As we continue searching for exoplanets, we wonder if life and technological species capable of communicating with us exists on any of them. As geoscientists, we can also wonder how important is the presence or absenc...As we continue searching for exoplanets, we wonder if life and technological species capable of communicating with us exists on any of them. As geoscientists, we can also wonder how important is the presence or absence of plate tectonics for the evolution of technological species. This essay considers this question, focusing on tectonically active roclw （silicate） planets, like Earth, Venus, and Mars. The development of technological species on Earth provides key insights for understanding evolution on exoplanets, including the likely role that plate tectonics may play. An Earth-sized silicate planet is likely to experience several tectonic styles over its lifetime, as it cools and its lithosphere thickens, strengthens, and becomes denser. These include magma ocean, various styles of stagnant lid, and perhaps plate tectonics. Abundant liquid water favors both life and plate tectonics. Ocean is required for early evolution of diverse single-celled organisms, then colonies of cells which specialized further to form guts, ap- pendages, and sensory organisms up to the complexity of fish （central nervous system, appendages, eyes）. Large expanses of dry land also begin in the ocean, today produced above subduction zones in juvenile arcs and by their coalescence to form continents, although it is not clear that plate tectonics was required to create continental crust on Earth. Dry land of continents is required for further evolution of technological species, where modification of appendages for grasping and manipulating, and improve- ment of eyes and central nervous system could be perfected. These bioassets allowed intelligent crea- tures to examine the night sky and wonder, the beginning of abstract thinking, including religion and science. Technology arises from the exigencies of daily living such as tool-making, agriculture, clothing, and weapons, but the pace of innovation accelerates once it is allied with science. Finally, the importance of plate tectonics for developing a technological species is examined via a thought experiment using two otherwise identical planets： one with plate tectonics and the other without. A planet with oceans, continents, and plate tectonics maximizes opportunities for speciation and natural selection, whereas a similar planet without plate tectonics provides fewer such opportunities. Plate tectonics exerts envi- ronmental pressures that drive evolution without being capable of extinguishing all life. Plate tectonic processes such as the redistribution of continents, growth of mountain ranges, formation of land bridges, and opening and closing of oceans provide a continuous but moderate environmental pressure that stimulates populations to adapt and evolve. Plate tectonics may not be needed in order for life to begin, but evolution of technological species is favored on planets with oceans, continents, plate tectonics, and intermittently clear night sky.展开更多
Four future missions for deep space exploration and future space-based exoplanet surveys on habitable planets by 2030 are scheduled to be launched.Two Mars exploration missions are designed to investigate geological s...Four future missions for deep space exploration and future space-based exoplanet surveys on habitable planets by 2030 are scheduled to be launched.Two Mars exploration missions are designed to investigate geological structure,the material on Martian surface,and retrieve returned samples.The asteroids and main belt comet exploration is expected to explore two objects within 10 years.The small-body mission will aim to land on the asteroid and get samples return to Earth.The basic physical characteristics of the two objects will be obtained through the mission.The exploration of Jupiter system will characterize the environment of Jupiter and the four largest Moons and understand the atmosphere of Jupiter.In addition,we further introduce two space-based exoplanet survey by 2030,Miyin Program and Closeby Habitable Exoplanet Survey(CHES Mission).Miyin program aims to detect habitable exoplanets using interferometry,while CHES mission expects to discover habitable exoplanets orbiting FGK stars within 10 pc through astrometry.The above-mentioned missions are positively to achieve breakthroughs in the field of planetary science.展开更多
High-contrast imaging coronagraphs, used for the detection of exoplanets, have always adopted passive coronagraph optical components. It is therefore impossible to actively optimize the coronagraphs to achieve their b...High-contrast imaging coronagraphs, used for the detection of exoplanets, have always adopted passive coronagraph optical components. It is therefore impossible to actively optimize the coronagraphs to achieve their best performance. To solve this problem, we propose a novel high-contrast imaging coronagraph which combines a liquid crystal array （LCA） for active pupil apodization and a deformable mirror （DM） for phase correction. The LCA we use is an amplitude-only spatial light mod- ulator. The LCA is well calibrated and compensates for its amplitude non-uniformity and nonlinear intensity responsivity. We measured the imaging contrasts of the coron- agraph system with the LCA only and without the DM deployed. Imaging contrasts of 10-4 and 10-5 can be reached at an inner working angular distance of 2.5 and 5A/D, respectively. A simulation shows that the phase errors on the coronagraph pupil limit the contrast performance. The contrast could be further improved if a DM is deployed to correct the phase errors induced by the LCA and coronagraph optics.展开更多
