Habitable zone for complex life
This article or section possibly contains synthesis of material that does not verifiably mention or relate to the main topic. (February 2024) |
A Habitable Zone for Complex Life (HZCL) is a range of distances from a star suitable for complex aerobic life. Different types of limitations preventing complex life give rise to different zones.[1] Conventional habitable zones are based on compatibility with water.[2] Most zones start at a distance from the host star and then end at a distance farther from the star. A planet would need to orbit inside the boundaries of this zone. With multiple zonal constraints, the zones would need to overlap for the planet to support complex life. The requirements for bacterial life produce much larger zones than those for complex life, which requires a very narrow zone.[3][4][5]
Exoplanets
[edit]The first confirmed exoplanets was discovered in 1992, several planets orbiting the pulsar PSR B1257+12.[6] Since then the list of exoplanets has grown to the thousands.[7] Most exoplanets are hot Jupiter planets, that orbit very close the star.[8] Many exoplanets are super-Earths, that could be a gas dwarf or large rocky planet, like Kepler-442b at a mass 2.36 times Earths.[9]
Star
[edit]Unstable stars are young and old stars, or very large or small stars. Unstable stars have changing solar luminosity that changes the size of the life habitable zones. Unstable stars also produce extreme solar flares and coronal mass ejections. Solar flares and coronal mass ejections can strip away a planet's atmosphere that is not replaceable. Thus life habitable zones require and very stable star like the Sun, at ±0.1% solar luminosity change.[10][11] Finding a stable star, like the Sun, is the search for a solar twin, with solar analogs that have been found.[12] Proper star metallicity, size, mass, age, color, and temperature are also very important to having low luminosity variations.[13][14][15] The Sun is unique as it is metal rich for its age and type, a G2V star. The Sun is currently in its most stable stage and has the correct metallicity to make it very stable.[16] Dwarf stars (red dwarf/orange dwarf/brown dwarf/subdwarf) are not only unstable, but also emit low energy, so the habitable zone is very close to the star and planets become tidally locked on the timescales needed for the development of life.[17] Giant stars (subgiant/giant star/red giant/red supergiant) are unstable and emit high energy, so the habitable zone is very far from the star.[18] Multiple-star systems are also very common and are not suitable for complex life, as the planet orbit would be unstable due to multiple gravitational forces and solar radiation. Liquid water is possible in Multiple-star systems.[19][20][21][22]
Named habitable zones
[edit]A conventional habitable zone is defined by liquid water.
- Habitable zone (HZ) (also called the circumstellar habitable zone), the orbit around a star that would allow liquid water to remain for a short period of time (a given period of time) on at least a small part of the planet's surface. Thus within the HZ, water, (H2O) is between 0 °C (32 °F; 273 K) and 100 °C (212 °F; 373 K) temperature.[23][24][25] This zone is a temperature zone, set by the star's radiation and distance from the star. In the Solar System the planet Mars is just at the outer boundary of the habitable zone. The planet Venus is at the inner edge of the habitable zone, but due to its thick atmosphere it has no water. The HZ includes planets with elliptic orbits; such planets might orbit into and out of the HZ. When a planet moves out of the HZ, all its water would freeze to ice on the outside of the HZ, and/or all water would become steam on the inner side. The HZ could be defined as the region where bacteria, a form of life, could possibly survive for a short period of time. The HZ is also sometimes called the "Goldilocks" zone.
