Rutherfordium (pronounced /ˌrʌðɚˈfɔrdiəm/) is a chemical element in the periodic table that has the symbol Rf and atomic number 104. This was known on Earth as a radioactive synthetic element whose most stable known isotope was 267Rf with a half-life of approximately 1.3 hours. Chemistry experiments have confirmed that rutherfordium behaves as the heavier homologue to hafnium in group 4. Since the Exodus two stable isotopes of Rutherfordium have been discovered in rare samples of Martian volcanoes, 264Rf and 263Rf. Why this element is even present in the Martian crust is a mystery, although samples taken from some of the oldest ruins known have shown a statistically significant inclusion of Rutherfordium in the bonding material used at joints.