View source for Astronomy:Eagle (Meridiani Planum crater)

{{short description|Crater on Mars}}
{{Infobox crater data
| titlecolor  = #FA8072
| title       = Eagle
| image       = [[File:Eagle crater panorama.jpg|280px|Eagle Crater]]
| region      = [[Astronomy:Meridiani Planum|Meridiani Planum]]
| coordinate_title = [[Astronomy:Mars#Geography|Coordinates]]
| globe       = Mars
| coordinates = {{coord|1.95|S|354.47|E|globe:mars_type:landmark|display=inline,title}}
| diameter    = 22 m<ref name="MERFacts" />
| depth       = 3 m<ref name="MERFacts"/>
| discoverer  = ''Opportunity'' rover
| eponym      = See list below
}}

'''Eagle''' is a 22-metre long [[Astronomy:Impact crater|impact crater]] located on the [[Astronomy:Meridiani Planum|Meridiani Planum]] extraterrestrial plain, situated within the [[Astronomy:Margaritifer Sinus quadrangle|Margaritifer Sinus quadrangle]] (MC-19) portion of the planet [[Astronomy:Mars|Mars]]. The ''Opportunity'' rover came to rest inside Eagle crater when it landed in 2004. Scientists were delighted that the rover landed there, as the crater contains [[Engineering:Opportunity mission timeline#"Opportunity Ledge" outcroppings|rocky outcroppings]] that helped prove that Meridiani was once an ocean floor.

This crater should not be confused with the other, much larger Martian crater ''[[Astronomy:Eagle (Acidalia Planitia crater)|Eagle]]'', which was officially named by IAU's Working Group for Planetary System Nomenclature in 1976.<ref name="Gazetteer" />

== Name ==
[[File:Oppland02a.jpg|thumb|HiRISE image of the Martian crater Eagle – the dot in the middle of the crater is the lander.]]

The name is a triple reference: in honor of the first crewed spacecraft to land on the [[Astronomy:Moon|Moon]] in 1969; in honor of the launching country, the {{wipe|United States}}, whose symbol is an [[Biology:Eagle|eagle]]; and in reference to the golf term ''eagle'', referring to sinking a ball two strokes under par. The third reference extended the golf metaphor begun with a description of landing in the crater as "a hole in one".

== Discoveries in the crater ==
[[File:Opportunity - Cratera Eagle.jpg|thumb|left|The crater, with Opportunity lander, as seen by ''Opportunity'' rover.]]

Mission scientists were intrigued by the abundance of rock outcrops dispersed throughout the crater, as well as the crater's soil, which appeared to be a mixture of coarse gray grains and fine reddish grains. Upon closer, in-situ examination of the outcrops, whose layers are no thicker than a finger, it was confirmed that Meridiani Planum was once the location of an ancient, somewhat acidic and salty sea,<ref>[http://marsrovers.jpl.nasa.gov/newsroom/pressreleases/20041202a.html "Reports Detail Rover Discoveries of Wet Martian History"] (2 Dec 2004) JPL. Retrieved 22 August 2011.</ref> though much more information on the history of this area would start being collected more than three months later, when ''Opportunity'' visited the much larger crater [[Astronomy:Endurance (crater)|Endurance]] to the east.

[[File:Opportunity photo of Mars outcrop rock.jpg|thumb|Spherules still in their originating strata.]]
The [[Chemistry:Hematite|hematite]] observed from orbit, whose presence decided the landing site in the first place, was found to be encased in millions of tiny hematite [[Astronomy:Martian spherules|spherules]], nicknamed "blueberries", by mission scientists, due to their shape, although they are actually much smaller than real blueberries. These concretions were found soon to be covering not just the outcrops in Eagle crater, but covered the plains beyond as well. The origin of the blueberries was quickly discovered. They appeared to be being eroded out of the outcrops by wind. Images from the rover's microscope discovered blueberries at several stages of this process, with most completely separated, but some still attached by a thin "stalk".

== Rocks and outcrops in the crater ==
[[File:PIA05482 modest.jpg|thumb|Approximate [[24-bit color|true-color]] photo of Last Chance.]]

A number of rocks and outcrops were investigated with ''Opportunity''{{'}}s Instrument Deployment Device (IDD). They were given informal names by mission scientists. These include:
* Berry Bowl, an outcrop rich in Martian spherules
* Carousel, a layered outcrop most likely to have been formed in a wet environment
* Cookies 'N' Cream, a dark soil target near Carousel
* [[Astronomy:El Capitan (Mars)|El Capitan]], another layered outcrop
* [[Astronomy:Last Chance (Mars)|Last Chance]], another layered outcrop

The locations of these rocks and outcrops can be seen in the panorama below:
{{-}}
{{Wide image|MERB outcrop map 01-mw-01-labels-B041R1 br.jpg|1600px|This panoramic image, showing the locations of rocks and outcrops at the northwestern rim of Eagle crater, was taken with ''Opportunity'' still on its lander. These layered rocks measure only 10 centimeters (4 inches) tall and were thought at that time to be either volcanic ash deposits or sediments carried by water or wind. [[:File:Eagle crater on the Mars PIA05163.jpg|Click here for a version of this image without annotations.]] (Courtesy NASA/JPL-Caltech)}}

== See also ==
* Geography of Mars
* [[Astronomy:List of craters on Mars|List of craters on Mars]]

