4 October 2009

What Colour Is Mercury??

Posted by Dan Satterfield

That sounds like a silly question, doesn’t it?.

Just look through a telescope right?

Actually if you think about it. Colours look different in different light, and when you are nearer or further for the sun than we are on earth, the light is definitely not the same. We also have an atmosphere of Nitrogen and Oxygen. This thin layer of gas  scatters out the blue light from the sun. This is why we here on earth see a yellow sun and a blue sky. Astronauts and Cosmonauts see a sun that looks brilliant white.

Images of Mercury from Messenger. Upper left is grey scale. The rest are in true colour. .

Images of Mercury from Messenger. Upper left is grey scale. The other versions are in true colour. From NASA/Johns Hopkins University. Mouse the image for a larger picture

There was even a great deal of discussion over the colour of the Moon, when Apollo 8 first visited on Christmas Eve in 1968. In general the majority of visitors have said it’s just like it looks in the pictures. Grey.

The NASA Messenger spacecraft had it’s 3rd flyby of Mercury on Friday night and the pictures have been sent back. It passed within 228 km of the surface.

Getting a perfect true colour photo of Mercury is actually not as high a priority as looking at Mercury in the different wavelengths of light that can tell what it’s made of. The spacecraft has different sensors to look in red, green and blue light.

So here are the images of Mercury sent back Friday. The upper left picture is in grey scale. The others are views of Mercury made by combining the red, green and blue channels together in slightly different ways, to attempt a true colour picture of the closest planet to the sun.

This picture also has closeup views of Mercury never seen before. As the researchers looking at the pictures have pointed out- “colour is in the eye of the beholder”.

If you have ever compared the colours in pictures from your digital camera to what you saw when you took the picture- you likely understand this!

(So is the spelling of the word by the way! Americans write “color”, while other english speaking countries use “colour”.)

So take your pick of the one you like best. I think most people would think the bottom right is closest to what most people would see, if they were there!