In the news this month: trees on Mars?
Dark sand cascades down sand dunes on Mars as the carbon dioxide ice thaws in the Martian spring CREDIT: HiRISE, MRO, LPL (U. Arizona), NASA
And finally: The HiRISE instrument on board the Mars Reconnaissance Orbiter has been taking spectacular images since the probe entered orbit around the planet in 2006. One particular image, posted to Astronomy Picture of the Day on January 19th, caused something of a stir.
The image shows a series of pinkish-coloured sand dunes covered with a light frost, located near the North pole of Mars, taken on the 7th of April 2008 during the Martian spring. As the Sun started to melt the carbon dioxide ice, the sand started to shift, cascading down the dunes in dark streaks which look uncannily like trees in the image taken by the HiRISE instrument on board the orbiter. The image covers an area of roughly one square kilometre and resolves objects as small as 25 cm. The colour variations in the ice around the streaks are thought to be caused by dust kicked up as the material shifts and settles on the surface.