4120:
144:
1460:(4.1–3.7 Ga). It is unclear how Mars's orbital pattern, which places it even further from the Sun, and the faintness of the young Sun could have produced what is thought to have been a very warm and wet climate on Mars. Scientists debate over which geomorphological features can be attributed to shorelines or other water flow markers and which can be ascribed to other mechanisms. Nevertheless, the geologic evidence, including observations of widespread fluvial erosion in the southern highlands, are generally consistent with an early warm and semi-arid climate.
79:
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4180:
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1355:. According to Shaviv, the early Sun had emitted a stronger solar wind that produced a protective effect against cosmic rays. In that early age, a moderate greenhouse effect comparable to today's would have been sufficient to explain a largely ice-free Earth. Evidence for a more active early Sun has been found in
51:'s output would be only 70 percent as intense during that epoch as it is during the modern epoch. The paradox is this: with the young Sun's output at only 70 percent of its current output, early Earth would be expected to be completely frozen, but early Earth seems to have had liquid water and supported life.
1322:
However, around 2021, a team led by René Heller in
Germany argued that such estimates were simplistic and that in some plausible models tidal heating might have contributed on the order of 10 watts per square meter and increased the equilibrium temperature by up to five degrees Celsius on a timescale
1437:
holds that biological processes work to maintain a stable surface climate on Earth to maintain habitability through various negative feedback mechanisms. While organic processes, such as the organic carbon cycle, work to regulate dramatic climate changes, and that the surface of Earth has presumably
1407:
Another proposed mechanism of cloud cover reduction relates a decrease in cosmic rays during this time to reduced cloud fraction. However, this mechanism does not work for several reasons, including the fact that ions do not limit cloud formation as much as cloud condensation nuclei, and cosmic rays
1403:
both in the form of wind-blown dust and biogenic sources. A lower albedo allows a higher fraction of solar radiation to penetrate to the surface. Goldblatt and Zahnle (2011) investigated whether a change in cloud fraction could have been sufficiently warming and found that the net effect was equally
1374:
It has been proposed several times that mass loss from the faint young Sun in the form of stronger solar winds could have compensated for the low temperatures from greenhouse gas forcing. In this framework, the early Sun underwent an extended period of higher solar wind output. Based on exoplanetary
1502:
greenhouse is a plausible scenario suggested recently for early Mars. Intermittent bursts of methane may have been another possibility. Such greenhouse gas combinations appear necessary because carbon dioxide alone, even at pressures exceeding a few bar, cannot explain the temperatures required for
1202:
could have prevented this destruction of ammonia and allowed it to continue acting as a greenhouse gas during this time; however, by 2001, this idea was tested using a photochemical model and discounted. Furthermore, such a haze is thought to have cooled Earth's surface beneath it and counteracted
1214:
was present in higher concentrations during this period of lower solar radiation. It was first proposed and tested as part of Earth's atmospheric evolution in the late 1970s. An atmosphere that contained about 1,000 times the present atmospheric level (or PAL) was found to be consistent with the
1455:
Mars has its own version of the faint young Sun paradox. Martian terrains show clear signs of past liquid water on the surface, including outflow channels, gullies, modified craters, and valley networks. These geomorphic features suggest Mars had an ocean on its surface and river networks that
1468:-dominated atmosphere has been proposed as a way to produce such a temperature increase. This would depend upon the carbon cycle and the rate of volcanism throughout the pre-Noachian and Noachian, which is not well known. Volatile outgassing is thought to have occurred during these periods.
1382:
eon, this mass loss must have occurred over an interval of about one billion years. Records of ion implantation from meteorites and lunar samples show that the elevated rate of solar wind flux only lasted for a period of 100 million years. Observations of the young Sun-like star
1253:
The amount of carbon dioxide levels is still under debate. In 2001, Sleep and Zahnle suggested that increased weathering on the sea floor on a young, tectonically active Earth could have reduced carbon dioxide levels. Then in 2010, Rosing et al. analyzed marine sediments called
110:
in the Sun's core, from four protons and electrons each to one helium nucleus and two electrons. Fewer particles would exert less pressure. A collapse under the enormous gravity is prevented by an increase in temperature, which is both cause and effect of a higher rate of
1514:
is composed of 96% carbon dioxide. Billions of years ago, when the Sun was 25 to 30% dimmer, Venus's surface temperature could have been much cooler, and its climate could have resembled current Earth's, complete with a hydrological cycle—before it experienced a
1323:
of 100 million years. Such a contribution would partially resolve the paradox but is insufficient to solve the faint young paradox on its own without additional factors such as greenhouse heating. The underlying assumption of Moon's formation just outside of the
1318:
heating than experienced today. Original estimates found that even early tidal heating would be minimal, perhaps 0.02 watts per square meter. (For comparison, the solar energy incident on the Earth's atmosphere is on the order of 1,000 watts per square meter.)
1424:
on gravitationally bound systems are returning inconclusive results as of 2022, it was noted that orbital expansion with a fraction of local Hubble expansion rate may explain the observed anomalies in orbital evolution, including a faint young Sun paradox.
1463:
Given the orbital and solar conditions of early Mars, a greenhouse effect would have been necessary to increase surface temperatures at least 65 K in order for these surface features to have been carved by flowing water. A much denser,
1241:
Specifically, using 1-D models, which represent Earth as a single point (instead of something that varies across 3 dimensions) scientists have determined that at 4.5 Ga, with a 30% dimmer Sun, a minimum partial pressure of 0.1 bar of
2476:
Heller, René; Duda, Jan-Peter; Winkler, Max; Reitner, Joachim; Gizon, Laurent (December 2021). "Habitability of the early Earth: liquid water under a faint young Sun facilitated by strong tidal heating due to a closer Moon".
1375:
data, this caused a mass loss from the Sun of 5−6 percent over its lifetime, resulting in a more consistent level of solar luminosity (as the early Sun had more mass, resulting in more energy output than was predicted).
118:
More recent modeling studies have shown that the Sun is currently 1.4 times as bright today than it was 4.6 billion years ago (Ga), and that the brightening has accelerated considerably. At the
1838:
Baraffe, Isabelle; Homeier, Derek; Allard, France; Chabrier, Gilles (2015). "New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit".
1278:), a reduced mineral and saw that they formed during the first half of Earth's history (and not afterward). The minerals' relative coexistence suggested an analogous balance between CO
1438:
remained habitable, this hypothesis has been criticized as intractable. Furthermore, life has existed on the surface of Earth through dramatic changes in climate, including
3122:
Křížek, Michal; Gueorguiev, Vesselin G.; Maeder, André (2022), "An
Alternative Explanation of the Orbital Expansion of Titan and Other Bodies in the Solar System",
1734:
David
Morrison, NASA Lunar Science Institute, "Catastrophic Impacts in Earth's History", video-recorded lecture, Stanford University (Astrobiology), 2010 Feb. 2,
1366:. The reduced solar impact later results in a stronger impact of cosmic ray flux, which is hypothesized to lead to a relationship with climatological variations.
1182:. However, it has since been shown that while ammonia is an effective greenhouse gas, it is easily destroyed photochemically in the atmosphere and converted to
4015:
3724:
147:
This conceptual graph shows the relationship between solar radiation and the greenhouse effect – in this case dominated by modulations in carbon dioxide.
