fr en es pt
       RSS astronoo  


Io the galilean moon

 Automatic translationAutomatic translation Category: moons
Updated June 01, 2013

Io is one of four Galilean moons of Jupiter, the closest to the planet.
It pulls its name of Io, loving conquest of Zeus persecuted by the wife of this last one, Hera, whose a priestess she had been. Io is especially remarkable for its active volcanism, observed that on the Earth.
The energy necessary for this activity results probably from interactions of tide between Io, Europe, Ganymede and Jupiter. Although Io always presents the same in front of Jupiter, the presence of Europe and Ganymede makes it vacillate a little.
This interaction deforms the surface of Io which lifts up itself and falls up to 100 meters and produces of the heat by internal friction.

Io (Jupiter I)Characteristics
Apoapsis423 000 km
Periapsis420 000 km
Semi-major axis421 700 km
Diameter3243.2 km
Mass8.931938×1022 kg
Average orbital speed17.334 km/s
Orbital period1.769137786 d
Rotation periodsynchronous
Inclination to Jupiter's equator0.05°
Discovered byGalileo Galilei
Discovery dateJanuary 8, 1610

Io pulled in all directions


Before even the discovery of the volcanic eruptions of Io, these had been foreseen by a team of American researchers, steered by S. Peale. Io is subjected to a double effect of tide which stretches its surface and its internal layers everywhere.
With 3 680 km in diameters, Io seems tiny when she walks past the enormous globe of Jupiter the diameter of which is 143 000 km.
Its orbit is very low, Io puts in 42 hours and 27 minutes to make the tour of Jupiter. So by shaving the huge planet, it is subjected to an enormous effect of tide which deforms it and warms, not only its surface but also its internal layers.
For that purpose of tide, is added the second, that of another moon of Jupiter, a little smaller Europe with its 3 122 km in diameters.
Placed on a higher orbit, Europe makes the tour of Jupiter in 85 hours. Io, faster, thus catches up it and exceeds it both tours of orbit.
On every meeting, both moons incur and deform mutually. Pulled so between Jupiter and Europe, deformed every 42 hours by tides of big amplitudes (until 100 m), Io warms up and loosens billions of kilowatts of heat or 40 times more than the Earth, while she is not bigger than the Moon.


All this makes that this celestial body the internal layers of which are in fusion in a permanent, present way ceaseless and gigantic volcanic eruptions amount on average to 10 000 tons of lava per second and by volcano.
The surface of Io thus presents a big variety of grounds characterized by depressions which correspond to the calderas of volcanoes, eminences, high trays, mountains and chains of craters.
The sulfur and its compounds look to these landscapes of the colorful colors. Certain regions constitute a magnificent contrasted palette where dominate the yellow, the green and the red.
Changeable tints of lava flows reflect, partially, the chemical states of the sulfur which changes according to the temperature.

 Io and Jupiter

Image: We perceive on this tiny photography Io with its shadow being reflected on the gigantic surface of Jupiter. Indeed with its 3680 km in diameters, Io seems tiny when she walks past the enormous globe of Jupiter (143000 km in diameter). It makes the tour, on a very low orbit, in 42 hours and 27 minutes. Photo taken by the probe Cassini-Huygens in December, 2000.

Io the volcanic moon


Io watch on the photo opposite, its intense activity because three volcanic panache are visible in spite of the smallness of the image.
The most spectacular panache is the one which amounts to 290 kilometers above the volcano Tvashtar near the north pole.
Two other smaller panache are hardly visible. The first one is the one of the volcano Prometheus, at "9 hours", and the second that of the volcano Amirani, between Prometheus and Tvashtar along the border at day-night on the moon.
The light which crosses the tiny particles of dusts ejected by volcanoes, gives this bluish light while on the base of the panache of Tvashtar, we can see a red light which lets us guess the incandescent lava of the volcano.