- Optimistic habitable zone (OHZ): a zone where liquid surface water could have been on a planet at some time in its past history. This zone would be larger than the HZ. Mars is an example of a planet in the OHZ.: it is just beyond the HZ today, but had liquid water for a short time span before the Mars carbonate catastrophe, some 4 billion years ago.[26][27]
- Continuously habitable zone (CHZ): a zone where liquid water persists on the surface of a planet for years. This requires a near-circular planetary orbit and a stable star. The zone may be much smaller than the habitable zone.[28][26]
- Conservative habitable zone: a zone where liquid surface water remains on a planet over a long time span, as on Earth. This might also need a greenhouse effect provided by gases such as CO2 and water vapor to maintain the correct temperature. Rayleigh scattering would also be needed.[26][11]
Named habitable zones for complex life
[edit]Over time and with more research, astronomers, cosmologists and astrobiologist have discovered more parameters needed for life. Each parameter could have a corresponding zone. Some of the named zones include:[29][30]
- Ultraviolet habitable zone: a zone where the ultraviolet (UV) radiation from a star is neither too weak nor too strong for life to exist.[31] Life needs the correct amount of ultraviolet for synthesis of biochemicals. The extent of the zone depends on the amount of ultraviolet radiation from the star, the range of UV wavelengths, the age of the star, and the atmosphere of the planet. In humans UV is used to produce vitamin D.[32][33] Extreme ultraviolet (EUV) can cause atmospheric loss.[10]
- Photosynthetic habitable zone: a zone where both long-term liquid water and oxygenic photosynthesis can occur.[34]
- Tropospheric habitable zone, or ozone habitable zone: a zone where the planet would have the correct amount of ozone needed for life. Inhaling too much ozone causes inflammation and irritation,[35] whereas too little troposphere ozone would produce biochemical smog. On Earth, the troposphere ozone is part of the ground-level ozone protection. Tropospheric ozone is formed by the interaction of ultraviolet light with hydrocarbons and nitrogen oxides.[2][36][37]
- Planet rotation rate habitable zone: the zone where a planet's rotation rate is best for life. If rotation is too slow, the day/night temperature difference is too great. The rotation rate also changes the planet's reflectivity[clarification needed] and thus temperature. A fast rotation rate increases wind speed on the planet. The rotation rate affects the planet's clouds and their reflectivity. Slowing the rotation rate changes cloud distributions, cloud altitudes, and cloud opacities. These changes in the clouds changes the temperature of the planet. A high rotation rate also can cause continuous, very fast winds[quantify] on the surface.[38][39][40]
- Planet rotation axis tilt habitable zone, or obliquity habitable zone: the region where a stable axial tilt for a planet's rotation is maintained.[41] Earth's axis is tilted 23.5°; this gives seasons, providing snow and ice that can melt to provide water run off in the summer.[42][43] Obliquity has a major impact on a planet's temperature, thus its habitable zone.[44][45][46][47]
- Tidal habitable zone. Planets too close to the star become tidally locked. The mass of the star and the distance from the star set the tidal habitable zone. A planet tidally locked has one side of the planet facing the star, this side would be very hot. The face away from the star would be well below freezing. A planet too close to the star will also have tidal heating from the star. Tidal heating can vary the planet's orbital eccentricity. Too far from the star and the planet will not receive enough solar heat.[48][49][50]
- Astrosphere habitable zone: the zone in which a planet's astrosphere will be strong enough to protect the planet from the solar wind and cosmic rays. The astrosphere must be long lasting to protect the planet. Mars lost its water and most of its atmosphere after the losing its magnetic field and Mars carbonate catastrophe event.[51][52] Star-Sun's solar wind is made of charged particles, including plasma, electrons, protons and alpha particles. The solar wind is different for each star. Earth's magnetic field is very large and has protected Earth since its formation.[53][54][55]
- Atmosphere electric field habitable zone: the place in which the ambipolar electric field is correct for the planet's electric field to help ions overcome gravity.[56][failed verification] The planet's ionosphere must be correct to protect against the loss of the atmosphere. This is addition to a strong magnetic field to protect against the solar wind stripping away the atmosphere and water into outer space.[57][58][59]
- Orbital eccentricity habitable zone: the zone in which planets maintain a nearly circular orbit. As orbits with eccentricity have the planets move in and out of the habitable zones.[60] In the solar system, the grand tack hypothesis proposes the theory of the unique placement of the gas giants, the solar system belts and the planets near circular orbits.[61][62][63]
- Coupled planet-moon - Magnetosphere habitable zone: the zone that planet's moon and the planet's core produce a strong magnetosphere, magnetic field to protect against the solar wind stripping away the planet's atmosphere and water into outer space. Just as Mars had a magnetic field for a short time. Earth's Moon had a large magnetosphere for several hundred million years after its formation, as proposed in a 2020 study by Saied Mighani. The Moon's magnetosphere would have given added protection of Earth's atmosphere as the early Sun was not as stable as it today. In 2020, James Green modeled the coupled planet-moon-magnetosphere habitable zone. The modeling showed a coupled planet–moon magnetosphere that would give planet the protection from stellar wind in the early Solar System. In the case of Earth, the Moon was closer to Earth in the early formation of the solar system, giving added protection. This protection was needed then as the Sun was less stable.[10][64]