1395:
If greenhouse gas concentrations did not compensate completely for the fainter Sun, the moderate temperature range may be explained by a lower surface
1412:, and a consensus has yet to be reached on how changes in cloud spatial patterns and cloud type may have affected Earth's climate during this time.
892:
155:
3437:
Ramirez, R. M.; Kopparapu, R.; Zugger, M. E.; Robinson, T. D.; Freedman, R.; Kasting, J. F. (2014). "Warming early Mars with CO2 and H2".
1404:
as likely to have been negative as positive. At most the effect could have raised surface temperatures to just above freezing on average.
4020:
1982:
Pavlov, Alexander; Brown, Lisa; Kasting, James (October 2001). "UV shielding of NH3 and O2 by organic hazes in the
Archean atmosphere".
1936:
Sagan, Carl; Chyba, Christopher (23 May 1997). "The early faint sun paradox: organic shielding of ultraviolet-labile greenhouse gases".
2643:
Caffe, M. W.; Hohenberg, C. M.; Swindle, T. D.; Goswami, J. N. (February 1, 1987). "Evidence in meteorites for an active early sun".
1387:
match this rate of decline in the stellar wind output, suggesting that a higher mass loss rate cannot by itself resolve the paradox.
3718:
1175:
Sagan and Mullen suggested during their descriptions of the paradox that it might be solved by high concentrations of ammonia gas,
1408:
have been found to have little impact on global mean temperature. Clouds continue to be the dominant source of uncertainty in 3-D
4232:
185:
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1442:
episodes. There are also strong and weak versions of the Gaia hypothesis, which has caused some tension in this research area.
29:
26:
How can the early Earth have had liquid water if the Sun's output is theorized to have been only 70% as intense as it is today?
3343:
Ramirez, Ramirez R.; Craddock, Robert A. (2018). "The geological and climatological case for a warmer and wetter early Mars".
2590:
Shaviv, N. J. (2003). "Toward a solution to the early faint Sun paradox: A lower cosmic ray flux from a stronger solar wind".
1750:
Solar and
Stellar Variability: Impact on Earth and Planets, Proceedings of the International Astronomical Union, IAU Symposium
3893:
3804:
3690:
3612:
3106:
1665:
1636:
3241:"An intense terminal epoch of widespread fluvial activity on early Mars: 1. Valley network incision and associated deposits"
2382:
Rosing, Minik; Bird, Dennis K; Sleep, Norman; Bjerrum, Christian J. (2010). "No climate paradox under the faint early Sun".
2133:
1891:
Kuhn, W. R.; Atreya, S. K (1979). "Ammonia photolysis and the greenhouse effect in the primordial atmosphere of the earth".
1362:
The temperature minimum around 2.4 Ga goes along with a cosmic ray flux modulation by a variable star formation rate in the
3643:
1238:
rates would be reduced, allowing for the build-up of carbon dioxide in the atmosphere on timescales of 0.5 million years.
106:
predict a brightening of the Sun. The brightening is caused by a decrease in the number of particles per unit mass due to
2688:
Minton, David; Malhotra, Renu (2007). "Assessing the
Massive Young Sun Hypothesis to Solve the Warm Young Earth Puzzle".
1226:
concentrations is the carbon cycle. On large timescales, the inorganic branch of the carbon cycle, which is known as the
1234:
between the atmosphere and the surface of Earth. In particular, during a time of low surface temperatures, rainfall and
3200:"An Intense Terminal Epoch of Widespread Fluvial Activity on Early Mars: 2. Increased Runoff and Paleolake Development"
2261:"The Carbonate–Silicate Geochemical Cycle and its Effect on Atmospheric Carbon Dioxide over the Past 100 Million Years"
3413:
1207:
revived the idea, arguing that the ammonia hypothesis is a viable contributor if the haze formed a fractal pattern.
4119:
2043:
Wolf, E. T.; Toon, O. B. (4 June 2010). "Fractal
Organic Hazes Provided an Ultraviolet Shield for Early Earth".
952:
750:
2017:
3928:
1476:
1227:
810:
1475:-rich atmosphere is to examine carbonate deposits. A primary sink for carbon in Earth's atmosphere is the
3901:
1748:
Ribas, Ignasi (February 2010), "The Sun and stars as the primary energy input in planetary atmospheres",
426:
178:
2886:
Wood, Bernard (2002). "Measured mass loss rates of solar-like stars as a function of age and activity".
2206:
Pavlov, Alexander A.; Kasting, James F.; Brown, Lisa L.; Rages, Kathy A.; Freedman, Richard (May 2000).
4110:
2347:
Sleep, N.H.; Zahnle, K (2001). "Carbon dioxide cycling and implications for climate on ancient Earth".
1314:
was originally much closer to the Earth, which rotated faster than it does today, resulting in greater
3039:
Krissansen-Totton, J.; Davies, R. (2013). "Investigation of cosmic ray–cloud connections using MISR".
514:
4005:
3885:
3696:
1516:
1400:
1053:
770:
66:, astrophysical influences, or combinations of these suggestions. The predominant theory is that the
2794:
4227:
4217:
3756:
3636:
1684:
Sagan, C.; Mullen, G. (1972). "Earth and Mars: Evolution of
Atmospheres and Surface Temperatures".
730:
394:
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1204:
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91:
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1991:
1945:
1900:
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1693:
1589:
1539:
410:
143:
103:
2833:
Wood, Bernard (2005). "New mass-loss measurements from astrospheric Ly alpha absorption".
8:
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3629:
1511:
912:
871:
3569:
3517:
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Wordsworth, Y.Kalugina; Lokshtanov, A.Vigasin; Ehlmann, J.Head; Sanders, H.Wang (2017).
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1995:
1949:
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and George Mullen in 1972. Proposed resolutions of this paradox have taken into account
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2815:
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Gurumath, Shashanka R.; Hiremath, K. M.; Ramasubramanian, V.; Acharyya, Kinsuk (2022),
2723:
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2625:
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2571:
2543:
2512:
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2458:
2415:
2182:
2076:
1873:
1847:
1779:
1753:
1717:
1654:
1625:
1605:
1579:
1484:
1399:. At the time, a smaller area of exposed continental land would have resulted in fewer
1033:
932:
830:
3491:
3396:
Haberle, R.; Catling, D.; Carr, M; Zahnle, K (2017). "The Early Mars
Climate System".
4041:
3608:
3581:
3577:
3476:
3409:
3382:
3161:
3102:
3078:
3024:
2999:
2807:
2743:
A possible solution for the faint young Sun paradox: Clues from the exoplanetary data
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2516:
2450:
2419:
2407:
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2186:
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2080:
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1961:
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1709:
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1609:
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127:
99:
59:
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1877:
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1721:
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4010:
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3019:
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2504:
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1999:
1953:
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1818:
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1701:
1597:
1550:
1528:
1421:
1348:
1328:
123:
83:
2767:"The faint young Sun paradox: An observational test of an alternative solar model"
1957:
1869:
4046:
3855:
3681:
1434:
1013:
1705:
4196:
4124:
3671:
3554:"Runaway and moist greenhouse atmospheres and the evolution of Earth and Venus"
2566:
2531:
2508:
1439:
1302:) may therefore have contributed to the warming in addition to carbon dioxide.
