LARGE IMPACTS EVENTS DELIVER VAST AMOUNTS OF HEAT TO PLANETARY SURFACES AND UPPER CRUSTS PARTICULARLY EARLY IN THE HISTORY OF A PLANET WHEN POST-ACCRETIONARY BOMBARDMENT RATES ARE HIGH. IN ADDITION SPIKES IN THE NUMBER OF IMPACT EVENTS SIMILAR TO THE LATE HEAVY BOMBARDMENT THAT THE INNER SOLAR SYSTEM LIKELY EXPERIENCED ABOUT 3.9 BILLION YEARS AGO MAY BECOME SIGNIFICANT LATER IN A PLANET'S HISTORY. SIGNATURES OF BOTH TYPES OF BOMBARDMENTS HAVE BEEN DETECTED IN EXTRASOLAR SYSTEMS BY THE SPITZER SPACE TELESCOPE. WE PROPOSE TO UNDERTAKE A FOCUSED STUDY OF THE BIOLOGICAL EFFECTS OF IMPACT BOMBARDMENTS ON A WIDE RANGE OF EARTH-LIKE EXTRASOLAR PLANETS TO FURTHER CONSTRAIN CONDITIONS NEEDED FOR LIFE TO ARISE AND EVOLVE.