Planet Earth font here refers to the font used in the title of Planet Earth, which is a 2006 television series produced by the BBC Natural History Unit.
The font used for the title of the TV series is probably Helvetica Neue Pro Ext Thin. The font is a commercial one and you can purchase and download it here.
Download Helvetica Font
The Helvetica font identified above is not available for free, please follow the link above and purchase a font license to download and use the font. Meanwhile, you can take a look at our collection of fonts for cars, pop music and apparel as well as round-ups of new & fresh fonts around the web.