Atmosphere of Io

Last updated May 16, 2024

The atmosphere of Io is the extremely thin blanket of gases surrounding Jupiter's third largest moon Io. The atmosphere is primarily composed of sulfur dioxide (SO₂), along with sulfur monoxide (SO), sodium chloride (NaCl), and monoatomic sulfur and oxygen.^[1] Dioxygen is also expected to be present.

Origin

Io is considered to be the most volcanically active body in our solar system. Pele type volcanism is believed to be the cause of sulfur components in the atmosphere. Volcanic plumes pump 10⁴ kg of SO₂ (sulfur dioxide) per second into Io's atmosphere on average, though most of this is deposited back onto the surface. Sunlight sublimates this solid SO₂, turning it into the gaseous state and creating a thin atmosphere. Due to this, atmospheric pressure is significantly higher near volcanoes, about 0.5 to 4 mPa (5 to 40 nbar), around 5,000 to 40,000 times larger than that of the night side of Io. Apart from this, minor components like NaCl, SO, O are also formed by other processes. The main source of NaCl and KCl is thought to be volcanic.^[2] Some volcanic vents are thought to expel NaCl and KCl but little to no SO₂. Sputtering of the surface by charged particles from Jupiter's magnetosphere is thought to be the origin of the NaCl, SO, O, and S. They are also formed from direct volcanic outgassing. Photodissociation is thought to be the origin of SO, Na, K, and Cl.^{[ clarification needed ]} Photodissociation plays an important role in the atmosphere at higher latitudes. Because the process happens more often during daytime, the concentration of Na is believed to be higher during daytime.^[1]^[3]

Physical characteristics

SO₂ is the main constituent, comprising 90% of the atmospheric pressure. About 3%–10% is SO. The atmospheric pressure varies from 0.033 to 0.3 mPa or 0.33 to 3 nbar ^{[ disgrees figures above ]}, seen on Io's anti-Jupiter hemisphere and along the equator, and temporally in the early afternoon when the temperature of surface frost peaks. On the night side^{[ clarification needed ]}, SO₂ freezes, decreasing the atmospheric pressure to 0.1 × 10⁻⁷ to 1 × 10⁻⁷ Pa (0.0001 to 0.001 nbar).^[4] Some studies suggest that the night side atmosphere consists of non-condensable gases like atomic O and SO. The atmosphere on the side facing away from Jupiter is not just denser but also extends over a greater range of latitudes than the side facing Jupiter. The vertical column density at the equator ranges from 1.5 × 10¹⁶ cm⁻² at sub-Jovian longitudes to 15 × 10¹⁶ cm⁻²at anti-Jovian longitudes.^[5] On the surface, sulfur dioxide is in vapor pressure equilibrium with frost. The temperatures increases to 1,800 K at higher altitudes where the lower atmospheric density permits heating from plasma in the Io plasma torus and from Joule heating from the Io flux tube. The day-side atmosphere is mostly confined to within 40° of the equator, where the surface is warmest and most active volcanic plumes are found.^[6] The polar atmospheric pressure is only 2% of the equatorial atmospheric pressure. At about ±40° latitude, the atmospheric pressure will be half of that at the equator. The atmospheric density increases the closer Io gets to the Sun.^[7] Farther away from the surface, higher the concentration of O and S₂^{[ clarification needed ]} gets. This is because of the lower mass of oxygen and sulphur atoms compared to others. The O/SO₂ ratio is estimated to be between 10% and 20% in the upper atmosphere. These gases exist up to a distance of 10 times the radius of Io.

Io has a sodium tail similar to the Sodium tail of the Moon. Io also has an ionosphere with a density of 2.8 × 10¹⁰ m⁻³ at 80 km altitude, comparable to the ionospheres of Mars and Venus. Occultation studies by Pioneer 10 revealed that the night-side ionosphere is significantly less dense for the first time.^{[ clarification needed ]} Based on the six occultations conducted by the Galileo probe in 1997, the ionosphere is asymmetrical: the plasma density varies by longitude. The interpretation of the observations assumes that the increased plasma density is distributed in a spherically symmetrical bound ionosphere with a dense downstream wake. Depending on the location, peak densities of about 5 × 10¹⁰ m⁻³ were found, reaching a maximum of about 2.5 × 10¹¹ m⁻³ in one of the occultations. Due to its thinness, Io's atmosphere does not cause that much effect on the surface, other than moving SO₂ ice around and expanding the size of plume deposit rings when plume material re-enters the denser dayside atmosphere. Every second, almost one tonne of gases escape from Io's atmosphere into outer space due to Jupiter's magnetosphere. Due to this^{[ clarification needed ]}, the atmosphere should be constantly replenished. These gases orbit Jupiter along with Io, creating a Io plasma torus.

