Green Valley is a region on

Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...

within Vastitas Borealis that was chosen as the landing site of

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

's 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.A Green Valley for Phoenix – Planetary News , The Planetary Society
Mars from Phoenix

The name "Green Valley" is not officially recognised by the

International Astronomical Union The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...

. 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. Green Valley has relatively few of the large boulders that could have tipped the lander if it had hit one during touchdown. 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 ( ice-wedge polygons) or by the effects of wind-blown dust (sand-wedge polygons). Water ice is thought to be just below the surface. During the local winter as much as three feet of carbon dioxide ice is expected to appear on the surface. Shortly before Phoenix's scheduled landing, the Mars Reconnaissance Orbiter photographed a pair of kilometer-tall dust devils in the Green Valley area.Dust devils spotted at Mars probe's landing site – space – 7 May 2008 – New Scientist Space
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References

Further reading