Jump to content

Exploration of Mercury: Difference between revisions

From Wikipedia, the free encyclopedia
Browse history interactively
← Previous edit
Content deleted Content added
VisualWikitext
No edit summary
m →External links: add WP:TEMPLATECAT to remove from template; genfixes
 
(377 intermediate revisions by more than 100 users not shown)
Line 1: Line 1:
{{Short description|Sending probes to the smallest planet}}
The '''exploration of [[Mercury (planet)|Mercury]]''' has taken only a minor role in the space interests of the world. It is the least explored [[solarsystem|inner planet]] (JHU/APL, 2006). As of 2007, the [[Mariner 10]] and [[MESSENGER]] missions have been the only missions that have made close observations of Mercury. [[MESSENGER]], made a fly-by of Mercury on [[14 January]] [[2008]], to further investigate the observations made by Mariner 10 in 1975 (Munsell, 2006b). A third mission to Mercury, [[BepiColombo]], is to include two [[space probe|probes]] and a [[lander (spacecraft)|lander]]. BepiColombo is a joint mission between [[Japan]] and the [[European Space Agency]]. MESSENGER and BepiColombo are intended to gather complementary data to help scientists understand many of the mysteries discovered by Mariner 10’s [[Gravitational slingshot|flybys]].
{{Use mdy dates|date=March 2019}}
{{multiple image
| align = right
| direction = vertical
| width = 230
| image1 = Mariner 10.jpg
| caption1 = The first probe to visit Mercury was ''[[Mariner 10]]''.
| image2 = Mercury Mariner10.jpg
| caption2 = View of Mercury from ''[[Mariner 10]]'' in March 1975.
}}
The '''exploration of [[Mercury (planet)|Mercury]]''' has a minor role in the space interests of the world. It is the least explored [[terrestrial planet|inner planet]].<ref name=JHUAPL>JHU/APL (2006). [http://messenger.jhuapl.edu/ MESSENGER: MErcury Surface, Space ENvironment, GEochemistry, and Ranging] Retrieved on 2007-01-27</ref> As of 2015, the ''[[Mariner 10]]'' and ''[[MESSENGER]]'' missions have been the only missions that have made close observations of [[Mercury (planet)|Mercury]]. ''MESSENGER'' made three [[planetary flyby|flyby]]s before entering orbit around Mercury.<ref name=Munsell2006b>Munsell Kirk-editor (November 6, 2006). [http://solarsystem.jpl.nasa.gov/missions/profile.cfm?Sort=Target&Target=Mercury&MCode=MESSENGER NASA: Solar System Exploration: Missions to Mercury] {{Webarchive|url=https://web.archive.org/web/20060929093809/http://solarsystem.jpl.nasa.gov/missions/profile.cfm?Sort=Target&Target=Mercury&MCode=MESSENGER |date=September 29, 2006 }}. Retrieved on 2007-01-27.</ref> A third mission to Mercury, ''[[BepiColombo]]'', a joint mission between the [[Japan Aerospace Exploration Agency]] (JAXA) and the [[European Space Agency]], is to include two [[space probe|probes]]. ''MESSENGER'' and ''BepiColombo'' are intended to gather complementary data to help scientists understand many of the mysteries discovered by ''Mariner 10''{{'}}s flybys.


Compared to other planets, Mercury is difficult to explore. The speed required to reach it is relatively high, and its proximity to the Sun makes it difficult to maneuver a spacecraft into a stable orbit around it.<ref name=ESA2007/> ''MESSENGER'' was the first probe to orbit Mercury.
==Interest in Mercury==
Mercury has not been a primary focus of many [[space program]]s because the planet has had little to offer. Since the planet is so close to the [[Sun]] and [[rotation|rotates]] on its own axis very slowly its surface temperature varies from 801 °[[Fahrenheit]] to -279 °Fahrenheit (427 °[[Celsius]] to -173 °Celsius) (Munsell, 2006a). There is discussion of the possibility of [[terraforming]] Mercury and inhabiting the [[geographical pole|poles]] of the planet, but that is a possibility far in the future, and significantly less practical than terraforming [[Mars]]. The current interest in Mercury is derived from the difficult to explain observations of Mariner 10. Before Mariner 10, it was thought that the planet simply rotated around the sun in a highly [[elliptic orbit|elliptical orbit]] (Munsell, 2006a). The planet had been observed through ground based [[telescope]]s, and scientists felt that they were able to draw a great many inferences from such observations. Mariner 10 provided data that contradicted many of these (Munsell, 2006b).


== Interest in Mercury ==
Another reason why so few missions have targeted Mercury is that it is very difficult to obtain a [[Artificial satellite orbit|satellite orbit]] around the planet on account of its proximity to the Sun. This causes the Sun’s [[gravitation|gravitational]] field to pull on any satellite that would be set into Mercury's [[orbital revolution|orbit]]. Furthermore, satellites must slow themselves en route to Mercury, so that as they get closer to the Sun they experience an even greater gravitational pull. This is contrary to the exploration of planets beyond Earth’s orbit where the satellite works against the pull of the Sun. Mercury's lack of an [[atmosphere]] poses further challenges because a probe attempting to land on Mercury would not be able to aerobrake or use a parachute type device (Munsell, 2006a). Thus it requires a great amount of energy to reach and observe the planet.


