IoVolcanism

McEwenActive Volcanism on IoScience 297, 2220-2221,2002.: 

McEwen Active Volcanism on Io Science 297, 2220-2221,2002. 今週の科学2002.10.4

Facts on Io: 

Facts on Io Jupiter’s Moon found in 1610 by Galileo Galilei Diameter: 3630km Mass(Earth=1): 0.015 Gravity(Earth=1): 0.183 Density: 3.57g/cm3 Orbital period: 1.77day Rotational period: 1.77day From Jupiter: 421,600km

Voyager1 Expedition in 1979: 

Voyager1 Expedition in 1979 volcanoes rugged mountains colorful surface rich in sulfurous materials giant plumes of gas and dust Nature of the volcanism sulfur volcanism burying a silicate subcrust or silicate volcanism and crust with thin sulfurous coating ~700K 1300-1450K (earth’s basaltic lava)

Galileo Expedition from 1989-: 

Galileo Expedition from 1989- First Io flyby in 1995 delay of launch failure in expansion of high-gain antenna tape recorder anomaly NO DATA Six flybys 1999-2002 some detectors were dead or degraded on NIMS Solid State Imaging (SSI) Near-Infrared Mapping Spectometer(NIMS)

Galileo Image of Io: 

Galileo Image of Io

distant Galileo observations1996-1998: 

distant Galileo observations 1996-1998 found 41 hotspots above ~1000K all in the dark patches

Six close Io flybys 1999-2002: 

Six close Io flybys 1999-2002 hot silicate sulfur dioxide frost 150-300 major hotspots - lava flows - lava lakes -caldera-like depressions

Dramatic eruption at Pillan Patera in 1997: 

Dramatic eruption at Pillan Patera in 1997 4 April 1997 19 September 1997 400km lava flows (Arizona-size) 120km high plume High temperature ~1800K

High temperature volcanism: 

High temperature volcanism High temperature > 1500K Today’s Earth basaltic eruption: 1300-1450K Hottest terrestrial lava at 1700-1900K are ancient (age>2000my) The study of Io may thus provide important clues to understanding the early Earth

Mg rich volcanism: 

Mg rich volcanism The ancien high-temperature lavas on earth are rich in Mg Spectral data shows absorption band at ~900nm in dark patches = orthopyroxene spectra Io is an ultramafilc world? The idea seems at odds with mantle segregation…… Keszthelyi et al. (1999) Io’s lower mantle could be a crystal-rich magma ocean upper mantle would consists of orthopyroxene-rich magma overlying crust is about the same density of upper mantle hot mantle suppress convection in Io’s core - no magnetic field difficult to explain how Io first got into that state

Galileo Today: 

Galileo Today 32 days to Amalthea flyby Largest of Jupiter’s smaller moons - 270*170*150km - irregular “potato” shape Orbit inside the orbit of Io -Only 2.5 Jupiter radi Reddest object in the solar system