- Pressure-dependent habitable zone: the zone in which planets may have the correct atmospheric pressure to have liquid surface water. With a low atmospheric pressure, the temperature at which water boils is much lower, and at pressures below that of the triple point, liquid water cannot exist.[65][66] The average surface pressure on Mars today is close to that of the triple point of water; thus, liquid water cannot exist there.[67][68] Planets with high-pressure atmospheres may have liquid surface water, but life forms would have difficulty with respiratory systems at high-pressure[quantify] atmospheres.[69][70]
- Galactic habitable zone (GHZ): The GHZ, also called the Galactic Goldilocks zone, is the place in a galaxy in which heavy elements needed for a rocky planet and life are present, but also a place where strong cosmic rays will not kill life and strip the atmosphere off the planet. The term Goldilocks zone is used, as it is a fine balance between the two sites (heavy element and strong cosmic rays). Galactic habitable zone is the place a planet will have the needed parameters to support life. Not all galaxies are able to support life.[71] In many galaxies, life-killing events such as gamma-ray bursts can occur. About 90% of galaxies have long and frequent gamma ray bursts, thus no life. Cosmic rays pose a threat to life. Galaxies with many stars too close together or without any dust protection also are not hospitable for life. Irregular galaxies and other small galaxies do not have enough heavy elements. Elliptical galaxies are full of lethal radiation and lack heavy elements. Large spiral galaxies, like the Milky Way, have the heavy element needs for life at its center and out to about half distance from center bar.[72] Not all large spiral galaxies are the same, spiral galaxies with too much active star formation can kill the galaxy and life.[73][74] Too little star formation and the spiral arms will collapse.[75] Not all spiral galaxies have the correct galactic ram pressure stripping parameters; too much ram pressure can deplete the galaxy of gas and thus end star formation. The Milky Way is a barred spiral galaxy, the bar is important to star formation and metallicity of the galaxy's stars and planets. Barred spiral galaxy, must have stable arms with the just right star formation. Bars galaxies are in about 65% of spiral galaxies, but most have too much star formation.[76] Peculiar galaxies lack stable spiral arms,[77] while irregular galaxies contain too many new stars and lack heavy elements.[78][79] Unbarred spiral galaxy, do not correct star formation and metallicity for a galactic goldilocks zone.[76][80] For long term life on a planet, the spiral arms must be stable for a long period of time, as in the Milky Way. The spiral arms must not be too close to each other, or there will be too much ultraviolet radiation. If the planet moves into or across a spiral arm the orbits of the planets could change, from gravitational disturbances. Movement across a spiral arms also would cause deadly asteroid impacts and high radiation.[81][82][83] The planet must be in the correct place in the spiral galaxy: near the galactic center, radiation and gravitational forces are too great for life, whereas the outskirts of a spiral galaxy are metal-poor. The Sun in 28,000 light years from the center bar, in the galactic Goldilocks zone. At this distance, the Sun revolves in the galaxy at the same rate as the spiral-arm rotation, thus minimizing arm crossings.[84][16][85]
- Supergalactic habitable zone: a place in a supercluster of galaxies that can provide for habitability of planets. The supergalactic habitable zone takes into account events in galaxies that can end habitability not only in a galaxy, but all galaxies nearby, such as galaxies merging, active galactic nucleus, starburst galaxy, supermassive black holes and merging black holes, all which output intense radiation. The supergalactic habitable zone also takes into account the abundance of various chemical elements in the galaxy, as not all galaxies or regions within have all the needed elements for life.[86][87][88][89]
- Habitable zone for complex life (HZCL): the place that all the life habitable zones overlap for a long period of time, as in the Solar System.[90] The list of habitable zones for complex life has grown longer with increasing understanding of the Universe, galaxies, and the Solar System.[91][92][93][94] Complex life is normally defined as eukaryote life forms, including all animals, plants, fungi, and most unicellular organisms. Simple life forms are normally defined as prokaryotes.[95]
Other orbital-distance related factors
[edit]Some factors that depend on planetary distance and may limit complex aerobic life have not been given zone names. These include:
- Milankovitch cycle The Milankovitch cycle and ice age have been key is shaping Earth.[96][97] Life on Earth today is using water melting from the last ice age. The ice ages cannot be too long or too cold for life to survive. Milankovitch cycle has an impact on the planet's obliquity also.[98][99][100]
Life
[edit]Life on Earth is carbon-based. However, some theories suggest that life could be based on other elements in the periodic table.[101] Other elements proposed have been silicon, boron, arsenic, ammonia, methane and others. As more research has been done on life on Earth, it has been found that only carbon's organic molecules have the complexity and stability to form life.[102][103][104] Carbon properties allows for complex chemical bonding that produces covalent bonds needed for organic chemistry. Carbon molecules are lightweight and relatively small in size. Carbon's ability to bond to oxygen, hydrogen, nitrogen, phosphorus, and sulfur (called CHNOPS) is key to life.[105] [106][107]
Gallery
[edit]-
Photosynthetic habitable zone has the need parameters for photosynthesis in plants. The carbohydrates produced are stored in or used by the plant. Photosynthesis is foundation of food on Earth
-
Troposphere habitable (Ozone habitable) zone as the correct atmospheric circulation and ozone for life. The Three Cell Model of the circulation of the planetary atmosphere of the Earth, of which the troposphere is the lowest layer.
