Chemistry - Why does Bromine-80 not occur in nature?

[OrangeJELL-O]

Homework Statement

I had the following question in my chemistry book...

A mass spectrum of Br2 has three peaks, with the mass numbers 158, 160, and 162. Use this information to determine which isotopes of Bromine occur in nature.

Homework Equations

The Attempt at a Solution

From this info, I originally hypothesized the isotopes of Bromine to be Bromine-79, Bromine-80, and Bromine-81. However, it turns out that Bromine-80 does not occur in nature and the peak at 160 is the result of a molecule of Bromine-79 and Bromine-81 isotopes. What information from the question am I missing that might hint at Bromine-80 not occurring in nature?

 

[pmsrw3]

What would happen if a 79 and an 80 formed a molecule together?