Paper
Mars in the Solar System
Published 1992 · P. Cattermole
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Abstract
Mars has occupied a very special place in the history of scientific thinking since the late sixteenth century. It was then that the imperious Danish astronomer, Tycho Brahe, made careful observations of the movements of Mars which subsequently enabled the brilliant German mathematician, Johannes Kepler, to formulate his three fundamental laws of planetary motion. The first two of these were published in 1609 after the latter realised, having calculated the distance of Mars from the Sun at different points in its circumsolar journey, that its orbit was not, as hitherto had been supposed, a circle but an ellipse, one focus of which was occupied by the Sun. He appreciated, too, that this was true of the other planets, a conclusion which led him to formulate the first of his three laws which stated simply that planets move around the Sun in elliptical orbits, with the Sun at one focus. As it happens, the Earth has an orbit which departs little from a circle (eccentricity 0.017) but Mars follows an orbit which is much more eccentric. Thus its distance from the Sun is 207 million km when at its closest (perihelion), while at its furthest point (aphelion) it is 249 million km distant. This gives the eccentricity a value of 0.093.
Mars has an eccentric orbit, with a distance from the Sun varying between 207 million km and 249 million km, and its distance from the Sun is 0.093 times greater than that of the Earth.
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