var obj = {
"1":{"mass":"2012-03-01","foo":"1010.00"},
"2":{"mass":"2012-03-10","foo":"100.00"},
"3":{"mass":"2012-03-15","foo":"10.00"},
"4":{"mass":"2012-03-21","foo":"500.00"}
};
var mass = [];
var foo = [];
$.each(obj, function(index, value){mass.push(value.mass); foo.push(value.foo);});
alert(mass, foo);