Few missions have targeted Mercury because it is very difficult to obtain a [[Orbital spaceflight|satellite orbit]] around the planet. Mercury [[orbit]]s the Sun very quickly (between {{convert|24.25|mi/s}} and {{convert|30|mi/s}}), so spacecraft must be travelling very fast to reach it. Mercury's close proximity to the Sun means that spacecraft are accelerated even further by the Sun's [[gravitation]]al pull, requiring significant fuel expenditure in order to decelerate for [[orbit insertion]].<ref name="ley196807">{{Cite magazine
==Mariner 10==
|last=Ley
[[Image:Mariner10.gif|thumb|Mariner 10 probe]]
|first=Willy
[[Mariner 10]] was a [[probe]] whose primary objective was to observe the atmosphere, surface, and physical characteristics of Mercury and [[Venus]]. It was a low cost mission completed for under 98 million [[United States Dollar]]s (Shirely, 2003). Mariner 10 was launched 9:45 p.m. [[Pacific Time Zone|PST]] on [[November 2]], [[1973]]. It was launched out of [[Kennedy Space Center|Cape Kennedy]] just seconds from the scheduled launch time (Dunne, 1978, p. 45). Since Mercury is so close to the Sun it was difficult and energy inefficient to have a satellite orbit Mercury, so Mariner 10 orbited around the Sun. In order to reach its destination, the satellite was [[gravitational slingshot|accelerated]] with the [[gravitational field|gravity field]] of Venus. It then passed close to Mercury on [[March 29]], [[1974]], as it flew towards the Sun. This was the first observation made of Mercury at close range. Mariner 10 then made orbits around the Sun in the opposite direction of both Earth’s and Mercury’s orbit. This allowed the probe to pass by Mercury two additional times before completing the mission; these encounters were made on [[September 21]], [[1974]] and [[March 16]], [[1975]]. However, since the same side of Mercury was illuminated during each of the flybys, at the conclusion of the mission Mariner 10 had only photographed 45% of its surface. The mission was terminated by simply stopping contact with Mariner 10 on [[March 24]], [[1975]]. This was forced by a loss of fuel (Munsell, 2006b).
|date=July 1968
|title=Interplanetary Communications
|department=For Your Information
|url=https://archive.org/stream/Galaxy_v26n06_1968-07#page/n117/mode/2up
|magazine=Galaxy Science Fiction
|pages=116–124
}}</ref> Mercury's lack of any significant [[atmosphere]]<ref name=Munsell2006a>Munsell Kirk-editor (November 6, 2006). [http://solarsystem.jpl.nasa.gov/planets/profile.cfm?Object=Mercury&Display=Overview NASA: Solar System Exploration: Planet Mercury] {{Webarchive|url=https://web.archive.org/web/20060929082455/http://solarsystem.jpl.nasa.gov/planets/profile.cfm?Object=Mercury&Display=Overview |date=September 29, 2006 }}. Retrieved on 2007-01-27.</ref> poses further challenges because it precludes [[aerobraking]]. Thus a landing mission would have even more demanding fuel requirements.<ref>{{Cite web | url=http://www.esa.int/For_Media/Press_Releases/Critical_decisions_on_Cosmic_Vision |title = Critical decisions on Cosmic Vision}}</ref>


==Missions==
The close observations collected two important sets of data. The probe detected Mercury’s [[magnetic field]], which is very similar to Earth’s. This was a surprise to scientists, because Mercury’s rotation, on its own axis, is at such a low speed. This will be a source of further investigation for the current explorations of Mercury. Secondly, visual data was provided, which showed the high number of [[impact crater|craters]] that have impacted the planet (Dunne, 1978, p. 74). The visual data also allowed scientists to determine that Mercury had “not experienced significant [[geology of Mercury|crustal modification]]” (Dunne, 1978, p. 101). This also added to the mystery of the magnetic field, as it was previously believed that the magnetic fields are caused by a molten dynamo effect, but since there was little crustal modification this provided evidence against that idea. The visual data also provided data that allowed scientists to investigate the composition and age of the planet (Dunne, 1978, p. 103).
===Past missions===


==== ''Mariner 10'' ====
==MESSENGER==
{{Main|Mariner 10}}
[[MESSENGER]] is a probe launched by [[NASA]] that is currently en route to Mercury. MESSENGER stands for ''MErcury Surface, Space ENvironment, GEochemistry, and Ranging''. It was launched from [[Cape Canaveral Air Force Station|Cape Canaveral]] on [[August 3]], [[2004]]. This was the second launch date. The original launch date, [[August 1]], [[2004]], was changed due to inclement weather (Rayl, 2004). To correct the speed of the satellite it will pass by the gravity fields of several planets several times. It passed by the Earth in February 2005 and then Venus in October 2006 (Munsell, 2006b) and again in 2007. The total travel time before entering orbit is about six and a half years (JHU/APL, 2006). <!-- A picture of the projected trajectory of MESSENGER is provided below. Image with unknown copyright status removed: [[Image:traj_helioecl_earth2moi_01162007.jpg]] -->
''[[Mariner 10]]'' was a [[NASA]] [[Space probe|probe]] whose primary objective was to observe the atmosphere, surface, and physical characteristics of Mercury and [[Venus]]. It was a low-cost mission completed for under [[United States dollar|$]]98 million.<ref>Shirley, 2003</ref> ''Mariner 10'' was launched at 12:45 am [[Eastern Time Zone|EST]] on November 3, 1973, from [[Kennedy Space Center|Cape Canaveral]].<ref name="Dunne1978p45">Dunne, James A. (1978). The Voyage of Mariner 10: Mission to Venus and Mercury (NASA SP-424). U.S. Government Printing Office. p. 45. ASIN B000C19QHA.</ref> Since Mercury is so close to the Sun it was too difficult to incorporate an orbit around Mercury in the route so ''Mariner 10'' orbited the Sun. In order to reach its destination, the satellite was [[Gravity assist|accelerated]] with the [[gravitational field|gravity field]] of Venus. It then passed close to Mercury on March 29, 1974, as it flew towards the Sun. This was the first observation made of Mercury at close range. After the encounter ''Mariner 10'' was in an orbit around the Sun such that for every one of its orbits Mercury made two, and the spacecraft and the planet would be able to meet again. This allowed the probe to pass by Mercury two additional times before completing the mission; these encounters were made on September 21, 1974, and March 16, 1975. However, since the same side of Mercury was illuminated during each of the flybys, at the conclusion of the mission ''Mariner 10'' had only photographed approximately 45 percent of its surface.<ref>{{Cite book |last=Mix |first=Lucas John |title=Life in Space: Astrobiology for Everyone |date=2009 |publisher=Harvard University Press |isbn=978-0-674-03321-4 |location=Cambridge, Massachusetts London, England}}</ref> The mission ended when the probe's [[Spacecraft attitude control|attitude control]] gas ran out on March 24, 1975. As the spacecraft was no longer controllable without its nitrogen gas thrusters, a command was sent to the probe to shut down its transmitter.<ref>{{cite book | last1 = Murray| first1 = Bruce | last2 = Burgess | first2 = Eric | title = Flight to Mercury| url = https://archive.org/details/flighttomercury00bruc| url-access = registration| publisher = [[Columbia University Press]] | date = 1977| location = New York| page = [https://archive.org/details/flighttomercury00bruc/page/138 138]| isbn = 9780231039963 }}</ref>


