Editing Mercury (planet) (section)

=== Research with space probes ===
{{Main|Exploration of Mercury}}
[[File:MESSENGER Assembly.jpg|thumb|left|''MESSENGER'' being prepared for launch]]
[[File:PIA18389-MarsCuriosityRover-MercuryTransitsSun-20140603.gif|thumb|Mercury transiting the [[Sun]] as viewed by the Mars rover [[Curiosity (rover)|''Curiosity'']] (June 3, 2014).<ref name="NASA-20140610">{{cite web |last=Webster |first=Guy |title=Mercury Passes in Front of the Sun, as Seen From Mars |url=http://www.jpl.nasa.gov/news/news.php?release=2014-183 |date=June 10, 2014 |website=[[NASA]] |access-date=June 10, 2014 |archive-date=February 15, 2020 |archive-url=https://web.archive.org/web/20200215091810/https://www.jpl.nasa.gov/news/news.php?release=2014-183 |url-status=live }}</ref>]]

Reaching Mercury from Earth poses significant technical challenges, because it orbits so much closer to the Sun than Earth. A Mercury-bound spacecraft launched from Earth must travel over {{Convert|91|e6km|e6mi|abbr = off}} into the Sun's gravitational [[potential well]]. Mercury has an [[orbital speed]] of {{Convert|47.4|km/s|abbr = on}}, whereas Earth's orbital speed is {{Convert|29.8|km/s|abbr = on}}.<ref name=Williams2019>{{cite web | first=David R. | last=Williams | date=October 21, 2019 | title=Planetary Fact Sheet – Metric | publisher=NASA | url=https://nssdc.gsfc.nasa.gov/planetary/factsheet/ | access-date=April 20, 2021 | archive-date=July 19, 2012 | archive-url=https://archive.today/20120719082605/http://nssdc.gsfc.nasa.gov/planetary/factsheet/ | url-status=live }}</ref> Therefore, the spacecraft must make a larger change in [[velocity]] ([[delta-v]]) to get to Mercury and then enter orbit,<ref>{{cite book | title=Inner Solar System: Prospective Energy and Material Resources | first=Kris | last=Zacny | isbn=9783319195698 | date=July 2, 2015 | publisher=Springer International Publishing | page=154 | url=https://books.google.com/books?id=ZrAYCgAAQBAJ&pg=PA154 | access-date=March 19, 2023 | archive-date=April 11, 2023 | archive-url=https://web.archive.org/web/20230411141121/https://books.google.com/books?id=ZrAYCgAAQBAJ&pg=PA154 | url-status=live }}</ref> as compared to the delta-v required for, say, [[Exploration of Mars|Mars planetary missions]].

The [[potential energy]] liberated by moving down the Sun's potential well becomes [[kinetic energy]], requiring a delta-v change to do anything other than pass by Mercury. Some portion of this [[delta-v budget]] can be provided from a [[gravity assist]] during one or more fly-bys of Venus.<ref>{{cite journal | title=Hybrid Algorithm for Multiple Gravity-Assist and Impulsive Delta-V Maneuvers | first1=Sam | last1=Wagner | first2=Bong | last2=Wie | journal=Journal of Guidance, Control, and Dynamics | volume=38 | issue=11 | pages=2096–2107 | date=November 2015 | bibcode=2015JGCD...38.2096W | doi=10.2514/1.G000874 }}</ref> To land safely or enter a stable orbit the spacecraft would rely entirely on rocket motors. [[Aerobraking]] is ruled out because Mercury has a negligible atmosphere. A trip to Mercury requires more rocket fuel than that required to [[escape velocity|escape]] the Solar System completely. As a result, only three space probes have visited it so far.<ref name="JPLprofile1">{{cite web | url=https://www.jpl.nasa.gov/education/images/pdf/ss-mercury.pdf | title=Mercury | publisher=[[NASA]] Jet Propulsion Laboratory | date=May 5, 2008 | access-date=April 26, 2021 | archive-date=February 9, 2017 | archive-url=https://web.archive.org/web/20170209135719/http://www.jpl.nasa.gov/education/images/pdf/ss-mercury.pdf | url-status=live }}</ref> A proposed alternative approach would use a [[solar sail]] to attain a Mercury-synchronous orbit around the Sun.<ref>{{cite journal |last1=Leipold |first1=Manfred E. |last2=Seboldt |first2=W. |last3=Lingner |first3=Stephan |last4=Borg |first4=Erik |last5=Herrmann |first5=Axel Siegfried |last6=Pabsch |first6=Arno |last7=Wagner |first7=O. |last8=Brückner |first8=Johannes |title=Mercury sun-synchronous polar orbiter with a solar sail |year=1996 |journal=Acta Astronautica |volume=39 |issue=1 |pages=143–151 |doi=10.1016/S0094-5765(96)00131-2 |bibcode=1996AcAau..39..143L}}</ref>
{{clear}}