-
Orbital eccentricity habitable zone is low enough orbital eccentricity to support life. Elliptic orbit by eccentricity
0.0 · 0.2 · 0.4 · 0.6 · 0.8
See also
[edit]- Exoplanet orbital and physical parameters
- Habitability of natural satellites – liquid water on a moon
- Habitability of yellow dwarf systems – liquid water on yellow dwarf star
- Habitability of red dwarf systems – liquid water on red dwarf star
- Planetary habitability in the Solar System – liquid water in our Solar System
- Habitability of binary star systems – liquid water on binary stars
- Habitability of F-type main-sequence star systems – liquid water on planets orbiting F-type stars
- Superhabitable planet – a hypothetical exoplanet
References
[edit]- ^ "Not All Habitable Zones Are Created Equal". www.spacedaily.com.
- ^ a b Schwieterman, Edward W.; Reinhard, Christopher T.; Olson, Stephanie L.; Harman, Chester E.; Lyons, Timothy W. (June 10, 2019). "A Limited Habitable Zone for Complex Life". The Astrophysical Journal. 878 (1): 19. arXiv:1902.04720. Bibcode:2019ApJ...878...19S. doi:10.3847/1538-4357/ab1d52.
- ^ "New Discovery Shows 'Habitable Zone for Complex Life' is Much More Narrow than Original Estimates – NASA". June 10, 2019.
- ^ Williams, Matt; Today, Universe. "Complex life might require a very narrow habitable zone". phys.org.
- ^ How do you form a habitable planet?, Georgia State University Research
- ^ Wolszczan, A.; Frail, D. A. (1992). "A planetary system around the millisecond pulsar PSR1257 + 12". Nature. 355 (6356): 145–147. Bibcode:1992Natur.355..145W. doi:10.1038/355145a0. S2CID 4260368.
- ^ "Exoplanet and Candidate Statistics". exoplanetarchive.ipac.caltech.edu.
- ^ "Orbital Evolution of planets in Extra-solar systems". users.auth.gr. 5 February 2024.
- ^ Valencia, V.; Sasselov, D. D.; O'Connell, R. J. (2007). "Radius and structure models of the first super-earth planet". The Astrophysical Journal. 656 (1): 545–551. arXiv:astro-ph/0610122. Bibcode:2007ApJ...656..545V. doi:10.1086/509800. S2CID 17656317.
- ^ a b c Green, James; Boardsen, Scott; Dong, Chuanfei (February 20, 2021). "Magnetospheres of Terrestrial Exoplanets and Exomoons: Implications for Habitability and Detection". The Astrophysical Journal Letters. 907 (2): L45. arXiv:2012.11694. Bibcode:2021ApJ...907L..45G. doi:10.3847/2041-8213/abd93a.
- ^ a b Brasch, Klaus R. (July 7, 2023). "Is Earth the only Goldilocks planet? | Astronomy.com".
- ^ "Solar Variability and Terrestrial Climate – NASA Science". science.nasa.gov.
- ^ "Stellar Luminosity Calculator". astro.unl.edu.
- ^ The Effects of Solar Variability on Earth's Climate: A Workshop Report. National Academies Press. November 12, 2012. doi:10.17226/13519. ISBN 978-0-309-26564-5.
- ^ "Most of Earth's twins aren't identical, or even close! | ScienceBlogs". scienceblogs.com.
- ^ a b "NASA Astrobiology". astrobiology.nasa.gov.
- ^ Barnes, Rory, ed. (2010). Formation and Evolution of Exoplanets. John Wiley & Sons. p. 248. ISBN 978-3527408962. Archived from the original on 2023-08-06. Retrieved 2016-08-16.
- ^ Voisey, Jon (February 23, 2011). "Plausibility Check - Habitable Planets around Red Giants".
- ^ "Multiple Star Systems - NASA Science". science.nasa.gov.
- ^ Busetti, F.; Beust, H.; Harley, C. (2018). "Stability of planets in triple star systems". Astronomy & Astrophysics. 619: A91. arXiv:1811.08221. Bibcode:2018A&A...619A..91B. doi:10.1051/0004-6361/201833097.