1211:
112:
107:
67:
3405:
3374:
3153:
2764:
2302:"Climate consequences of very high CO2 levels in the Earth's early atmosphere"
1775:
4206:
3958:
3705:
3549:
2325:
1409:
1094:
2673:
2064:
1327:
is not certain, however: a magnetized disk of debris could have transported
78:
4212:
4148:
3964:
3796:
3666:
3585:
2811:
2454:
2411:
2333:
2245:
2178:
2072:
1965:
1713:
1487:
in this way because the greenhouse effect would have been outstripped by CO
1246:
is required to maintain an above-freezing surface temperature; 10 bar of CO
1216:
972:
710:
126:(via slight increases in temperature and radius), which on Earth is termed
87:
2975:
2940:
2285:
2260:
43:
describes the apparent contradiction between observations of liquid water
3988:
3526:
3265:
3240:
3224:
3199:
2900:
2847:
2803:
2702:
2621:
2604:
2368:
2236:
2207:
2169:
2003:
1921:
1601:
1352:
1324:
1291:
656:
618:
119:
44:
2403:
4051:
3982:
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3652:
2740:
2160:
1344:
1340:
1235:
992:
55:
4191:
3070:
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3198:
Irwin, R. P.; Howard, Alan; Craddock, Robert; Moore, Jeffrey (2005).
1363:
1356:
1259:
502:
442:
18:
3553:
2446:
2301:
2094:
Hart, M. H. (1978). "The evolution of the atmosphere of the EArth".
3508:
3357:
3299:
3184:
3136:
2917:
2864:
2751:
2719:
2664:
2548:
2491:
1852:
1823:
1798:
1536:– of a planet, dependent on reflectivity of its surface and clouds.
1457:
1271:
1191:
1183:
1074:
523:
505:
3602:
3489:
3451:
3053:
2957:
1758:
1584:
1379:
1295:
1258:
and found large amounts of various iron-rich minerals, including
1176:
590:
557:
1420:
Although both simulations and direct measurements of effects of
3400:. Cambridge, UK: Cambridge University Press. pp. 526–568.
1547: – List of statements that appear to contradict themselves
1396:
1199:
567:
539:
63:
3436:
3621:
1339:
A minority view propounded by the
Israeli-American physicist
1119:
474:
70:
carbon dioxide contributed most to the warming of the Earth.
1837:
1286:. In the analysis, Rosing et al. connected the atmospheric H
2765:
Gaidos, Eric J.; Güdel, Manuel; Blake, Geoffrey A. (2000).
1315:
1311:
548:
4143:
3285:
Wordsworth, Robin D. (2016). "The Climate of Early Mars".
2259:
Berner, Robert; Lasaga, Antonio; Garrels, Robert (1983).
1156:
1115:
48:
3395:
3197:
2475:
3038:
2530:
Mullen, Patrick D.; Gammie, Charles F. (October 2020).
3338:
3336:
3334:
3121:
3099:
Atmospheric Evolution on Inhabited and Lifeless Worlds
2381:
1570:
Feulner, Georg (2012). "The faint young Sun problem".
1471:
One way to ascertain whether Mars possessed a thick CO
4108:
3492:"Transient reducing greenhouse warming on early Mars"
3092:
3090:
3088:
1230:
is responsible for determining the partitioning of CO
3176:
LOCAL HUBBLE EXPANSION: CURRENT STATE OF THE PROBLEM
1656:
Earth's Earliest Biosphere: Its Origin and Evolution
1503:
the presence of surface liquid water on early Mars.
1203:
the greenhouse effect. Around 2010, scholars at the
4016:
Carl Sagan Award for Public Appreciation of Science
3725:
Extraordinary claims require extraordinary evidence
3331:
2258:
1683:
1294:. Anaerobic, single-celled organisms that produced
150:
3085:
2426:
1981:
1653:
1624:
1331:leading to a less massive Moon in a higher orbit.
1198:) gases. It was suggested (again by Sagan) that a
3280:
3278:
3276:
4204:
2433:Kasting, James (2010). "Faint young Sun redux".
1222:The primary mechanism for attaining such high CO
94:compared to the present Sun. After Ribas (2010).
3342:
2938:
2299:
1660:. Princeton, N.J.: Princeton University Press.
1378:In order to explain the warm conditions in the
1347:combined with a hypothesis of Danish physicist
1250:has been suggested as a plausible upper limit.
3273:
3096:
3032:
2687:
2293:
2141:Origins of Life and Evolution of the Biosphere
3637:
3603:Bengtsson, Lennart; Hammer, Claus U. (2004).
3287:Annual Review of Earth and Planetary Sciences
3101:. Cambridge, UK: Cambridge University Press.
3097:Catling, David C.; Kasting, James F. (2017).
2991:
2127:
2125:
1977:
1975:
1479:. However it would have been difficult for CO
179:
122:of the Sun, more fusion power means a higher
20:
3605:Geosphere-Biosphere Interactions and Climate
2529:
1679:
1677:
4021:Carl Sagan Prize for Science Popularization
3389:
3239:Howard, Alan D.; Moore, Jeffrey M. (2005).
3238:
2346:
1796:
47:and the astrophysical expectation that the
3644:
3630:
3284:
3232:
2681:
2375:
2252:
2122:
1972:
1935:
1890:
186:
172:
3525:
3507:
3450:
3356:
3298:
3264:
3223:
3191:
3183:
3135:
3052:
3023:
2997:
2974:
2956:
2899:
2846:
2793:
2750:
2701:
2672:
2603:
2565:
2547:
2532:"A Magnetized, Moon-forming Giant Impact"
2490:
2340:
2284:
2235:
2168:
1929:
1920:
1851:
1822:
1757:
1674:
1583:
1456:resemble current Earth's during the late
1415:
3719:Search for extraterrestrial intelligence
3000:"Cosmoclimatology: a new theory emerges"
2941:"Clouds and the Faint Young Sun Paradox"
2879:
2826:
2636:
2349:Journal of Geophysical Research: Planets
2300:Kasting, J. F.; Ackerman, T. P. (1986).
2042:
1984:Journal of Geophysical Research: Planets
1741:
142:
77:
3548:
3542:
2432:
1884:
1799:"More Solar Models and Neutrino Fluxes"
1622:
1569:
16:Paradox concerning water on early Earth
4205:
4058:Pale Blue Dot: A Tribute to Carl Sagan
3837:The Varieties of Scientific Experience
2589:
2199:
2131:
1651:
1152:
3894:God, the Universe and Everything Else
3625:
3173:
2939:Goldblatt, C.; Zahnle, K. J. (2011).
1747:
1369:
164:
30:(more unsolved problems in astronomy)
2885:
2832:
2583:
2093:
1797:Abraham, Zulema; Iben, Icko (1971).
1390:
1128:
1104:
1083:
1063:
1042:
1022:
1002:
981:
961:
941:
921:
901:
881:
860:
840:
819:
799:
779:
759:
739:
719:
699:
153:
54:The issue was raised by astronomers
3317:10.1146/annurev-earth-060115-012355
2134:"Carbon dioxide on the early earth"
1445:
138:
13:
3596:
3398:The Atmosphere and Climate of Mars
1428:
1343:uses climatological influences of
1290:concentrations with regulation by
73:
14:
4244:
2212:in the atmosphere of early Earth"
2132:Walker, James C. G. (June 1985).