The close observations collected two important sets of data. The probe detected Mercury's [[magnetic field]], which is very similar to Earth's. This was a surprise to scientists, because Mercury spins so slowly on its axis. Secondly, visual data was provided, which showed the high number of [[impact crater|craters]] on the surface of the planet.<ref>Dunne, 1978, p. 74</ref> The visual data also allowed scientists to determine that Mercury had "not experienced significant [[geology of Mercury|crustal modification]]”.<ref>Dunne, 1978, p. 101</ref> This also added to the mystery of the magnetic field, as it was previously believed that the magnetic fields are caused by a molten dynamo effect, but since there was little crustal modification this undermined that idea. The visual data also allowed scientists to investigate the composition and age of the planet.<ref>Dunne, 1978, p. 103</ref>
Before entering orbit the probe will pass by Mercury three times. MESSENGER will have a “chemical bi-propellant system both to reach Mercury and brake into orbit” (McNutt, 2004). MESSENGER is scheduled to enter orbit around Mercury in 2011. The mission is scheduled to end sometime in 2012, when there is no longer enough fuel to maintain the probe's orbit (Planetary Society, 2007).


==== ''MESSENGER'' ====
The information collected by MESSENGER will be used to try to answer six questions about Mercury:
{{Main|MESSENGER}}
#Why is the planet so [[density|dense]]?
[[File:Animation of MESSENGER trajectory around Mercury.gif|thumb |right|Animation of ''[[MESSENGER]]''{{'s}} trajectory around [[Mercury (planet)|Mercury]] from March 15, 2011 to December 30, 2014<br>{{legend2|magenta| ''[[MESSENGER]]''}}{{·}}{{legend2| Blue |[[Mercury (planet)|Mercury]]}}|202x202px]]
#What is Mercury's [[Geologic time scale|geologic history]]?
[[File:MESSENGER first photo of unseen side of mercury.jpg|thumb|alt=Mercury from MESSENGER's first flyby|Photograph of Mercury from MESSENGER's first flyby of the planet, showing many previously unknown features|195x195px]]
#What is the structure of Mercury's [[planetary core|core]]?
''[[MESSENGER]]'' (Mercury Surface, Space Environment, Geochemistry, and Ranging) was a [[NASA]] orbital probe of Mercury. It was launched from [[Cape Canaveral Air Force Station|Cape Canaveral]] on August 3, 2004, after a one-day delay due to bad weather.<ref>Malik, T. (2004). [http://www.space.com/206-mercury-messenger-launch-postponed-tuesday.html Mercury ''MESSENGER'' Launch Postponed]. Retrieved 2015-07-18.</ref><ref>NBC News (2004). [https://www.nbcnews.com/id/wbna5577224 NASA launches spacecraft to Mercury]. Retrieved 2015-07-18.</ref> It took the probe about six and a half years before it entered orbit around Mercury. In order to correct the speed of the satellite it undertook several gravitational slingshot flybys of Earth, Venus and Mercury. It passed by the Earth in February 2005 and then Venus in October 2006<ref name=Munsell2006b/> and in October 2007. Furthermore, the probe made three passes of Mercury, one in January 2008, one in October 2008 and one in September 2009, before entering orbit in 2011. During these flybys of Mercury, enough data was collected to produce images of over 95% of its surface.
#What is the nature of Mercury's magnetic field?
#What are the unusual materials at Mercury's poles?
#What [[volatiles]] are important on Mercury?” (JHU/APL, 2006)


''MESSENGER'' used a chemical [[Bipropellant rocket|bi-propellant]] system both to reach Mercury and achieve orbit.<ref name=McNutt2004/> ''MESSENGER''{{'}}s scheduled orbital insertion took place successfully on March 18, 2011. In November 2012, NASA reported that ''MESSENGER'' had discovered a possibility of both [[Ice|water ice]] and organic compounds in permanently shadowed craters in Mercury's north pole.<ref>{{Cite web |date=2019-08-02 |title=The Moon and Mercury May Have Thick Ice Deposits - NASA |url=https://www.nasa.gov/solar-system/the-moon-and-mercury-may-have-thick-ice-deposits/ |access-date=2024-11-19 |language=en-US}}</ref> The mission was scheduled to end sometime in 2012, when it was estimated that there would no longer be enough fuel to maintain the probe's orbit.<ref>Planetary Society(2007) [http://planetary.org/explore/topics/messenger/ Space Topics: ''MESSENGER''] {{Webarchive|url=https://web.archive.org/web/20120423174455/http://planetary.org/explore/topics/messenger/ |date=April 23, 2012 }}. Retrieved September 11, 2010</ref> The primary mission was completed on March 17, 2012, having collected close to 100,000 images.<ref name="jhuap14">{{cite press release|url= http://messenger.jhuapl.edu/news_room/details.php?id=198|title= MESSENGER Provides New Look at Mercury's Landscape, Metallic Core, and Polar Shadows|date= March 21, 2012|publisher= [[Johns Hopkins University]]|access-date= March 22, 2012|url-status= dead|archive-url= https://web.archive.org/web/20130513081020/http://messenger.jhuapl.edu/news_room/details.php?id=198|archive-date= May 13, 2013}}</ref> ''MESSENGER'' achieved 100% mapping of Mercury on March 6, 2013, and completed its first year-long extended mission on March 17, 2013.<ref name=ExMissionCompleted2013>{{cite web|url=http://messenger.jhuapl.edu/news_room/details.php?id=237|title=MESSENGER Completes Its First Extended Mission at Mercury|publisher=JHU–APL|date=March 17, 2013|access-date=July 8, 2013|url-status=dead|archive-url=https://web.archive.org/web/20130729044412/http://messenger.jhuapl.edu/news_room/details.php?id=237|archive-date=July 29, 2013}}</ref> In February 2013, NASA published the most detailed and accurate 3D map of Mercury to date, assembled from thousands of images taken by ''MESSENGER.''<ref>{{Cite journal |last=Cho |first=Adrian |date=2017-03-01 |title=Scientists unveil the most detailed map of dark matter to date |url=http://dx.doi.org/10.1126/science.aal0847 |journal=Science |doi=10.1126/science.aal0847 |issn=0036-8075}}</ref> The probe continued collecting scientific data until April 30, 2015, when under a decaying orbit, the probe was allowed to crash onto the surface of Mercury.<ref name="Wu 2015">{{cite news |last=Wu |first=Brian |url=http://www.sciencetimes.com/articles/5077/20150330/nasa-set-extend-mercury-mission-another-month.htm |title=NASA Set to Extend Mercury Mission for Another Month |work=Johns Hopkins University APL |publisher=The Science Times |date=April 3, 2014 |access-date=2015-04-04 }}</ref><ref name="Extension 2015">{{cite news |url=http://spaceref.com/mercury/messengers-operations-at-mercury-extended.html |archive-url=https://archive.today/20150404230945/http://spaceref.com/mercury/messengers-operations-at-mercury-extended.html |url-status=dead |archive-date=April 4, 2015 |title=MESSENGER's Operations at Mercury Extended |work=Johns Hopkins University APL |publisher=Space Ref |date=April 3, 2014 |access-date=2015-04-04 }}</ref>
The satellite is equipped with special equipment to provide answers to each of these questions. <!--A list of equipment is provided below in the comparison of BepiColombo and MESSENGER missions.-->
[[File:Baranauskas crater MESSENGER WAC IGF to RGB.jpg|thumb|Baranauskas crater (center) on Mercury. Bright patches within the crater are [[Hollows (Mercury)|Hollows]]. Approximate color representation combining three images acquired by MESSENGER]]
The ''MESSENGER'' mission was designed to study the characteristics and environment of Mercury from orbit. Specifically, the scientific objectives of the mission were:<ref name="Objectives1">{{cite web | url = https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2004-030A | title = MESSENGER - Mission description | access-date = July 8, 2013 | publisher = NASA}}</ref><ref>{{cite web | url = http://discovery.nasa.gov/messenger.cfml | title = Discovery Program: MESSENGER | access-date = July 8, 2013 | publisher = NASA | url-status = dead | archive-url = https://web.archive.org/web/20130603184332/http://discovery.nasa.gov/messenger.cfml | archive-date = June 3, 2013 }}</ref>
* characterize the chemical composition of Mercury's surface.
* study the geologic history.
* elucidate the nature of [[Mercury's magnetic field]] ([[magnetosphere]]).
* determine the size and state of the [[Planetary core|core]].
* determine the volatile inventory at the poles.
* study the nature of Mercury's [[exosphere]].


