In November 1915 he announced to have observed craters on Mars, and being the second person to do so after E. E. Barnard. Both claims are disputed to this day, but he is still credited to be the first human to recognize craters on Mars using the great 40-inch Yerkes refractor.
A crater on Mars (Mellish) was named in his honor.
In 1931, Mellish confessed to committing incest with his 15-year-old daughter.[5] Astronomers advocated that he be spared jail time because of his value to science,[5][6][7] and it was proposed that he be sterilized.[8] Mellish was held in the Kane County Jail from September 1931 to April 1933, when he was paroled,[9][10] and he moved to California.[11][12] His wife divorced him in May 1933 and was given custody of their eight children.[12]
^"United States Census, 1900," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MM2P-J9H : accessed 22 January 2019), John E Mellish in household of Arthur Mellish, St Lawrence town, Waupaca, Wisconsin, United States; citing enumeration district (ED) 138, sheet 7A, family 126, NARA microfilm publication T623 (Washington, D.C.: National Archives and Records Administration, 1972.); FHL microfilm 1,241,823.
^Technical World Magazine. Armour Institute of Technology. 1910. pp. 456. technical world magazine john winthrop.