When it comes to the Galilean moons of Jupiter, we tend to focus a lot of attention on the icy moon of Europa due to the potential of it being home to a subsurface ocean. However, Europa is not alone in being a fascinating place among these four moons; between it and Jupiter sits Io, the most geologically active place in the solar system – and that’s just one of the facts relating to it.
As the 4th largest Moon in the solar system and the third largest of the Jupiter’s Galilean moons, Io is slightly larger than our own Moon and has more than 400 active volcanoes across its surface. In addition, it has both the highest density and strongest surface gravity of any moon in the solar system. Its extreme volcanism is powered by gravitational flexing, the result of Io constantly being pulled in different directions by the gravities of Jupiter and the other three Galilean moons generating tidal heating deep in Io’s core, the same mechanism which is thought give Europa it’s possibly liquid water ocean. but on a much hotter and more violent scale.
Io’s volcanism is such that the almost constant lava flows mean the moon’s surface is constantly being re-formed outside of its volcanic peaks, whilst the allotropes and compounds of sulphur carried to the surface by both eruptions and lava flows give rise to the moon’s unique colouring. In addition, many of the volcanoes pump material high enough above Io to form a strange, tenuous atmosphere, noticeably more dense around such eruptions than elsewhere. This ejecta also gives rise to a large plasma torus around Jupiter.
The Jovian system has been the subject of extensive study by NASA’s Juno mission since it originally arrived in its extended orbit around the planet in July 2016. Since then, the vehicle had made more than 50 complete passes around the planet in a roughly polar orbit, and some of those have periodically allowed the spacecraft to observe the major moons of Jupiter, including Io. Two of the most recent of these flybys – in May and July 2023 – focused on Io, once again revealing the moon is incredible detail.
The May 16th, 2023 flyby brought the Juno spacecraft to just 35,500 km of Io, allowing the imagers on the spacecraft to capture the moon simultaneously in both visible light wavelength and in the infrared, revealing a stunning amount of details on the moon’s volcanism.
In July, Juno passed even closer, at just 22,000 km from the moon’s surface. This allowed an actual eruption to be imaged by the spacecraft – not the first time this has happened, but one which captured Io’s “old faithful” once again in action.
“Old faithful” is the name given to the Prometheus Patera, a volcanic pit on the side of the moon facing away from Jupiter (Io is tidally locked to Jupiter), an area given to near-continuous eruptions which have been observed by both of the Voyager spacecraft, together with Galileo, and New Horizons, as well as Juno. Outflow from the eruptions in the pit covers an area of almost 7,000 square km, and it causes an observable plume of material rising up to 100 km above the moon’s surface.
What is particularly remarkable about Juno’s images of Io and the other Galilean moons is not only the amount of information they are providing, but the fact the spacecraft wasn’t ever designed to study them; its instruments were specifically designed to uncover secrets of Jupiter’s atmosphere and interior. But as remarkable as these images are, they are just a foretaste of what is to come.
Three more even closer flybys of Io will come in October and December before the spacecraft makes its closest approach of the mission to date, passing just 1,500 km above the Moon’s surface. Meanwhile, to mark Juno’s May and July 2023 flybys, NASA released a video offering a “starship captain’s” view of Io as the spacecraft passed around Jupiter’s limb. The music featured in the video is from Juno to Jupiter, by Vangelis. This was the Greek composer’s last studio album prior to his passing in May 2022, and the last of a series of albums and shorter pieces he wrote for both NASA and ESA between 2001 and 2021 and born of his almost life-long passion for science and space exploration.
Russia Heads Back to the Moon
At 23:10 UTC on August 10th, 2023 (09:10, August 11th, local time) a Soyuz 2.1b/Fregat booster lifted-off from Russia’s far eastern Vostochny Cosmodrome to mark the first lunar mission Russia has undertaken in 47 years. Originally called Luna-Glob, the mission is designed to place a robust lander within the crater Boguslawsky in the lunar South Polar Region.
Initial concepts for the mission started in 1998, and Russia had planned to garner international involvement, looking to partner with (at various times) the likes of the Indian Space Research Organisation (ISRO), the Japan Aerospace Exploration Agency (JAXA), the European Space Agency and the Swedish National Space Agency (SNSA) and the project gradually matured. However, given the 20+ year gestation for the mission, ISRO and JAXA switched to their own lunar-focused programmes whilst SNSA eventually partnered with China, flying their LINA-XSAN instrument aboard Chang’e 4 in 2019. ESA also withdrew from cooperation with Russia as a result of the invasion of Ukraine.
As a national mission, the project and its lander were renamed Luna 25, intended to suggest a direct lineage back to 1976’s Luna 24 sample return mission. It was launched very much in the public eye: Russia Television broadcast and streamed the event live in a 90-minute programme which featured the launch itself, coupled with a strange mix of a choir of young children singing under a huge photograph of Yuri Gagarin, a candlelit display.
Filmed at the Exhibition of Achievements of National Economy, Moscow, this portion of the programme also featured interviews with cosmonauts Oleg Artemyev and Oleg Blinov and more music, this time from Russian rock/pop group UMA2RMAN.
The mission is seen as the starting point for Russia’s own renewed lunar aspirations. A prime aim of the spacecraft is to test new landing technologies and systems which could be used in future missions to the Moon, including those by crews – in this respect, Artemyev and Blinov discussed the development of lunar habitats from a small-scale outpost (with artwork supplied by Roscosmos) through to a large-scale base (with a rendering by Russia Television, rather than anything official).
As well as lander research, the 1.7-tonne lander will conduct studies of the upper layer of the lunar regolith, appraise the ultra-thin lunar atmosphere and search for signs of water ice in the south pole region. To achieve this, the upper platform of the lander contains 30 kg of science payload. The landing itself is scheduled for August 21st, 2023, after a spiral cruise out to the Moon, and which means that Luna 25 should touch down some two days ahead of India’s Chanrayaan-3 lander launched in July and which achieved its initial orbit around the Moon on August 6th.
Continue reading “Space Sunday: volcanoes, going to the Moon and a helicopter”
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