saturn’s north pole hexagonal cloud pattern
DESCRIPTION
Saturn’s North Pole Hexagonal Cloud Pattern. Raúl Cacho Martínez Dpto. Astrofísica UCM 13 de Enero de 2011. Primera observación. D.A . Godfrey en 1988 con datos de las sondas Voyager 1 (Noviembre 1980) y Voyager 2 (Agosto 1981). Confirmado por la sonda Cassini-Huygens (2006). - PowerPoint PPT PresentationTRANSCRIPT
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Saturn’s North Pole Hexagonal Cloud Pattern
Raúl Cacho MartínezDpto. Astrofísica UCM13 de Enero de 2011
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Primera observaciónD.A. Godfrey en 1988 con datos de las sondas Voyager 1 (Noviembre 1980) y Voyager 2 (Agosto 1981).Confirmado por la sonda Cassini-Huygens (2006)
Voyager I (1980)
Cassini (2006)
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Características físicasTormenta ciclónica a latitud 76º, con mucha subestructura
Periodo de rotación: 10h 39m 24s (igual al de emisión radio)Tamaño del lado: 13800 km (8% más que el diámetro terrestre)
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Composición químicaSin diferencias sensibles con respecto a la del resto del planeta
(H, He, NH3, CH4, H2O, …)No hay variaciones sensibles en PH3 (trazador troposférico)
The meridional distribution of PH3, a tracer for tropospheric motion, is shown within 20° of each pole.
L N Fletcher et al. Science 2008;319:79-81
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Temperatura
Zonal mean temperatures in the stratosphere (A and B) and troposphere (C and D) for the northern [(A) and (C)] and
southern [(B) and (D)] hemispheres.L N Fletcher et al. Science 2008;319:79-81
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Profundidad
Orthographic projection of Saturn's polar temperatures in the troposphere at 100 mbar (A and B) and the stratosphere at 1
mbar (C and D).L N Fletcher et al. Science 2008;319:79-81
A partir de imágenes térmicas se ha determinado su profundidad:
100 km
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Velocidad
Baines et al. 2009, Planetary and Space Science, 57, 1671–1681
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Vorticidad
Baines et al. 2009, Planetary and Space Science, 57, 1671–1681
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¿Por qué un hexágono?No se tiene muy claro el origen del patrón hexagonalOndas de Rossby estacionarias (movimientos del “aire” de los polos hacia el ecuador debido a diferencia de temperaturas)
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Simulaciones de laboratorioSimulación en el laboratorio con una mezcla de agua y glicerol, variando factores topográficos (β), velocidad de rotación (número de Rossby, Ro) y viscosidad (número de Ekman, E)
Barbosa et al. 2010 Icarus, Volume 206, 2, 755-763
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¿Por qué no en el polo sur?
Baines et al. 2009, Planetary and Space Science, 57, 1671–1681
Las velocidades son parecidas
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¿Por qué no en el polo sur?
Baines et al. 2009, Planetary and Space Science, 57, 1671–1681
La composición química es diferente, hay más PH3 en el polo Sur
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¿Por qué no en el polo sur?La clave está en la temperatura
L N Fletcher et al. Science 2008;319:79-81
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¿Por qué no en el polo sur?En el polo sur hay un punto caliente que genera convección.La convección destruye los patrones que puedan formarse.
Cassini, JPL/NASA
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Patrones hexagonalesEl hexágono es una de las geometrías más estables de la naturaleza
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Referencias• Allison et al. 1990, A wave dynamical interpretation of Saturn's polar hexagon.
Science, Vol. 247, p1061-1063• Baines et al. 2009, Saturn's north polar cyclone and hexagon at depth revealed by
Cassini/VIMS.Planetary and Space Science, Vol. 57, Issue14-15, p 1671-1681
• Barbosa Aguiar et al. 2010, A laboratory model of Saturn’s North Polar hexagon.Icarus, Vol. 206, Issue 2, p 755-763
• Efremov 2003, On the origin of Circular and hexagonal formations in galaxies.Astronomical and Astrophysical transactions, Vol. 22, Issue 3, p 245-262
• Fletcher et al. 2007, Saturn's Polar Dynamics from Cassini/CIRS.Bulletin of the American Astronomical Society, Vol 39, p 488
• Fletcher et al. 2008, Temperature and Composition of Saturn’s Polar Hot Spots and Hexagon. Science, Vol. 319, Issue 5859, p 79
• Godfrey 1988, The rotation rate of Saturn’s polar hexagon.Bulletin of the American Astronomical Society, Vol 20, p 880
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Referencias• Godfrey 1988, A hexagonal feature around Saturn's North Pole.
Icarus, Vol. 76, p 355-356• Kochemasov 2010, Saturnian north polar region: a triangle inside the hexagon?
EGU General Assembly, held 2-7• Momary et al. 2008, Saturn's Dynamic Atmosphere at Depth: Physical Characteristics and
Zonal Winds Derived from Clouds Near the 2-bar Level and Their Dynamical Implications from Cassini-Huygens/VIMS.Bulletin of the American Astronomical Society, Vol 40, p 472
• Orton et al. 2009, Saturn Atmospheric Science in the Next Decade.American Astronomical Society, DPS meeting #41, #16.03
• Sánchez-Lavega et al. 1993, Temporal behaviour and cloud morphologies and motions in Saturn’s atmosphere.Journal of Geophysical research, Vol. 98, Issue E10, p 18857-18872
• Vasavada et al. 2006, Cassini imaging of Saturn: Southern hemisphere winds and vortices.Journal of Geophysical research, Vol. 111, Issue E5, CiteID E05400
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¡Gracias!