Because Mars with its famous red coloration is readily visible from Earth, it is unknown who first discovered it; NASA lists the planet as "known by the ancients." There are records of its existence as far back as ancient Egypt.
Although Mars has been readily visible to the human eye as long as there have been humans, much has been discovered about the planet since ancient times. For example, Aristotle first noted that Mars can disappear behind Earth's moon, indicating that it is farther away. Telescopes with resolutions capable of viewing the planet's surface only first appeared in the 19th century, and in modern times, NASA has sent rovers to the planet itself to analyze the planet's geology and take high-resolution pictures. As of 2014, the most recent NASA rover to land is Curiosity.