Mars - Early Telescopic Views Of Mars

The Italian astronomer Galileo Galilei (1564–1642) was probably the first to see Mars through a telescope. He noticed that sometimes it appeared larger than at other times. He believed that its distance from Earth was changing over time. During the seventeenth century Johannes Kepler (1571–1630) studied Mars' movement for years. His observations helped him to develop the laws of planetary motion for which he would become famous.

As telescopes improved, astronomers reported seeing dark and light patches on Mars that also varied in size over time. Some people thought these were patches of vegetation changing in response to the changing seasons. Others believed that they represented contrasting areas of land and sea.

In 1659 Dutch astronomer Christiaan Huygens (1629–1695) recorded his Mars observations and noticed an odd-shaped feature that came to be called the hourglass sea. Huygens kept an eye on the location of the sea over time and figured out that the Martian day lasts about twenty-four hours. The same conclusion was reached independently by the French astronomer Giovanni Cassini (1625–1712).

During the 1700s astronomers performed more detailed observations of Mars' dark and light patches, particularly the whitish spots at the north and south poles. They could see that the spots changed in size over time, but did not guess that these were caps of ice. It was commonly believed that Mars was inhabited by some kind of beings. In 1774 the English astronomer Frederic William Herschel (1738–1822) speculated that Martians lived on a world much like Earth, with oceans on the surface and clouds flying overhead.