2018:"A Fix for the "Faint Young Sun""
1270:), an oxidized mineral alongside
4190:
4178:
4166:
4154:
4142:
4130:
4118:
4093:
4092:
3025:10.1111/j.1468-4004.2007.48118.x
1752:, vol. 264, pp. 3–18,
1305:
3483:
3430:
3245:Journal of Geophysical Research
3204:Journal of Geophysical Research
3167:
3115:
2932:
2758:
2734:
2592:Journal of Geophysical Research
2523:
2469:
2216:Journal of Geophysical Research
2087:
2036:
2010:
4233:Unsolved problems in astronomy
3805:Shadows of Forgotten Ancestors
3651:
3607:. Cambridge University Press.
1831:
1790:
1728:
1645:
1616:
1563:
1334:
698:
1:
1958:10.1126/science.276.5316.1217
1556:
1215:evolutionary path of Earth's
21:Unsolved problem in astronomy
3578:10.1016/0019-1035(88)90116-9
3496:Geophysical Research Letters
3041:Geophysical Research Letters
2774:Geophysical Research Letters
2116:10.1016/0019-1035(78)90021-0
1913:10.1016/0019-1035(79)90126-X
1840:Astronomy & Astrophysics
7:
4047:Carl Sagan Memorial Station
3902:Cosmos: A Spacetime Odyssey
2265:American Journal of Science
1870:10.1051/0004-6361/201425481
1706:10.1126/science.177.4043.52
1545:List of cosmology paradoxes
1522:
1494:A volcanically-outgassed CO
1483:to have accumulated in the
1153:
913:Earliest multicellular life
383:
133:
10:
4249:
3004:Astronomy & Geophysics
2998:Svensmark, Henrik (2007).
2509:10.1007/s12542-021-00582-7
4088:
4072:
4029:
4006:Carl Sagan Memorial Award
3998:
3951:
3920:
3886:Cosmos: A Personal Voyage
3877:
3870:
3847:
3740:
3733:
3659:
3406:10.1017/9781139060172.017
3375:10.1038/s41561-018-0093-9
3154:10.1134/S0202289322020086
3124:Gravitation and Cosmology
2888:The Astrophysical Journal
2835:The Astrophysical Journal
2690:The Astrophysical Journal
2645:The Astrophysical Journal
2536:The Astrophysical Journal
2208:"Greenhouse warming by CH
1803:The Astrophysical Journal
1776:10.1017/S1743921309992298
1631:. New York: Wiley Press.
1517:runaway greenhouse effect
1401:cloud condensation nuclei
3757:Mars and the Mind of Man
3174:Dumin, Yurii V. (2016),
2567:10.3847/2041-8213/abbffd
2326:10.1126/science.11539665
1506:
1477:carbonate–silicate cycle
1351:for a cooling effect of
1228:carbonate–silicate cycle
339:−1000 —
319:−1500 —
299:−2000 —
279:−2500 —
259:−3000 —
239:−3500 —
219:−4000 —
199:−4500 —
196:
45:early in Earth's history
3910:Cosmos: Possible Worlds
3821:The Demon-Haunted World
3677:Faint young Sun paradox
3016:2007A&G....48a..18S
2065:10.1126/science.1183260
1862:2015A&A...577A..42B
1627:The Evolving Continents
1450:
1210:It is now thought that
359:−500 —
82:Evolution of the Sun's
62:, changes to planetary
41:faint young Sun problem
37:faint young Sun paradox
1416:Local Hubble expansion
1256:banded iron formations
1205:University of Colorado
148:
95:
3829:Billions and Billions
3789:The Cold and the Dark
3749:The Cosmic Connection
3714:The Planetary Society
3687:Voyager Golden Record
2976:10.5194/cp-7-203-2011
2286:10.2475/ajs.283.7.641
1572:Reviews of Geophysics
1534:Effective temperature
1410:global climate models
1292:biotic methanogenesis
1219:and solar evolution.
146:
92:effective temperature
81:
4037:Carl Sagan Institute
3527:10.1002/2016GL071766
3266:10.1029/2005JE002459
3225:10.1029/2005JE002460
2804:10.1029/1999GL010740
2622:10.1029/2003JA009997
2369:10.1029/2000JE001247
2237:10.1029/1999JE001134
2004:10.1029/2000JE001448
1990:(E10): 26267–23287.
1623:Windley, B. (1984).
1602:10.1029/2011RG000375
1540:Isua Greenstone Belt
104:standard solar model
4064:Symphony of Science
3971:Linda Salzman Sagan
3765:The Dragons of Eden
3570:1988Icar...74..472K
3518:2017GeoRL..44..665W
3461:2014NatGe...7...59R
3367:2018NatGe..11..230R
3309:2016AREPS..44..381W
3257:2005JGRE..11012S14H
3216:2005JGRE..11012S15I
3146:2022GrCo...28..122K
3063:2013GeoRL..40.5240K
2967:2011CliPa...7..203G
2945:Climate of the Past
2910:2002ApJ...574..412W
2857:2005ApJ...628L.143W
2786:2000GeoRL..27..501G
2712:2007ApJ...660.1700M
2657:1987ApJ...313L..31C
2614:2003JGRA..108.1437S
2558:2020ApJ...903L..15M
2501:2021PalZ...95..563H
2404:10.1038/nature08955
2396:2010Natur.464..744R
2361:2001JGR...106.1373S
2318:1986Sci...234.1383K
2312:(4782): 1383–1385.
2277:1983AmJS..283..641B
2228:2000JGR...10511981P
2222:(E5): 11981–11990.
2153:1985OrLi...16..117W
2108:1978Icar...33...23H
2057:2010Sci...328.1266W
2051:(5983): 1266–1268.
2022:Sky & Telescope
1996:2001JGR...10623267P
1950:1997Sci...276.1217S
1944:(5316): 1217–1221.
1905:1979Icar...37..207K
1815:1971ApJ...170..157A
1768:2010IAUS..264....3R
1698:1972Sci...177...52S
1652:Schopf, J. (1983).
1594:2012RvGeo..50.2006F
893:Sexual reproduction
872:Huronian glaciation
4080:900 Stewart Avenue
2161:10.1007/BF01809466
1512:Venus's atmosphere
1485:Martian atmosphere
1370:Mass loss from Sun
1200:photochemical haze
1140:Quaternary ice age
1075:Earliest tetrapods
1034:Cambrian explosion
993:Cryogenian ice age
852:Atmospheric oxygen
831:Pongola glaciation
459:Multicellular life
411:Single-celled life
149:
96:
60:greenhouse effects
4106:
4105:
4042:Sagan Planet Walk
3947:
3946:
3866:
3865:
3660:Scientific career
3614:978-0-521-78238-8
3439:Nature Geoscience
3345:Nature Geoscience
3108:978-0-521-84412-3
3071:10.1002/grl.50996
3047:(19): 5240–5245.
2390:(7289): 744–747.
2355:(E1): 1373–1399.
