NASA\u2019s Juno spacecraft spies a tiny inner moon of Jupiter, Amalthea.<\/em><\/p>\n It\u2019s tiny, but it\u2019s there. By now, we\u2019re all used to seeing amazing photos of Jupiter courtesy of NASA\u2019s Juno mission on a routine basis. Many of these are processed by volunteer \u2018citizen scientists,\u2019 and they show the swirling cloud-tops of Jove courtesy of the spacecraft\u2019s JunoCam in stunning detail.<\/p>\n <\/p>\n Recently, JunoCam captured something special. Look closely at the side-by-side images of Jupiter from March 7th<\/sup>, 2024, and you\u2019ll see a tiny speck transiting the Great Red Spot in the left lead image, that isn\u2019t in the right. That\u2019s the tiny inner moon Amalthea, just 84 kilometers across. The image was captured during the 59th<\/sup> perijove (close flyby) of the \u2018King of the Planets,\u2019 at a range of 265,000 kilometers distant (about two-thirds of the Earth-Moon distance).<\/p>\n The elusive moon was discovered by prolific astronomer and observer E.E. Barnard on the night of September 9th<\/sup>, 1892. Barnard used the 91-centimeter diameter refractor telescope at the Lick observatory to spot the +14th<\/sup> magnitude moon, which never strays more than 30\u201d from Jupiter (less than the apparent diameter of the planet) on its 12 hour orbit. Amalthea holds the distinction of being the last moon discovered via direct visual observation, and the first moon of Jupiter discovered since Galileo first spotted the four major Galilean moons in 1610. Today, Jupiter has 95 known moons, mostly captured asteroids. These were mainly discovered photographically and during spacecraft flybys. <\/p>\n Like other small moonlets, Amalthea isn\u2019t big enough to pull itself into a true sphere. Instead, like the Martian moons Phobos and Deimos, Amalthea is a potato-shaped, captured asteroid.<\/p>\n The moon is also the reddest object in the solar system, and no doubt undergoes some serious tidal flexing thanks to the enormous gravitational field of nearby Jove. Amalthea is located 180,000 kilometers from Jove, just a little over 100,000 kilometers outside of Jupiter\u2019s Roche limit radius. Any closer to Jove would tear Amalthea apart. The very innermost moon Metis just skims this limit. <\/p>\n Voyagers 1 and 2 gave us the first blurry views of the moon. NASA\u2019s only other Jupiter orbiter Galileo has provided us with the best images of Amalthea to date, with a flyby 374,000 kilometers distant on November 26, 1999. Those images reveal a misshapen world, not unlike Mars\u2019 moon Deimos. From the surface of Amalthea, Jupiter would provide an amazing sight, spanning nearly half the sky at 42 degrees across.<\/p>\n Juno launched from the Cape on August 5th<\/sup>, 2011, and arrived at Jupiter on July 5th<\/sup>, 2016. The mission probes the interior of Jupiter and its magnetic and radiation environment. Juno will answer key questions, including whether the planet has a solid core. Juno is the first solar-powered (as opposed to nuclear\/plutonium-fueled) mission to the outer planets, meaning its nominal wide-ranging orbit was meant to avoid radiation damage to the solar panels. Engineers only allowed the spacecraft to venture in past the inner moons of Jupiter during the extended and final phase of the mission. Juno will operate until at least September 2025.<\/p>\n Two more missions are headed to Jupiter; ESA\u2019s JUICE (Jupiter Icy moons Explorer) launched on April 14th<\/sup> 2023, and NASA\u2019s Europa Clipper, set to launch in October 2024.<\/p>\n Watch for more amazing images courtesy of Juno, as the mission enters its final months and days.<\/p>\nAmalthea: An Origin Story<\/h2>\n
![\"Solar](\"https:\/\/www.universetoday.com\/wp-content\/uploads\/2024\/05\/junosolarpan.jpg\")
Amalthea: None More Red<\/h2>\n
![\"Amalthea\"](\"https:\/\/www.universetoday.com\/wp-content\/uploads\/2024\/05\/Amalthea_Voyager-1.png\")
![\"Galileo\"](\"https:\/\/www.universetoday.com\/wp-content\/uploads\/2024\/05\/Amalthea.png\")
Juno and the Present Status of the Mission<\/h2>\n
![\"Jupiter\"](\"https:\/\/www.universetoday.com\/wp-content\/uploads\/2024\/05\/Juppy-from-Amal-1024x681.jpg\")
Like this:<\/h3>\n