==== ''Mariner 10'' ====
{{Main|Mariner 10}}
[[File:Mariner 10.jpg|thumb|''Mariner 10'', the first probe to visit Mercury]]

The first spacecraft to visit Mercury was NASA's {{nowrap|''Mariner 10''}} (1974–1975).<ref name="Dunne" /> The spacecraft used the gravity of Venus to adjust its orbital velocity so that it could approach Mercury, making it both the first spacecraft to use this gravitational "slingshot" effect and the first NASA mission to visit multiple planets.<ref name="DunneCh4">{{cite book |title=The Voyage of Mariner&nbsp;10 – Mission to Venus and Mercury |last1=Dunne |first1=James A. |last2=Burgess |first2=Eric |name-list-style=amp |chapter-url=https://history.nasa.gov/SP-424/ch4.htm |publisher=NASA History Office |date=1978 |chapter=Chapter Four |url=https://history.nasa.gov/SP-424/ |access-date=May 28, 2008 |archive-date=November 17, 2017 |archive-url=https://web.archive.org/web/20171117190025/https://history.nasa.gov/SP-424/ |url-status=dead }}</ref> {{nowrap|''Mariner 10''}} provided the first close-up images of Mercury's surface, which immediately showed its heavily cratered nature, and revealed many other types of geological features, such as the giant scarps that were later ascribed to the effect of the planet shrinking slightly as its iron core cools.<ref>{{cite web |date=October 1976 |first=Tony |last=Phillips |url=http://www.nasa.gov/vision/universe/solarsystem/20oct_transitofmercury.html |title=NASA 2006 Transit of Mercury |website=SP-423 Atlas of Mercury |publisher=NASA |access-date=April 7, 2008 |archive-date=March 25, 2008 |archive-url=https://web.archive.org/web/20080325090336/http://www.nasa.gov/vision/universe/solarsystem/20oct_transitofmercury.html |url-status=dead }}</ref> Unfortunately, the same face of the planet was lit at each of {{nowrap|''Mariner 10''{{'s}}}} close approaches. This made close observation of both sides of the planet impossible,<ref>{{cite web |url=http://sci.esa.int/bepicolombo/56015-missions-to-mercury/ |title=BepiColumbo – Background Science |publisher=European Space Agency |access-date=June 18, 2017 |archive-date=July 1, 2017 |archive-url=https://web.archive.org/web/20170701093446/http://sci.esa.int/bepicolombo/56015-missions-to-mercury/ |url-status=live }}</ref> and resulted in the mapping of less than 45% of the planet's surface.<ref name="USATMessenger">{{cite news |url=https://www.usatoday.com/tech/news/2004-08-16-mercury-may-shrink_x.htm |title=MESSENGER to test theory of shrinking Mercury |newspaper=USA Today |first=Tariq |last=Malik |date=August 16, 2004 |access-date=May 23, 2008 |archive-date=July 26, 2011 |archive-url=https://web.archive.org/web/20110726231423/http://www.usatoday.com/tech/news/2004-08-16-mercury-may-shrink_x.htm |url-status=live }}</ref>

