History
By the early 1980s, it was obvious that the SNC group of meteorites (Shergottites, Nakhlites, Chassignites) were significantly different from most other meteorite types. Among these differences were younger formation ages, a different oxygen isotopic composition, the presence of aqueous weathering products, and some similarity in chemical composition to analyses of the martian surface rocks in 1976 by the Viking landers. Several workers suggested these characteristics implied the origin of SNC meteorites from a relatively large parent body, possibly Mars (e.g., Smith et al. and Treiman et al.). Then in 1983, various trapped gases were reported in impact-formed glass of the EET79001 shergottite, gases which closely resembled those in the martian atmosphere as analyzed by Viking. These trapped gases provided direct evidence for a martian origin. In 2000, an article by Treiman, Gleason and Bogard gave a survey of all the arguments used to conclude the SNC meteorites (of which 14 had been found at the time) were from Mars. They wrote, "There seems little likelihood that the SNCs are not from Mars. If they were from another planetary body, it would have to be substantially identical to Mars as it now is understood."
Read more about this topic: Martian Meteorite
Famous quotes containing the word history:
“Anyone who is practically acquainted with scientific work is aware that those who refuse to go beyond fact rarely get as far as fact; and anyone who has studied the history of science knows that almost every great step therein has been made by the “anticipation of Nature.””
—Thomas Henry Huxley (1825–95)
“The disadvantage of men not knowing the past is that they do not know the present. History is a hill or high point of vantage, from which alone men see the town in which they live or the age in which they are living.”
—Gilbert Keith Chesterton (1874–1936)
“We have need of history in its entirety, not to fall back into it, but to see if we can escape from it.”
—José Ortega Y Gasset (1883–1955)