Post-ecliptic brightening

Io's atmospheric density is directly related to surface temperature. When Io falls into the shadow of Jupiter during an eclipse, the temperature falls. This causes deposition of the SO₂, and results in an 80% decrease in the atmospheric pressure.^[8] This increases the albedo of Io; thus Io appears brighter when covered with frost immediately after an eclipse. After about 15 minutes the brightness returns to normal, presumably because the frost has disappeared through sublimation. Post-ecliptic brightening can be observed with ground telescopes. Cassini spacecraft captured post-eclipse brightening in near-infrared wavelengths.^[9] Further evidence for this theory came in 2013 when the Gemini Observatory was used to directly measure the collapse of Io's SO₂ atmosphere during, and its reformation after, eclipse by Jupiter.^[10]

Aurora

Io hosts Aurora events, even though the atmosphere is extremely thin. Unlike other celestial bodies where an aurora occurs at the North and South poles, aurora on Io occurs near the equator. This is because aurorae on other bodies are caused by the interactions of the body's magnetosphere with the solar wind. In contrast, Io has no magnetic field of its own. Instead of solar wind, charged particles from Jupiter's magnetosphere interact with Io's atmosphere, creating aurora.^[11]

Sodium atoms cause a green glow in the aurora. Here blue glows caused by SO₂ are nearer to the surface than red glows caused by oxygen. This is because SO₂ is heavier than oxygen, and as a result will be more gravitationally bound to the surface. Due to this, red glows reach up to a height of 900 km (560 miles). The aurora moves across Io, as it changes its orientation with respect to Jupiter's magnetosphere as it orbits the planet.

Related Research Articles

In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior dynamo.

Europa, or Jupiter II, is the smallest of the four Galilean moons orbiting Jupiter, and the sixth-closest to the planet of all the 95 known moons of Jupiter. It is also the sixth-largest moon in the Solar System. Europa was discovered independently by Simon Marius and Galileo Galilei and was named after Europa, the Phoenician mother of King Minos of Crete and lover of Zeus.

An aurora , also commonly known as the northern lights or southern lights, is a natural light display in Earth's sky, predominantly seen in high-latitude regions. Auroras display dynamic patterns of brilliant lights that appear as curtains, rays, spirals, or dynamic flickers covering the entire sky.

Ganymede, or Jupiter III, is the largest and most massive natural satellite of Jupiter and in the Solar System. It is the largest Solar System object without a substantial atmosphere, despite being the only moon in the Solar System with a substantial magnetic field. Like Titan, Saturn's largest moon, it is larger than the planet Mercury, but has somewhat less surface gravity than Mercury, Io, or the Moon due to its lower density compared to the three.

An atmosphere is a layer of gasses that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosphere is the outer region of a star, which includes the layers above the opaque photosphere; stars of low temperature might have outer atmospheres containing compound molecules.

Io, or Jupiter I, is the innermost and second-smallest of the four Galilean moons of the planet Jupiter. Slightly larger than Earth's moon, Io is the fourth-largest moon in the Solar System, has the highest density of any moon, the strongest surface gravity of any moon, and the lowest amount of water by atomic ratio of any known astronomical object in the Solar System. It was discovered in 1610 by Galileo Galilei and was named after the mythological character Io, a priestess of Hera who became one of Zeus's lovers.

<span class="mw-page-title-main">Sulfur monoxide</span> Chemical compound

Sulfur monoxide is an inorganic compound with formula SO. It is only found as a dilute gas phase. When concentrated or condensed, it converts to S₂O₂ (disulfur dioxide). It has been detected in space but is rarely encountered intact otherwise.

The magnetosphere of Saturn is the cavity created in the flow of the solar wind by the planet's internally generated magnetic field. Discovered in 1979 by the Pioneer 11 spacecraft, Saturn's magnetosphere is the second largest of any planet in the Solar System after Jupiter. The magnetopause, the boundary between Saturn's magnetosphere and the solar wind, is located at a distance of about 20 Saturn radii from the planet's center, while its magnetotail stretches hundreds of Saturn radii behind it.

