Climate
Mercury's equatorial plane is inclined less than 2° to its orbital plane (Klaasen, 1976; Murray and others, 1981, p. 28); its rotation period of 58.64 terrestrial days is in two- thirds resonance with its orbital period of 87.97 terrestrial days (Colombo, 1965; Colombo and Shapiro, 1966). The resulting lag and orbital eccentricity create a variation of mean temperature not only with latitude, as on the Earth, but also with longitude. However, because of Mercury's relatively slow rotational period, diurnal variations in temperature probably greatly exceed mean-temperature variations along latitude and longitude, even in the high latitudes. Its pronounced orbital eccentricity (0.2563) causes the apparent solar intensity at Mercury to vary by more than a factor of 2 throughout a Mercurian year, corresponding to about a 20 percent change in equilibrium temperature. Further, conservation of orbital angular momentum and spin-orbit coupling cause considerable variation in the length of daylight. Dawns and sunsets are prolonged by the long transit time of the Mercurian horizon across the solar disk, so that daylight is lengthened and nighttime reduced by several terrestrial days at sunset and vice versa at sunrise (Robert Wildey, U.S. Geological Survey, oral commun., 1982). Despite these considerations and despite the daily range in surface temperatures of several hundred kelvins, the subsurface temperature in the polar regions always remains well below freezing (Murray, 1975).
Read more about this topic: Borealis Quadrangle
Famous quotes containing the word climate:
“If often he was wrong and at times absurd,
To us he is no more a person
Now but a whole climate of opinion.”
—W.H. (Wystan Hugh)
“When we consider how much climate contributes to the happiness of our condition, by the fine sensation it excites, and the productions it is the parent of, we have reason to value highly the accident of birth in such a one as that of Virginia.”
—Thomas Jefferson (1743–1826)
“Is not their climate foggy, raw, and dull,
On whom, as in despite, the sun looks pale,
Killing their fruit with frowns?”
—William Shakespeare (1564–1616)