Vastitas Borealis

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Vastitas Borealis is the large low elevation area at the top of this topograpical map.

Vastitas Borealis (vastitas, Latin, widespread lowlands; borealis, Latin, northern) is the largest lowland region of Mars. It is in the northernly latitudes of the planet and encircles the northern polar region. Vastitas Borealis is often simply referred to as the Northern plains or Northern lowlands of Mars. The plains lie 4–5 km below the mean radius of the planet. To the north lies Planum Boreum.

Two distinct basins are recognized within the Vastitas Borealis: the North Polar Basin and Utopia Planitia. Some scientists have speculated the plains were covered by an ocean at some point in Mars' history and putative shorelines have been suggested for its southern edges. Today these mildly sloping plains are marked by ridges, low hills, and sparse cratering. The Vastitas Borealis are noticeably smoother than similar topographical areas in the south.

In 2005 the European Space Agency's Mars Express spacecraft imaged a substantial quantity of water ice in a crater in the Vastitas Borealis region. The environmental conditions at the locality of this feature are suitable for water ice to remain stable. It was revealed after overlaying frozen carbon dioxide sublimated away at the commencement of the Northern Hemisphere Summer and is believed to be stable throughout the Martian year.