Ever because the Voyager mission despatched residence photographs of Jupiter’s moon Io spewing materials into house, we have regularly constructed up a clearer image of Io’s volcanic exercise. It slowly turned clear that Io, which is a bit smaller than Mercury, is essentially the most volcanically energetic physique within the Photo voltaic System, with all that exercise pushed by the gravitational pressure attributable to Jupiter and its three different big moons. There may be a lot volcanism that its floor has been utterly transformed, with no indicators of influence craters.
A number of extra particulars about its violence got here to gentle this week, with new photographs being launched of the moon’s options, together with an island in a lake of lava, taken by the Juno orbiter. On the similar time, imaging accomplished utilizing an Earth-based telescope has offered some indications that this volcanism has been reshaping Io from nearly the second it fashioned.
Fiery, glassy lakes
The Juno orbiter’s mission is primarily targeted on finding out Jupiter, together with the dynamics of its storms and its inner composition. However lots of its orbital passes have taken it proper previous Io, and this week, the Jet Propulsion Laboratory launched a number of the greatest photographs from these flybys. They embrace a shot of Loki Patera, a lake of lava that has an island inside it. Additionally featured: the impossibly sheer slopes of Io’s Steeple Mountain.
Trying extra intently on the lake, the Juno crew discovered that a number of the areas inside it have been extremely clean, elevating the chance that obsidian glass had fashioned on the floor the place it had cooled sufficient to solidify. Given the extent of volcanism on Io, this can be extra widespread than the Loki Patera.
Volcanic ash would additionally create a comparatively clean floor, and is prone to be much more widespread, however it could have considerably completely different reflective properties.
How lengthy has this been occurring?
However we do not have to ship {hardware} to Jupiter to be taught one thing about Io. A US-based crew bought time on the Atacama Massive Millimeter Array (ALMA) and used it to file emissions from atoms in Io’s sparse ambiance. By combining the imaging energy of a number of smaller telescopes scattered throughout a plateau, ALMA is ready to spot regional variations within the presence of particular parts in Io’s ambiance, in addition to establish completely different isotopes of these parts.
What can isotopes inform us? Any atoms that attain Io’s higher ambiance are prone to being misplaced to house. And, due to their relative atomic weights, heavier isotopes have the next likelihood of being misplaced. So, it is doable to match the current ratio of parts within the ambiance with the anticipated ratio, and we are able to make inferences in regards to the historical past of lack of lighter isotopes. And, because the materials is put into the ambiance by volcanoes within the first place, that tells us one thing in regards to the historical past of volcanism.
The analysis crew targeted on two specific parts: sulfur and chlorine. Sulfur has two widespread non-radioactive isotopes, 32S and 34S, and chlorine, its neighbor on the periodic desk, has 35Cl and 37Cl. There are variations within the ratio of those isotopes all through the our bodies of the Photo voltaic System, however these variations are usually small. And, as a result of we expect we all know what kind of materials contributed to the formation of Io, we are able to deal with the ratios present in our bodies which have an identical origin.
Chlorine enters the ambiance from volcanoes primarily within the type of sodium and potassium salts. These have a really brief half-life earlier than they’re break up up by publicity to gentle and radiation. The ALMA information indicated each these chemical substances have been current in localized areas, possible comparable to energetic volcanic plumes. The info from the chlorine isotopes have been a bit noisy, so have been largely used as a sanity test for those obtained from sulfur isotopes.