Image: Photography of the croissants of Io ' on the upper left) and of Europe (below to the right), taken on March 2nd, 2007 by the probe New horizons in 4,6 million kilometers of Io and 3,8 million kilometers of Europe, the moons separated from 800 000 kilometers one of the other one.
The Sun is to the left of the photo and the Jupiter to the right, moreover we can notice that the night-side of Io is enlightened by the light reflected by Jupiter, Europe being absolutely dark on the other hand.
Image taken by the instrument MVIC (Multispectral Visual Imaging Camera) of New Horizons. 
Source NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute


Moons of Jupiter


Jupiter, the largest planet in our solar system is surrounded by more than 60 moons.
The moons of Jupiter were first discovered in 1610. Galileo Galilei discovered at that time the four largest Jovian satellites system Io, Europa, Ganymede and Callisto. These Galilean moons called for, were the first to be observed except that of Earth.
Today, thanks to space probes, we have a more comprehensive view of the Jovian system. This is the series of Voyager missions which helped lift the veil on the Jovian system by discovering in 1979, Metis, and Thebe Adrastea.
Before the space age, astronomers have discovered Amalthea (1892), Himalia (1904), Elara (1905), Pasiphae (1908), Sinope (1914), and Lysithea Carme (1938), Ananke (1951), Leda (1974 ) and Themisto (1975. Between 1979 and 1999, no new satellite of Jupiter was not discovered and it was not until October 6, 1999, for the Spacewatch program discovers a new moon to Jupiter, Callirrhoe.


Observations in 2000 revealed ten new moons, bringing the number of satellites to 28 after the rediscovery of Themisto, Kalyke, Iocasta, Erinome, Harpalyke, Isonoe, Praxidike, Megaclite, Taygete, Chaldene and S/2000 J 11. The following year, eleven other moons were discovered, bringing the total to 39, Hermippe, Eurydome, Sponde, Kale, Autonoe, Thyone, Pasithee, Euanthe, Orthosie, Europie, Aitne.
In 2002, only one moon, Arche, was discovered.
In 2003 there discovered 23 new satellites, Eukelade, S/2003 J 2, S/2003 J 3, S/2003 J 4, S/2003 J 5, Helice, Aoede, hegemone, S/2003 J 9, S / 2003 J 10, Kallichore, S/2003 J 12, Cyllene, S/2003 J 14 S/2003 J 15 S/2003 J 16 S/2003 J 17 S/2003 J 18 S/2003 J 19 , Carpo, Mneme, Thelxinoe and S/2003 J 23. Most of the 47 satellites discovered after the 2000s are small moons of a few kilometers in diameter, the largest accounting for just 9 km.
In 2006, 63 were known moons of Jupiter, the record of the solar system.

Moons of Jupiter Diameter
axis (km)
Ganymede (Jupiter III) 5262 1 070 400
Callisto (Jupiter IV) 4821 1 882 700
Io (Jupiter I) 3643 421 800
Europa (Jupiter II) 3122 671 100
Amalthea (Jupiter V) 262x146x134 181 365
Himalia (Jupiter VI) 170 11 493 550
Thebe (Jupiter XIV) 110x90 221 889
Elara (Jupiter VII) 86 11 676 677
Pasiphae (Jupiter VIII) 60 23 912 238
Carme (Jupiter XI) 46 24 097 020
Sinope (Jupiter IX) 38 23 368 614
Lysithea (Jupiter X) 36 11 665 380
Ananke (Jupiter XII) 28 20 439 111
Adrastea (Jupiter XV) 26×20×16 129 000
Leda (Jupiter XIII) 16 11 098 480
Callirrhoe (Jupiter XVII) 9 24 103 000
1997-2013 © - Astronomy, Astrophysics, Evolution and Earth science.
Reproduction prohibited without permission of the author.
Orbits of the moons of Jupiter
Two new moons
of Jupiter...
enceladus moon of saturn
Enceladus and its scratch...
dione moon of saturn
Dione, water and ice...