The plasmasphere, or inner magnetosphere, is a region of the Earth's magnetosphere consisting of low-energy (cool) plasma. It is located above the ionosphere. The outer boundary of the plasmasphere is known as the plasmapause, which is defined by an order of magnitude drop in plasma density. In 1963 American scientist Don Carpenter and Soviet astronomer Konstantin Gringauz proved the plasmasphere and plasmapause's existence from the analysis of very low frequency (VLF) whistler wave data. Traditionally, the plasmasphere has been regarded as a well behaved cold plasma with particle motion dominated entirely by the geomagnetic field and, hence, co-rotating with the Earth.

The atmosphere of Venus is the very dense layer of gasses surrounding the planet Venus. Venus's atmosphere is composed of 96.5% carbon dioxide and 3.5% nitrogen, with other chemical compounds present only in trace amounts. It is much denser and hotter than that of Earth; the temperature at the surface is 740 K, and the pressure is 93 bar (1,350 psi), roughly the pressure found 900 m (3,000 ft) under water on Earth. The atmosphere of Venus supports decks of opaque clouds of sulfuric acid that cover the entire planet, making optical Earth-based and orbital observation of the surface impossible. Information about surface topography has been obtained exclusively by radar imaging.

The magnetosphere of Jupiter is the cavity created in the solar wind by Jupiter's magnetic field. Extending up to seven million kilometers in the Sun's direction and almost to the orbit of Saturn in the opposite direction, Jupiter's magnetosphere is the largest and most powerful of any planetary magnetosphere in the Solar System, and by volume the largest known continuous structure in the Solar System after the heliosphere. Wider and flatter than the Earth's magnetosphere, Jupiter's is stronger by an order of magnitude, while its magnetic moment is roughly 18,000 times larger. The existence of Jupiter's magnetic field was first inferred from observations of radio emissions at the end of the 1950s and was directly observed by the Pioneer 10 spacecraft in 1973.

Pele is an active volcano on the surface of Jupiter's moon Io. It is located on Io's trailing hemisphere at 18.7°S 255.3°W. A large, 300-kilometer (190 mi) tall volcanic plume has been observed at Pele by various spacecraft starting with Voyager 1 in 1979, though it has not been persistent. The discovery of the Pele plume on March 8, 1979 confirmed the existence of active volcanism on Io. The plume is associated with a lava lake at the northern end of the mountain Danube Planum. Pele is also notable for a persistent, large red ring circling the volcano resulting from sulfurous fallout from the volcanic plume.

Volcanism on Io, a moon of Jupiter, is represented by the presence of volcanoes, volcanic pits and lava flows on the surface. Io's volcanic activity was discovered in 1979 by Linda Morabito, an imaging scientist working on Voyager 1. Observations of Io by passing spacecraft and Earth-based astronomers have revealed more than 150 active volcanoes. As of 2004, up to 400 such volcanoes are predicted to exist based on these observations. Io's volcanism makes the satellite one of only four known currently volcanically or cryovolcanically active worlds in the Solar System

The atmosphere of Triton is the layer of gases surrounding Triton. Like the atmospheres of Titan and Pluto, Triton's atmosphere is composed primarily of nitrogen, with smaller amounts of methane and carbon monoxide. It hosts a layer of organic haze extending up to 30 kilometers above its surface and a deck of thin bright clouds at about 4 kilometers in altitude. Due to Triton's low gravity, its atmosphere is loosely bound, extending over 800 kilometers from its surface.

Surt is an active volcano on Jupiter's moon Io. It is located on Io's Jupiter-facing hemisphere at 45.21°N 336.49°W. Surt consists of an oblong volcanic pit, 75 by 40 kilometres in diameter, surrounded by reddish sulfur and bright sulfur dioxide deposits to its south and east. The volcano was first observed in images acquired by the Voyager 1 spacecraft in March 1979. Later that year, the International Astronomical Union named this feature after Surtr, a leader of the fire giants of Norse mythology.

<span class="mw-page-title-main">Amirani (volcano)</span> Volcano on Io

Amirani is an active volcano on Jupiter's moon Io, the inner-most of the Galilean Moons. It is located on Io's leading hemisphere at 24.46°N 114.68°W. The volcano is responsible for the largest active lava flow in the entire Solar System, with recent flows dwarfing those of even other volcanos on Io.

