Green Valley (Mars)

{{Short description|Region in the northern hemisphere of Mars; landing site of NASA's Phoenix lander}} {{Use dmy dates|date=May 2023}} {{Infobox feature on celestial object |name = Green Valley |image = [[File:PSP 001497 2480 RED detail 25cm.jpg|250px]] |caption = [[HiRISE]] image of a patch of land in the Green Valley region showing scattered small boulders and a polygonal fracture pattern. |coordinates = {{coord|68.35|N|233|E|globe:mars_type:landmark|display=inline,title}} |naming = Informal name based on danger assessment map color }}

'''Green Valley''' is a region on [[Mars]] within [[Vastitas Borealis]] that was chosen as the landing site of [[NASA]]'s [[Phoenix (spacecraft)|Phoenix]] lander. It is located at 68.35 degrees north, 233 degrees east. The valley is about 50 kilometres wide, but only about 250 metres deep; either it was filled in, or was never any deeper than that. The edges are not visible from the middle of the valley.<ref name=planetaryorg>[http://www.planetary.org/news/2007/0125_A_Green_Valley_for_Phoenix.html A Green Valley for Phoenix – Planetary News | The Planetary Society] {{webarchive|url=https://web.archive.org/web/20080513154224/http://www.planetary.org/news/2007/0125_A_Green_Valley_for_Phoenix.html |date=13 May 2008 }}</ref> [[File:Mars from Phoenix.jpg|thumb|150px|left|Polygonal patterns at Phoenix landing site]] The name "Green Valley" is not officially recognised by the [[International Astronomical Union]]. It came from the decision process by which it was selected as Phoenix's landing site: prospective landing areas were color-coded based on how hazardous they were, with red being most hazardous through yellow to green being the safest.<ref name=planetaryorg /> Green Valley has relatively few of the large boulders that could have tipped the lander if it had hit one during touchdown.<ref>[https://www.newscientist.com/article/dn13661-mars-lander-aims-for-touchdown-in-green-valley.html Mars lander aims for touchdown in 'Green Valley' – space – 11 April 2008 – New Scientist Space]</ref>

The ground within Green Valley is covered with polygonal features several metres across and roughly ten centimetres high, thought to be caused either by thermal contraction ([[Patterned ground|ice-wedge polygon]]s) or by the effects of wind-blown dust (sand-wedge polygons). Water ice is thought to be just below the surface.<ref name=planetaryorg /> During the local winter as much as three feet of [[carbon dioxide ice]] is expected to appear on the surface.<ref>[http://www.space.com/missionlaunches/070201_phoenix_update.html SPACE.com – Phoenix Lander Readied For Mars Exploration]</ref>

Shortly before Phoenix's scheduled landing, the [[Mars Reconnaissance Orbiter]] photographed a pair of kilometer-tall [[dust devil]]s in the Green Valley area.<ref>[https://www.newscientist.com/article/dn13852-dust-devils-spotted-at-mars-probes-landing-site.html Dust devils spotted at Mars probe's landing site – space – 7 May 2008 – New Scientist Space]</ref> {{clear}}

==References== {{Reflist}}

==Further reading== *{{cite journal|author=Arvidson|title=Mars Exploration Program 2007 Phoenix landing site selection and characteristics|year=2008|journal=[[Journal of Geophysical Research]]|volume=113|doi=10.1029/2007JE003021|last2=Adams|first2=D.|last3=Bonfiglio|first3=G.|last4=Christensen|first4=P.|last5=Cull|first5=S.|last6=Golombek|first6=M.|last7=Guinn|first7=J.|last8=Guinness|first8=E.|last9=Heet|first9=T.|issue=E6|pages=E00A03|bibcode = 2008JGRE..113.0A03A |display-authors=1|doi-access=free}} {{clear}}

[[Category:Valleys and canyons on Mars]] [[Category:Mare Boreum quadrangle]]