Editing Triton (moon) (section)

== Observation and exploration ==
[[File:PIA23874-NeptuneMoonTriton-TridentMission-20200616.jpg|thumb|left|NASA illustration detailing the studies of the proposed Trident mission]]
[[File:Voyager 2 Neptune and Triton.jpg|thumb|Neptune (top) and Triton (bottom) three days after flyby of ''Voyager 2'']]
The orbital properties of Triton were already determined with high accuracy in the 19th century. It was found to have a retrograde orbit, at a very high angle of inclination to the plane of Neptune's orbit. The first detailed observations of Triton were not made until 1930. Little was known about the satellite until ''[[Voyager 2]]'' flew by in 1989.<ref name="EncycSolSys-Triton"/>

Before the [[Planetary flyby|flyby]] of ''Voyager 2'', astronomers suspected that Triton might have [[liquid nitrogen]] seas and a nitrogen/methane atmosphere with a density as much as 30% that of Earth. Like the famous overestimates of the [[Atmosphere of Mars|atmospheric density of Mars]], this proved incorrect. As with Mars, a denser atmosphere is postulated for its early history.<ref name="Lunine1992-massive"/>

The first attempt to measure the diameter of Triton was made by [[Gerard Kuiper]] in 1954. He obtained a value of 3,800&nbsp;km. Subsequent measurement attempts arrived at values ranging from 2,500 to 6,000&nbsp;km, or from slightly smaller than the Moon (3,474.2&nbsp;km) to nearly half the diameter of Earth.<ref name="Cruikshank1979-diameterreflectance"/> Data from the approach of ''Voyager 2'' to Neptune on August 25, 1989, led to a more accurate estimate of Triton's diameter (2,706&nbsp;km).<ref name="Stone1989-Voyager 2-Neptune"/>

In the 1990s, various observations from Earth were made of the limb of Triton using the [[occultation]] of nearby stars, which indicated the presence of an atmosphere and an exotic surface. Observations in late 1997 suggest that Triton is heating up and the atmosphere has become significantly denser since ''Voyager 2'' flew past in 1989.<ref name="Hubblesite"/>

[[Neptune Orbiter|New concepts for missions to the Neptune system]] to be conducted in the 2010s were proposed by [[NASA]] scientists on numerous occasions over the last decades. All of them identified Triton as being a prime target and a separate Triton lander comparable to the [[Huygens (spacecraft)|''Huygens'' probe]] for [[Titan (moon)|Titan]] was frequently included in those plans. No efforts aimed at Neptune and Triton went beyond the proposal phase and NASA's funding for missions to the outer Solar System is currently focused on the Jupiter and Saturn systems.<ref name="NASAgov-428154"/> A proposed lander mission to Triton, called ''[[Triton Hopper]]'', would mine nitrogen ice from the surface of Triton and process it to be used as a propellant for a small rocket, enabling it to fly or 'hop' across the surface.<ref>{{cite magazine |last=Ferreira |first=Becky |date=August 28, 2015 |title=Why We Should Use This Jumping Robot to Explore Neptune |url=https://www.vice.com/en/article/neptune-or-bust/ |magazine=[[Vice Motherboard]] |access-date=March 20, 2019}}</ref><ref name='Oleson 2015'>{{cite web |url=https://www.nasa.gov/feature/triton-hopper-exploring-neptunes-captured-kuiper-belt-object/ |title=Triton Hopper: Exploring Neptune's Captured Kuiper Belt Object |date=May 7, 2015 |first=Steven |last=Oleson |publisher=NASA Glenn Research Center |access-date=February 11, 2017 }}</ref> Another concept, involving a flyby, was formally proposed in 2019 as part of NASA's [[Discovery Program]] under the name ''[[Trident (spacecraft)|Trident]]''.<ref name="NYT-Trident">{{cite news |last=Brown |first=David W. |date=March 19, 2019 |title=Neptune's Moon Triton Is Destination of Proposed NASA Mission |url=https://www.nytimes.com/2019/03/19/science/triton-neptune-nasa-trident.html |work=[[The New York Times]] |access-date=March 20, 2019}}</ref> [[Neptune Odyssey]] is a mission concept for a Neptune orbiter with a focus on Triton being studied beginning April 2021 as a possible [[large strategic science mission]] by NASA that would launch in 2033 and arrive at the Neptune system in 2049.<ref name="Rymer">{{cite web |author1=Abigail Rymer |author2=Brenda Clyde |author3=Kirby Runyon |title=Neptune Odyssey: Mission to the Neptune-Triton System |url=https://science.nasa.gov/science-pink/s3fs-public/atoms/files/Neptune%20Odyssey.pdf |access-date=April 18, 2021 |date=August 2020 |archive-date=December 15, 2020 |archive-url=https://web.archive.org/web/20201215003151/https://science.nasa.gov/science-pink/s3fs-public/atoms/files/Neptune%20Odyssey.pdf |url-status=dead }}</ref> Two lower-cost mission concepts were subsequently developed for the [[New Frontiers program]]: the first the following June and the second in 2023. The first is ''Triton Ocean World Surveyor'', which would launch in 2031 and arrive in 2047,<ref name="TOWS">{{Cite web|url=https://science.nasa.gov/wp-content/uploads/2023/10/t-ows-triton-ocean-worlds-surveyor.pdf|date=June 7, 2021|title=Triton Ocean Worlds Surveyor concept study |website=NASA|last1=Hansen-Koharcheck|first1=Candice|last2=Fielhauer|first2=Karl}}</ref> and the second is ''Nautilus'', which would launch August 2042 and arrive in April 2057.<ref name="Steckel Conrad Dekarske Dolan 2023">{{cite journal | last1=Steckel | first1=Amanda | last2=Conrad | first2=Jack William | last3=Dekarske | first3=Jason | last4=Dolan | first4=Sydney | last5=Downey | first5=Brynna Grace | last6=Felton | first6=Ryan | last7=Hanson | first7=Lavender Elle | last8=Giesche | first8=Alena | last9=Horvath | first9=Tyler | last10=Maxwell | first10=Rachel | last11=Shumway | first11=Andrew O | last12=Siddique | first12=Anamika | last13=Strom | first13=Caleb | last14=Teece | first14=Bronwyn | last15=Todd | first15=Jessica | last16=Trinh | first16=Kevin T | last17=Velez | first17=Michael A | last18=Walter | first18=Callum Andrew | last19=Lowes | first19=Leslie L | last20=Hudson | first20=Troy | last21=Scully | first21=Jennifer E. C. | title=The Science Case for Nautilus: A Multi-Flyby Mission Concept to Triton | journal=AGU - Agu23 | publisher=AGU | date=December 12, 2023 | url=https://agu.confex.com/agu/fm23/meetingapp.cgi/Paper/1425806 | access-date=January 11, 2024}}</ref><ref name="Jason Dekarske 2023">{{cite web | title=Planetary Science Summer School · Jason Dekarske | website=Jason Dekarske | date=December 19, 2023 | url=https://www.jasondekarske.com/research/psss/ | access-date=January 25, 2024}}</ref>