When it comes to planets, there’s a lot more than meets the eye. Thankfully false
colour images show us what our eyes are missing.
Hey guys! Amy with you on DNews talking pretty things in space.
Thanks to decades of science missions, we’ve learned a lot about what the planets are made
of, and that has let us figure out what their true colours are. Mars is red because the
rocks are rusty. Venus’ surface is actually grey but we can only see the thick sulphuric
acid atmosphere that envelops the whole planet. Uranus and Neptune are both primarily made
of methane, a gas that absorbs red light and bounces back blue-green light. That’s why
both planets have a rich, blue tone to them.
So if these are the planets’ true colours, why do we sometimes see them looking like
a psychedelic vision? Because false colour is a thing that scientists love.
Across the whole electromagnetic spectrum, the human eye can only see a small section,
the so-called visible light spectrum from violet to red that corresponds to a wavelength
range of 400 - 700 nanometers. The human eye can’t see longer or shorter wavelengths
outside the visible range, infrared and radio on the longer end of the spectrum and ultraviolet
on the shorter end. So scientists use tools to see in these wavelengths.
In some cases, imaging a body in a different wavelength reveals things we can’t see.
This composite image of Saturn’s moon Titan was taken in infrared light by the Cassini
spacecraft’s visual and infrared mapping spectrometer. In visible light, Titan only
shows is hazy atmosphere, but in the near-infrared we can see through the clouds to the surface.
Radar is another way to look through what we can’t in visible light. This image of
Venus was made using radar data from the Magellan spacecraft. The radar penetrated through the
dense atmosphere to reveal Venus’ surface topography, and this colour-coded map makes
the information easy to read.
Sometimes looking in different wavelengths is a way to see more detail. On the left is
Jupiter in true colour. On the right is a false colour image made from three separate
pictures taken through filters focussing on specific spectral regions: two were taken
through filters looking for the absorption of the gas methane and one taken in a red
continuum that wouldn’t show any absorption. The result shows details in Jupiter's atmosphere
that are invisible to the naked eye.
Some false colour images are designed to highlight differences in surface material, like this
one of Mercury. Grey in visible light owing to the iron rocks that litter its surface,
Mercury looks vibrant when colour is used to enhance the separation between chemical,
mineralogical, and physical variation within the surface material.
Another striking image is this one of the dwarf planet Pluto. Red in visible light because
of tholins, this false colour image was made using a technique called principal component
analysis that highlights the subtle color differences between regions on the planet’s
surface.
There’s a lot to learn about the planets from all kinds of stunning images, but it’s
not the case that whoever sees something first can claim it as their own. There is such a
thing as space law, and TestTube News talks about it in this video right here.
And there’s a lot more to space than just planets! If you want to come explore other
facets of space with me, come check out my own channel, Vintage Space!
We’ll have a link in the description if you’re on mobile.
So do you guys like false colour images or do you prefer your planets au naturale? Let
us know in the comments below and don’t forget to subscribe for more DNews every day
of the week.
So do you guys like false colour images or do you prefer your planets au naturale? Let
us know in the comments below and keep coming back to Test Tube for more DNews every single
day of the week.
So do you guys like false colour images or do you prefer your planets au naturale? Let
us know on the Discovery News Facebook page or on Twitter @DNews. And you can find me;
I’m @astvintagespace. Thanks for watching!