===Ongoing missions===
==BepiColombo==

This mission to Mercury is to include two satellites and a ground lander: the Mercury Planetary Orbiter (MPO), the Mercury Magnetospheric Orbiter (MMO), and the Mercury Surface Element (MSE). Each orbiter has a distinct purpose: the MPO is to take images of Mercury, and the MMO is to study the [[magnetosphere]]. The European Space Agency and Japan are working in conjunction on BepiColombo and will each provide one of the orbiters. The ESA will provide MPO and MSE, while Japan will provide MMO (ESA, 2007). The BepiColombo was designed with 12 specific objectives:
==== ''BepiColombo'' ====
[[File:BepiColombo spacecraft model.png|thumb|Artist's depiction of the ''BepiColombo'' mission, with the Mercury Planetary Orbiter (left) and Mercury Magnetospheric Orbiter (right)]]
{{Main|BepiColombo}}
''BepiColombo'' consists of two spacecraft: the Mercury Planetary Orbiter (MPO) and Mio (Mercury Magnetospheric Orbiter, MMO). Each orbiter has a distinct purpose: the MPO is to acquire images in several wavelengths to map the surface and exosphere composition of Mercury, and Mio's is to study the [[magnetosphere]]. It is a joint mission of the European Space Agency and Japan Aerospace Exploration Agency; ESA provided the MPO, while JAXA provided Mio.<ref name=ESA2007>ESA (2007). [http://sci.esa.int/science-e/www/area/index.cfm?fareaid=30 BepiColombo]. Retrieved 2007-02-01.</ref> The ''BepiColombo'' mission will attempt to gather enough information to answer these questions:


#What can we learn from Mercury about the composition of the [[solar nebula]] and the formation of the [[planetary system]]?
#What can we learn from Mercury about the composition of the [[solar nebula]] and the formation of the [[planetary system]]?
#Why is Mercury's normalized density markedly higher than that of all other terrestrial planets, the [[Moon]] included?
#Why is Mercury's normalized density markedly higher than that of all other terrestrial planets, as well as the [[Moon]]?
#Is the core of Mercury liquid or solid?
#Is the core of Mercury liquid or solid?
#Is Mercury tectonically active today?
#Is Mercury tectonically active today?
#Why does such a small planet possess an intrinsic magnetic field, while Venus, Mars and the Moon do not have any?
#Why does such a small planet possess an intrinsic magnetic field, while Venus, Mars, and the Moon do not have any?
#Why do [[spectroscopic]] observations not reveal the presence of any [[iron]], while this [[chemical element|element]] is supposedly the major constituent of Mercury?
#Why do [[spectroscopic]] observations not reveal the presence of any [[iron]], while this [[chemical element|element]] is supposedly the major constituent of Mercury?
#Do the permanently shadowed craters of the polar regions contain [[sulphur]] or water ice?
#Do the permanently shadowed craters of the polar regions contain [[sulfur]] or water ice?
#Is the unseen hemisphere of Mercury markedly different from that imaged by Mariner 10?
#What are the production mechanisms of the [[exosphere]]?
#What are the production mechanisms of the [[exosphere]]?
#In the absence of any [[ionosphere]], how does the magnetic field interact with the [[solar wind]]?
#In the absence of any [[ionosphere]], how does the magnetic field interact with the [[solar wind]]?
#Is Mercury's magnetised environment characterized by features reminiscent of the [[Aurora (astronomy)|aurorae]], [[Van Allen radiation belt|radiation belts]] and [[magnetosphere|magnetospheric]] substorms observed on Earth?
#Is Mercury's magnetised environment characterized by features reminiscent of the [[Aurora (astronomy)|aurorae]], [[Van Allen radiation belt|radiation belts]] and [[magnetosphere|magnetospheric]] substorms observed on Earth?
#Since the advance of Mercury's [[Apsis|perihelion]] was explained in terms of [[space-time]] curvature, can we take advantage of the proximity of the Sun to test [[general relativity]] with improved accuracy? (ESA, 2007)
#Since the advance of Mercury's [[Apsis|perihelion]] was explained in terms of [[space-time]] curvature, can we take advantage of the proximity of the Sun to test [[general relativity]] with improved accuracy?<ref name=ESA2007/>