- ^ Martin, David V. (June 9, 2018). Deeg, Hans J.; Belmonte, Juan Antonio (eds.). Handbook of Exoplanets. Springer International Publishing. pp. 1–26. doi:10.1007/978-3-319-30648-3_156-1 – via Springer Link.
- ^ https://scholar.archive.org/work/cmmv5cns2ffvrlchovuaccjpne/access/wayback/https://www.uta.edu/physics/main/faculty/musielak/info/CEM.pdf Stringent Criteria For Stable And Unstable Planetary Orbits In Stellar Binary Systems, M. Cuntz,1 J. Eberle,1 and Z. E. Musielak1, 2007 August 27]
- ^ "Big Idea 2.1 – NASA Science". science.nasa.gov.
- ^ "What Is the Habitable Zone?". Exoplanet Exploration: Planets Beyond our Solar System.
- ^ "Planets in the habitable zone". www.esa.int.
- ^ a b c "Which habitable zone planets are the best candidates for detecting life? | astrobites".
- ^ "Second Earth-sized World Found in System's Habitable Zone". Exoplanet Exploration: Planets Beyond our Solar System.
- ^ "The Habitable Zone | Astronomy 801: Planets, Stars, Galaxies, and the Universe". www.e-education.psu.edu.
- ^ Taylor, Stuart Ross (29 July 2004). "Why can't planets be like stars?". Nature. 430 (6999): 509. Bibcode:2004Natur.430..509T. doi:10.1038/430509a. PMID 15282586. S2CID 12316875.
- ^ Stern, Alan. "Ten Things I Wish We Really Knew In Planetary Science". Retrieved 2009-05-22.
- ^ Cowing, Keith (March 30, 2023). "The Ultraviolet Habitable Zone Of Exoplanets". Astrobiology.
- ^ Spinelli, Riccardo; Borsa, Francesco; Ghirlanda, Giancarlo; Ghisellini, Gabriele; Haardt, Francesco (April 13, 2023). "The ultraviolet habitable zone of exoplanets". Monthly Notices of the Royal Astronomical Society. 522 (1): 1411–1418. arXiv:2303.16229. doi:10.1093/mnras/stad928.
- ^ "Habitable zones :: Vera Dobos". veradobos.webnode.page.
- ^ Hall, C.; Stancil, P. C.; Terry, J. P.; Ellison, C. K. (May 1, 2023). "A New Definition of Exoplanet Habitability: Introducing the Photosynthetic Habitable Zone". The Astrophysical Journal Letters. 948 (2): L26. arXiv:2301.13836. Bibcode:2023ApJ...948L..26H. doi:10.3847/2041-8213/acccfb.
- ^ Association, American Lung. "Ozone". www.lung.org.
- ^ Proedrou, Elisavet; Hocke, Klemens (June 1, 2016). "Characterising the three-dimensional ozone distribution of a tidally locked Earth-like planet". Earth, Planets and Space. 68 (1): 96. Bibcode:2016EP&S...68...96P. doi:10.1186/s40623-016-0461-x.
- ^ "Photochemical Smog - an overview | ScienceDirect Topics". www.sciencedirect.com.
- ^ Yang, Jun; Boué, Gwenaël; Fabrycky, Daniel C.; Abbot, Dorian S. (May 1, 2014). "Strong Dependence of the Inner Edge of the Habitable Zone on Planetary Rotation Rate". The Astrophysical Journal. 787 (1): L2. arXiv:1404.4992. Bibcode:2014ApJ...787L...2Y. doi:10.1088/2041-8205/787/1/L2 – via NASA ADS.
- ^ "Rotation of planets influences habitability". phys.org.
- ^ Jansen, T. (March 19, 2021). "Effects of Rotation Rate on the Habitability of Earth-like Planets using NASA's ROCKE-3D GCM". Bulletin of the AAS. 53 (3): 0603. Bibcode:2021BAAS...53c0603J – via baas.aas.org.
- ^ The Moon's Role in the Habitability of the Earth, Georgia State University Research
- ^ Seasons, Georgia State University Research
- ^ Ecliptic Plane, Georgia State University Research
- ^ Axis Tilt is Critical for Life, Georgia State, astr.gsu.edu
- ^ Starr, Michelle (July 8, 2021). "This One Planetary Feature May Be Crucial For The Rise of Complex Life in The Universe". ScienceAlert.
- ^ Conference, Goldschmidt. "Goldilocks planets 'with a tilt' may develop more complex life". phys.org.
- ^ Jenkins, Gregory S. (March 27, 2000). "Global climate model high-obliquity solutions to the ancient climate puzzles of the Faint-Young Sun Paradox and low-altitude Proterozoic glaciation". Journal of Geophysical Research: Atmospheres. 105 (D6): 7357–7370. Bibcode:2000JGR...105.7357J. doi:10.1029/1999JD901125 – via CrossRef.