Atmospheric escape is a key process controlling the long term evolution of planets. Radiative cooling competes for energy against atmospheric escape in planetary upper atmospheres. In this work, we use a population ba...Atmospheric escape is a key process controlling the long term evolution of planets. Radiative cooling competes for energy against atmospheric escape in planetary upper atmospheres. In this work, we use a population balance method and a Monte Carlo model to calculate the previously ignored emissions of metals(C, N, O and their ions) and compare them with radiative recombination of H II and Ly-α emission of H I, which are the most efficient cooling mechanisms currently recognized in the upper atmospheres of hot Jupiters.The results show that the emissions of C, N, O and their ions are strong non-linear functions of environmental parameters(temperature,density, etc.) and are likely to be efficient cooling mechanisms in the upper atmospheres of close-in exoplanets.展开更多
Atmospheric composition is an important indicator of habitability and life.The presence or absence of a large exomoon around an Earth-size exoplanet could have important consequences for planet climate stability.Thus ...Atmospheric composition is an important indicator of habitability and life.The presence or absence of a large exomoon around an Earth-size exoplanet could have important consequences for planet climate stability.Thus the detection of exomoons and retrieval of information regarding atmospheric composition of Earth-size exoplanets are important goals of future exoplanet observations.Here a data analysis method is developed to achieve both goals simultaneously,based on reflection spectra of exoplanet-exomoon systems.We show that the existence of exomoons,the size of exomoons,and the concentrations of some atomic and molecular species in the atmospheres of their hosting Earth-like exoplanets can be retrieved with high levels of reliability.In addition,the method can provide well-constrained fractions of basic surface types on the targets because of the characteristic spectral features of atmospheric species and surface types in the analyzed spectral range.展开更多
The transiting exoplanet system HAT-P-24 was observed by using CCD cameras at Yunnan Observatory and Hokoon Astronomical Centre, China in 2010 and 2012. In order to enhance the signal to noise ratio of transit events,...The transiting exoplanet system HAT-P-24 was observed by using CCD cameras at Yunnan Observatory and Hokoon Astronomical Centre, China in 2010 and 2012. In order to enhance the signal to noise ratio of transit events, the observed data are corrected for systematic errors according to Collier Cameron et al.＇s coarse de- correlation and Tamuz et al.＇s SYSREM algorithms. Three new complete transit light curves are analyzed by means of the Markov chain Monte Carlo technique, and the new physical parameters of the system are derived. They are consistent with the old ones from the discovered paper except for a new larger radius Rp = 1.364 Rj of HAT- P-24b, which confirms its inflated nature. By combining the five available epochs of mid-transit derived from complete transit light curves, the orbital period of HAT-P- 24b is refined to P = 3.3552479 d and no obvious transit timing variation signal can be found from these five transit events during 2010-2012.展开更多
This paper critically re-examines the anthropocentric“Goldilocks Zone”paradigm that has dominated the search for extraterrestrial life.As of 2024,more than 5,500 exoplanets have been identified,yet only about 2%are ...This paper critically re-examines the anthropocentric“Goldilocks Zone”paradigm that has dominated the search for extraterrestrial life.As of 2024,more than 5,500 exoplanets have been identified,yet only about 2%are located within the traditionally defined habitable zone(National Aeronautics and Space Administration(NASA)Exoplanet Archive,2024;Kane et al.,2023).Moreover,the discovery of extremophiles-organisms thriving in high-radiation,extreme heat,or vacuum environments-demonstrates that the boundaries of life far exceed Earth-like conditions(Rothschild&Mancinelli,2001).展开更多
1.Introduction As the planets closest to the outer edge of the solar system,Uranus and Neptune,namely that of ice giants,retained a significant amount of gas from the early stages of the solar system's formation.T...1.Introduction As the planets closest to the outer edge of the solar system,Uranus and Neptune,namely that of ice giants,retained a significant amount of gas from the early stages of the solar system's formation.This gas contains the physical conditions of the protostellar cloud and position information about planet formation,making ice giants important prototypes for studying both the solar system and exoplanets.展开更多
Our knowledge of the solar system encourages us to believe that we might expect exomoons to be present around some known exoplanets. With present hardware and existing optical astronomy methods, we do not expect to be...Our knowledge of the solar system encourages us to believe that we might expect exomoons to be present around some known exoplanets. With present hardware and existing optical astronomy methods, we do not expect to be able to find exomoons for at least 10 years, and even then, it will be a hard task to detect them. Using data from the Exoplanet Orbit Database（EOD） we find stars with Jovian exoplanets within 50 light years. Most of them will be fully accessible by the new radio telescope, the Five-hundred-meter Aperture Spherical radio Telescope（FAST）, under construction which is now in the test phase. We suggest radio astronomy based methods to search for possible exomoons around two exoplanets.展开更多
基金supported by a generous grant from the Gordon and Betty Moore Foundation
