The article states, "According to the Teacher's Guide to the Universe from Princeton University, the distance between Earth and Mars was first determined by Giovanni Cassini in 1672 using the parallax method. Cassini achieved this by sending his fellow astronomer Jean Richer to French Guiana to carry out measurements while he remained in Paris. They took measurements of the position of Mars and triangulated those measurements with the known distance between Paris and French Guiana. Cassini's calculation was only off by 7% compared to today's more accurate measurements."
This parallax using telescopes along with Kepler's laws opened up the distances between Earth and Mars and the size of the solar system that previously was chiefly unknown. Consider that during the period of Tycho Brahe, the Earth - Sun distance was considered to be about 1200 earth radii (~ 0.05 au using modern astronomical unit of 1 au), no real difference than in the 2nd century AD using Claudius Ptolemy work.
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