Measurements of Martian emission and reflection reveal wide variations of surface properties and indicate the presence of a larger atmospheric contribution to the observed radiances than was anticipated. Temperatures observed during the Viking primary mission range from 130 to 290 K. Surface thermal inertias from 1.6 to 11×10−3 cal cm−2 s−1/2 K−1 are mapped, and they correlate with surficial geologic units. An equatorial map of bolometric albedo generally correlates with prior narrowband observations. These albedos range from 0.09 to 0.43; some regional brightenings are atmospheric in origin. The photometric behavior implies quasi‐Lambertian surface reflectance plus a strongly forward‐scattering atmosphere. Brightness temperatures at large emission angles are strongly influenced by atmospheric infrared opacity and by the presence of rocks on the surface. The correlation and grouping of albedo and thermal inertia indicate that there are two major components of Martian surface material, with bright regions having a fine particulate covering. Winter polar temperatures show spatial and temporal variations, suggesting variation of atmospheric composition; a strong atmospheric temperature inversion exists above the south polar cap during winter. Surface CO2 condensation may also occur locally near the equator before dawn. Rising temperatures before dawn in a region near Arsia Mons imply the presence of daily local water ice fogs.

Viking Orbiter 2 images of the north polar region reveal an enormous sand sea (erg) covering an area of >5 x 105 km 2 around the perennial ice cap. All dunes are either transverse or barchan. The various dune morphologies and modification of primary dune types reflect a wind regime having more than one wind direction. In the summer, two major wind directions prevail: (1) off-pole winds that become easterly due to coriolis forces and (2) on-pole winds that become westerly. During the winter and/or spring, only the on-pole winds exist. Strong winds (>75 m/s) are required for sand accumulation to form the thick transverse dunes. The strongest winds in the north polar region are thought to exist during summer over the transverse dune field between 110øW and 220øW ß this area is a relatively •varm belt (temperature >230 K) between two ice zones (temperature <220 K). A frequent cyclogenetic process in this area may cause sand storms. The dunes seem to be currently active. The lack of well-developed longitudinal dunes implies that the dune field is young. The relationship of the present dune field to the perennial ice indicates that the dunes began to form after the formation of the present ice cap. Introduction One of the many discoveries to come from the Viking mission was the existence of vast dune fields in the north polar region of Mars [Cutts et al., 1976]. The circumpolar dune field is the only major sand sea (erg) discovered thus far on Mars, comprising an area of about 7 x 105 to 8 x 105 km 2, which is greater than Rub A1 Khali in Arabia, the largest active erg on Earth (5 x 105 km 2' Wilson [1973]). Most of the dunes occur between 110øW and 220øW and between 77øN and 83øN, although scattered dunes are found between 240øW and 90øW. The field corresponds to the dark north polar collar that was observed to follow the recession of the north polar ice cap by Mariner 9 (Figure 1). From Mariner 9 results, the collar was interpreted to be a wind eroded region [Leovy et al., 1973; Sagan et al., 1973; Burk, 1976]. In addition to the sand dunes the north polar region of Mars includes several other geological units, including various plains units, layered deposits, and perennial ice [Cutts et al., 1976; Scott and Carr, 1978; Squyres, 1978]. The plains units in the north polar region are smooth, may be mantled, and have very few craters, suggesting a young age. Their classification as cratered plains by previous investigators based on poor resolution Mariner 9 images [Scott and Carr, 1978] is rather a misnomer. The perennial ice layer is composed of H20 plus dust [Kieffer et al., 1976] and is exposed to the sun shortly after summer solstice [Soderblom et al., 1973].

Supplemental instruction classes have been shown in many studies to enhance performance in the supported courses and even to improve graduation rates. Generally, there has been little evidence of a differential impact on students from different ethnic/racial backgrounds. At San Francisco State University, however, supplemental instruction in the Introductory Biology I class is associated with even more dramatic gains among students from underrepresented minority populations than the gains found among their peers. These gains do not seem to be the product of better students availing themselves of supplemental instruction or other outside factors. The Introductory Biology I class consists of a team-taught lecture component, taught in a large lecture classroom, and a laboratory component where students participate in smaller lab sections. Students are expected to master an understanding of basic concepts, content, and vocabulary in biology as well as gain laboratory investigation skills and experience applying scientific methodology. In this context, supplemental instruction classes are cooperative learning environments where students participate in learning activities that complement the course material, focusing on student misconceptions and difficulties, construction of a scaffolded knowledge base, applications involving problem solving, and articulation of constructs with peers.

Comparisons between participants and non-participants in supplemental instruction classes at San Francisco State University over a six-year period show positive impacts in terms of increased student performance and progression through subsequent courses in a sequence, despite the lower academic indicators of the supplemental instruction participants. More females participated than were represented in the course as a whole, but the effects were greater for males. Effects were particularly striking for students from underrepresented minority groups, particularly in introductory courses.

ChemPrep was developed to be a stand-alone preparatory short-course to help students succeed in general chemistry. It is Web-based and delivered using the OWL system. Students reported that the ChemPrep materials (short information pages, parameterized questions with detailed feedback, tutorials, and answers to questions through the OWL message system) permitted them to work independently without the need for textbook or lecture. On average, students who completed ChemPrep had higher grades in the subsequent GenChem, Nursing, and Honors chemistry courses, with a greater percentage achieving a grade of C- or higher. Participation in ChemPrep was voluntary, and more women than men responded. Students in the Honors course enrolled in ChemPrep in higher percentages than students in GenChem and Nursing. SAT and departmental math placement exam scores were used as proxy measures of prior achievement and ability. Based on these, Honors chemistry ChemPrep users were on par with their peers but performed better in the course than non-users. In GenChem and Nursing chemistry courses, ChemPrep helped students of high prior achievement and ability perform better than their achievement scores would predict. Weaker or less motivated students did not respond to the voluntary offerings of ChemPrep in the same numbers as stronger or more motivated students, and we are seeking alternate ways to reach this population.