The spacecraft made three close approaches to Mercury, the closest of which took it to within {{Convert|327|km|abbr=on}} of the surface.<ref name="AtlasM10">{{cite book |url=https://history.nasa.gov/SP-423/sp423.htm |title=Atlas of Mercury |publisher=[[NASA]] Office of Space Sciences |first=Merton E. |last=Davies |display-authors=etal |date=1978 |chapter=Mariner&nbsp;10 Mission and Spacecraft |chapter-url=https://history.nasa.gov/SP-423/mariner.htm |access-date=May 30, 2008 |name-list-style=vanc |archive-date=October 9, 2019 |archive-url=https://web.archive.org/web/20191009033507/https://history.nasa.gov/SP-423/sp423.htm |url-status=live }}</ref> At the first close approach, instruments detected a magnetic field, to the great surprise of planetary geologists—Mercury's rotation was expected to be much too slow to generate a significant [[dynamo]] effect. The second close approach was primarily used for imaging, but at the third approach, extensive magnetic data were obtained. The data revealed that the planet's magnetic field is much like Earth's, which deflects the solar wind around the planet. For many years after the {{nowrap|''Mariner 10''}} encounters, the origin of Mercury's magnetic field remained the subject of several competing theories.<ref name="Ness1">{{cite journal |last=Ness |first=Norman F. |year=1978 |title=Mercury – Magnetic field and interior |journal=Space Science Reviews |volume=21 |issue=5 |pages=527–553 |bibcode=1978SSRv...21..527N |doi=10.1007/BF00240907|s2cid=120025983 }}</ref><ref>{{cite journal |last1=Aharonson |first1=Oded |last2=Zuber |first2=Maria T |last3=Solomon |first3=Sean C |title=Crustal remanence in an internally magnetized non-uniform shell: a possible source for Mercury's magnetic field? |journal=Earth and Planetary Science Letters |year=2004 |volume=218 |issue=3–4 |pages=261–268 |doi=10.1016/S0012-821X(03)00682-4 |bibcode=2004E&PSL.218..261A}}</ref>

On March 24, 1975, just eight days after its final close approach, {{nowrap|''Mariner 10''}} ran out of fuel. Because its orbit could no longer be accurately controlled, mission controllers instructed the probe to shut down.<ref name="DunneCh8">{{cite book |title=The Voyage of Mariner&nbsp;10 – Mission to Venus and Mercury |last1=Dunne |first1=James A. |last2=Burgess |first2=Eric |name-list-style=amp |chapter-url=https://history.nasa.gov/SP-424/ch8.htm |publisher=NASA History Office |date=1978 |chapter=Chapter Eight |url=https://history.nasa.gov/SP-424/ |access-date=July 12, 2017 |archive-date=November 17, 2017 |archive-url=https://web.archive.org/web/20171117190025/https://history.nasa.gov/SP-424/ |url-status=dead }}</ref> {{nowrap|''Mariner 10''}} is thought to be still orbiting the Sun, passing close to Mercury every few months.<ref>{{cite web |date=April 2, 2008 |first=Ed |last=Grayzeck |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1973-085A |title=Mariner&nbsp;10 |website=NSSDC Master Catalog |publisher=NASA |access-date=April 7, 2008 |archive-date=September 8, 2018 |archive-url=https://web.archive.org/web/20180908063158/https://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1973-085A |url-status=live }}</ref>

