Can trees grow on Mars?

Related: Space

1. Headlines
   1. Mars orbiter spies on probes of the past

      Science editor Alan Boyle's blog: Color pictures taken from Martian orbit feature the landing spots for two of NASA's dearly departed probes on the Red Planet. Can you spot them?

   2. Updated 12 minutes ago 2/9/2012 4:35:19 PM +00:00 NASA stretches a penny—all the way to Mars 
   3. Close encounters for moon, planets and stars
   4. Is our galaxy's black hole gobbling asteroids?
   5. Photo reveals majestic nebula's hidden secrets
   6. Europe's Vega rocket set for inaugural launch
   7. Twisted galaxy warped by 'stealth merger'
2. Multimedia
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      Video
      Stunning aurora visible from space
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      Tectonic shifts through time
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      Low self-esteem linked to poor Facebook behavior
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      Ralph Nader takes on hidden airline fees