The  Lowell Letters

Mars Through Time
Mars Craters

   About 4.6 billion years ago, the planets were formed. These comprise the outer gas giants of Jupiter, Saturn, Uranus and Neptune and the inner rocky planets of Mercury, Venus, Earth, and Mars. They were formed from the same dust and gas nebula as our sun, Sol, which took up around 99.9% of the material in the Nebula.

   The existence of the planets (apart from Uranus and Neptune, which were found with the aid of a telescope in 1781 and 1846) was known to ancient civilisations like the Babylonians and Egyptians. The Greeks called them “planetas” or “wandering stars” to distinguish them from the “fixed stars”.

   The usual belief was that the Earth was at the centre of the Universe, and everything revolved around us. The Church took up this belief and it prevailed for around a thousand years. Complex theories were adopted to explain the observed motions of the heavenly bodies. Their name for Mars was ‘Ares’ – the names we use now in Western languages are derived from the Latin used by the Romans. Some of the important developments since that time are:

1530: Nicolaus Copernicus, put forward a theory that placed The Sun at the centre of the Universe, with the planets and “fixed stars” revolving around it.

1583: Tycho Brahe, a Danish observer and not a supporter of Copernicus, recorded a retrograde motion of Mars near opposition and was forced to conclude that the planet could approach nearer to the Earth than The Sun could. He evolved a complex compromise theory whereby the Earth remained at the centre of the Universe, with The Sun orbiting it and the other planets in turn orbiting The Sun.

1609: Johannes Kepler, who had originally worked with Brahe, published a book on the motions of Mars, making use of the observations of both Copernicus and Brahe.

1609: Galileo Galilei, a Professor of Mathematics in Padua, made his pioneering astronomical telescopic observations. These included noting that the observable face of Mars was not perfectly round (a gibbous phase). This would fit in with heliocentric theories but not the old beliefs that placed Earth at the centre.

1659: Using better telescopic equipment, Christian Huygens was able to determine, by observation of the large feature called Syrtis Major (what Lowell called the Hourglass Sea) that Mars rotated and to estimate its rotation period.


1686: Isaac Newton, using Kepler’s work, put forward a theory of universal gravitation.

1783: William Herschel, the discoverer of Uranus two years previously, made extensive telescopic observations of Mars, including the polar regions, and concluded that the planet had similarities to our own.

1877: Asaph Hall identified Phobos and Deimos. the two tiny satellites of Mars.

1877: Giovanni Virginio Schiaparelli identified canals on Mars, using the term ‘canali’ to describe them. The Italian word means ‘channels’ OR ‘canals’. Schiaparelli is often thought to be the first to see the canals. In fact, a number of other astronomers had identified them earlier, although in lesser number.

1892: Camille Flammarion published his La Planète Mars, a compilation of and commentary on previous research.

1894: Percival Lowell famously observed the canals and was active in publishing his observations. See Chapter 10 of The Lowell Letters.

1898: Herbert George Wells published The War of the Worlds in book form.

1938: Orson Welles caused widespread panic with his Mercury Theatre’s broadcast of a radio play based on Wells’ novel.

1956: As in 1924 and 1941, major dust storms made close observation of the planet’s surface at opposition impossible.

1965: Mariner IV made a close fly-past of Mars. No canals were identified.

1972: More detailed photographic observations were possible with Mariner IX and better images of Mars were obtained, including those of valley networks and outflow channels, showing the probability that the planet had once extensive running water on its surface.

1975: Vikings I and II were launched and made planetary landings. A cold, dry surface and thin atmosphere were concluded.

2003: In the 2003 opposition, Mars made its closest approach to Earth in sixty thousand years.

2021: The Mars’ Ingenuity Helicopter flights, undertaken by NASA, took place.

2021 NASA announced its belief that huge regional dust storms played a major role in the dying out of Mars.

2022: The Sols 3414-3416 and 3417-3418 ‘Curiosity’ Rover projects are continuing.