimit the emergence and persistence of biology in any context. In this perspective, we argue that targeted chemistry- and biology-inspired experiments are informative to the development of instruments for space missions, and essential for interpreting the data they generate. This approach is especially useful for studying Venus because if it were an exoplane...
The composition, sizes and shapes of particles in the clouds of Venus have previously been studie... more The composition, sizes and shapes of particles in the clouds of Venus have previously been studied with a variety of in situ and remote sensor measurements. A number of major questions remain unresolved, however, motivating the development of an exploratory mission that will drop a small probe, instrumented with a single-particle autofluorescence nephelometer (AFN), into Venus’s atmosphere. The AFN is specifically designed to address uncertainties associated with the asphericity and complex refractive indices of cloud particles. The AFN projects a collimated, focused, linearly polarized, 440 nm wavelength laser beam through a window of the capsule into the airstream and measures the polarized components of some of the light that is scattered by individual particles that pass through the laser beam. The AFN also measures fluorescence from those particles that contain material that fluoresce when excited at a wavelength of 440 nm and emit at 470–520 nm. Fluorescence is expected from s...
Quick, D. H. Grinspoon, S. M. Hörst, E. S. Lakdawalla, K. E. Mandt, M. Milazzo, J. Piatek, L. M. ... more Quick, D. H. Grinspoon, S. M. Hörst, E. S. Lakdawalla, K. E. Mandt, M. Milazzo, J. Piatek, L. M. Prockter, E. G. Rivera-Valentin, A. S. Rivkin, C. Thomas, M. S. Tiscareno E. P. Turtle, J. A. Vertesi, N. Zellner, Planetary Science Institute (rathbun@psi.edu), Jet Propulsion Laboratory, California Institute of Technology, Center for Earth and Planetary Studies, Smithsonian Institution, Johns Hopkins University, The Planetary Society, Johns Hopkins Applied Physics Lab, USGS, Central Connecticut State University, Lunar and Planetary Institute, Arecibo Obsevatory, SETI Institute, Princeton Universiy, Albion College.
arXiv: Instrumentation and Methods for Astrophysics, 2019
The search for life in the universe is a major theme of astronomy and astrophysics for the next d... more The search for life in the universe is a major theme of astronomy and astrophysics for the next decade. Searches for technosignatures are complementary to searches for biosignatures, in that they offer an alternative path to discovery, and address the question of whether complex (i.e. technological) life exists elsewhere in the Galaxy. This approach has been endorsed in prior Decadal Reviews and National Academies reports, and yet the field still receives almost no federal support in the US. Because of this lack of support, searches for technosignatures, precisely the part of the search of greatest public interest, suffers from a very small pool of trained practitioners. A major source of this issue is institutional inertia at NASA, which avoids the topic as a result of decades-past political grandstanding, conflation of the effort with non-scientific topics such as UFOs, and confusion regarding the scope of the term "SETI." The Astro2020 Decadal should address this issue ...
Introduction: Venus’ clouds are responsible for nearly half of the energy absorbed from the sun b... more Introduction: Venus’ clouds are responsible for nearly half of the energy absorbed from the sun by the planet at wavelengths < 600 nm [1], yet the many identities of the absorbers responsible across the solar spectrum are still unknown. While more than a dozen possible absorbers have been proposed, no individual candidate satisfactorily explains the contrasts and temporal evolution of the cloud features. Recently, the potential for bioorganic contributions to Venus’ contrasts has been discussed [2]. The possibility of life was explored earlier by Morowitz and Sagan [3] and investigated further by Cockell [4] and discussed by Grinspoon [5], Grinspoon and Bullock [6] and others [7-9] Life could have evolved on Venus independently when it had liquid water on its surface with the same life sustaining biochemistry present in Earth’s early atmosphere [10, 11]. In the lower cloud layer (47.5-50.5 km), the estimated pH of the aerosols is ~0, the atmospheric pressure is ~ 1 atm, and tempe...
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