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 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.