Like Mariner 10 and MESSENGER, BepiColombo will use gravity slingshots from Venus and Earth. BepiColombo will use Solar Electric Propulsion and then also use similar manoeuvres at the Moon, Venus, and Mercury. These techniques will slow the orbiters as they approach Mercury. It is essential to avoid using fuel to slow the orbiters as they get closer to the Sun to minimize the gravitational influence of the Sun (Munsell, 2006b). The MSE will be attached to the MMO until the MMO is in orbit, then the MSE will use a “chemical propulsion module and soft land airbags” (Munsell, 2006b). On some of the ESA deployment figures the MSE are [http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=38828 excluded]; however, all documents on the ESA website list the MSE as part of the launch plan. There was discussion about removing the MSE from the launch because of the difficulty in getting precision equipment (such as cameras) to land safely on the surface of Mercury, but there is no documentation for the removal of the MSE to date ([[2007-02-02]]).
Like ''Mariner 10'' and ''MESSENGER'', ''BepiColombo'' will use [[Gravity assist|gravity slingshots]] from Venus and Earth. ''BepiColombo'' will use [[solar electric propulsion]] (ion engines) and then also use similar maneuvers at the Moon, Venus, and Mercury. These techniques will slow the orbiters as they approach Mercury. It is essential to avoid using fuel to slow the orbiters as they get closer to the Sun to minimize the gravitational influence of the Sun.<ref name=Munsell2006b/>


The ''BepiColombo'' mission was approved in November 2009,<ref>{{Cite web |url=http://www.esa.int/Our_Activities/Space_Science/BepiColombo_overview2 |title=BepiColombo Overview |publisher=[[European Space Agency]] |date=September 5, 2016 |access-date=March 13, 2017}}</ref> and successfully launched on October 20, 2018. It is scheduled to enter orbit around Mercury in December 2025. Its primary mission will last until May 2027, with a possible extension to May 2028.<ref>{{cite web |url=http://sci.esa.int/bepicolombo/47346-fact-sheet/ |title=BepiColombo: Fact Sheet |publisher=European Space Agency |date=September 1, 2019 |access-date=March 9, 2020}}</ref>
BepiColombo is set for launch in August 2013. It is scheduled to enter orbit around Mercury in August of 2019. It will then gather data for one, or possibly two years.


===Proposed missions===
==Comparison of MESSENGER and BepiColombo==
BepiColombo was designed to complement the findings of MESSENGER and is equipped with far more measuring equipment than MESSENGER. BepiColombo is being sent to obtain a larger range of data. The orbit patterns of BepiColombo and MESSENGER are significantly different (McNutt, 2004).
<!--The following tables are a comparison of the equipment payloads. MMO is the Mercury Magnetosphere Orbiter and MPO is the Mercury Planetary Orbiter, which are both part of the BepiColombo mission:-->
<!-- Image with unknown copyright status removed: [[Image:MESSENGER_BEPI_PAYLOAD.gif]] -->
<!-- Image with unknown copyright status removed: [[Image:BEPI_PAYLOAD.gif]] -->
<!--(McNutt, 2004).As is evident from the instrument payload, the -->
<!--Here is a picture of the different orbits. Again, MMO and MPO are both part of the BepiColumbo exploratory mission.-->
<!-- Image with unknown copyright status removed: [[Image:MESSENGER_BEPI_ORBIT.gif]] -->
The MPO will basically have a circular orbit much closer to Mercury. The reason for this orbit is that the MPO will be taking photos of Mercury, and the close orbit will aid in picture quality. On the other hand, the MMO and MESSENGER will take largely [[elliptical orbit]]s. This is because of the stability of the orbit and the lower amount of fuel required to obtain and maintain the orbit (Mukai, 2006). Another reason for the different orbits of MMO and MESSENGER is to provide complementary data. The data of the two combined satellites will aid in more accurate measurements (McNutt, 2004).


[[Mercury-P]] (Меркурий-П) is a proposed lander mission to Mercury by the Russian Space Agency. The proposed launch date is 2031.{{Citation needed|date=April 2019}}
These constitute the major differences in the two missions. It is notable that some of the questions that BepiColombo is seeking answers for are very similar to those of MESSENGER. The inexplicably strong magnetic field, for example, is of interest to both missions. A more detailed discussion of differences is provided by ''An international program for Mercury exploration: synergy of MESSENGER and BepiColombo'' (McNutt, 2004).

In August 2020, the [[Applied Physics Laboratory]] proposed the [[Mercury Lander]] for NASA's [[New Frontiers program]]. If selected, it would launch in March 2035 and land in April 2045.<ref name="Space@APL">{{cite web | title=Mercury Lander | website=Space@APL |date=August 8, 2020 |url=https://space.jhuapl.edu/projects-and-studies/mercury-lander | access-date=April 20, 2024}}</ref>

===Canceled missions===
[[Mercury Observer]] was a cancelled proposal in the [[Planetary Observer]] program.

==Comparison of ''MESSENGER'' and ''BepiColombo''==
''BepiColombo'' was designed to complement the findings of ''MESSENGER'' and is equipped with far more measuring equipment than ''MESSENGER'' to obtain a larger range of data. The orbit patterns of ''BepiColombo'' and ''MESSENGER'' are significantly different.<ref name=McNutt2004>{{cite journal|doi=10.1016/S0273-1177(03)00439-3|title=An international program for Mercury exploration: Synergy of MESSENGER and Bepi ''Colombo''|journal=Advances in Space Research|volume=33|issue=12|pages=2126–2132|year=2004|last1=McNutt|first1=Ralph L.|last2=Solomon|first2=Sean C.|last3=Grard|first3=Réjean|last4=Novara|first4=Mauro|last5=Mukai|first5=Toshifumi|bibcode=2004AdSpR..33.2126M }}</ref>

The BepiColombo mission comprises two satellites launched together: the Mercury Planetary Orbiter (MPO) and Mio (Mercury Magnetospheric Orbiter, MMO). The MPO will have a circular orbit much closer to Mercury. The reason for this orbit is that the MPO will be measuring the composition of the surface and exosphere, and the close orbit will aid on data quality. On the other hand, Mio (MMO) and ''MESSENGER'' took largely [[elliptical orbit]]s. This is because of the stability of the orbit and the lower amount of fuel required to obtain and maintain the orbit.<ref name=Mukai2006>{{cite journal|doi=10.1016/j.asr.2005.09.038|title=Present status of the Bepi ''Colombo''/Mercury magnetospheric orbiter|journal=Advances in Space Research|volume=38|issue=4|pages=578–582|year=2006|last1=Mukai|first1=T.|last2=Yamakawa|first2=H.|last3=Hayakawa|first3=H.|last4=Kasaba|first4=Y.|last5=Ogawa|first5=H.|bibcode=2006AdSpR..38..578M }}</ref> Another reason for the different orbits of Mio and ''MESSENGER'' was to provide complementary data. The data of the two combined satellites will provide more accurate measurements.<ref name=McNutt2004 />