- ^ Becker, Juliette; Seligman, Darryl Z.; Adams, Fred C.; Styczinski, Marshall J. (March 1, 2023). "The Influence of Tidal Heating on the Habitability of Planets Orbiting White Dwarfs". The Astrophysical Journal Letters. 945 (2): L24. arXiv:2303.02217. Bibcode:2023ApJ...945L..24B. doi:10.3847/2041-8213/acbe44.
- ^ Hasler, Caroline (February 17, 2022). "Tidally Locked and Loaded with Questions". Eos.
- ^ "New conditions for life on other planets: Tidal effects change 'habitable zone' concept". ScienceDaily.
- ^ Vladimir S. Airapetian, “Space Weather Affected Habitable Zones around Active Stars,” AASTCS5 Radio Exploration of Planetary Habitability, Proceedings of the Conference, May 7–12, 2017 in Palm Springs, CA, published in the Bulletin of the American Astronomical Society 49, no. 3, id. 101.05
- ^ Smith, David S.; Scalo, John M. (September 20, 2009). "Habitable zones exposed: astrosphere collapse frequency as a function of stellar mass". Astrobiology. 9 (7): 673–681. Bibcode:2009AsBio...9..673S. doi:10.1089/ast.2009.0337. PMID 19778278 – via PubMed.
- ^ Time History of the Martian Dynamo from Crater Magnetic Field Analysis Journal of Geophysical Research: Planets 118, no. 7 (July 2013), by Robert J. Lillis et al., page 1488–1511
- ^ Timing of the Martian Dynamo Nature 408, by G. Schubert, C. T. Russell, and W. B. Moore, December 7, 2000: page 666–667
- ^ Langlais, Benoit; Thébault, Erwan; Houliez, Aymeric; Purucker, Michael E.; Lillis, Robert J. (2019). "A New Model of the Crustal Magnetic Field of Mars Using MGS and MAVEN". Journal of Geophysical Research: Planets. 124 (6): 1542–1569. Bibcode:2019JGRE..124.1542L. doi:10.1029/2018JE005854. ISSN 2169-9100. PMC 8793354. PMID 35096494.
- ^ "Space Radiation is Risky Business for the Human Body – NASA". September 19, 2017.
- ^ Collinson, Glyn A.; Frahm, Rudy A.; Glocer, Alex; Coates, Andrew J.; Grebowsky, Joseph M.; Barabash, Stas; Domagal-Goldman, Shawn D.; Fedorov, Andrei; Futaana, Yoshifumi; Gilbert, Lin K.; Khazanov, George; Nordheim, Tom A.; Mitchell, David; Moore, Thomas E.; Peterson, William K.; Winningham, John D.; Zhang, Tielong L. (June 28, 2016). "The electric wind of Venus: A global and persistent "polar wind"-like ambipolar electric field sufficient for the direct escape of heavy ionospheric ions". Geophysical Research Letters. 43 (12): 5926–5934. Bibcode:2016GeoRL..43.5926C. doi:10.1002/2016GL068327. S2CID 54886960 – via CrossRef.
- ^ Collinson, Glyn; Mitchell, David; Glocer, Alex; Grebowsky, Joseph; Peterson, W. K.; Connerney, Jack; Andersson, Laila; Espley, Jared; Mazelle, Christian; Sauvaud, Jean-André; Fedorov, Andrei; Ma, Yingjuan; Bougher, Steven; Lillis, Robert; Ergun, Robert; Jakosky, Bruce (November 16, 2015). "Electric Mars: The first direct measurement of an upper limit for the Martian "polar wind" electric potential". Geophysical Research Letters. 42 (21): 9128–9134. Bibcode:2015GeoRL..42.9128C. doi:10.1002/2015GL065084 – via CrossRef.
- ^ "Strong 'electric wind' strips planets of oceans and atmospheres". UCL News. June 20, 2016.
- ^ "Eccentric Habitable Zones". Exoplanet Exploration: Planets Beyond our Solar System.
- ^ Zubritsky, Elizabeth. "Jupiter's Youthful Travels Redefined Solar System". NASA. Archived from the original on 1 March 2017. Retrieved 4 November 2015.
- ^ Beatty, Kelly (16 October 2010). "Our "New, Improved" Solar System". Sky & Telescope. Retrieved 4 November 2015.
- ^ Sanders, Ray (23 August 2011). "How Did Jupiter Shape Our Solar System?". Universe Today. Retrieved 4 November 2015.