In astronomy, a regular moon or a regular satellite is a natural satellite following a relatively close, stable, and circular orbit which is generally aligned to its primary's equator. They form within discs of debris and gas that once surrounded their primary, usually the aftermath of a large collision or leftover material accumulated from the protoplanetary disc. Young regular moons then begin to accumulate material within the circumplanetary disc in a process similar to planetary accretion, as opposed to irregular moons, which formed independently before being captured into orbit around the primary.

The exploration of Io, Jupiter's innermost Galilean and third-largest moon, began with its discovery in 1610 and continues today with Earth-based observations and visits by spacecraft to the Jupiter system. Italian astronomer Galileo Galilei was the first to record an observation of Io on January 8, 1610, though Simon Marius may have also observed Io at around the same time. During the 17th century, observations of Io and the other Galilean satellites helped with the measurement of longitude by map makers and surveyors, with validation of Kepler's Third Law of planetary motion, and with measurement of the speed of light. Based on ephemerides produced by astronomer Giovanni Cassini and others, Pierre-Simon Laplace created a mathematical theory to explain the resonant orbits of three of Jupiter's moons, Io, Europa, and Ganymede. This resonance was later found to have a profound effect on the geologies of these moons. Improved telescope technology in the late 19th and 20th centuries allowed astronomers to resolve large-scale surface features on Io as well as to estimate its diameter and mass.

Thor is an active volcano on Jupiter's moon Io. It is located on Io's anti-Jupiter hemisphere at 39.15°N 133.14°W. A major eruption with high thermal emission and a large, volcanic plume was observed during a Galileo flyby on August 6, 2001, when the spacecraft flew through the outer portions of the plume allowing for direct sampling. The eruption continued into Galileo's next flyby in October 2001. As seen during high-resolution images taken during the eruption, Thor consists of a series of dark lava flows emanating from a set of nearby volcanic depressions. Before the eruption, the area consisted of red-brown plains, composed of irradiated sulfur, typical of Io's mid- to high-northern latitudes and a set of yellow flows, possibly consisting of sulfur or silicate flows covered by diffuse sulfur deposits. During the New Horizons encounter in February 2007, Thor was still active, with the spacecraft observing thermal emission in the near-infrared and a volcanic plume at the volcano.

The Plasma Instrument for Magnetic Sounding (PIMS) is a Faraday cup based instrument that will fly on board the Europa Clipper orbiter to explore Jupiter's moon Europa. PIMS will measure the plasma that populates Jupiter's magnetosphere and Europa's ionosphere.

References

1 2 Lellouch, E.; et al. (2007). "Io's atmosphere". In Lopes, R. M. C.; and Spencer, J. R. (eds.). Io after Galileo. Springer-Praxis. pp. 231–264. ISBN 978-3-540-34681-4.
↑ De Pater, Imke; Goldstein, David; Lellouch, Emmanuel (2023). "The Plumes and Atmosphere of Io". Io: A New View of Jupiter's Moon. Astrophysics and Space Science Library. Vol. 468. pp. 233–290. doi:10.1007/978-3-031-25670-7_8. ISBN 978-3-031-25669-1 . Retrieved 25 October 2023– via Springer Link.
↑ Walker, A. C.; et al. (2010). "A Comprehensive Numerical Simulation of Io's Sublimation-Driven Atmosphere". Icarus. in. press (1): 409–432. Bibcode:2010Icar..207..409W. doi:10.1016/j.icarus.2010.01.012.
↑ Moore, C. H.; et al. (2009). "1-D DSMC simulation of Io's atmospheric collapse and reformation during and after eclipse". Icarus. 201 (2): 585–597. Bibcode:2009Icar..201..585M. doi:10.1016/j.icarus.2009.01.006.
↑ Spencer, A. C.; et al. (2005). "Mid-infrared detection of large longitudinal asymmetries in Io's SO₂ atmosphere" (PDF). Icarus. 176 (2): 283–304. Bibcode:2005Icar..176..283S. doi:10.1016/j.icarus.2005.01.019.
↑ Feaga, L. M.; et al. (2009). "Io's dayside SO₂ atmosphere". Icarus. 201 (2): 570–584. Bibcode:2009Icar..201..570F. doi:10.1016/j.icarus.2009.01.029.
↑ Spencer, John (8 June 2009). "Aloha, Io". The Planetary Society Blog. The Planetary Society.
↑ Geissler, P. E.; Goldstein, D. B. (2007). "Plumes and their deposits". In Lopes, R. M. C.; Spencer, J. R. (eds.). Io after Galileo. Springer-Praxis. pp. 163–192. ISBN 978-3-540-34681-4.
↑ Nelson, Robert M.; et al. (February 1993). "The Brightness of Jupiter's Satellite Io Following Emergence from Eclipse: Selected Observations, 1981–1989". Icarus. 101 (2): 223–233. Bibcode:1993Icar..101..223N. doi:10.1006/icar.1993.1020.
↑ Moullet, A.; et al. (2010). "Simultaneous mapping of SO₂, SO, NaCl in Io's atmosphere with the Submillimeter Array". Icarus. press (1): 353–365. Bibcode:2010Icar..208..353M. doi:10.1016/j.icarus.2010.02.009.
↑ Bagenal, Fran; Dols, Vincent (2020). "The Space Environment of Io and Europa". Journal of Geophysical Research: Space Physics. 125 (5). Bibcode:2020JGRA..12527485B. doi:10.1029/2019JA027485. S2CID 214689823 . Retrieved 25 October 2023.

