# Shall we say now that Pluto is “larger than Mercury” ?

http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150717-3

"Scientists working with NASA’s New Horizons spacecraft have observed Pluto’s atmosphere as far as 1,000 miles (1,600 kilometers) above the surface of the planet, demonstrating that Pluto’s nitrogen-rich atmosphere is quite extended."

I note that conventional descriptions of the gas giants' sizes include mostly atmosphere.

• Agreed. And I don't think Pluto would be much bigger if you used a 1 bar definition for the height of its atmosphere! I believe the surface pressure is of order $10^{-4}$ bar! – Rob Jeffries Jul 20 '15 at 20:44