- ^ See, V.; Jardine, M.; Vidotto, A. A.; Petit, P.; Marsden, S. C.; Jeffers, S. V.; Nascimento, J. D. do (October 1, 2014). "The effects of stellar winds on the magnetospheres and potential habitability of exoplanets". Astronomy & Astrophysics. 570: A99. arXiv:1409.1237. Bibcode:2014A&A...570A..99S. doi:10.1051/0004-6361/201424323 – via www.aanda.org.
- ^ "Planetary Habitability page of the Trieste Astrobiology Group". wwwuser.oats.inaf.it.
- ^ Vladilo, Giovanni; Murante, Giuseppe; Silva, Laura; Provenzale, Antonello; Ferri, Gaia; Ragazzini, Gregorio (March 25, 2013). "The Habitable Zone Of Earth-Like Planets With Different Levels Of Atmospheric Pressure". The Astrophysical Journal. 767 (1): 65. arXiv:1302.4566. Bibcode:2013ApJ...767...65V. doi:10.1088/0004-637x/767/1/65.
- ^ "Mars & Comets – NASA". mars.nasa.gov.
- ^ Nair, C. P. Reghunadhan; Unnikrishnan, Vibhu (April 18, 2020). "Stability of the Liquid Water Phase on Mars: A Thermodynamic Analysis Considering Martian Atmospheric Conditions and Perchlorate Brine Solutions". ACS Omega. 5 (16): 9391–9397. doi:10.1021/acsomega.0c00444. PMC 7191838. PMID 32363291.
- ^ "How Does Barometric Pressure Affect Humans?". MedicineNet.
- ^ Tarver, William J.; Volner, Keith; Cooper, Jeffrey S. (January 20, 2023). "Aerospace Pressure Effects". StatPearls. StatPearls Publishing. PMID 29262037 – via PubMed.
- ^ Complex life may be possible in only 10% of all galaxies, 24 Nov 2014, By Adrian Cho cience.org]
- ^ "Which Galaxies are Best Suited for the Evolution of Alien Life?". Discover Magazine.
- ^ "What's killing galaxies? Large survey reveals how star formation is shut down in extreme regions of the Universe".
- ^ Canada, National Research Council (November 2, 2021). "What's killing galaxies? Large survey reveals how star formation is shut down in extreme regions of the Universe". nrc.canada.ca.
- ^ "New study examines which galaxies are best for intelligent life". ScienceDaily.
- ^ a b Vera, Matias; Alonso, Sol; Coldwell, Georgina (November 1, 2016). "Effect of bars on the galaxy properties". Astronomy & Astrophysics. 595: A63. arXiv:1607.08643. Bibcode:2016A&A...595A..63V. doi:10.1051/0004-6361/201628750 – via www.aanda.org.
- ^ What is a peculiar galaxy?, Monthly Notices of the Royal Astronomical Society, Volume 286, Issue 4, April 1997, Pages 969–978, by O. Lahav and A. Nairn
- ^ "Star Formation in Irregular Galaxies". ned.ipac.caltech.edu.
- ^ "Irregular Galaxy: A Unique Collections of Stars – Let's Talk Stars". www.letstalkstars.com. February 17, 2023.
- ^ The connection between star formation and metallicity evolution in barred spiral galaxies, Monthly Notices of the Royal Astronomical Society, Volume 431, Issue 3, 21 May 2013, Pages 2560–2575, doi.org/10.1093/mnras/stt354, 20 March 2013
- ^ Yu, Si-Yue; Ho, Luis C. (January 31, 2019). "On the Connection between Spiral Arm Pitch Angle and Galaxy Properties". The Astrophysical Journal. 871 (2): 194. arXiv:1812.06010. Bibcode:2019ApJ...871..194Y. doi:10.3847/1538-4357/aaf895.
- ^ "What process creates and maintains the beautiful spiral arms around spiral galaxies? I've been told that density waves are responsible—so where do the density waves come from?". Scientific American.
- ^ Hall, Shannon. "The Milky Way's Spiral Arms May Have Carved Earth's Continents". Scientific American.
- ^ "The origin of elements, by Miller, astro.umd.edu" (PDF).
- ^ Mahoney, Trevor (July 13, 2020). "Why Different Types of Galaxies May Affect the Development of Life".
- ^ Mason, Paul (January 1, 2018). "The Supergalactic Habitable Zone". American Astronomical Society. 231: 401.04. Bibcode:2018AAS...23140104M – via NASA ADS.
