Tycho Brahe
1609
Johannes Kepler (1571 - 1630), a student of Tycho Brahe, publishes Astronomia Nova (New Astronomy), which contain his first two laws of planetary motion. Kepler's first law assumes that Mars has an elliptical orbit, which was a revolutionary idea at the time. Until then, the classical belief held that a circle was perfect, and therefore all orbits must be circular.
1609
Galileo Galilei (1564 - 1642) observes Mars with a primitive telescope, becoming the first person to use it for astronomical purposes.
1659
The Dutch astronomer Christiaan Huygens (1629 - 1695) draws Mars using an advanced telescope of his own design. He records a large, dark spot on Mars, probably Syrtis Major. He notices that the spot returns to the same position at the same time the next day, and calculates that Mars has a 24 hour period.
1666
Giovanni Cassini (1625 - 1712) observes Mars and determines that the rotational period, or length of one Mars day is 24h, 40m.
1672
Huygens is the first to notice a white spot at the south pole, probably the southern polar cap.
1698
Huygens publishes Cosmotheros, which discusses what is required of a planet to support life, and speculates about intelligent extraterrestrials. This is one of the first published expositions of extraterrestrial life.
Historical Perspective...
The Trial of Galileo
The 1600s were not an easy time in which to study science. The church was a powerful institution and had its own ideas about the nature of the universe. Galileo was a beliver in the Copernican theory that the solar system revolves around the sun. He was advised by Cardinal Bellarmino to be cautious and not to imply the the Copernican theory were real. He published a book, Siderius Nuncius (Starry Messenger) which was considered controversial and in opposition with the ideas of the Roman Catholic Church, and was arrested and tried in the Inquisition. Galileo was found guilty of heresy and was sentenced to life imprisonment and forced to recant. In secret, he wrote another book, which was smuggled out of the country and published in France. His work is now considered the foundation of modern physics.
