Which event might limit a cattail population

How is the composition of a meteorite relevant to finding out the composition of earth's core?

In 2002, the rare earth elements mine in mountain pass, california was closed because

The bond energy for the van der waals bond between two helium atoms is 7.9×10−4ev. assuming that the average kinetic energy of a helium atom is (3/2)kbt, at what temperature is the average kinetic energy equal to the bond energy between two helium atoms