New spectroscopic images of Mercury are a rainbow of colour

Images taken by NASA's Messenger spacecraft and released in the probe's final days use colour to reveal the mineral composition of Mercury's surface.

NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

New images of Mercury show the planet as we've never seen it before: in a psychedelic profusion of colours. The images don't show how Mercury looks in the visible light spectrum. Rather, they are composites, composed of years of data collated by the Mercury Atmosphere and Surface Composition Spectrometer instrument aboard NASA's Messenger spacecraft and have provided researchers with new insights about Mercury.

The spacecraft, which has been in orbit around the planet for four years, is due to be retired on Thursday -- by crashing into Mercury's surface at a speed of more than 8,750 miles per hour (3.91 kilometres per second). This will be done on the side closest to Earth so that NASA researchers can observe the impact in real time and receive data from the probe as it descends.

Ever since the probe entered Mercury's orbit in 2011, it has been diligently collecting measurements of the surface of the planet, in hundreds of different wavelengths of light, from ultraviolet through to near-infrared. These wavelengths and combinations of wavelengths were then mapped into red, green and blue colours.

You can probably make out a little bit of what they show, which was the purpose of colour-coding the wavelengths in the first place. Some show the mineral composition of the surface; while others show the age of craters, or volcanic vents. This allows these relatively small features to be studied much more easily.

NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Key findings include compelling support for the hypothesis that ice is abundant on Mercury in its permanently shadowed polar craters in found 2012, with data indicating that the ice would be two miles thick and spread over an area the size of Washington.

Another discovery was a dark layer over those ice deposits, thought to be rich in organic compounds. Researchers hypothesise that the ice and the organic compounds came to Mercury from the outer solar system.

"The water now stored in ice deposits in the permanently shadowed floors of impact craters at Mercury's poles most likely was the impacts of comets and volatile-rich asteroids," said Messenger principal investigator Sean Solomon, director of Columbia University's Lamont-Doherty Earth Observatory in Palisades, N.Y. "Those same impacts also likely delivered the dark organic material."

NASA/JHU APL/Carnegie Institution of Washington

Other contributions made by the Messenger mission include technological firsts such as the development of a heat-resistant and highly reflective ceramic cloth sunshade to protect the probe's instruments from solar radiation and temperatures in excess of 300 degrees Celsius (570 degrees Fahrenheit).

"For the first time in history we now have real knowledge about the planet Mercury that shows it to be a fascinating world," said John Grunsfeld, associate administrator for the Science Mission Directorate at NASA Headquarters in Washington.

"While spacecraft operations will end, we are celebrating Messenger as more than a successful mission. It's the beginning of a longer journey to analyse the data that reveals all the scientific mysteries of Mercury."