==See also==
* [[Colonization of Mercury]]


==References==
==References==
{{Reflist|30em}}
*Dunne, James A. (1978). The Voyage of Mariner 10: Mission to Venus and Mercury (NASA SP-424). U.S. Government Printing Office. ASIN B000C19QHA.
*Shirley, Donna L. (August 2003). The Mariner 10 mission to Venus and Mercury. ''Acta Astronautica'', Aug 2003, Vol. 53, Issue 4-10, p375, 11p; (AN 11471527).
*Munsell Kirk-editor (November 06, 2006a). [http://solarsystem.jpl.nasa.gov/planets/profile.cfm?Object=Mercury&Display=Overview NASA: Solar System Exploration: Planet Mercury]. Retrieved on [[2007-01-27]].
*Munsell Kirk-editor (November 06, 2006b). [http://solarsystem.jpl.nasa.gov/missions/profile.cfm?Sort=Target&Target=Mercury&MCode=MESSENGER NASA: Solar System Exploration: Missions to Mercury]. Retrieved on [[2007-01-27]].
*JHU/APL (2006). [http://messenger.jhuapl.edu/ MESSENGER: MErcury Surface, Space ENvironment, GEochemistry, and Ranging] Retrieved on [[2007-01-27]]
*McNutt, Ralph L.; Solomon, Sean C.; Grard, Rejean; Novara, Mauro; and Mukai, Toshifumi. (2004). [http://www.sciencedirect.com/college/article/B6V3S-4BH62RK-H/2/0f9db92b4a615e263b4a621bdb46d4c7 An international program for Mercury exploration: synergy of MESSENGER and BepiColombo], ''Advances in Space Research'', Volume 33, Issue 12, Mercury, Mars and Saturn, 2004, Pages 2126-2132.
*Mukai, T.; Yamakawa, H.; Hayakawa, H.; Kasaba, Y.; and Ogawa, H (2006). [http://www.sciencedirect.com/college/article/B6V3S-4HHH61S-3/2/c94747d0517eb557ad5121593ea8ad20 Present status of the BepiColombo/Mercury magnetospheric orbiter]. ''Advances in Space Research'', Volume 38, Issue 4, Mercury, Mars and Saturn, 2006, Pages 578-582.
*ESA (2007). [http://sci.esa.int/science-e/www/area/index.cfm?fareaid=30 BepiColombo]. Retrieved [[2007-02-01]].
*Planetary Society (2007). [http://planetary.org/explore/topics/messenger/ Space Topics: MESSENGER]. Retrieved [[2007-01-28]].
*Rayl, A.J.S. (2004). [http://www.planetary.org/news/2004/0801_MESSENGER_Launch_to_Mercury_Postponed.html MESSENGER Launch to Mercury Postponed]. Retrieved [[2007-02-04]].


==External links==
==External links==
*[http://www.jpl.nasa.gov/missions/past/mariner10.html Mariner 10]
* [https://web.archive.org/web/20050905000210/http://www.jpl.nasa.gov/missions/past/mariner10.html ''Mariner 10'']
*[http://messenger.jhuapl.edu/ MESSENGER probe]
* [http://messenger.jhuapl.edu/ ''MESSENGER'' probe]
* Shirley, Donna L. (August 2003). The ''Mariner 10'' mission to Venus and Mercury. ''Acta Astronautica'', Aug 2003, Vol. 53, Issue 4–10, p375, 11p; (AN 11471527).


{{Planetary exploration}}
{{Planetary exploration}}
{{Mercury Footer}}
{{Mercury spacecraft}}
{{Mercury (planet)}}

{{Solar System}}
[[Category:Space exploration]]
{{Authority control}}


[[Category:Spaceflight]]
[[it:Esplorazione di Mercurio]]
[[Category:Mercury (planet)]]
[[Category:Discovery and exploration of the Solar System]]
[[Category:Missions to Mercury|*]]
[[Category:Solar System]]

Latest revision as of 20:03, 5 December 2024

The first probe to visit Mercury was Mariner 10.
View of Mercury from Mariner 10 in March 1975.

The exploration of Mercury has a minor role in the space interests of the world. It is the least explored inner planet.[1] As of 2015, the Mariner 10 and MESSENGER missions have been the only missions that have made close observations of Mercury. MESSENGER made three flybys before entering orbit around Mercury.[2] A third mission to Mercury, BepiColombo, a joint mission between the Japan Aerospace Exploration Agency (JAXA) and the European Space Agency, is to include two probes. MESSENGER and BepiColombo are intended to gather complementary data to help scientists understand many of the mysteries discovered by Mariner 10's flybys.

Compared to other planets, Mercury is difficult to explore. The speed required to reach it is relatively high, and its proximity to the Sun makes it difficult to maneuver a spacecraft into a stable orbit around it.[3] MESSENGER was the first probe to orbit Mercury.

Interest in Mercury

[edit]

Few missions have targeted Mercury because it is very difficult to obtain a satellite orbit around the planet. Mercury orbits the Sun very quickly (between 24.25 miles per second (39.03 km/s) and 30 miles per second (48 km/s)), so spacecraft must be travelling very fast to reach it. Mercury's close proximity to the Sun means that spacecraft are accelerated even further by the Sun's gravitational pull, requiring significant fuel expenditure in order to decelerate for orbit insertion.[4] Mercury's lack of any significant atmosphere[5] poses further challenges because it precludes aerobraking. Thus a landing mission would have even more demanding fuel requirements.[6]

Missions

[edit]

Past missions

[edit]

