Subsatellite

Terms used in scientific literature for subsatellites include "submoons" and "moon-moons". Colloquial terms that have been suggested include moonitos, moonettes, and moooons.{{cite news |last=Daley |first=Jason |title=If a Moon Has a Moon, Is Its Moon Called a Moonmoon? - A new study suggests it's possible some moons could have moons and the internet wants to give them a name—but scientists have yet to actually find one |url=https://www.smithsonianmag.com/smart-news/earths-moon-could-host-moonmoon-if-moonmoons-are-thing-180970520/ |date=11 October 2018 |work=Smithsonian |access-date=10 September 2020 }}

File:Rhean rings PIA10246 Full res.jpg

There is a possible detection{{cite journal

|url=http://www.sciencemag.org/cgi/content/abstract/319/5868/1380

|title=The Dust Halo of Saturn's Largest Icy Moon, Rhea |volume=319 |issue=5868 |pages=1380–1384 |journal=Science

|display-authors=3 |vauthors=Jones GH, Roussos E, Krupp N, Beckmann U, Coates AJ, Crary F, Dandouras I, Dikarev V, Dougherty MK, Garnier P, Hansen CJ, Hendrix AR, Hospodarsky GB, Johnson RE, Kempf S, Khurana KK, Krimigis SM, Krüger H, Kurth WS, Lagg A, McAndrews HJ, Mitchell DG, Paranicas C, Postberg F, Russell CT, Saur J, Seiß M, Spahn F, Srama R, Strobel DF, Tokar R, Wahlund JE, Wilson RJ, Woch J, Young D

|date=7 March 2008

|doi=10.1126/science.1151524

|pmid=18323452 |bibcode=2008Sci...319.1380J |s2cid=206509814 |access-date=12 October 2018

|url-access=subscription }} of a ring system around Saturn's natural satellite Rhea that led to calculations that indicated that satellites orbiting Rhea would have stable orbits. The rings suspected were thought to be narrow,{{cite web

|url=https://www.newscientist.com/article/dn13421-saturn-satellite-reveals-first-moon-rings.html

|title=Saturn satellite reveals first moon rings |date=6 March 2008 |last=Hecht |first=Jeff

|access-date=12 October 2018

|work=New Scientist

}} a phenomenon normally associated with shepherd moons; however, targeted images taken by the Cassini spacecraft failed to detect any subsatellites or rings associated with Rhea, at least no particles larger than a few millimeters, making the chance of a ring system around Rhea slim.{{Cite journal |last1=Tiscareno |first1=Matthew S. |last2=Burns |first2=Joseph A. |last3=Cuzzi |first3=Jeffrey N. |last4=Hedman |first4=Matthew M. |date=July 2010 |title=Cassini imaging search rules out rings around Rhea |arxiv=1008.1764 |journal=Geophysical Research Letters |volume=37 |issue=14 |page=L14205 |doi=10.1029/2010GL043663 |bibcode=2010GeoRL..3714205T |s2cid=59458559 |url-status=dead |archive-url=https://web.archive.org/web/20100810121201/http://www.agu.org/pubs/crossref/2010/2010GL043663.shtml |archive-date=2010-08-10 |url=http://www.agu.org/pubs/crossref/2010/2010GL043663.shtml }}

It has also been proposed that Saturn's satellite Iapetus possessed a subsatellite in the past; this is one of several hypotheses that have been put forward to account for its unusual equatorial ridge.{{cite web |last=Fitzpatrick |first=Tony |date=13 December 2010 |title=How Iapetus, Saturn's outermost moon, got its ridge |url=http://news.wustl.edu/news/Pages/21600.aspx |access-date=12 October 2018 |website= |publisher=Washington University in St. Louis}} An ancient giant impact on Iapetus could have produced a subsatellite; as Saturn despun Iapetus, the subsatellite's orbit would then decay until it crossed Iapetus' Roche limit, forming a transient ring which then impacted Iapetus to form a ridge. Such a scenario could have happened on the other giant-planet satellites as well, but only for Iapetus and perhaps Oberon would the resulting ridge have formed after the Late Heavy Bombardment and thus survived to the present day.{{cite journal |last1=Dombard |first1=Andrew J. |last2=Cheng |first2=Andrew F. |first3=William B. |last3=McKinnon |first4=Jonathan P. |last4=Kay |date=2012 |title=Delayed formation of the equatorial ridge on Iapetus from a subsatellite created in a giant impact |journal=Journal of Geophysical Research: Planets |volume=117 |issue=E3 |pages= |doi=10.1029/2011JE004010 |bibcode=2012JGRE..117.3002D |doi-access=free }}

