The Giotto probe found that ORGANIZATION@1 's nucleus reflects approximately NUMBER@1 % of the light that falls on it , and Deep Space NUMBER@2 discovered that Comet Borrelly 's surface reflects NUMBER@3 -- NUMBER@4 % of the light that falls on it .

When light shone on ORGANIZATION@1 's nucleus , the comet reflected only NUMBER@1 % of the light back to us .