==== ''MESSENGER'' ====
{{Main|MESSENGER}}
[[File:Details of MESSENGER's Impact Location.jpg|thumb|Estimated details of the impact of ''MESSENGER'' on April 30, 2015]]
A second NASA mission to Mercury, named ''MESSENGER'' (MErcury Surface, Space ENvironment, GEochemistry, and Ranging), was launched on August 3, 2004. It made a fly-by of Earth in August 2005, and of Venus in October 2006 and June 2007 to place it onto the correct trajectory to reach an orbit around Mercury.<ref>{{cite web |year=2005 |url=http://www.spaceref.com/news/viewsr.html?pid=18956 |title=MESSENGER Engine Burn Puts Spacecraft on Track for Venus |publisher=SpaceRef.com |access-date=March 2, 2006}}</ref> A first fly-by of Mercury occurred on January 14, 2008, a second on October 6, 2008,<ref name="MessCountdown">{{cite web |url=http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?gallery_id=2&image_id=115 |title=Countdown to MESSENGER's Closest Approach with Mercury |date=January 14, 2008 |publisher=Johns Hopkins University Applied Physics Laboratory |access-date=May 30, 2008 |url-status=dead |archive-url=https://web.archive.org/web/20130513080731/http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?gallery_id=2&image_id=115 |archive-date=May 13, 2013}}</ref> and a third on September 29, 2009.<ref>{{cite web |title=MESSENGER Gains Critical Gravity Assist for Mercury Orbital Observations |url=http://messenger.jhuapl.edu/news_room/details.php?id=136 |date=September 30, 2009 |publisher=MESSENGER Mission News |access-date=September 30, 2009 |url-status=dead |archive-url=https://web.archive.org/web/20130510175510/http://messenger.jhuapl.edu/news_room/details.php?id=136 |archive-date=May 10, 2013}}</ref> Most of the hemisphere not imaged by {{nowrap|''Mariner 10''}} was mapped during these fly-bys. The probe successfully entered an elliptical orbit around the planet on March 18, 2011. The first orbital image of Mercury was obtained on March 29, 2011. The probe finished a one-year mapping mission,<ref name="MessCountdown" /> and then entered a one-year extended mission into 2013. In addition to continued observations and mapping of Mercury, ''MESSENGER'' observed the 2012 [[solar maximum]].<ref name="Extended2013">{{cite news | url=http://www.upi.com/Top_News/US/2011/11/15/NASA-extends-spacecrafts-Mercury-mission/UPI-55131321408343/ | title=NASA extends spacecraft's Mercury mission | work=United Press International | date=November 15, 2011 | access-date=November 16, 2011 | archive-date=May 31, 2013 | archive-url=https://web.archive.org/web/20130531103344/http://www.upi.com/Top_News/US/2011/11/15/NASA-extends-spacecrafts-Mercury-mission/UPI-55131321408343/ | url-status=live }}</ref>

[[File:MercuryTopo.png|thumb|right|Topography of Mercury based on MDIS (Mercury Dual Imaging System) data]] The mission was designed to clear up six key issues: Mercury's high density, its geological history, the nature of its magnetic field, the structure of its core, whether it has ice at its poles, and where its tenuous atmosphere comes from. To this end, the probe carried imaging devices that gathered much-higher-resolution images of much more of Mercury than {{nowrap|''Mariner 10''}}, assorted [[spectrometer]]s to determine the abundances of elements in the crust, and [[magnetometer]]s and devices to measure velocities of charged particles. Measurements of changes in the probe's orbital velocity were expected to be used to infer details of the planet's interior structure.<ref name="messenger_faq">{{cite web |url=http://messenger.jhuapl.edu/Resources/Resources/MESSENGER_FS22811_PRESS.PDF |title=MESSENGER: Fact Sheet |publisher=[[Applied Physics Laboratory]] |date=February 2011 |access-date=August 21, 2017 |archive-date=August 22, 2017 |archive-url=https://web.archive.org/web/20170822012453/http://messenger.jhuapl.edu/Resources/Resources/MESSENGER_FS22811_PRESS.PDF |url-status=live }}</ref> ''MESSENGER''{{'s}} final maneuver was on April 24, 2015, and it crashed into Mercury's surface on April 30, 2015.<ref name="results 2015">{{cite news |last=Wall |first=Mike |url=http://www.space.com/28948-messenger-mercury-probe-final-days.html |title=NASA Mercury Probe Trying to Survive for Another Month |work=Space.com |date=March 29, 2015 |access-date=April 4, 2015 |archive-date=April 3, 2019 |archive-url=https://web.archive.org/web/20190403102620/https://www.space.com/28948-messenger-mercury-probe-final-days.html |url-status=live }}</ref><ref name="NYT-20150427">{{cite news |last=Chang |first=Kenneth |title=NASA's Messenger Mission Is Set to Crash Into Mercury |url=https://www.nytimes.com/2015/04/28/science/nasas-messenger-mission-is-set-to-crash-into-mercury.html |archive-url=https://web.archive.org/web/20150429030725/http://www.nytimes.com/2015/04/28/science/nasas-messenger-mission-is-set-to-crash-into-mercury.html |archive-date=April 29, 2015 |url-access=subscription |url-status=live |date=April 27, 2015 |work=[[The New York Times]] |access-date=April 27, 2015}}</ref><ref name="NYT-20150430">{{cite news |last=Corum |first=Jonathan |title=Messenger's Collision Course With Mercury |url=https://www.nytimes.com/interactive/2015/04/30/science/space/messenger-collides-with-mercury.html |date=April 30, 2015 |work=[[The New York Times]] |access-date=April 30, 2015 |archive-date=March 31, 2019 |archive-url=https://web.archive.org/web/20190331205609/https://www.nytimes.com/interactive/2015/04/30/science/space/messenger-collides-with-mercury.html |url-status=live }}</ref> The spacecraft's impact with Mercury occurred at 3:26:01&nbsp;p.m. [[Eastern Time Zone|EDT]] on April 30, 2015, leaving a crater estimated to be {{convert|16|m|ft|abbr=on}} in diameter.<ref>{{cite web |date=June 3, 2015 |title=Best Determination of MESSENGER's Impact Location |url=https://messenger.jhuapl.edu/Explore/Science-Images-Database/gallery-image-1605.html |archive-url=https://web.archive.org/web/20230411141108/https://messenger.jhuapl.edu/Explore/Science-Images-Database/gallery-image-1605.html |archive-date=April 11, 2023 |access-date=October 6, 2023 |website=messenger.jhuapl.edu |publisher=[[Johns Hopkins Applied Physics Laboratory]]}}</ref>

