Astronomy – Extraterrestrial Volcanism | nd-aktuell.de

Astronomers have discovered a new volcano on Jupiter’s innermost moon Io thanks to high-resolution images from the Juno space probe. However, the mountain had not hidden itself: the area near the equator was also mapped in detail using earlier images, such as those taken by the “Galileo” space probe in 1997 – but they showed neither larger structures nor signs of impending increased geological activity.

However, a new volcano does not come as a complete surprise, as Io is considered the most volcanically active body in the solar system, as was already shown in images taken by the “Voyager 1” space probe in 1979. Observations carried out since then, using ground-based telescopes and space probes, have recorded more than 150 active volcanoes.

Large, reddish sulfur deposits can be seen in the images on one flank of the new volcano, while on the other side there are two solidified lava flows that are around 100 kilometers long. The flows consist largely of silicate minerals, which emerge at temperatures of more than 1000 degrees Celsius and evaporate all material in their path on the surface – clearly visible through smooth, gray structures along the lava flow and round “hollows” at the end of the flows, where the lava flows to the There was a standstill.

The images show two lava flows around 100 kilometers long.

As in the case of the new volcano, the moon’s geological activity can be seen in its diverse surface. In general, it is quite young at just a few million years old and shows almost no craters that are typical of meteorite impacts. On the other hand, pronounced calderas, cauldron-shaped depressions in the surface that are created by volcanic eruptions or collapses of chambers near the surface, are numerous and can be several kilometers deep and hundreds of kilometers in diameter.

The “lava” that emerges from Io’s volcanoes consists largely of sulfur and low-viscosity sulfur compounds. It can flow quickly and widely, producing flat, shield-like volcanoes (similar to Earth’s shield volcanoes – but here it is liquid rock, magma, that emerges to the Earth’s surface as lava). The sulfur compounds show a wide spectrum of colors: Io does not follow the typical moon gray-on-gray, but has an unusually colorful surface. Infrared investigations were also able to detect “hot spots,” localized areas with extremely high temperatures of more than 1,700 degrees Celsius, which cannot be explained by molten sulfur but rather indicate liquid silicates.

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The fact that Jupiter’s moon, similar in size and mass to our Earth’s moon, is not crater-strewn and geologically inactive is due to Jupiter’s enormous tidal forces, which knead and deform the moon in its slightly elliptical orbit in such a way that enough frictional heat is created to cause geological activity to develop. In addition, there are the neighboring moons Europa and Ganymede, whose gravity exerts additional forces.

Io’s volcanism therefore has a completely different cause than that of Earth. Earth’s volcanism cannot be traced back to external causes, but rather shows the “inner values” of our planet: primordial heat, which has been retained from the earth’s formation phase, and radioactive decay processes (mainly of potassium, uranium and thorium) generate the necessary heat, the convection processes in the viscous earth’s mantle (up to 3500 degrees Celsius at the border to the earth’s core) and plate tectonics.

But volcanism can also occur where it might be less expected at first glance: on icy moons like Enceladus or Triton. Eternal ice worlds on the outside, the heat inside is just enough to expel gases and volatile substances such as ammonia or salt water, mixed with rock particles, in a “volcano-like” manner. Ice or cryovolcanism creates plumes of nitrogen and dust up to eight kilometers high on Neptune’s moon Triton. And in 2009, the Cassini space probe recorded more than 30 water ice fountains of very different sizes and intensities on Saturn’s moon Enceladus, spectacularly backlit by the sun.