Frozen lake shines bright in Martian crater
* 15:15 29 July 2005
* NewScientist.com news service
* Damian Carrington
A bright patch of water ice sitting serenely on the floor of a crater near the Martian north pole has been imaged by the Mars Express spacecraft.
The image was taken by the High Resolution Stereo Camera on board the European Space Agency (ESA) probe and has a resolution of about 15 metres per pixel.
The impact crater is located on Vastitas Borealis, a broad plain that covers much of the far northern latitudes on Mars. It is 35 kilometres (21 miles) wide and drops down to 2 km (1.2 miles) beneath the crater rim.
The ice is present all year round, as the temperature and pressure are not high enough to allow the sublimation of water ice, say ESA scientists. And it cannot be frozen carbon dioxide since carbon dioxide ice had already disappeared from the north polar cap by the time the image was taken - late Martian summer.
Faint traces of water ice are also visible along the rim of the crater and on the crater walls. The absence of ice along the north-west rim and walls may occur because this area receives more light due to the Red Planet’s orientation in relation to the Sun.
