June 12, 1998

NASA's MARS GLOBAL SURVEYOR SPACECRAFT CAPTURES WINTER ON MARS

The first image shows a winter morning with upper atmospheric hazes in Tharsis, a volcanic region in Mars' northern hemisphere. The image was taken on June 1, 1998.

The second image shows detailed cloud patterns in the Tempe Terra/Kasei Vallis region of the northern hemisphere. These winter cloud patterns were observed on June 4, 1998.

Mars Global Surveyor is currently in a fixed 11.5-hour orbit around Mars, coming as close as 170 kilometers (106 miles) above the surface of Mars during each looping orbit. The spacecraft will resume aerobraking to lower and circularize its orbit for the start of the mapping mission in mid-March 1999.

NEW MARS GLOBAL SURVEYOR IMAGES

http://mars.jpl.nasa.gov/mgs/msss/camera/images/6_12_98_color_wa_release/p339/index.html http://mars.jpl.nasa.gov/mgs/msss/camera/images/6_12_98_color_wa_release/p345/index.html The image caption are appended below.

Ron Baalke

Mars Global Surveyor
Mars Orbiter Camera

Mars Orbiter Camera (MOC) Low Resolution Images
SPO-2 Observations:
Winter Morning in Northern Tharsis

(A) Warning: This color composite does not represent the "true" color of Mars. MOC wide angle images 33901 (red-band) and 33902 (blue-band) were combined with a green-band synthesized by averaging the red and blue bands. The images have been geometrically projected to account for optical and motion-induced distortion. North is up, illumination is from the right.

(B) Same image with volcanoes Olympus Mons and Ascraeus Mons labeled for context.

You may need to adjust the images for the gamma of your monitor to insure proper viewing.

CAPTION

Mars Global Surveyor's camera, MOC, provided this hemispheric view of the northern Tharsis region on June 1, 1998. This picture shows the giant volcano, Olympus Mons, and one of the Tharsis Montes volcanoes, Ascraeus Mons. Another volcano, Alba Patera, is lurking under the haze and clouds at the top of the image. Olympus Mons is about 550 kilometers (340 miles) wide.

MGS is now in a "morning" orbit (when it arrived at Mars in September 1997, it was inserted into a "late afternoon" orbit). The orbit will continue to change, about one hour a month, until aerobraking into a circular orbit is complete about seven months from now. When this picture was taken, the local time on the ground beneath the spacecraft was about 9:30 a.m. The terminator-- the line that divides night and day-- was located west of Olympus Mons (left part of the image). It is winter in the northern hemisphere of Mars, and the high latitudes (i.e., north of Olympus Mons in this picture) exhibit clouds and haze. These clouds most likely contain water ice.

MOC images 33901 (the red wide angle image) and 33902 (the blue wide angle image) were obtained on Mars Global Surveyor's 339th orbit about the planet. The pictures were taken around 7:37 p.m. PDT on June 1, 1998.

Mars Global Surveyor
Mars Orbiter Camera

Mars Orbiter Camera (MOC) Low Resolution Images
SPO-2 Observations:
Detailed Cloud Patterns in Martian Northern Hemisphere

(B) Same image with geographic features labeled for context. Perepelkin Crater is about 100 kilometers (62 miles) wide and located at 53°N, 65°W. Tempe Terra is a broad flat region criss-crossed with faults and troughs. Kasei Vallis is a large flood channel around 28°N, 65°W. Cold and cloudy mornings; cool, hazy afternoons. High winds aloft and weather fronts moving slowly to the east. It is winter in the Martian northern hemisphere. One of the many reasons to study Mars is that, at times, its weather is very "Earth-like." At this time of the Martian year, clouds are abundant, especially in the morning and especially in the high northern latitudes. Clouds and fogs are also observed in low-lying areas farther to the south, in some lowlands they are as far south as the equator.

The above color composite images, obtained by Mars Global Surveyor's camera on June 4, 1998, illustrate this Martian "weather report." Most of the thick, white clouds seen here occur north of latitude 35°N (roughly equivalent to Albuquerque NM, Memphis TN, and Charlotte NC). Fog (seen as bright orange because it is lighter than the ground but some of the ground is still visible) occupies the lowest portions of the Kasei Valles outflow channel around 30°N and at 25°N.

Several different types of cloud features are seen. The repetitious, wash-board pattern of parallel lines are "gravity" wave clouds. These commonly form, in the lee--downwind side--of topographic features such as mountain ranges (on Earth) or crater rims (on Mars), under very specific atmospheric conditions (low temperatures, high humidity, and high wind speeds). In this area, the wave clouds are lower in the atmosphere than some of the other clouds. These other clouds show attributes reflecting more the regional weather pattern, occasionally showing the characteristic "slash" shape (southwest to northeast) of a weather front. These clouds probably contain mostly crystals of water ice but, depending on the temperature at high altitude (and more likely closer to the pole), some could also contain frozen carbon dioxide ("dry ice").

MOC images 34501 (the red wide angle image) and 34502 (the blue wide angle image) were obtained on Mars Global Surveyor's 345th orbit about the planet. The pictures were taken around 5:34 p.m. PDT on June 4, 1998. Winter in the northern hemisphere began in mid-February, 1998, and continues to mid-July, 1998.

Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

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