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.

[IobookChap10-1] 1 2 Lellouch, E.; et al. (2007). "Io's atmosphere". In Lopes, R. M. C.; and Spencer, J. R. (eds.). Io after Galileo. Springer-Praxis. pp. 231–264. ISBN 978-3-540-34681-4.

[2] De Pater, Imke; Goldstein, David; Lellouch, Emmanuel (2023). "The Plumes and Atmosphere of Io". Io: A New View of Jupiter's Moon. Astrophysics and Space Science Library. Vol. 468. pp. 233–290. doi:10.1007/978-3-031-25670-7_8. ISBN 978-3-031-25669-1 . Retrieved 25 October 2023– via Springer Link.

[Walker2010-3] Walker, A. C.; et al. (2010). "A Comprehensive Numerical Simulation of Io's Sublimation-Driven Atmosphere". Icarus. in. press (1): 409–432. Bibcode:2010Icar..207..409W. doi:10.1016/j.icarus.2010.01.012.

[Moore2009-4] Moore, C. H.; et al. (2009). "1-D DSMC simulation of Io's atmospheric collapse and reformation during and after eclipse". Icarus. 201 (2): 585–597. Bibcode:2009Icar..201..585M. doi:10.1016/j.icarus.2009.01.006.

[Spencer2005-5] Spencer, A. C.; et al. (2005). "Mid-infrared detection of large longitudinal asymmetries in Io's SO₂ atmosphere" (PDF). Icarus. 176 (2): 283–304. Bibcode:2005Icar..176..283S. doi:10.1016/j.icarus.2005.01.019.

[Feaga2009-6] Feaga, L. M.; et al. (2009). "Io's dayside SO₂ atmosphere". Icarus. 201 (2): 570–584. Bibcode:2009Icar..201..570F. doi:10.1016/j.icarus.2009.01.029.

[AlohaIo-7] Spencer, John (8 June 2009). "Aloha, Io". The Planetary Society Blog. The Planetary Society.

[autogenerated2-8] Geissler, P. E.; Goldstein, D. B. (2007). "Plumes and their deposits". In Lopes, R. M. C.; Spencer, J. R. (eds.). Io after Galileo. Springer-Praxis. pp. 163–192. ISBN 978-3-540-34681-4.

[9] Nelson, Robert M.; et al. (February 1993). "The Brightness of Jupiter's Satellite Io Following Emergence from Eclipse: Selected Observations, 1981–1989". Icarus. 101 (2): 223–233. Bibcode:1993Icar..101..223N. doi:10.1006/icar.1993.1020.

[Moullet2010-10] Moullet, A.; et al. (2010). "Simultaneous mapping of SO₂, SO, NaCl in Io's atmosphere with the Submillimeter Array". Icarus. press (1): 353–365. Bibcode:2010Icar..208..353M. doi:10.1016/j.icarus.2010.02.009.

[11] Bagenal, Fran; Dols, Vincent (2020). "The Space Environment of Io and Europa". Journal of Geophysical Research: Space Physics. 125 (5). Bibcode:2020JGRA..12527485B. doi:10.1029/2019JA027485. S2CID 214689823 . Retrieved 25 October 2023.

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

[9]

[10]

[11]