文摘As we continue searching for exoplanets, we wonder if life and technological species capable of communicating with us exists on any of them. As geoscientists, we can also wonder how important is the presence or absence of plate tectonics for the evolution of technological species. This essay considers this question, focusing on tectonically active roclw （silicate） planets, like Earth, Venus, and Mars. The development of technological species on Earth provides key insights for understanding evolution on exoplanets, including the likely role that plate tectonics may play. An Earth-sized silicate planet is likely to experience several tectonic styles over its lifetime, as it cools and its lithosphere thickens, strengthens, and becomes denser. These include magma ocean, various styles of stagnant lid, and perhaps plate tectonics. Abundant liquid water favors both life and plate tectonics. Ocean is required for early evolution of diverse single-celled organisms, then colonies of cells which specialized further to form guts, ap- pendages, and sensory organisms up to the complexity of fish （central nervous system, appendages, eyes）. Large expanses of dry land also begin in the ocean, today produced above subduction zones in juvenile arcs and by their coalescence to form continents, although it is not clear that plate tectonics was required to create continental crust on Earth. Dry land of continents is required for further evolution of technological species, where modification of appendages for grasping and manipulating, and improve- ment of eyes and central nervous system could be perfected. These bioassets allowed intelligent crea- tures to examine the night sky and wonder, the beginning of abstract thinking, including religion and science. Technology arises from the exigencies of daily living such as tool-making, agriculture, clothing, and weapons, but the pace of innovation accelerates once it is allied with science. Finally, the importance of plate tectonics for developing a technological species is examined via a thought experiment using two otherwise identical planets： one with plate tectonics and the other without. A planet with oceans, continents, and plate tectonics maximizes opportunities for speciation and natural selection, whereas a similar planet without plate tectonics provides fewer such opportunities. Plate tectonics exerts envi- ronmental pressures that drive evolution without being capable of extinguishing all life. Plate tectonic processes such as the redistribution of continents, growth of mountain ranges, formation of land bridges, and opening and closing of oceans provide a continuous but moderate environmental pressure that stimulates populations to adapt and evolve. Plate tectonics may not be needed in order for life to begin, but evolution of technological species is favored on planets with oceans, continents, plate tectonics, and intermittently clear night sky.
基金Supported by the B-type Strategic Priority Program of the Chinese Academy of Sciences(XDB41000000)the National Natural Science Foundation of China(11773081,11573073)CAS Interdisciplinary Innovation Team,Foundation of Minor Planets of the Purple Mountain Observatory and Youth Innovation Promotion Association。
文摘Four future missions for deep space exploration and future space-based exoplanet surveys on habitable planets by 2030 are scheduled to be launched.Two Mars exploration missions are designed to investigate geological structure,the material on Martian surface,and retrieve returned samples.The asteroids and main belt comet exploration is expected to explore two objects within 10 years.The small-body mission will aim to land on the asteroid and get samples return to Earth.The basic physical characteristics of the two objects will be obtained through the mission.The exploration of Jupiter system will characterize the environment of Jupiter and the four largest Moons and understand the atmosphere of Jupiter.In addition,we further introduce two space-based exoplanet survey by 2030,Miyin Program and Closeby Habitable Exoplanet Survey(CHES Mission).Miyin program aims to detect habitable exoplanets using interferometry,while CHES mission expects to discover habitable exoplanets orbiting FGK stars within 10 pc through astrometry.The above-mentioned missions are positively to achieve breakthroughs in the field of planetary science.
基金supported by the "Strategic Priority Research Program" of the Chinese Academy of Sciences(Grant No.XDA04070600)the National Natural Science Foundation of China(Grant Nos.11003031 and 10873024)+1 种基金as well as the National Astronomical Observatories' Special Fund for Astronomy-2009Part of the work described in this paper was carried out at California State University Northridge,with support from the National Science Foundation under Grant ATM-0841440
文摘High-contrast imaging coronagraphs, used for the detection of exoplanets, have always adopted passive coronagraph optical components. It is therefore impossible to actively optimize the coronagraphs to achieve their best performance. To solve this problem, we propose a novel high-contrast imaging coronagraph which combines a liquid crystal array （LCA） for active pupil apodization and a deformable mirror （DM） for phase correction. The LCA we use is an amplitude-only spatial light mod- ulator. The LCA is well calibrated and compensates for its amplitude non-uniformity and nonlinear intensity responsivity. We measured the imaging contrasts of the coron- agraph system with the LCA only and without the DM deployed. Imaging contrasts of 10-4 and 10-5 can be reached at an inner working angular distance of 2.5 and 5A/D, respectively. A simulation shows that the phase errors on the coronagraph pupil limit the contrast performance. The contrast could be further improved if a DM is deployed to correct the phase errors induced by the LCA and coronagraph optics.
