On a logarithmic scale, Pluto is 2 units from Mercury.
The default base for logarithms is 10, so saying that something is 2 units means that we are raising the base 10 to the power of 2.
[tex]10^2=100[/tex]
Written as a logarithm, this would be:
[tex]log_{10}100=2[/tex]
Whatever number you plug into the function, the answer will be whatever power the base needs to be raised to in order to equal the original number.
For example:
[tex]log_{2}8=3[/tex]
because
[tex]2^3 = 8[/tex]