1736:access 2016-05-10
1667:978-0-691-08323-0
1638:978-0-471-90376-5
1391:Changes in clouds
1173:
1172:
1157:million years ago
1148:
1147:
1127:
1126:
1103:
1102:
1082:
1081:
1062:
1061:
1054:Andean glaciation
1041:
1040:
1021:
1020:
1001:
1000:
980:
979:
960:
959:
940:
939:
920:
919:
900:
899:
880:
879:
859:
858:
839:
838:
818:
817:
798:
797:
778:
777:
758:
757:
738:
737:
718:
717:
128:radiative forcing
102:, especially the
100:stellar structure
4240:
4195:
4194:
4183:
4182:
4181:
4171:
4170:
4169:
4159:
4158:
4157:
4147:
4146:
4135:
4134:
4133:
4123:
4122:
4114:
4096:
4095:
4011:Carl Sagan Medal
3913:(2020 TV series)
3905:(2014 TV series)
3889:(1980 TV series)
3875:
3874:
3738:
3737:
3646:
3639:
3632:
3623:
3622:
3618:
3590:
3589:
3546:
3540:
3539:
3529:
3511:
3487:
3481:
3480:
3469:10.1038/ngeo2000
3454:
3434:
3428:
3427:
3393:
3387:
3386:
3360:
3340:
3329:
3328:
3302:
3282:
3271:
3270:
3268:
3236:
3230:
3229:
3227:
3195:
3189:
3188:
3187:
3171:
3165:
3164:
3139:
3119:
3113:
3112:
3094:
3083:
3082:
3056:
3036:
3030:
3029:
3027:
2995:
2989:
2988:
2978:
2960:
2936:
2930:
2929:
2903:
2901:astro-ph/0203437
2883:
2877:
2876:
2850:
2848:astro-ph/0506401
2841:(2): L143–L146.
2830:
2824:
2823:
2797:
2771:
2762:
2756:
2755:
2754:
2738:
2732:
2731:
2705:
2703:astro-ph/0612321
2696:(2): 1700–1706.
2685:
2679:
2678:
2676:
2674:2060/19850018239
2640:
2634:
2633:
2607:
2605:astro-ph/0306477
2587:
2581:
2579:
2569:
2551:
2527:
2521:
2520:
2494:
2473:
2467:
2466:
2430:
2424:
2423:
2379:
2373:
2372:
2344:
2338:
2337:
2297:
2291:
2290:
2288:
2256:
2250:
2249:
2239:
2203:
2197:
2196:
2194:
2193:
2172:
2138:
2129:
2120:
2119:
2091:
2085:
2084:
2040:
2034:
2033:
2031:
2029:
2014:
2008:
2007:
1979:
1970:
1969:
1933:
1927:
1926:
1924:
1888:
1882:
1881:
1855:
1835:
1829:
1828:
1826:
1794:
1788:
1787:
1761:
1745:
1739:
1732:
1726:
1725:
1681:
1672:
1671:
1659:
1649:
1643:
1642:
1630:
1620:
1614:
1613:
1587:
1567:
1551:Paleoclimatology
1529:Cool early Earth
1446:On other planets
1349:Henrik Svensmark
1329:angular momentum
1134:
1129:
1110:
1105:
1089:
1084:
1069:
1064:
1048:
1043:
1028:
1023:
1008:
1003:
987:
982:
973:Earliest animals
967:
962:
947:
942:
927:
922:
907:
902:
887:
882:
866:
861:
846:
841:
825:
820:
805:
800:
785:
780:
771:Earliest fossils
765:
760:
745:
740:
725:
720:
705:
700:
679:
648:
610:
608:
582:
580:
487:
380:
375:
370:
365:
360:
355:
350:
345:
340:
335:
330:
325:
320:
315:
310:
305:
300:
295:
290:
285:
280:
275:
270:
265:
260:
255:
250:
245:
240:
235:
230:
225:
220:
215:
210:
205:
200:
188:
181:
174:
168:
158:
151:
139:Greenhouse gases
124:solar luminosity
22:
4248:
4247:
4243:
4242:
4241:
4239:
4238:
4237:
4228:1972 in science
4218:Climate history
4203:
4202:
4201:
4189:
4179:
4177:
4167:
4165:
4155:
4153:
4141:
4131:
4129:
4117:
4109:
4107:
4102:
4084:
4068:
4025:
3994:
3943:
3916:
3862:
3843:
3729:
3699:Family Portrait
3682:Cosmic Calendar
3655:
3650:
3615:
3599:
3597:Further reading
3594:
3593:
3547:
3543:
3488:
3484:
3435:
3431:
3416:
3394:
3390:
3341:
3332:
3283:
3274:
3251:(E12): E12S14.
3237:
3233:
3210:(E12): E12S15.
3196:
3192:
3172:
3168:
3120:
3116:
3109:
3095:
3086:
3037:
3033:
2996:
2992:
2937:
2933:
2884:
2880:
2831:
2827:
2795:10.1.1.613.1511
2769:
2763:
2759:
2739:
2735:
2686:
2682:
2641:
2637:
2588:
2584:
2528:
2524:
2474:
2470:
2447:10.1038/464687a
2441:(7289): 687–9.
2431:
2427:
2380:
2376:
2345:
2341:
2298:
2294:
2257:
2253:
2211:
2204:
2200:
2191:
2189:
2136:
2130:
2123:
2092:
2088:
2041:
2037:
2027:
2025:
2016:
2015:
2011:
1980:
1973:
1934:
1930:
1889:
1885:
1836:
1832:
1795:
1791:
1746:
1742:
1733:
1729:
1692:(4043): 52–56.
1682:
1675:
1668:
1650:
1646:
1639:
1621:
1617:
1568:
1564:
1559:
1525:
1509:
1501:
1497:
1490:
1482:
1474:
1467:
1453:
1448:
1435:Gaia hypothesis
1431:
1429:Gaia hypothesis
1418:
1393:
1385:π Ursae Majoris
1372:
1337:
1308:
1301:
1289:
1285:
1281:
1277:
1269:
1265:
1249:
1245:
1233:
1225:
1197:
1189:
1180:
1169:
1168:
1160:
1144:
1143:
1132:
1123:
1122:
1108:
1099:
1098:
1087:
1078:
1077:
1067:
1058:
1057:
1046:
1037:
1036:
1026:
1017:
1016:
1014:Ediacaran biota
1006:
997:
996:
985:
976:
975:
965:
956:
955:
953:Earliest plants
945:
936:
935:
925:
916:
915:
905:
896:
895:
885:
876:
875:
864:
855:
854:
844:
835:
834:
823:
814:
813:
811:Earliest oxygen
803:
794:
793:
783:
774:
773:
763:
754:
753:
743:
734:
733:
723:
714:
713:
703:
696:
695:
694:
689:
688:
687:
682:
681:
680:
676:
674:
672:
670:
668:
666:
664:
662:
660:
658:
655:
651:
650:
649:
645:
643:
641:
639:
637:
635:
633:
631:
629:
627:
625:
624:
623:
622:
621:
620:
619:
617:
613:
612:
611:
606:
604:
602:
600:
598:
596:
594:
593:
592:
591:
589:
585:
584:
583:
578:
576:
574:
572:
570:
568:
566:
562:
561:
560:
553:
552:
551:
544:
543:
542:
535:
534:
533:
528:
527:
526:
519:
518:
517:
510:
509:
508:
498:
497:
496:
491:
490:
489:
485:
483:
481:
479:
477:
475:
470:
469:
468:
463:
462:
461:
454:
453:
452:
447:
446:
445:
438:
437:
436:
431:
430:
429:
422:
421:
420:
415:
414:
413:
406:
405:
404:
399:
398:
397:
390:
389:
388:
381:
378:
376:
373:
371:
368:
366:
363:
361:
358:
356:
353:
351:
348:
346:
343:
341:
338:
336:
333:
331:
328:
326:
323:
321:
318:
316:
313:
311:
308:
306:
303:
301:
298:
296:
293:
291:
288:
286:
283:
281:
278:
276:
273:
271:
268:
266:
263:
261:
258:
256:
253:
251:
248:
246:
243:
241:
238:
236:
233:
231:
228:
226:
223:
221:
218:
216:
213:
211:
208:
206:
203:
201:
198:
192:
166:
160:
156:
141:
136:
76:
74:Solar evolution
33:
32:
27:
24:
17:
12:
11:
5:
4246:
4236:
4235:
4230:
4225:
4220:
4215:
4200:
4199:
4187:
4175:
4163:
4151:
4139:
4127:
4104:
4103:
4101:
4100:
4089:
4086:
4085:
4083:
4082:
4076:
4074:
4070:
4069:
4067:
4066:
4061:
4054:
4049:
4044:
4039:
4033:
4031:
4027:
4026:
4024:
4023:
4018:
4013:
4008:
4002:
4000:
3996:
3995:
3993:
3992:
3986:
3980:
3974:
3968:
3962:
3955:
3953:
3949:
3948:
3945:
3944:
3942:
3941:
3933:
3924:
3922:
3918:
3917:
3915:
3914:
3906:
3898:
3890:
3881:
3879:
3872:
3868:
3867:
3864:
3863:
3861:
3860:
3851:
3849:
3845:
3844:
3842:
3841:
3833:
3825:
3817:
3809:
3801:
3793:
3785:
3777:
3769:
3761:
3753:
3744:
3742:
3735:
3731:
3730:
3728:
3727:
3722:
3716:
3711:
3710:
3709:
3694:
3684:
3679:
3674:
3672:Pioneer plaque
3669:
3663:
3661:
3657:
3656:
3649:
3648:
3641:
3634:
3626:
3620:
3619:
3613:
3598:
3595:
3592:
3591:
3564:(3): 472–494.