- ^ Mason, P. A.; Biermann, P. L. (November 1, 2017). "The Large-Scale Structure of Habitability in the Universe". Habitable Worlds 2017. 2042: 4149. Bibcode:2017LPICo2042.4149M – via NASA ADS.
- ^ Mason, Paul (January 1, 2019). "The dawn of habitable conditions for complex life in the Universe". American Astronomical Society Meeting. 233: 432.06. Bibcode:2019AAS...23343206M – via NASA ADS.
- ^ "The Cosmic Blueprint | Paul Davies". cosmos.asu.edu.
- ^ "New study dramatically narrows the search for advanced life in the universe | UCR News | UC Riverside". news.ucr.edu.
- ^ Gribbin, John (2011). Alone in the Universe: Why our planet is unique. Wiley
- ^ Ward, Peter D.; Brownlee, Donald (2000). Rare Earth: Why Complex Life is Uncommon in the Universe. Copernicus Books (Springer Verlag). ISBN 978-0-387-98701-9.
- ^ Gonzales, Guillermo; Richards, Jay W (2004). The Privileged Planet. Regnery Publishing, Inc.
- ^ "Lucky Planet - Why Earth is Exceptional & Life In The Universe".
- ^ "The origin and rise of complex life | Royal Society". royalsociety.org. 7 December 2022.
- ^ "Ice, Snow, and Glaciers and the Water Cycle | U.S. Geological Survey". www.usgs.gov.
- ^ Deitrick, Russell; Barnes, Rory; Quinn, Thomas R.; Armstrong, John; Charnay, Benjamin; Wilhelm, Caitlyn (January 16, 2018). "Exo-Milankovitch Cycles. I. Orbits and Rotation States". The Astronomical Journal. 155 (2): 60. arXiv:1712.10060. Bibcode:2018AJ....155...60D. doi:10.3847/1538-3881/aaa301.
- ^ Deitrick, Russell; Barnes, Rory; Bitz, Cecilia; Fleming, David; Charnay, Benjamin; Meadows, Victoria; Wilhelm, Caitlyn; Armstrong, John; Quinn, Thomas R. (June 1, 2018). "Exo-Milankovitch Cycles. II. Climates of G-dwarf Planets in Dynamically Hot Systems". The Astronomical Journal. 155 (6): 266. arXiv:1805.00283. Bibcode:2018AJ....155..266D. doi:10.3847/1538-3881/aac214.
- ^ Tereza Pultarova (June 14, 2022). "Milankovitch cycles: What are they and how do they affect Earth?". Space.com.
- ^ Laboratory, By Alan Buis, NASA's Jet Propulsion. "Milankovitch (Orbital) Cycles and Their Role in Earth's Climate". Climate Change: Vital Signs of the Planet.
{{cite web}}
: CS1 maint: multiple names: authors list (link) - ^ "Knowledge reference for national forest assessments – modeling for estimation and monitoring". www.fao.org. Archived from the original on January 13, 2020. Retrieved Feb 20, 2019.
- ^ Allison, Steven D.; Vitousek, Peter M. (2005-05-01). "Responses of extracellular enzymes to simple and complex nutrient inputs". Soil Biology and Biochemistry. 37 (5): 937–944. Bibcode:2005SBiBi..37..937A. doi:10.1016/j.soilbio.2004.09.014. ISSN 0038-0717.
- ^ "Astrobiology". Biology Cabinet. September 26, 2006. Retrieved 2011-01-17.
- ^ "Polycyclic Aromatic Hydrocarbons: An Interview With Dr. Farid Salama". Astrobiology magazine. 2000. Archived from the original on 2008-06-20. Retrieved 2008-10-20.
- ^ Lipkus, Alan H.; Yuan, Qiong; Lucas, Karen A.; et al. (2008). "Structural Diversity of Organic Chemistry. A Scaffold Analysis of the CAS Registry". The Journal of Organic Chemistry. 73 (12). American Chemical Society (ACS): 4443–4451. doi:10.1021/jo8001276. PMID 18505297.
- ^ Molnar, Charles; Gair, Jane (May 14, 2015). "2.3 Biological Molecules". Introduction to the Chemistry of Life – via opentextbc.ca.
- ^ Education (2010). "CHNOPS: The Six Most Abundant Elements of Life". Pearson Education. Pearson BioCoach. Archived from the original on 27 July 2017. Retrieved 2010-12-10.
Most biological molecules are made from covalent combinations of six important elements, whose chemical symbols are CHNOPS. ... Although more than 25 types of elements can be found in biomolecules, six elements are most common. These are called the CHNOPS elements; the letters stand for the chemical abbreviations of carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur.