Amazon's Nova Pro:
``` Marathon Crater was discovered in the early 20th century, likely around the 1920s or 1930s. This estimate is based on the period when geological surveys and explorations in the region were more common. ```
https://kagi.com/assistant/8f270eab-cba3-4f39-976c-113ea4392...
Likely around the 1920's or 1930's... Bro, not only is a crater discovery in those decades unlikely, the date certainly wouldn't have gone unnoted.