Light-curve analysis suggests that Saturn's irregular satellite Kiviuq is extremely prolate, and is likely a contact binary or even a binary moon.{{cite conference

|title=Cassini Observations of Saturn's Irregular Moons

|url=https://www.hou.usra.edu/meetings/lpsc2019/pdf/2654.pdf

|first1=T. |last1=Denk

|first2=S. |last2=Mottola

|conference=50th Lunar and Planetary Science Conference

|publisher=Lunar and Planetary Institute

|number=2132

|year=2019}} Other candidates among the Saturnian irregulars include Bestla, Erriapus, and Bebhionn.{{cite book |last1=Denk |first1=T. |url=https://tilmanndenk.de/wp-content/uploads/DenkEtAl2018_IrregularMoons.pdf |title=Enceladus and the Icy Moons of Saturn |last2=Mottola |first2=S. |last3=Bottke |first3=W. F. |last4=Hamilton |first4=D. P. |date=2018 |publisher=University of Arizona Press |isbn=9780816537488 |volume=322 |pages=409–434 |chapter=The Irregular Satellites of Saturn |bibcode=2018eims.book..409D |doi=10.2458/azu_uapress_9780816537075-ch020}}

Stamp depicting the first extraterrestrial orbiter ([[Luna 10) other than in heliocentric orbit and its flightpath, the first artificial satellite around a natural satellite.|thumb|upright=0.6]]

Many spacecraft have orbited the Moon since the first one in 1966 (Luna 10).

{{As of|2024|}}, no spacecraft has successfully orbited any natural satellite other than the Moon. In 1988, the Soviet Union unsuccessfully attempted to put two robotic probes on quasi-orbits around the Martian moon Phobos.{{Cite web |url=https://nssdc.gsfc.nasa.gov/planetary/phobos.html |title=Phobos Project Information |author=Edwin V. Bell II |date=11 April 2016 |website=NASA Space Science Data Coordinated Archive |publisher=NASA |access-date=2018-10-15}}

Launched June 18, 2009, the Lunar Reconnaissance Orbiter (LRO) is a NASA robotic spacecraft currently orbiting the Moon in an eccentric polar mapping orbit. Data collected by LRO have been described as essential for planning NASA's future human and robotic missions to the Moon. Its detailed mapping program is identifying safe landing sites, locating potential resources on the Moon, characterizing the radiation environment, and demonstrating new technologies.

CAPSTONE is a project that successfully launched on June 28, 2022. Composed of a 12-unit collection of CubeSats which spent a few months in transit to the Moon to arrive on November 14, 2022. It has spend over 2 years in the Moon's Near-rectilinear halo orbit. CAPSTONE is testing and verifying the viability of the planned NRHO of planned future Lunar Gateway and its communication efficiency.{{cite web |last=Figliozzi |first=Gianine |date=May 20, 2022 |title=CAPSTONE Spacecraft Launch Targeted No Earlier Than June 6 |url=https://blogs.nasa.gov/artemis/2022/05/20/capstone-spacecraft-launch-targeted-no-earlier-than-june-6/ |accessdate=May 25, 2022 |work=NASA}}

The interplanetary spacecraft JUICE launched in 2023 will enter an orbit around Ganymede in 2032, becoming the first spacecraft to orbit a moon other than Earth's.

Additionally, the multi-agency supported Lunar Gateway human-rated space station began construction in April 2024 in a near-rectilinear halo orbit (NRHO), primarily in support of the later stage NASA Artemis program missions to the Moon. Lunar Gateway will also potentially support future missions to Mars and outlying asteroids.

{{div col|colwidth=30em}}

• 152830 Dinkinesh – an asteroid with a contact binary satellite
• Binary asteroid
• {{annotated link|Circumplanetary disk}}
• Minor-planet moon
• Moons of Jupiter
• Moons of Neptune
• Moons of Saturn
• Moons of Uranus
• Satellite system (astronomy)
• Three-body problem

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{{Reflist}}

• {{Commons category-inline|Extrasolar moons}}
• [http://www.space.com/scienceastronomy/shadow_moons_021008-1.html Shadow Moons: The Unknown Sub-Worlds that Might Harbor Life]
• [http://www.space.com/scienceastronomy/planet_photo_040910.html Likely First Photo of Planet Beyond the Solar System]
• [https://web.archive.org/web/20060916161707/http://www.dtm.ciw.edu/boss/definition.html Working Group on Extrasolar Planets – Definition of a "Planet"] Position statement on the definition of a planet. (IAU)
• [https://arxiv.org/abs/1201.0752 The Hunt for Exomoons with Kepler (HEK): I. Description of a New Observational Project]

{{Solar System moons}}

{{exoplanet}}

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Moons

Category:Hypothetical moons

Category:Hypothetical astronomical objects