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Mars In The Classroom

Nix Olympus

Early Observations of Mars

 

The first telescopic observation of Mars was probably undertaken by Galileo Galilei around 1608 to 1610, but it was not until 1636 that the first records were taken, this time by Francisco Fontana. Unfortunately, his sketches seem to show more the problems of his telescope than the structure of the planet, with a central black spot and a dark outer ring. Telescope design gradually improved throughout the 17th century, and by 1659, Christian Huygens had made probably the first informative sketch of Mars. His observations (taken over a number of weeks) show a triangular feature which is still recognisable today, known as Syrtis Major. Huygens' results were so reliable that he even used the reappearance of this feature to measure the rotational period of Mars as 24 hours, less than 1 hour away from the value recognised today. Huygens was also able to crudely sketch the presence of a polar ice cap to the south of the planet, although he did not at the time identify it as such.

1666 saw Giovanni Cassini making some more precise measurements of Mars. He calculated the rotational period to be just under 24 hours 40 minutes, almost 37.5 minutes longer than Earth's and very close to the presently accepted value. He is also heralded as the man who discovered and identified the polar ice caps on Mars, which were not described any more fully until 1719 by Giacomo Miraldi. The Martian polar caps in fact bear striking similarities to the Arctic and Antarctic caps on Earth, but almost a century passed before the German born English astronomer William Herschel suggested the caps may be made of ice or snow.

LIFE!? - Nearing the end of the 18th century, the German born astronomer William Herschel made many interesting comparisons of the Earth and Mars, sparking off the idea of there being life on Mars. His work saw the peak in early telescopic observations of the planets, and his observations of Mars heralded the beginning of the search for extra terrestrial intelligence. After all, where else should there be life other than on a planet which shows so many remarkable similarities to our own? Herschel's results were as follows:

a) Herschel determined the length of the Martian day as 24 hours, 39 minutes and 22 seconds, a mere 14 seconds below the currently accepted value.

b) He noted that the rotation axis of Mars is inclined at an angle of 25 to the ecliptic, compared to Earth's 23.5 . Similarly to Earth therefore, Herschel also noted the changing seasons, although the Martian equivalents are almost twice as long (because it takes almost two years to orbit the Sun). He even went as far as correctly associating the seasons with the growth and shrinkage of the polar ice caps (which he inferred were thin layers of ice and snow); In a Martian hemisphere, spring and summer sees the polar cap shrink and the dark surface features become more distinct. Conversely, autumn and winter see the polar cap begin to grow and the dark features fade.

c) Herschel finally detected changes in the light and dark patterns of the planet surface which he associated with cloud cover and cloud passage.

Due to all of this data, by the end of the 18th century, Mars was seen as being very much like Earth in many respects. Both have a day of approximately 24 hours, both show successive seasons resulting in variations in polar ice cap sizes, and both have clouds obscuring parts of the surface. The growing resemblance of Mars to Earth (similar rotation period and seasonal variations) soon led to the logical supposition that the dark features could be vegetation, growing in spring and summer before receding in the autumn and winter. This idea developed into the possibility of there also being intelligent life present and this theory became so strong that in 1802 the German mathematician Karl Friedrich Gauss proposed that the Martians be signalled by drawing huge geometric patterns in the Siberian snow! His suggestion was never carried out.

MARS MAPS - There is some confusion as to the exact date of the first map of Mars. Some claim there can be no exact date, stating just the 1830's, while others give the date as 1840. There is no argument however in the naming of the two men who completed the map: Wilhelm Beer and Johann von Madler, two German astronomers. The map was very poor, and almost no features seen can be linked to anything observed today. However, one important contribution was made, and is still used today: Beer and Madler first established a longitude and latitude system similar to Earth's.

In 1864, the Reverend William Dawes published a much improved map of the martian surface, and just three years later in 1867, a fellow Englishman, Richard Proctor first attempted the naming of the bright and dark markings observed. For reasons not known however, Proctor named no less than six areas after Dawes: Dawes Ocean, Dawes Continent, Dawes Sea, Dawes Strait, Dawes Island, and Dawes Bay. It comes as no surprise that Reverend Dawes was not as universally accepted as Proctor had first hoped, and this, combined with the fact that he had used the unreliable base map of Beer and Madler, resulted in the near complete disregard of his work.