Mariner 10

[edit]
Main article: Mariner 10

Mariner 10 was a NASA probe whose primary objective was to observe the atmosphere, surface, and physical characteristics of Mercury and Venus. It was a low-cost mission completed for under $98 million.[7] Mariner 10 was launched at 12:45 am EST on November 3, 1973, from Cape Canaveral.[8] Since Mercury is so close to the Sun it was too difficult to incorporate an orbit around Mercury in the route so Mariner 10 orbited the Sun. In order to reach its destination, the satellite was accelerated with the gravity field of Venus. It then passed close to Mercury on March 29, 1974, as it flew towards the Sun. This was the first observation made of Mercury at close range. After the encounter Mariner 10 was in an orbit around the Sun such that for every one of its orbits Mercury made two, and the spacecraft and the planet would be able to meet again. This allowed the probe to pass by Mercury two additional times before completing the mission; these encounters were made on September 21, 1974, and March 16, 1975. However, since the same side of Mercury was illuminated during each of the flybys, at the conclusion of the mission Mariner 10 had only photographed approximately 45 percent of its surface.[9] The mission ended when the probe's attitude control gas ran out on March 24, 1975. As the spacecraft was no longer controllable without its nitrogen gas thrusters, a command was sent to the probe to shut down its transmitter.[10]

The close observations collected two important sets of data. The probe detected Mercury's magnetic field, which is very similar to Earth's. This was a surprise to scientists, because Mercury spins so slowly on its axis. Secondly, visual data was provided, which showed the high number of craters on the surface of the planet.[11] The visual data also allowed scientists to determine that Mercury had "not experienced significant crustal modification”.[12] This also added to the mystery of the magnetic field, as it was previously believed that the magnetic fields are caused by a molten dynamo effect, but since there was little crustal modification this undermined that idea. The visual data also allowed scientists to investigate the composition and age of the planet.[13]

MESSENGER

[edit]
Main article: MESSENGER
Animation of MESSENGER's trajectory around Mercury from March 15, 2011 to December 30, 2014
   MESSENGER ·   Mercury
Mercury from MESSENGER's first flyby
Photograph of Mercury from MESSENGER's first flyby of the planet, showing many previously unknown features

MESSENGER (Mercury Surface, Space Environment, Geochemistry, and Ranging) was a NASA orbital probe of Mercury. It was launched from Cape Canaveral on August 3, 2004, after a one-day delay due to bad weather.[14][15] It took the probe about six and a half years before it entered orbit around Mercury. In order to correct the speed of the satellite it undertook several gravitational slingshot flybys of Earth, Venus and Mercury. It passed by the Earth in February 2005 and then Venus in October 2006[2] and in October 2007. Furthermore, the probe made three passes of Mercury, one in January 2008, one in October 2008 and one in September 2009, before entering orbit in 2011. During these flybys of Mercury, enough data was collected to produce images of over 95% of its surface.

MESSENGER used a chemical bi-propellant system both to reach Mercury and achieve orbit.[16] MESSENGER's scheduled orbital insertion took place successfully on March 18, 2011. In November 2012, NASA reported that MESSENGER had discovered a possibility of both water ice and organic compounds in permanently shadowed craters in Mercury's north pole.[17] The mission was scheduled to end sometime in 2012, when it was estimated that there would no longer be enough fuel to maintain the probe's orbit.[18] The primary mission was completed on March 17, 2012, having collected close to 100,000 images.[19] MESSENGER achieved 100% mapping of Mercury on March 6, 2013, and completed its first year-long extended mission on March 17, 2013.[20] In February 2013, NASA published the most detailed and accurate 3D map of Mercury to date, assembled from thousands of images taken by MESSENGER.[21] The probe continued collecting scientific data until April 30, 2015, when under a decaying orbit, the probe was allowed to crash onto the surface of Mercury.[22][23]

Baranauskas crater (center) on Mercury. Bright patches within the crater are Hollows. Approximate color representation combining three images acquired by MESSENGER

The MESSENGER mission was designed to study the characteristics and environment of Mercury from orbit. Specifically, the scientific objectives of the mission were:[24][25]

  • characterize the chemical composition of Mercury's surface.
  • study the geologic history.
  • elucidate the nature of Mercury's magnetic field (magnetosphere).
  • determine the size and state of the core.
  • determine the volatile inventory at the poles.
  • study the nature of Mercury's exosphere.

Ongoing missions

[edit]

BepiColombo

[edit]
Artist's depiction of the BepiColombo mission, with the Mercury Planetary Orbiter (left) and Mercury Magnetospheric Orbiter (right)
Main article: BepiColombo

BepiColombo consists of two spacecraft: the Mercury Planetary Orbiter (MPO) and Mio (Mercury Magnetospheric Orbiter, MMO). Each orbiter has a distinct purpose: the MPO is to acquire images in several wavelengths to map the surface and exosphere composition of Mercury, and Mio's is to study the magnetosphere. It is a joint mission of the European Space Agency and Japan Aerospace Exploration Agency; ESA provided the MPO, while JAXA provided Mio.[3] The BepiColombo mission will attempt to gather enough information to answer these questions:

  1. What can we learn from Mercury about the composition of the solar nebula and the formation of the planetary system?
  2. Why is Mercury's normalized density markedly higher than that of all other terrestrial planets, as well as the Moon?
  3. Is the core of Mercury liquid or solid?
  4. Is Mercury tectonically active today?
  5. Why does such a small planet possess an intrinsic magnetic field, while Venus, Mars, and the Moon do not have any?
  6. Why do spectroscopic observations not reveal the presence of any iron, while this element is supposedly the major constituent of Mercury?
  7. Do the permanently shadowed craters of the polar regions contain sulfur or water ice?
  8. What are the production mechanisms of the exosphere?
  9. In the absence of any ionosphere, how does the magnetic field interact with the solar wind?
  10. Is Mercury's magnetised environment characterized by features reminiscent of the aurorae, radiation belts and magnetospheric substorms observed on Earth?
  11. Since the advance of Mercury's perihelion was explained in terms of space-time curvature, can we take advantage of the proximity of the Sun to test general relativity with improved accuracy?[3]

Like Mariner 10 and MESSENGER, BepiColombo will use gravity slingshots from Venus and Earth. BepiColombo will use solar electric propulsion (ion engines) and then also use similar maneuvers at the Moon, Venus, and Mercury. These techniques will slow the orbiters as they approach Mercury. It is essential to avoid using fuel to slow the orbiters as they get closer to the Sun to minimize the gravitational influence of the Sun.[2]

The BepiColombo mission was approved in November 2009,[26] and successfully launched on October 20, 2018. It is scheduled to enter orbit around Mercury in December 2025. Its primary mission will last until May 2027, with a possible extension to May 2028.[27]

Proposed missions

[edit]

Mercury-P (Меркурий-П) is a proposed lander mission to Mercury by the Russian Space Agency. The proposed launch date is 2031.[citation needed]

In August 2020, the Applied Physics Laboratory proposed the Mercury Lander for NASA's New Frontiers program. If selected, it would launch in March 2035 and land in April 2045.[28]

Canceled missions

[edit]

Mercury Observer was a cancelled proposal in the Planetary Observer program.

