Editing Galileo project (section)

===Amalthea===
[[File:Galileo Amalthea artwork.jpg|thumb|right|Artist's concept of Galileo passing near Jupiter's small inner moon Amalthea|alt=Amalthea looks like a large rock.]]
Although ''Galileo''{{'s}} main mission was to explore the Galilean moons, it also captured images of four of the inner moons, [[Thebe (moon)|Thebe]], [[Adrastea (moon)|Adrastea]], [[Amalthea (moon)|Amalthea]], and [[Metis (moon)|Metis]]. Such images were only possible from a spacecraft; to Earth-based telescopes they were [[Diffraction-limited system|merely specks of light]].<ref name="The Galileo Mission to Jupiter and Its Moons" /> Two years of Jupiter's intense radiation took its toll on the spacecraft's systems, and its fuel supply was running low in the early 2000s. ''Galileo''{{'s}} cameras were deactivated on January 17, 2002, after they had sustained irreparable radiation damage.<ref>{{cite web |title= 30 Years Ago: Galileo off to Orbit Jupiter |date= October 17, 2019 |publisher= NASA |url= https://www.nasa.gov/feature/30-years-ago-galileo-off-to-orbit-jupiter |access-date= December 6, 2020 |archive-date= August 31, 2020 |archive-url= https://web.archive.org/web/20200831053435/https://www.nasa.gov/feature/30-years-ago-galileo-off-to-orbit-jupiter/ |url-status= live }}</ref>

NASA engineers were able to recover the damaged tape-recorder electronics, and ''Galileo'' continued to return scientific data until it was deorbited in 2003, performing one last scientific experiment: a measurement of Amalthea's mass as the spacecraft swung by it. This was tricky to arrange; to be useful, ''Galileo'' had to fly within {{convert|300|km|sp=us}} of Amalthea, but not so close as to crash into it. This was complicated by its irregular {{convert|146|by|262|km|sp=us|adj=on}} potato-like shape. It was tidally locked, pointing its long axis towards Jupiter. A successful flyby meant knowing which direction the asteroid was pointed in relation to ''Galileo'' at all times.<ref name="The Long Goodbye">{{cite magazine |last=Carroll |first=M. |year=2003 |title=The Long Goodbye |magazine=[[Astronomy (magazine)|Astronomy]] |issn=0091-6358 |volume=31 |issue=10 |pages=36–41 |via=ProQuest |url-access=subscription |url=https://www.proquest.com/docview/215919054 |access-date=23 May 2024|id={{ProQuest|215919054}} }}</ref>

''Galileo'' flew by Amalthea on November 5, 2002, during its 34th orbit<!-- 21 September 2002 11:58:55.818 UTC to 28 January 2003 00:58:55.815 UTC -->, allowing a measurement of the moon's mass as it passed within {{convert|160|km|mi|abbr=on}} of its surface<!-- S030916A.LBL uses "Altitude"; presumably the uncertainty comes from Amalthea's irregular shape -->.{{sfn|Meltzer|2007|p=280}} The results startled the scientific team; they revealed that Amalthea had a mass of {{convert|2.08e18|kg}}, and with a volume of {{convert|2.43e6|km3|sp=us}}, it therefore had a density of 857 ± 99 kilograms per cubic meter, less than that of water.<ref name="The Long Goodbye" />{{sfn|Anderson et al.|2005|pp=1291–1293}}

A final discovery occurred during the last two orbits of the mission. When the spacecraft passed the orbit of Amalthea, the star scanner detected unexpected flashes of light that were reflections from seven to nine moonlets. None of the individual moonlets was reliably sighted twice, so no orbits were determined. It is believed that they were most likely debris ejected from Amalthea that formed a tenuous, and perhaps temporary, ring around Jupiter.{{sfn|Fieseler et al.|2004|pp=399–400}}

{{multiple image |align=center |direction=horizontal |total_width=900
 |image1=Jupiter's Main Ring and Halo (PIA01622).jpg
 |width1=1019 |height1=577 |caption1=Jupiter's rings. Enhanced top image shows the halo of ring particles suspended by Jupiter's powerful electromagnetic field. |alt1=refer to caption
 |image2=Jupiter's moon Amalthea photographed by Galileo.jpg
 |width2=798 |height2=573 |caption2=Inner moon Amalthea |alt2=refer to caption
 |image3=Thebe.jpg
 |width3=229 |height3=229 |caption3=Inner moon Thebe |alt3=refer to caption
}}