基金supported by the National Natural Science Foundation of China (11661161014)Tsinghua University Initiative Science Research Program (523001028)
文摘Atmospheric escape is a key process controlling the long term evolution of planets. Radiative cooling competes for energy against atmospheric escape in planetary upper atmospheres. In this work, we use a population balance method and a Monte Carlo model to calculate the previously ignored emissions of metals(C, N, O and their ions) and compare them with radiative recombination of H II and Ly-α emission of H I, which are the most efficient cooling mechanisms currently recognized in the upper atmospheres of hot Jupiters.The results show that the emissions of C, N, O and their ions are strong non-linear functions of environmental parameters(temperature,density, etc.) and are likely to be efficient cooling mechanisms in the upper atmospheres of close-in exoplanets.
基金supported by the National Natural Science Foundation of China(1166116101,4164104)supported by the National Natural Science Foundation of China(41375102)+5 种基金support from the Spark Program,Tsinghua Universitysupport from "Institute National des Sciences de l’Univers"(INSU)the "Centre National de la Recherche Scientifique"(CNRS) and "Centre National d’Etude Spatiale"(CNES),through the "Programme National de Planétologie"the PICS programMEX/OMEGAMEX/PFS programs
文摘Atmospheric composition is an important indicator of habitability and life.The presence or absence of a large exomoon around an Earth-size exoplanet could have important consequences for planet climate stability.Thus the detection of exomoons and retrieval of information regarding atmospheric composition of Earth-size exoplanets are important goals of future exoplanet observations.Here a data analysis method is developed to achieve both goals simultaneously,based on reflection spectra of exoplanet-exomoon systems.We show that the existence of exomoons,the size of exomoons,and the concentrations of some atomic and molecular species in the atmospheres of their hosting Earth-like exoplanets can be retrieved with high levels of reliability.In addition,the method can provide well-constrained fractions of basic surface types on the targets because of the characteristic spectral features of atmospheric species and surface types in the analyzed spectral range.
基金supported by the National Natural Science Foundation of China(Grant No.10873031)the Chinese Academy of Sciences(KJCX2-YW-T24)
文摘The transiting exoplanet system HAT-P-24 was observed by using CCD cameras at Yunnan Observatory and Hokoon Astronomical Centre, China in 2010 and 2012. In order to enhance the signal to noise ratio of transit events, the observed data are corrected for systematic errors according to Collier Cameron et al.＇s coarse de- correlation and Tamuz et al.＇s SYSREM algorithms. Three new complete transit light curves are analyzed by means of the Markov chain Monte Carlo technique, and the new physical parameters of the system are derived. They are consistent with the old ones from the discovered paper except for a new larger radius Rp = 1.364 Rj of HAT- P-24b, which confirms its inflated nature. By combining the five available epochs of mid-transit derived from complete transit light curves, the orbital period of HAT-P- 24b is refined to P = 3.3552479 d and no obvious transit timing variation signal can be found from these five transit events during 2010-2012.
文摘This paper critically re-examines the anthropocentric“Goldilocks Zone”paradigm that has dominated the search for extraterrestrial life.As of 2024,more than 5,500 exoplanets have been identified,yet only about 2%are located within the traditionally defined habitable zone(National Aeronautics and Space Administration(NASA)Exoplanet Archive,2024;Kane et al.,2023).Moreover,the discovery of extremophiles-organisms thriving in high-radiation,extreme heat,or vacuum environments-demonstrates that the boundaries of life far exceed Earth-like conditions(Rothschild&Mancinelli,2001).
文摘1.Introduction As the planets closest to the outer edge of the solar system,Uranus and Neptune,namely that of ice giants,retained a significant amount of gas from the early stages of the solar system's formation.This gas contains the physical conditions of the protostellar cloud and position information about planet formation,making ice giants important prototypes for studying both the solar system and exoplanets.
基金supported by the Ministry of Education and Science of the Republic of Serbia through the project:176021‘Visible and Invisible Matter in Nearby Galaxies:Theory and Observations’
文摘Our knowledge of the solar system encourages us to believe that we might expect exomoons to be present around some known exoplanets. With present hardware and existing optical astronomy methods, we do not expect to be able to find exomoons for at least 10 years, and even then, it will be a hard task to detect them. Using data from the Exoplanet Orbit Database（EOD） we find stars with Jovian exoplanets within 50 light years. Most of them will be fully accessible by the new radio telescope, the Five-hundred-meter Aperture Spherical radio Telescope（FAST）, under construction which is now in the test phase. We suggest radio astronomy based methods to search for possible exomoons around two exoplanets.