==== ''BepiColombo'' ====
{{Main|BepiColombo}}
The [[European Space Agency]] and the [[Japanese Space Agency]] developed and launched a joint mission called ''BepiColombo'', which will orbit Mercury with two probes: one to map the planet and the other to study its magnetosphere.<ref name="ESAColumboGoAhead">{{cite web |title=ESA gives go-ahead to build BepiColombo |date=February 26, 2007 |publisher=[[European Space Agency]] |url=http://www.esa.int/esaSC/SEMC8XBE8YE_index_0.html |access-date=May 29, 2008 |archive-date=March 31, 2008 |archive-url=https://web.archive.org/web/20080331042423/http://www.esa.int/esaSC/SEMC8XBE8YE_index_0.html |url-status=live }}</ref> Launched on October 20, 2018, ''BepiColombo'' is expected to reach Mercury in 2025.<ref>{{cite web |title=BepiColombo Fact Sheet |url=http://sci.esa.int/bepicolombo/47346-fact-sheet/ |publisher=[[European Space Agency]] |access-date=December 19, 2016 |date=December 1, 2016 |archive-date=May 20, 2016 |archive-url=http://arquivo.pt/wayback/20160520023104/http://sci.esa.int/bepicolombo/47346%2Dfact%2Dsheet/ |url-status=live }}</ref> It will release a magnetometer probe into an elliptical orbit, then chemical rockets will fire to deposit the mapper probe into a circular orbit. Both probes will operate for one terrestrial year.<ref name="ESAColumboGoAhead" /> The mapper probe carries an array of spectrometers similar to those on ''MESSENGER'', and will study the planet at many different wavelengths including [[infrared]], [[ultraviolet]], [[X-ray]] and [[gamma ray]].<ref>{{cite web |title=Objectives |publisher=European Space Agency |url=http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=31350 |date=February 21, 2006 |access-date=May 29, 2008 |archive-date=September 28, 2006 |archive-url=https://web.archive.org/web/20060928055507/http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=31350 |url-status=live }}</ref> ''BepiColombo'' conducted the first of its six planned Mercury flybys on October 1, 2021,<ref>{{cite web|url=https://www.nasaspaceflight.com/2021/10/bepicolombo-first-mercury-flyby/|title=BepiColombo completes first Mercury flyby, science provides insight into planet's unique environment|website=[[NASA|NASA Spaceflight]]|date=October 24, 2021|accessdate=October 8, 2022|last1=Warren|first1=Haygen|archive-date=October 8, 2022|archive-url=https://web.archive.org/web/20221008121521/https://www.nasaspaceflight.com/2021/10/bepicolombo-first-mercury-flyby/|url-status=live}}</ref> and the sixth was completed on January 9, 2025. The spacecraft will enter the planet's orbit in 2026.<ref name="BBCBepi">{{cite web |last=Fullbrook |first=Danny |date=January 9, 2025 |title=New Images of Mercury Captured by UK Spacecraft |website=[[BBC]] |url=https://www.bbc.com/news/articles/cx2v2r1jm7go |access-date=January 10, 2025 }}</ref>