History of Mars observation
Within a century, astronomers discovered distinct albedo features on the planet, including the dark patch Syrtis Major Planum and polar ice caps.
When astronomers mistakenly thought they had detected the spectroscopic signature of water in the Martian atmosphere, the idea of life on Mars became popularized among the public.
By the 2nd millennium BCE they were familiar with the apparent retrograde motion of the planet, in which it appears to move in the opposite direction across the sky from its normal progression.
His list, in order of the nearest to the most distant from the Earth, was as follows: the Moon, Sun, Venus, Mercury, Mars, Jupiter, Saturn, and the fixed stars.
Observations of Mars had shown that the planet appeared to move 40% faster on one side of its orbit than the other, in conflict with the Aristotelian model of uniform motion.
He proposed that the order of the planets, by increasing distance, was: the Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn, and the fixed stars.
His model successfully explained why the planets Mars, Jupiter and Saturn were on the opposite side of the sky from the Sun whenever they were in the middle of their retrograde motions.
With access granted to Tycho's detailed observations of Mars, Kepler was set to work mathematically assembling a replacement to the Prutenic Tables.
[26] This instrument was too primitive to display any surface detail on the planet,[27] so he set the goal of seeing if Mars exhibited phases of partial darkness similar to Venus or the Moon.
During the oppositions of 1651, 1653 and 1655, when the planet made its closest approaches to the Earth, the Italian astronomer Giovanni Battista Riccioli and his student Francesco Maria Grimaldi noted patches of differing reflectivity on Mars.
On November 28, 1659, he made an illustration of Mars that showed the distinct dark region now known as Syrtis Major Planum, and possibly one of the polar ice caps.
During this year, the planet was moving past the point along its orbit where it was nearest to the Sun (a perihelic opposition), which made this a particularly close approach to the Earth.
[34] In 1704, Italian astronomer Jacques Philippe Maraldi "made a systematic study of the southern cap and observed that it underwent" variations as the planet rotated.
Most notable among these enhancements was the two-component achromatic lens of the German optician Joseph von Fraunhofer that essentially eliminated coma—an optical effect that can distort the outer edge of the image.
[41][42] During the opposition of Mars in 1830, the German astronomers Johann Heinrich Mädler and Wilhelm Beer used a 95 mm (3.7 in) Fraunhofer refracting telescope to launch an extensive study of the planet.
[48] At the University of Leipzig in 1862–64, German astronomer Johann K. F. Zöllner developed a custom photometer to measure the reflectivity of the Moon, planets and bright stars.
[55] The names of the two satellites, Phobos and Deimos, were chosen by Hall based upon a suggestion by Henry Madan, a science instructor at Eton College in England.
[59] In his 1892 work La planète Mars et ses conditions d'habitabilité, Camille Flammarion wrote about how these channels resembled man-made canals, which an intelligent race could use to redistribute water across a dying Martian world.
[61] The canali were found by other astronomers, such as Henri Joseph Perrotin and Louis Thollon using a 38 cm (15 in) refractor at the Nice Observatory in France, one of the largest telescopes of that time.
[64] Although these results were widely accepted, they became contested by Greek astronomer Eugène M. Antoniadi, English naturalist Alfred Russel Wallace and others as merely imagined features.
[66] Starting in 1909 Eugène Antoniadi was able to help disprove the theory of Martian canali by viewing through the great refractor of Meudon, the Grande Lunette (83 cm lens).
[67] A trifecta of observational factors synergize; viewing through the third largest refractor in the World, Mars was at opposition, and exceptional clear weather.
[72] Baltic German astronomer Hermann Struve used the observed changes in the orbits of the Martian moons to determine the gravitational influence of the planet's oblate shape.
[74] Using a vacuum thermocouple attached to the 2.54 m (100 in) Hooker Telescope at Mount Wilson Observatory, in 1924 the American astronomers Seth Barnes Nicholson and Edison Pettit were able to measure the thermal energy being radiated by the surface of Mars.
[79] In 1927, Dutch graduate student Cyprianus Annius van den Bosch made a determination of the mass of Mars based upon the motions of the Martian moons, with an accuracy of 0.2%.
In 1929, he noted that the polarized light emitted from the Martian surface is very similar to that radiated from the Moon, although he speculated that his observations could be explained by frost and possibly vegetation.
However, because he overestimated the surface pressure on Mars, Kuiper concluded erroneously that the ice caps could not be composed of frozen carbon dioxide.
[84] In 1948, American meteorologist Seymour L. Hess determined that the formation of the thin Martian clouds would only require 4 mm (0.16 in) of water precipitation and a vapor pressure of 0.1 kPa (1.0 mbar).
Earth-based telescopes equipped with charge-coupled devices can produce useful images of Mars, allowing for regular monitoring of the planet's weather during oppositions.
[97] Chemical analysis of the Martian meteorites found on Earth suggests that the ambient near-surface temperature of Mars has most likely been below the freezing point of water (0 °C) for much of the last four billion years.
