There is a temporary undocumented way:
Log in to the atmosphere website with the same information that you used to publish your package, and then in the javascript console in chrome, safari or firefox mode:
Meteor.call("deletePackage","<your package name>",function(err,result){ console.log(result || err) });
Replace <your package name> with <your package name> , the same as you could run mrt add <your package name> with.
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