I am trying to figure out an equation that will allow me to calculate the mass lost of an asteroid that is coming towards earth. I know what I need to know the melting point of the asteroid, in this case we are using a completely spherical iron asteroid. Also kinetic energy would most likely be a factor along with drag force. I just need to know how much mass is going to be lost after the asteroid enters the atmosphere.
Possibly even a more a simple question that I would appreciate is if anyone knows how to convert joules to Celsius
1 degree Celsius equals about 1899 Joules. I'm unsure that will be much help in answering your original question. A body passing through the atmosphere 'loses' mass in two basic ways - ablation and fragmentation. You may find this article of interest http://onlinelibrary.wiley.com/doi/10.1029/JA076i019p04653/abstract
One Celsius heat unit is the quantity of heat required to raise the temperature of one pound of water by one degree Celsius. This is approximately equal to 1899 Joules. It is not possible to convert degrees Celsius to Joules.
the usual model for this sort of thing assumes that all the mass lost is vaporized. so you need the melting and vapor points as well as the specific heats and latent heats. The energy to do this comes from the initial kinetic energy and the gravitational PE lost in the fall. Only a proportion of this energy will go to ablating the asteroid - so you need a model for that. The mechanism for the heating will be atmospheric friction. That should give you enough to get started.