3550:Kasting, J. F.
3541:
3502:(2): 665–671.
3482:
3429:
3414:
3388:
3351:(4): 230–237.
3330:
3272:
3231:
3190:
3166:
3130:(2): 122–132,
3114:
3107:
3084:
3031:
2990:
2951:(1): 203–220.
2931:
2918:10.1086/340797
2894:(1): 412–425.
2878:
2865:10.1086/432716
2825:
2780:(4): 501–504.
2757:
2733:
2720:10.1086/514331
2680:
2665:10.1086/184826
2635:
2582:
2522:
2485:(4): 563–575.
2468:
2425:
2374:
2339:
2292:
2271:(7): 641–683.
2251:
2209:
2198:
2147:(2): 117–127.
2121:
2086:
2035:
2024:. 18 July 2013
2009:
1971:
1928:
1899:(1): 207–213.
1883:
1830:
1824:10.1086/151197
1789:
1740:
1727:
1673:
1666:
1644:
1637:
1615:
1561:
1560:
1558:
1555:
1554:
1553:
1548:
1542:
1537:
1531:
1524:
1521:
1508:
1505:
1499:
1495:
1491:condensation.
1488:
1480:
1472:
1465:
1452:
1449:
1447:
1444:
1440:Snowball Earth
1430:
1427:
1417:
1414:
1392:
1389:
1371:
1368:
1336:
1333:
1307:
1304:
1299:
1287:
1283:
1279:
1275:
1267:
1263:
1247:
1243:
1231:
1223:
1212:carbon dioxide
1195:
1187:
1178:
1171:
1170:
1161:
1154:
1150:
1149:
1146:
1145:
1138:
1137:
1135:
1125:
1124:
1114:
1113:
1111:
1101:
1100:
1093:
1092:
1090:
1080:
1079:
1073:
1072:
1070:
1060:
1059:
1052:
1051:
1049:
1039:
1038:
1032:
1031:
1029:
1019:
1018:
1012:
1011:
1009:
999:
998:
991:
990:
988:
978:
977:
971:
970:
968:
958:
957:
951:
950:
948:
938:
937:
933:Earliest fungi
931:
930:
928:
918:
917:
911:
910:
908:
898:
897:
891:
890:
888:
878:
877:
870:
869:
867:
857:
856:
850:
849:
847:
837:
836:
829:
828:
826:
816:
815:
809:
808:
806:
796:
795:
791:LHB meteorites
789:
788:
786:
776:
775:
769:
768:
766:
756:
755:
749:
748:
746:
736:
735:
731:Earliest water
729:
728:
726:
716:
715:
709:
708:
706:
697:
692:
691:
690:
685:
684:
683:
654:
653:
652:
616:
615:
614:
588:
587:
586:
565:
564:
563:
556:
555:
554:
547:
546:
545:
538:
537:
536:
531:
530:
529:
522:
521:
520:
513:
512:
511:
501:
500:
499:
494:
493:
492:
473:
472:
471:
466:
465:
464:
457:
456:
455:
450:
449:
448:
441:
440:
439:
434:
433:
432:
427:Photosynthesis
425:
424:
423:
418:
417:
416:
409:
408:
407:
402:
401:
400:
393:
392:
391:
386:
385:
384:
382:
379:0 —
377:
372:
367:
362:
357:
352:
347:
342:
337:
332:
327:
322:
317:
312:
307:
302:
297:
292:
287:
282:
277:
272:
267:
262:
257:
252:
247:
242:
237:
232:
227:
222:
217:
212:
207:
202:
197:
194:
193:
191:
190:
183:
176:
165:
162:
161:
154:
140:
137:
135:
132:
113:nuclear fusion
108:nuclear fusion
75:
72:
68:greenhouse gas
28:
25:
19:
15:
9:
6:
4:
3:
2:
4245:
4234:
4231:
4229:
4226:
4224:
4221:
4219:
4216:
4214:
4211:
4210:
4208:
4198:
4193:
4188:
4186:
4176:
4174:
4164:
4162:
4152:
4150:
4145:
4140:
4138:
4128:
4126:
4121:
4116:
4115:
4112:
4099:
4091:
4090:
4087:
4081:
4078:
4077:
4075:
4071:
4065:
4062:
4060:
4059:
4055:
4053:
4050:
4048:
4045:
4043:
4040:
4038:
4035:
4034:
4032:
4028:
4022:
4019:
4017:
4014:
4012:
4009:
4007:
4004:
4003:
4001:
3997:
3990:
3987:
3984:
3981:
3978:
3975:
3973:(second wife)
3972:
3969:
3966:
3963:
3960:
3959:Lynn Margulis
3957:
3956:
3954:
3950:
3939:
3938:
3934:
3931:
3930:
3926:
3925:
3923:
3919:
3912:
3911:
3907:
3904:
3903:
3899:
3896:
3895:
3891:
3888:
3887:
3883:
3882:
3880:
3876:
3873:
3869:
3858:
3857:
3853:
3852:
3850:
3846:
3839:
3838:
3834:
3831:
3830:
3826:
3823:
3822:
3818:
3815:
3814:
3813:Pale Blue Dot
3810:
3807:
3806:
3802:
3799:
3798:
3794:
3791:
3790:
3786:
3783:
3782:
3778:
3775:
3774:
3773:Broca's Brain
3770:
3767:
3766:
3762:
3759:
3758:
3754:
3751:
3750:
3746:
3745:
3743:
3739:
3736:
3732:
3726:
3723:
3720:
3717:
3715:
3712:
3708:
3707:
3706:Pale Blue Dot
3703:
3702:
3701:
3700:
3695:
3692:
3688:
3685:
3683:
3680:
3678:
3675:
3673:
3670:
3668:
3665:
3664:
3662:
3658:
3654:
3647:
3642:
3640:
3635:
3633:
3628:
3627:
3624:
3616:
3610:
3606:
3601:
3600:
3587:
3583:
3579:
3575:
3571:
3567:
3563:
3559:
3555:
3551:
3545:
3537:
3533:
3528:
3523:
3519:
3515:
3510:
3505:
3501:
3497:
3493:
3486:
3478:
3474:
3470:
3466:
3462:
3458:
3453:
3448:
3444:
3440:
3433:
3425:
3421:
3417:
3415:9781139060172
3411:
3407:
3403:
3399:
3392:
3384:
3380:
3376:
3372:
3368:
3364:
3359:
3354:
3350:
3346:
3339:
3337:
3335:
3326:
3322:
3318:
3314:
3310:
3306:
3301:
3296:
3292:
3288:
3281:
3279:
3277:
3267:
3262:
3258:
3254:
3250:
3246:
3242:
3235:
3226:
3221:
3217:
3213:
3209:
3205:
3201:
3194:
3186:
3181:
3177:
3170:
3163:
3159:
3155:
3151:
3147:
3143:
3138:
3133:
3129:
3125:
3118:
3110:
3104:
3100:
3093:
3091:
3089:
3080:
3076:
3072:
3068:
3064:
3060:
3055:
3050:
3046:
3042:
3035:
3026:
3021:
3017:
3013:
3009:
3005:
3001:
2994:
2986:
2982:
2977:
2972:
2968:
2964:
2959:
2954:
2950:
2946:
2942:
2935:
2927:
2923:
2919:
2915:
2911:
2907:
2902:
2897:
2893:
2889:
2882:
2874:
2870:
2866:
2862:
2858:
2854:
2849:
2844:
2840:
2836:
2829:
2821:
2817:
2813:
2809:
2805:
2801:
2796:
2791:
2787:
2783:
2779:
2775:
2768:
2761:
2753:
2748:
2744:
2737:
2729:
2725:
2721:
2717:
2713:
2709:
2704:
2699:
2695:
2691:
2684:
2675:
2670:
2666:
2662:
2658:
2654:
2650:
2646:
2639:
2631:
2627:
2623:
2619:
2615:
2611:
2606:
2601:
2598:(A12): 1437.
2597:
2593:
2586:
2577:
2573:
2568:
2563:
2559:
2555:
2550:
2545:
2541:
2537:
2533:
2526:
2518:
2514:
2510:
2506:
2502:
2498:
2493:
2488:
2484:
2480:
2472:
2464:
2460:
2456:
2452:
2448:
2444:
2440:
2436:
2429:
2421:
2417:
2413:
2409:
2405:
2401:
2397:
2393:
2389:
2385:
2378:
2370:
2366:
2362:
2358:
2354:
2350:
2343:
2335:
2331:
2327:
2323:
2319:
2315:
2311:
2307:
2303:
2296:
2287:
2282:
2278:
2274:
2270:
2266:
2262:
2255:
2247:
2243:
2238:
2233:
2229:
2225:
2221:
2217:
2213:
2202:
2188:
2184:
2180:
2176:
2171:
2170:2027.42/43349
2166:
2162:
2158:
2154:
2150:
2146:
2142:
2135:
2128:
2126:
2117:
2113:
2109:
2105:
2101:
2097:
2090:
2082:
2078:
2074:
2070:
2066:
2062:
2058:
2054:
2050:
2046:
2039:
2023:
2019:
2013:
2005:
2001:
1997:
1993:
1989:
1985:
1978:
1976:
1967:
1963:
1959:
1955:
1951:
1947:
1943:
1939:
1932:
1923:
1922:2027.42/23696
1918:
1914:
1910:
1906:
1902:
1898:
1894:
1887:
1879:
1875:
1871:
1867:
1863:
1859:
1854:
1849:
1845:
1841:
1834:
1825:
1820:
1816:
1812:
1808:
1804:
1800:
1793:
1785:
1781:
1777:
1773:
1769:
1765:
1760:
1755:
1751:
1744:
1737:
1731:
1723:
1719:
1715:
1711:
1707:
1703:
1699:
1695:
1691:
1687:
1680:
1678:
1669:
1663:
1658:
1657:
1648:
1640:
1634:
1629:
1628:
1619:
1611:
1607:
1603:
1599:
1595:
1591:
1586:
1581:
1578:(2): RG2006.
1577:
1573:
1566:
1562:
1552:
1549:
1546:
1543:
1541:
1538:
1535:
1532:
1530:
1527:
1526:
1520:
1518:
1513:
1504:
1492:
1486:
1478:
1469:
1461:
1459:
1443:
1441:
1436:
1426:
1423:
1413:
1411:
1405:
1402:
1398:
1388:
1386:
1381:
1376:
1367:
1365:
1360:
1358:
1354:
1350:
1346:
1342:
1332:
1330:
1326:
1320:
1317:
1313:
1306:Tidal heating
1303:
1297:
1293:
1273:
1261:
1257:
1251:
1239:
1237:
1229:
1220:
1218:
1213:
1208:
1206:
1201:
1193:
1185:
1181:
1167:
1166:
1158:
1151:
1141:
1136:
1131:
1130:
1121:
1117:
1116:Earliest apes
1112:
1107:
1106:
1096:
1095:Karoo ice age
1091:
1086:
1085:
1076:
1071:
1066:
1065:
1055:
1050:
1045:
1044:
1035:
1030:
1025:
1024:
1015:
1010:
1005:
1004:
994:
989:
984:
983:
974:
969:
964:
963:
954:
949:
944:
943:
934:
929:
924:
923:
914:
909:
904:
903:
894:
889:
884:
883:
873:
868:
863:
862:
853:
848:
843:
842:
832:
827:
822:
821:
812:
807:
802:
801:
792:
787:
782:
781:
772:
767:
762:
761:
752:
747:
742:
741:
732:
727:
722:
721:
712:
707:
702:
701:
678:
647:
609:
581:
559:
550:
541:
525:
516:
507:
504:
488:
460:
444:
428:
412:
396:
195:
189:
184:
182:
177:
175:
170:
169:
163:
159:
157:Life timeline
152:
145:
131:
129:
125:
121:
116:
114:
109:
105:
101:
93:
89:
85:
80:
71:
69:
65:
61:
57:
52:
50:
46:
42:
38:
31:
4185:Solar System
4056:
3985:(third wife)
3965:Dorion Sagan
3961:(first wife)
3935:
3927:
3908:
3900:
3892:
3884:
3854:
3835:
3827:
3819:
3811:
3803:
3795:
3787:
3779:
3771:
3763:
3755:
3747:
3704:
3698:
3676:
3667:Project A119
3604:
3561:
3557:
3544:
3499:
3495:
3485:
3445:(1): 59–63.
3442:
3438:
3432:
3397:
3391:
3348:
3344:
3290:
3286:
3248:
3244:
3234:
3207:
3203:
3193:
3175:
3169:
3127:
3123:
3117:
3098:
3044:
3040:
3034:
3010:(1): 14–28.