== References ==
{{Reflist|refs=

<ref name="MERFacts">{{Cite news|title=NASA Facts: Mars Exploration Rover|publisher=NASA/JPL|url=http://www.jpl.nasa.gov/missions/mer/merfactsheet.pdf|date=24 October 2004|access-date=26 March 2009|archive-url=https://web.archive.org/web/20090327135047/http://www.jpl.nasa.gov/missions/mer/merfactsheet.pdf|archive-date=27 March 2009|url-status=dead}}</ref>

<ref name="Gazetteer">{{GPN|1703}}</ref>

}} <!-- end of reflist -->

== Further reading ==
* {{cite journal|author=Squyres|title=In Situ Evidence for an Ancient Aqueous Environment at Meridiani Planum, Mars|journal=Science|year=2004|volume=306|pages=1709–1714|doi=10.1126/science.1104559|pmid=15576604|last2=Grotzinger|first2=JP|last3=Arvidson|first3=RE|last4=Bell Jf|first4=3rd|last5=Calvin|first5=W|last6=Christensen|first6=PR|last7=Clark|first7=BC|last8=Crisp|first8=JA|last9=Farrand|first9=WH|issue=5702|bibcode = 2004Sci...306.1709S |display-authors=1|last10=Herkenhoff|first10=K. E.|last11=Johnson|first11=J. R.|last12=Klingelhöfer|first12=G.|last13=Knoll|first13=A. H.|last14=McLennan|first14=S. M.|last15=McSween|first15=H. Y.|last16=Morris|first16=R. V.|last17=Rice|first17=J. W.|last18=Rieder|first18=R.|last19=Soderblom|first19=L. A.|s2cid=16785189|url=http://www.ifa.hawaii.edu/%7Emeech/NAIJC/papers/MeridianiPlanum_Science2004_AqueousEnv.pdf}}
* {{cite journal|author=Squyres|title=Soils of Eagle Crater and Meridian Planum at the Opportunity Rover Landing Site|journal=Science|year=2004|volume=306|pages=1723–1726|doi=10.1126/science.1105127|pmid=15576606|last2=Anderson|first2=RC|last3=Arvidson|first3=RE|last4=Bell Jf|first4=3rd|last5=Cabrol|first5=NA|last6=Calvin|first6=W|last7=Christensen|first7=PR|last8=Clark|first8=BC|last9=Economou|first9=T|issue=5702|bibcode = 2004Sci...306.1723S |display-authors=1|last10=Ehlmann|first10=B. L.|last11=Farrand|first11=W. H.|last12=Fike|first12=D.|last13=Gellert|first13=R.|last14=Glotch|first14=T. D.|last15=Golombek|first15=M. P.|last16=Greeley|first16=R.|last17=Grotzinger|first17=J. P.|last18=Herkenhoff|first18=K. E.|last19=Jerolmack|first19=D. J.|last20=Johnson|first20=J. R.|last21=Jolliff|first21=B.|last22=Klingelhöfer|first22=G.|last23=Knoll|first23=A. H.|last24=Learner|first24=Z. A.|last25=Li|first25=R.|last26=Malin|first26=M. C.|last27=McLennan|first27=S. M.|last28=McSween|first28=H. Y.|last29=Ming|first29=D. W.|last30=Morris|first30=R. V.|s2cid=5693765|url=http://aram.ess.sunysb.edu/tglotch/TDG6.pdf}}
* {{cite journal|author=Squyres|title=The Opportunity Rover's Athena Science Investigation at Meridiani Planum, Mars|journal=Science|year=2004|volume=306|pages=1698–1703|doi=10.1126/science.1106171|pmid=15576602|last2=Arvidson|first2=RE|last3=Bell Jf|first3=3rd|last4=Brückner|first4=J|last5=Cabrol|first5=NA|last6=Calvin|first6=W|last7=Carr|first7=MH|last8=Christensen|first8=PR|last9=Clark|first9=BC|issue=5702|bibcode = 2004Sci...306.1698S |display-authors=1|last10=Crumpler|first10=L.|last11=Des Marais|first11=D. J.|last12=d'Uston|first12=C.|last13=Economou|first13=T.|last14=Farmer|first14=J.|last15=Farrand|first15=W.|last16=Folkner|first16=W.|last17=Golombek|first17=M.|last18=Gorevan|first18=S.|last19=Grant|first19=J. A.|last20=Greeley|first20=R.|last21=Grotzinger|first21=J.|last22=Haskin|first22=L.|last23=Herkenhoff|first23=K. E.|last24=Hviid|first24=S.|last25=Johnson|first25=J.|last26=Klingelhöfer|first26=G.|last27=Knoll|first27=A. H.|last28=Landis|first28=G.|last29=Lemmon|first29=M.|last30=Li|first30=R.|s2cid=7876861}}

== External links ==
* [http://marsrovers.jpl.nasa.gov Official Mars Rovers website]
* [https://web.archive.org/web/20090614203745/http://virtualexplorer.com.au/article/2004/87/the-eagle-crater-outcrop-on-mars Geology of Eagle Crater]
* [http://mars.nasa.gov/multimedia/images/?ImageID=5846 'Lion King' Panorama of Eagle Crater] (NASA)

{{Features visited by Opportunity}}
{{NASAMER}}
{{Geography of Mars}}

[[Category:Impact craters on Mars]]
[[Category:Margaritifer Sinus quadrangle]]

{{Sourceattribution|Eagle (Meridiani Planum crater)}}