Given the rationale, provide a reasonable question and answer. Step-by-step reasoning process: To answer this question, we should know that: Thanos' first appearance was in The Invincible Iron Man # 55 (February 1973), featuring a story by Jim Starlin that was co-scripted by Mike Friedrich.
 The question and answer:
Thanos' first appearance was in The Invincible Iron Man # 55 (February 1973), featuring a story by Jim Starlin that was co-scripted by Mike Friedrich. The storyline from that issue continued through Captain Marvel # 25 -- 33 (bi-monthly: March 1973 -- Jan. 1974), Marvel Feature # 12 (Nov. 1973), Daredevil # 107 (Jan. 1974), and Avengers # 125 (July 1974). He returned in an extended storyline that spanned Strange Tales # 178 -- 181 (Feb. -- Aug. 1975), Warlock # 9-11 (Oct. 1975 -- Jan. 1976), Marvel Team Up # 55 (March 1977), and the 1977 Annuals for Avengers and Marvel Two-in-One (Thanos does not actually appear until the end of Warlock # 9). He was also featured in a short backup story in Logan's Run # 6 (June 1977) and had a small role in the Death of Captain Marvel graphic novel (April 1982).

When did thanos first appear in the comics?
The answer is The Invincible Iron Man # 55 ( February 1973 )