During 1887 - 1891, the oppositions of Mars (when it is best to observe the planet) caused the planet to swing very close to Earth. Taking full advantage of this, Giovanni Schiaparelli, an Italian astronomer prepared a set of very detailed maps of Mars. His observations and subsequent naming, were based on the assumption that the lighter areas were land, and the darker more dull areas were seas and oceans. When naming the features he had seen, Schiaparelli wisely avoided calling them after real people and turned to a more classical combination of biblical and geographical names. For example, Atlantis is seen, as are Libya and Ausonia (Italy). This system was universally accepted and is still widely used today, with just two pit falls: firstly, the vast majority of modern day astronomers no longer have any formal training in Latin or Greek, and consequently find these names a little difficult to grasp; secondly, many of Schiaparelli's features are difficult to see on present day photographic images. To rectify this, a committee of the International Astronomical Union decided to identify 128 areas of special importance, and in 1958 produced a map, synthesising many previous maps and observations.

NO, REALLY, THERE IS LIFE!? - The most famous observation which suggested the presence of life on Mars must be that of `Martian canals'. It is often put forward that the Italian astronomer Giovanni Schiaparelli first noted these features during his mapping through the favourable opposition in 1877. However, it was in fact Father Pietro Secchi who first observed 40 or so linear, straight line features criss-crossing the Martian surface in 1869 which he termed canali, meaning `natural water channels'. This term was soon mistranslated into English as canals and the idea arose that an alien race was desperately constructing canals to store water so as they could survive on their fast drying planet. This theory was popularised by the wealthy American amateur Percival Lowell (1855 - 1906) who financed the construction of a major new observatory near Flagstaff Arizona which would be used primarily for continuing studies of Mars. By the end of the nineteenth century, Lowell had reported the observation of 160 canals.

Despite the public excitement brewing at theories of life on Mars, many astronomers still could not accept the features as being true canals. In 1894, the American astronomer Edward Barnard said `to save my soul I can't believe in the canals as Schiaparelli draws them'. However, these more sceptical views were easily drowned out by the exciting announcements of Lowell and his colleagues; it soon became fashionable to view the Martians as a race who constructed massive canals as irrigation networks, carrying water from the polar caps to vegetation near the equators. The reddish appearance of Mars was suggestive of a dying, desert-like planet whose occupants had to struggle to irrigate their farmlands. The prospect of Martian invasions became the typical plot for an explosion of science fiction novels, with the aliens abandoning their arid homeland to invade the Earth for its abundant resources.

CRATERS - During the early 20th century, an amateur astronomer, John Mellish, proclaimed that his friend and acclaimed astronomer E.E.Barnard had recorded Martian craters between 1892-1893, and that he himself had also observed them in November 1915. The actual drawings which Barnard made however had at the time gone missing, so evidence was a little flimsy, and despite Mellish's glamorous descriptions `...mountain ranges and peaks and craters and other things both dark and light..' fellow astronomers were a little sceptical having never themselves observed such features. Barnard's drawings were actually found in the summer of 1987 and are surprisingly disappointing, showing few features. As for Mellish, the evidence of his claims are purely circumstantial, but he did record some true craters, and there is no reason to doubt his observations as the rest of his claims about Barnard's drawings are accurate. If this is the case, then he alone can be credited with the discovery and observation of the first Martian craters.

The Discovery of Phobos and Deimos - The final part of the story prior to the spacecraft exploration of the 20th century came in 1877 when the American astronomer Asaph Hall observed two tiny moons orbiting Mars. he named them Phobos (fear) and Deimos (panic) after the two horses that pulled the chariot of Mars, the Greek God of War.


Mars in the Classroom Pages

Homepage | Basic information on Mars | Spacecraft exploration of Mars
Impact cratering experiment | Playdoh volcano experiment | Choccy rocks experiment | Mission planning


Other Pages

Hawai'i impact crater notes | Hawai'i Playdoh volcano notes | Hawai'i Edible Rocks pages
JPL's Marsweb |The Nine Planets


David J. Heather and Sarah K. Dunkin, 7 June 1999

UCL Starlink UCL Physics and Astronomy Dept. University College London