You will be given a definition of a task first, then some input of the task.
This task is about creating an unanswerable question based on a given passage. Construct a question that looks relevant to the given context but is unanswerable. Following are a few suggestions about how to create unanswerable questions:
(i) create questions which require satisfying a constraint that is not mentioned in the passage
(ii) create questions which require information beyond what is provided in the passage in order to answer
(iii) replace an existing entity, number, date mentioned in the passage with other entity, number, date and use it in the question
(iv) create a question which is answerable from the passage and then replace one or two words by their antonyms or insert/remove negation words to make it unanswerable.

Passage: "By May 1539, Conquistador Hernando de Soto skirted the coast of Florida, searching for a deep harbor to land. He described seeing a thick wall of red mangroves spread mile after mile, some reaching as high as 70 feet (21 m), with intertwined and elevated roots making landing difficult. Very soon, 'many smokes' appeared 'along the whole coast', billowing against the sky, when the Native ancestors of the Seminole spotted the newcomers and spread the alarm by signal fires". The Spanish introduced Christianity, cattle, horses, sheep, the Spanish language, and more to Florida.[full citation needed] Both the Spanish and French established settlements in Florida, with varying degrees of success. In 1559, Don Tristan de Luna y Arellano established a colony at present-day Pensacola, one of the first European settlements in the continental United States, but it was abandoned by 1561.
Output:
What happened in 1538?