Odd patches of bright and dark material that scientists have yet to identify also appear on its surface.

WSJ: Asteroid Vesta Gets a Close Study

In these areas, the water appears to be covered by a dark material that the researchers suspect might be complex organic molecules.

FORBES: NASA Has Discovered Water Ice On Mercury

But further measurements using a laser and looking for reflections showed that much of the ice is covered with a layer of dark material tens of centimetres thick.

BBC: Mercury's water ice at north pole finally proven

There was even speculation about a dark material on the tiny planet that could conceivably contain the same organic molecules being hunted on Mars, the carbon-based building blocks that are essential to all life.

BBC: New age of exploration in the hunt for extreme life

"The guess is that both the water and the dark material, which we think is organic-rich material, were delivered by the same objects impacting Mercury: some mixture of comets and the kinds of asteroids that are rich in organic and volatile material like water ice, " Prof Solomon said.

BBC: Mercury's water ice at north pole finally proven

Observations of the material coating the dark face of Iapetus indicate it has a similar composition to the surface material on Phoebe.

BBC: New ring detected around Saturn

That might attract more adults than went to see the Twilight films but at the same time it could keep away younger viewers who might find the material too dark.

FORBES: 'The Hunger Games' Has Already Earned $8 Million

The 7-Disc Limited Collector's Edition Blu-ray Trilogy includes all three films in high definition, Transformers: Dark of the Moon in high definition 3D, more than 10 hours of bonus material, as well as a plaque of movie images signed by director Michael Bay.

ENGADGET: Transformers: Dark of the Moon clip breaks down shooting movies, special effects in 3D (video)

The dark walls and single room in which the works are shown contribute to a hushed, meditative atmosphere, which supplementary material such as digital displays might easily disrupt.

WSJ: Masterpieces on a Shopping List | Michelangelo Master Drawings | Museum of Fine Arts Boston | By Cammy Brothers