Comparison of MESSENGER and BepiColombo

[edit]

BepiColombo was designed to complement the findings of MESSENGER and is equipped with far more measuring equipment than MESSENGER to obtain a larger range of data. The orbit patterns of BepiColombo and MESSENGER are significantly different.[16]

The BepiColombo mission comprises two satellites launched together: the Mercury Planetary Orbiter (MPO) and Mio (Mercury Magnetospheric Orbiter, MMO). The MPO will have a circular orbit much closer to Mercury. The reason for this orbit is that the MPO will be measuring the composition of the surface and exosphere, and the close orbit will aid on data quality. On the other hand, Mio (MMO) and MESSENGER took largely elliptical orbits. This is because of the stability of the orbit and the lower amount of fuel required to obtain and maintain the orbit.[29] Another reason for the different orbits of Mio and MESSENGER was to provide complementary data. The data of the two combined satellites will provide more accurate measurements.[16]

See also

[edit]

References

[edit]
  1. ^ JHU/APL (2006). MESSENGER: MErcury Surface, Space ENvironment, GEochemistry, and Ranging Retrieved on 2007-01-27
  2. ^ a b c Munsell Kirk-editor (November 6, 2006). NASA: Solar System Exploration: Missions to Mercury Archived September 29, 2006, at the Wayback Machine. Retrieved on 2007-01-27.
  3. ^ a b c ESA (2007). BepiColombo. Retrieved 2007-02-01.
  4. ^ Ley, Willy (July 1968). "Interplanetary Communications". For Your Information. Galaxy Science Fiction. pp. 116–124.
  5. ^ Munsell Kirk-editor (November 6, 2006). NASA: Solar System Exploration: Planet Mercury Archived September 29, 2006, at the Wayback Machine. Retrieved on 2007-01-27.
  6. ^ "Critical decisions on Cosmic Vision".
  7. ^ Shirley, 2003
  8. ^ Dunne, James A. (1978). The Voyage of Mariner 10: Mission to Venus and Mercury (NASA SP-424). U.S. Government Printing Office. p. 45. ASIN B000C19QHA.
  9. ^ Mix, Lucas John (2009). Life in Space: Astrobiology for Everyone. Cambridge, Massachusetts London, England: Harvard University Press. ISBN 978-0-674-03321-4.
  10. ^ Murray, Bruce; Burgess, Eric (1977). Flight to Mercury. New York: Columbia University Press. p. 138. ISBN 9780231039963.
  11. ^ Dunne, 1978, p. 74
  12. ^ Dunne, 1978, p. 101
  13. ^ Dunne, 1978, p. 103
  14. ^ Malik, T. (2004). Mercury MESSENGER Launch Postponed. Retrieved 2015-07-18.
  15. ^ NBC News (2004). NASA launches spacecraft to Mercury. Retrieved 2015-07-18.
  16. ^ a b c McNutt, Ralph L.; Solomon, Sean C.; Grard, Réjean; Novara, Mauro; Mukai, Toshifumi (2004). "An international program for Mercury exploration: Synergy of MESSENGER and Bepi Colombo". Advances in Space Research. 33 (12): 2126–2132. Bibcode:2004AdSpR..33.2126M. doi:10.1016/S0273-1177(03)00439-3.
  17. ^ "The Moon and Mercury May Have Thick Ice Deposits - NASA". August 2, 2019. Retrieved November 19, 2024.
  18. ^ Planetary Society(2007) Space Topics: MESSENGER Archived April 23, 2012, at the Wayback Machine. Retrieved September 11, 2010
  19. ^ "MESSENGER Provides New Look at Mercury's Landscape, Metallic Core, and Polar Shadows" (Press release). Johns Hopkins University. March 21, 2012. Archived from the original on May 13, 2013. Retrieved March 22, 2012.
  20. ^ "MESSENGER Completes Its First Extended Mission at Mercury". JHU–APL. March 17, 2013. Archived from the original on July 29, 2013. Retrieved July 8, 2013.
  21. ^ Cho, Adrian (March 1, 2017). "Scientists unveil the most detailed map of dark matter to date". Science. doi:10.1126/science.aal0847. ISSN 0036-8075.
  22. ^ Wu, Brian (April 3, 2014). "NASA Set to Extend Mercury Mission for Another Month". Johns Hopkins University APL. The Science Times. Retrieved April 4, 2015.
  23. ^ "MESSENGER's Operations at Mercury Extended". Johns Hopkins University APL. Space Ref. April 3, 2014. Archived from the original on April 4, 2015. Retrieved April 4, 2015.
  24. ^ "MESSENGER - Mission description". NASA. Retrieved July 8, 2013.
  25. ^ "Discovery Program: MESSENGER". NASA. Archived from the original on June 3, 2013. Retrieved July 8, 2013.
  26. ^ "BepiColombo Overview". European Space Agency. September 5, 2016. Retrieved March 13, 2017.
  27. ^ "BepiColombo: Fact Sheet". European Space Agency. September 1, 2019. Retrieved March 9, 2020.
  28. ^ "Mercury Lander". Space@APL. August 8, 2020. Retrieved April 20, 2024.
  29. ^ Mukai, T.; Yamakawa, H.; Hayakawa, H.; Kasaba, Y.; Ogawa, H. (2006). "Present status of the Bepi Colombo/Mercury magnetospheric orbiter". Advances in Space Research. 38 (4): 578–582. Bibcode:2006AdSpR..38..578M. doi:10.1016/j.asr.2005.09.038.
[edit]
  • Mariner 10
  • MESSENGER probe
  • Shirley, Donna L. (August 2003). The Mariner 10 mission to Venus and Mercury. Acta Astronautica, Aug 2003, Vol. 53, Issue 4–10, p375, 11p; (AN 11471527).
Retrieved from "https://en.wikipedia.org/enwiki/w/index.php?title=Exploration_of_Mercury&oldid=1261378260"