An amateur astronomer hunt down through old image from the Galileo mission spotted something everyone else had miss – an seeming impingement crater . Now , professional astronomers have cater grounds that what Jesper Sandberg find was the real affair , an asteroid impact Io ’s volcanic activity has yet to eliminate .
From the moment Galileo turned his telescope to the Moon , it was obvious our satellite was covered in craters . Although these were initially think to be the legacy of volcanoes – by far the most plebeian sort of crater the era ’s scientists knew from Earth – finally it was realize they were the products of rapid confrontation with space rocks .
Once missions began to other satellite it became clear that being report in crater is the Solar System average , gas colossus apart . Most earth , like our Moon , birth their crater proudly , with impacts date back billions of years on exhibit . steer or water have gnaw at most vestige on Earth , Mars , and Europa , but a few remain visible on each .
Galileo’s pass was not close enough to get great resolution, so this is the largest image we can squeeze out of it. However, it does reveal the bowl shape and surrounding halo that indicates its likely origins.Image Credit: NASA/Arizona State University
Io has been the exception . It ’s not because it never gets strike – indeed Jupiter ’s proximity to the asteroid whack means its moons thieve more than most . However , with more than 400 active volcano , fueled by Jupiter ’s tidal flexing , craters do n’t last long on Io before being filled in by flux lava . Yet it seems there is one still around .
Sandberg noticed something suspiciously round - look in Galileo datum at ~51.7˚S , 117.1˚W on the flank of a mesa ( level - topped Alfred Hawthorne ) . The range of a function can be seen in four physique , suggesting no whoremonger of the brightness .
On such a volcanic moon , the obvious suspicion is that this is the crater of a volcano , but at the American Geophysical Union league last calendar week , Professor David Williams of Arizona State University and NASA ’s Jet Propulsion Laboratory ’s Dr Rosaly Lopes presented grounds an wallop crater is the most likely explanation .
The crater is 7 - 8 pixels across in images have by Galileo on October 16 , 2001 , when its length place the resolution at 13 m / pixel , relieve oneself the volcanic crater 92 - 104 meters ( 300 - 360 substructure ) in diam . Besides the roundness , ejecta personal line of credit around the volcanic crater await more like that from a hit than from an eructation .
The localisation might seem especially unlikely since it is for certain not isolated from Io ’s ceaseless volcanism . “ The whole realm subsequently has been undergoing graduated processes , perhaps including deposition of bitter materials from nearby plume eruptions and degradation including slumping of stifling plain deposits , sublimation , or other processes , ” the presenter note .
Nevertheless , Williams toldEos , “ I really processed the Galileo SSI mosaics from that time . I get back , draw in it up , and looked up close – sure enough , there ’s a spot that could well be interpreted as an shock volcanic crater . ”
If that ’s what it is , the big question is if Galileo ( spacecraft not scientist ) happened to catch it during a abbreviated menstruation of natural selection , or if there are more on Io like this than we thought .
We have no update on whether the crater survives 20 age afterward , but that may change . The first part of the Juno missionary station was focused on Jupiter itself , and it only recently shifted its attention to the moons . After flybys of Ganymede and Europa , it was finally Io ’s turn in December 2022 . However , that , and a subsequent passport last twelvemonth , were still at distances far greater than Galileo ’s pass .
However , a closemouthed flyby is jell to happen on December 30 this year , followed by one on February 3 , 2024 . As their names suggest , neither theEuropa Clippernor theJupiter Icy Moons Explorer(JUICE ) have Io as a prime target , but it ’s possible one will get close enough to expect for other crater locations .
trot is Colorado - author of apreprintmapping Io ’s volcanism over more than 40 years . This report that since 2013 , volcanic activeness has been condense in the southerly trailing hemisphere . Though far in the Confederacy , Sandberg ’s crater land site is on Io ’s leading hemisphere , leaving some hope for survival .
The introduction ’s nonobjective can befound here .
