H. Jay Melosh (June 23, 1947 – September 11, 2020)[1] was an American geophysicist specialising in impact cratering.

[3][4] Melosh's research interests include impact craters, planetary tectonics, and the physics of earthquakes and landslides.

He was active in astrobiological studies that relate chiefly to the exchange of microorganisms between the terrestrial planets (a process known as panspermia or transpermia[5]).

[6] H. Jay Melosh took his first faculty role at Caltech between 1976 and 1979, where he researched the Moon's orientation in relation to mass concentrations (mascons) and large impacts, and was also a member of the GRAIL science team[7].

He then went on to take a position with SUNY Stonybrook as an associate professor of geophysics until 1982 when he left to join the University of Arizona as a faculty member in the planetary sciences[7], where he continued work on impact cratering until 2009.