The Cryogenic World of Triton Dr. Gary Peterson Department of Geological Sciences
San Diego State University
Triton is a large satellite in retrograde orbit around Neptune, the most distant (40AU) of the giant gaseous planets. Surface temperatures average about 40K and are cold enough to condense all of the heavier gases, including nitrogen. A pronounced tilting of Triton's spin axis gives rise to a strongly seasonal climate and the available imagery indicates a deteriorating south polar cap made of nitrogen. Evidently the released nitrogen is being transferred to the north pole and condensing there during the long winter season. Distant though the sun is, it evidently supplies enough energy to provide seasonal transfer of nitrogen much in the same manner that water alternately collects and melts at the earth's poles with the seasons. Triton has been resurfaced and shows little evidence of cratering. Probably the satellite has been heated, evaporating the surface ices and then the released gases have recondensed to provide a new surface. The energy source for the heating would appear to be tidal friction following capture by Neptune. The retrograde orbit of Triton would indicate capture and the lack of surface craters would suggest that the capture was a fairly recent event. Numerous irregular surface textures indicate repeated expansion and contraction and are compared with somewhat similar features on earth. Although the Earth/Triton surface features resemble one another, they would be composed of totally different material.
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