STRUCTURE OF THE MARTIAN NORTH POLAR-CAP AND VERNAL HOOD SYSTEM AT L(S) 61-DEGREES-66-DEGREES OF THE 1995 APPARITION

The boundary and internal structure of the north polar deposits and po lar hood vernal remnant on Mars have been mapped at L(s) 61 degrees-66 degrees on the hemisphere centered on longitude omega = 0 degrees, us ing images obtained in Feb-Mar 1995 with the Swedish Vacuum Solar Tele scope on La Palma. On red light images, several internal rifts, includ ing the historically well documented Rima Tenuis and Rima Hyperborea, as well as an internal, long absent, annular rift were mapped. The gro und cap was asymmetric with a mean boundary at 72 degrees N for omega = 270 degrees, increasing to 77 degrees N at omega = 90 degrees. Image s in green light showed the locations of high opacity hood clouds, inc luding an extensive outflow to 67 degrees N at omega approximate to 10 0 degrees. The state of the cap and hood is compared with the findings of previous studies and the historical significance of the annular ri ft structure is discussed. It is concluded, based on the structure of the deposited laminae, that the north polar climate was nearly, or pos sibly slightly milder than, normal at the northern hemisphere spring s eason studied.