Editing Europa (moon) (section)

====Composition====
[[File:Europa PIA2387x - Chaos Transition, Crisscrossing Bands & Chaos Near Agenor Linea.jpg|thumb|300px|Closeup views of Europa obtained on 26 September 1998; images clockwise from upper left show locations from north to south as indicated at lower left.]]
The ''Galileo'' orbiter found that Europa has a weak [[magnetic moment]], which is induced by the varying part of the Jovian magnetic field. The field strength at the magnetic equator (about 120 [[Tesla (unit)|nT]]) created by this magnetic moment is about one-sixth the strength of Ganymede's field and six times the value of Callisto's.<ref name="Zimmer">{{cite journal |last1=Zimmer |first1=C |title=Subsurface Oceans on Europa and Callisto: Constraints from Galileo Magnetometer Observations |journal=Icarus |date=October 2000 |volume=147 |issue=2 |pages=329–347 |doi=10.1006/icar.2000.6456 |bibcode=2000Icar..147..329Z |citeseerx=10.1.1.366.7700 }}</ref> The existence of the induced moment requires a layer of a highly electrically conductive material in Europa's interior. The most plausible candidate for this role is a large subsurface ocean of liquid saltwater.<ref name="Kivelson" />
{{Multiple image |header=Europa Closeups |caption_align=center |align=left |width=150 |direction=vertical |image1=PIA26332-JupiterMoonEuropaCloseupA.jpg |caption1=29 September 2022 |width1= |image2=PIA25696-Europa-JupiterMoon-20220929.jpg |caption2=9 September 2022 |width2= |footer= }}
Since the ''Voyager'' spacecraft flew past Europa in 1979, scientists have worked to understand the composition of the reddish-brown material that coats fractures and other geologically youthful features on Europa's surface.<ref>{{cite news |url=http://www.jpl.nasa.gov/news/news.php?feature=4602 |title=Europa Mission to Probe Magnetic Field and Chemistry |work=Jet Propulsion Laboratory |date=27 May 2015 |access-date=29 May 2015 |archive-date=2 December 2020 |archive-url=https://web.archive.org/web/20201202163713/https://www.jpl.nasa.gov/news/news.php?feature=4602 |url-status=live }}</ref> Spectrographic evidence suggests that the darker, reddish streaks and features on Europa's surface may be rich in salts such as [[magnesium sulfate]], deposited by evaporating water that emerged from within.<ref name="McCord1998">{{cite journal |title=Salts on Europa's Surface Detected by Galileo's Near Infrared Mapping Spectrometer |author1=McCord, Thomas B. |author2=Hansen, Gary B. |display-authors=etal |date=1998 |doi=10.1126/science.280.5367.1242 |volume=280 |issue=5367 |journal=Science |pages=1242–1245|pmid=9596573 |bibcode=1998Sci...280.1242M }}</ref> [[Sulfuric acid]] hydrate is another possible explanation for the contaminant observed spectroscopically.<ref name="Carlson2005">{{Cite journal | last1 = Carlson | first1 = R. W. | last2 = Anderson | first2 = M. S. | last3 = Mehlman | first3 = R. | last4 = Johnson | first4 = R. E. | title = Distribution of hydrate on Europa: Further evidence for sulfuric acid hydrate | doi = 10.1016/j.icarus.2005.03.026 | journal = Icarus | volume = 177 | issue = 2 | page = 461 | year = 2005 |bibcode = 2005Icar..177..461C }}</ref> In either case, because these materials are colorless or white when pure, some other material must also be present to account for the reddish color, and [[sulfur]] compounds are suspected.<ref name="Calvin">{{cite journal |last=Calvin |first=Wendy M. |author2=Clark, Roger N. |author3=Brown, Robert H. |author4= Spencer, John R. |title=Spectra of the ice Galilean satellites from 0.2 to 5 μm: A compilation, new observations, and a recent summary |journal=Journal of Geophysical Research |date=1995 |volume=100 |issue=E9 |pages=19,041–19,048 |bibcode=1995JGR...10019041C|doi=10.1029/94JE03349 }}</ref>