3007:
3003:
2993:
2948:
2944:
2934:
2891:
2887:
2881:
2838:
2834:
2828:
2777:
2773:
2760:
2742:
2736:
2693:
2689:
2683:
2648:
2644:
2638:
2595:
2591:
2585:
2539:
2535:
2525:
2482:
2478:
2471:
2438:
2434:
2428:
2387:
2383:
2377:
2352:
2348:
2342:
2309:
2305:
2295:
2268:
2264:
2254:
2219:
2215:
2201:
2190:. Retrieved
2144:
2140:
2102:(1): 23–39.
2099:
2095:
2089:
2048:
2044:
2038:
2026:. Retrieved
2021:
2012:
1987:
1983:
1941:
1937:
1931:
1896:
1892:
1886:
1843:
1839:
1833:
1806:
1802:
1792:
1749:
1743:
1730:
1689:
1685:
1655:
1647:
1626:
1618:
1575:
1571:
1565:
1510:
1493:
1470:
1462:
1454:
1432:
1422:Hubble's law
1419:
1406:
1394:
1377:
1373:
1361:
1338:
1321:
1309:
1252:
1240:
1221:
1217:carbon cycle
1209:
1174:
1163:
711:Earth formed
117:
97:
53:
40:
36:
34:
4173:Outer space
4161:Spaceflight
4030:Recognition
3989:Sasha Sagan
3293:: 381–408.
2651:: L31–L35.
1353:cosmic rays
1335:Cosmic rays
1325:Roche limit
167:This box:
4207:Categories
4052:2709 Sagan
3991:(daughter)
3983:Ann Druyan
3977:Nick Sagan
3878:Television
3653:Carl Sagan
3509:1610.09697
3358:1810.01974
3300:1606.02813
3185:1609.01793
3137:2201.05311
2752:2204.07515
2549:2010.04798
2542:(1): L15.
2492:2007.03423
2192:2010-01-30
1853:1503.04107
1557:References
1357:meteorites
1345:solar wind
1341:Nir Shaviv
1236:weathering
503:Arthropods
443:Eukaryotes
98:Models of
84:luminosity
56:Carl Sagan
4223:Paradoxes
4137:Astronomy
3937:Wanderers
3477:118520121
3452:1405.6701
3383:118915357
3162:245971372
3079:119299932
3054:1311.1308
2958:1102.3209
2790:CiteSeerX
2576:222291370
2517:244532427
2420:205220182
2187:206804461
2081:206524004
1784:119107400
1759:0911.4872
1610:119248267
1585:1204.4449
1364:Milky Way
1260:magnetite
524:Dinosaurs
4098:Category
3697:Voyager
3691:contents
3586:11538226
3552:(1988).
3424:92991460
3325:55266519
2985:54959670
2820:15264566
2812:11543273
2728:14526617
2630:11148141
2455:20360727
2412:20360739
2334:11539665
2246:11543544
2179:11542014
2073:20522772
1966:11536805
1878:67825852
1722:12566286
1714:17756316
1523:See also
1458:Noachian
1272:siderite
1192:hydrogen
1184:nitrogen
1165:Ice Ages
558:Primates
506:Molluscs
134:Theories
4197:Science
4125:Physics
4111:Portals
4073:Related
3929:Contact
3856:Contact
3848:Fiction
3741:Science
3566:Bibcode
3536:5295225
3514:Bibcode
3457:Bibcode
3363:Bibcode
3305:Bibcode
3253:Bibcode
3212:Bibcode
3142:Bibcode
3059:Bibcode
3012:Bibcode
2963:Bibcode
2926:1500425
2906:Bibcode
2873:7137741
2853:Bibcode
2782:Bibcode
2708:Bibcode
2653:Bibcode
2610:Bibcode
2554:Bibcode
2497:Bibcode
2463:4395659
2392:Bibcode
2357:Bibcode
2314:Bibcode
2306:Science
2273:Bibcode
2224:Bibcode
2149:Bibcode
2104:Bibcode
2053:Bibcode
2045:Science
1992:Bibcode
1946:Bibcode
1938:Science
1901:Bibcode
1858:Bibcode
1846:: A42.
1811:Bibcode
1809:: 157.
1764:Bibcode
1694:Bibcode
1686:Science
1590:Bibcode
1380:Archean
1296:methane
1133:←
1109:←
1088:←
1068:←
1047:←
1027:←
1007:←
986:←
966:←
946:←
926:←
906:←
886:←
865:←
845:←
824:←
804:←
784:←
764:←
744:←
724:←
704:←
540:Mammals
515:Flowers
374:–
369:—
364:–
354:–
349:—
344:–
334:–
329:—
324:–
314:–
309:—
304:–
294:–
289:—
284:–
274:–
269:—
264:–
254:–
249:—
244:–
234:–
229:—
224:–
214:–
209:—
204:–
120:surface
3999:Prizes
3952:Family
3940:(2014)
3932:(1997)
3897:(1988)
3859:(1985)
3840:(2006)
3832:(1997)
3824:(1995)
3816:(1994)
3808:(1993)
3800:(1985)
3792:(1984)
3784:(1980)
3781:Cosmos
3776:(1979)
3768:(1977)
3760:(1973)
3752:(1973)
3721:(SETI)
3611:
3584:
3558:Icarus
3534:
3475:
3422:
3412:
3381:
3323:
3160:
3105:
3077:
2983:
2924:
2871:
2818:
2810:
2792:
2726:
2628:
2574:
2515:
2461:
2453:
2435:Nature
2418:
2410:
2384:Nature
2332:
2244:
2185:
2177:
2096:Icarus
2079:
2071:
1964:
1893:Icarus
1876:
1782:
1720:
1712:
1664:
1635:
1608:
1397:albedo
1190:) and
1120:humans
693:
686:
532:
495:
467:
451:
435:
419:
403:
387:
88:radius
64:albedo
4149:Stars
3979:(son)
3967:(son)
3921:Films
3871:Media
3797:Comet
3734:Books
3532:S2CID
3504:arXiv
3473:S2CID
3447:arXiv
3420:S2CID
3379:S2CID
3353:arXiv
3321:S2CID
3295:arXiv
3180:arXiv
3158:S2CID
3132:arXiv
3075:S2CID
3049:arXiv
2981:S2CID
2953:arXiv
2922:S2CID
2896:arXiv
2869:S2CID
2843:arXiv
2816:S2CID
2770:(PDF)
2747:arXiv
2724:S2CID
2698:arXiv
2626:S2CID
2600:arXiv
2572:S2CID
2544:arXiv
2513:S2CID
2487:arXiv
2459:S2CID
2416:S2CID
2183:S2CID
2137:(PDF)
2077:S2CID
2028:9 May
1874:S2CID
1848:arXiv
1780:S2CID
1754:arXiv
1718:S2CID
1606:S2CID
1580:arXiv
1507:Venus
1316:tidal
1282:and H
1274:(FeCO
549:Birds
395:Water
3609:ISBN
3582:PMID
3410:ISBN
3103:ISBN
2808:PMID
2479:PalZ
2451:PMID
2408:PMID
2330:PMID
2242:PMID
2175:PMID
2069:PMID
2030:2022
1962:PMID
1710:PMID
1662:ISBN
1633:ISBN
1451:Mars
1433:The
1312:Moon
1310:The
751:LUCA
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