He had an abscess on the lung but the surgeon was unable to find it. Mersenne himself pointed out that the incision, which he asked for, had been attempted too low. Gassendi was there for Mersenne throughout his illness and remained with him until his death on 1 September 1648 in Paris, just 8 days from his 60th birthday.
Siya ay isang paltos sa baga ngunit ang siruhano ay hindi mo mahanap ito. Mersenne kanyang sarili pointed out na ang paghiwa, kung saan siya nagtanong para sa, had been pagtatangkang masyadong mababa. Gassendi ay doon para sa Mersenne sa kabuuan ng kanyang sakit at naiiwan sa kanya hanggang sa kanyang kamatayan sa 1 Setyembre 1648 sa Paris, lamang 8 araw mula sa kanyang ika-60 kaarawan.