[[File:Europa_%28NIRCam_image,_cropped%29_%28weic2323b%29.jpg|right|thumb|upright|[[Near-infrared spectroscopy|NIR]] image of Europa by the [[James Webb Space Telescope]], confirming the presence of carbon dioxide on the moon<ref>{{cite web | url=https://www.nasa.gov/solar-system/nasas-webb-finds-carbon-source-on-surface-of-jupiters-moon-europa/#:~:text=life%2C%20particularly%20carbon.-,Astronomers%20using%20data%20from%20NASA%27s%20James%20Webb%20Space%20Telescope%20have,meteorites%20or%20other%20external%20sources | title=NASA's Webb Finds Carbon Source on Surface of Jupiter's Moon Europa - NASA | date=21 September 2023 }}</ref>]]
Another hypothesis for the colored regions is that they are composed of abiotic [[organic compounds]] collectively called [[tholins]].<ref name='Tholins Europa'>{{cite journal|doi=10.1029/2002JE001841 | bibcode=2002JGRE..107.5114B | volume=107 | issue=E11 | title=A new energy source for organic synthesis in Europa's surface ice | year=2002 | journal=Journal of Geophysical Research: Planets | pages=24–1–24–5 | last1 = Borucki | first1 = Jerome G. | last2 = Khare | first2 = Bishun | last3 = Cruikshank | first3 = Dale P.| doi-access=free }}</ref><ref name='amino acids'>{{cite conference |bibcode=2017AAS...22913804W |title=MISE: A Search for Organics on Europa |conference=American Astronomical Society Meeting Abstracts #229 |volume=229 |pages=138.04 |last1=Whalen |first1=Kelly |last2=Lunine |first2=Jonathan I. |last3=Blaney |first3=Diana L.|author3-link= Diana Blaney |year=2017 }}</ref><ref name='JPL2015'>{{cite news |url=http://www.jpl.nasa.gov/news/news.php?feature=4602 |title=Europa Mission to Probe Magnetic Field and Chemistry |work=Jet Propulsion Laboratory |date=27 May 2015 |access-date=23 October 2017 |archive-date=2 December 2020 |archive-url=https://web.archive.org/web/20201202163713/https://www.jpl.nasa.gov/news/news.php?feature=4602 |url-status=live }}</ref> The morphology of Europa's impact craters and ridges is suggestive of fluidized material welling up from the fractures where [[pyrolysis]] and [[radiolysis]] take place. In order to generate colored tholins on Europa, there must be a source of materials (carbon, nitrogen, and water) and a source of energy to make the reactions occur. Impurities in the water ice crust of Europa are presumed both to emerge from the interior as [[Cryovolcano|cryovolcanic]] events that resurface the body, and to accumulate from space as interplanetary dust.<ref name='Tholins Europa'/> Tholins bring important [[Astrobiology|astrobiological]] implications, as they may play a role in prebiotic chemistry and [[abiogenesis]].<ref name='prebiotic chem'>{{cite journal| pmc=3796891 | pmid=24143126 | doi=10.2174/13852728113179990078 | volume=17 | issue=16 | title=Atmospheric Prebiotic Chemistry and Organic Hazes | year=2013 | journal=Curr Org Chem | pages=1710–1723 | last1 = Trainer | first1 = MG}}</ref><ref name='Coll 2010'>{{cite conference |bibcode=2010cosp...38..777C |title=Prebiotic chemistry on Titan ? The nature of Titan's aerosols and their potential evolution at the satellite surface |conference=38th Cospar Scientific Assembly |volume=38 |pages=11 |last1=Coll |first1=Patrice |last2=Szopa |first2=Cyril |last3=Buch |first3=Arnaud |last4=Carrasco |first4=Nathalie |last5=Ramirez |first5=Sandra I. |last6=Quirico |first6=Eric |last7=Sternberg |first7=Robert |last8=Cabane |first8=Michel |last9=Navarro-Gonzalez |first9=Rafael |last10=Raulin |first10=Francois |last11=Israel |first11=G. |last12=Poch |first12=O. |last13=Brasse |first13=C. |year=2010 }}</ref><ref>{{cite journal |last1=Ruiz-Bermejo |first1=Marta |last2=Rivas |first2=Luis A. |last3=Palacín |first3=Arantxa |last4=Menor-Salván |first4=César |last5=Osuna-Esteban |first5=Susana |title=Prebiotic Synthesis of Protobiopolymers Under Alkaline Ocean Conditions |journal=Origins of Life and Evolution of Biospheres |date=16 December 2010 |volume=41 |issue=4 |pages=331–345 |doi=10.1007/s11084-010-9232-z |pmid=21161385 |bibcode=2011OLEB...41..331R |s2cid=19283373 }}</ref>

The presence of [[sodium chloride]] in the internal ocean has been suggested by a 450&nbsp;nm absorption feature, characteristic of irradiated NaCl crystals, that has been spotted in [[Hubble Space Telescope|HST]] observations of the chaos regions, presumed to be areas of recent subsurface upwelling.<ref name="Trumbo2019">{{cite journal |last1=Trumbo |first1=Samantha K. |last2=Brown |first2=Michael E. |last3=Hand |first3=Kevin P. |title=Sodium chloride on the surface of Europa |journal=Science Advances |date=12 June 2019 |volume=5 |issue=6 |pages=eaaw7123 |doi=10.1126/sciadv.aaw7123 |pmid=31206026 |pmc=6561749 |bibcode=2019SciA....5.7123T }}</ref> The subterranean ocean of Europa contains carbon<ref>{{Cite news |last=Devlin |first=Hannah |date=21 September 2023 |title=Scientists excited to find ocean of one of Jupiter's moons contains carbon |newspaper=The Guardian |url=https://www.theguardian.com/science/2023/sep/21/scientists-excited-to-find-ocean-of-one-of-jupiters-moons-contains-carbon }}</ref> and was observed on the surface ice as a concentration of [[carbon dioxide]] within Tara Regio, a geologically recently resurfaced terrain.<ref>{{Cite journal |last=Trumbo |first=Samantha |date=September 2023 |title=The distribution of CO2 on Europa indicates an internal source of carbon |journal=Science |volume=381 |issue=6664 |pages=1308–1311|doi=10.1126/science.adg4155 |pmid=37733851 |arxiv=2309.11684 }}</ref> JWST [[NIRSpec]] observations show that the northern hemisphere show crystalline water [[ice]] beneath the surface and amorphous ice dominating the surface. In the southern hemisphere Regiones Tara and Powys crystalline water ice dominates both the surface and the deeper layers. These two regiones likely experience ongoing thermal (re)crystallization, as the radiation near Jupiter cause particle amorphization at the top 10 microns over a period of less than 15 days.<ref name="Cartwright2025">{{cite arXiv|eprint=2504.05283 |last1=Cartwright |first1=Richard J. |last2=Hibbits |first2=Charles A. |last3=Holler |first3=Bryan J. |last4=Raut |first4=Ujjwal |last5=Nordheim |first5=Tom A. |last6=Neveu |first6=Marc |last7=Protopapa |first7=Silvia |last8=Glein |first8=Christopher R. |last9=Leonard |first9=Erin J. |last10=Roth |first10=Lorenz |last11=Beddingfield |first11=Chloe B. |last12=Villanueva |first12=Geronimo L. |title=JWST Reveals Spectral Tracers of Recent Surface Modification on Europa |date=2025 |class=astro-ph.EP }}</ref>
[[File:CO2_Europa.png|thumb|upright=4|center|A series of images of Europa in different wavelengths by the James Webb Space Telescope. The different wavelengths show the presence of different forms of carbon dioxide on Europa.]]