April 16, 1997

This stunning image of Mars was taken by NASA's Hubble Space Telescope (HST) on March 10, 1997, which was the last day of spring on the planet's northern hemisphere.

As this picture was taken, the Martian days were growing longer and warmer. As a result, the carbon dioxide frost (dry ice) of the north polar region was rapidly sublimating (evaporating from solid to gas) and receding, revealing the much smaller permanent water ice cap. Also visible in this image are numerous bright clouds consisting of water ice, particularly along the volcanic mountain chain of the Tharsis Ridge, around the nearly 90,000-foot-high Olympus Mons, and around Elysium Mons. A diffuse haze covers much of the Martian tropics as well. The dark, circular region that surrounds the receding north polar ice cap is the Sea of Sand Dunes (Olympia Planitia).

Astronomers have good reasons for pointing the HST toward Mars just now and studying its surface and clouds. Two NASA spacecraft are on their way to the red planet -- the Mars Pathfinder and the Mars Global Surveyor. Mars Pathfinder is scheduled to land on the planet on July 4, 1997. The Global Surveyor will arrive about two months later, and map and study Mars from orbit.

Thus, astronomers are monitoring the Martian weather. They keep their fingers crossed that no global dust storm materializes that might interfere with the Pathfinder's landing and surface exploration or the Surveyor's mapping program.

The above portrait was taken with HST's Wide Field Planetary Camera-2 when Mars and Earth were nearly lined up on the same side of the Sun and made one of their closest passes to each other. On March 10, their separation was about 60 million miles. At this distance, a single picture element (pixel) in the Planetary Camera spanned thirteen miles on the Martian surface. The observations were made in nine different colors spanning the ultraviolet to the near infrared. The specific colors were chosen to clearly discriminate between airborne dust, ice clouds, and prominent Martian surface features. The above picture was created by combining images taken in the colors blue, green, and red.

More Cool Stuff

We obtained the above image from two press releases of the Space Telescope Science Institute (STScI-PRC97-09a and 09b, March 20, 1997) -- "Hubble's Sharpest View of Mars" and "Hubble Captures a Full Rotation of Mars":

http://oposite.stsci.edu/pubinfo/PR/97/09.html#Photos

We have featured Mars three times during the past year -- "1997 -- The Year of Mars" on January 1, 1997; "Live from Mars" on November 6, 1996; and "Viking on Mars -- 20 Years Ago" on July 10, 1996:

http://observe.ivv.nasa.gov/nasa/ootw/1997/ootw_970101/ootd.html

http://observe.ivv.nasa.gov/nasa/ootw/1996/ootw_961106/ob961106.html

http://observe.ivv.nasa.gov/nasa/ootw/1996/ootw_960710/ob960710.html

NASA's current missions to Mars -- the Mars Pathfinder and the Mars Global Surveyor -- are described on the following pages:

Mars Pathfinder:

http://mpfwww.jpl.nasa.gov/

http://nssdc.gsfc.nasa.gov/planetary/mesur.html

Mars Global Surveyor:

http://mars.jpl.nasa.gov/mgs/mgs-home.html

http://nssdc.gsfc.nasa.gov/planetary/marsurv.html

There are several other NASA-supported sites on the Web that offer information about the Sun's planetary system:

Mars Landing: Remote Sensing Tools, an educational module developed by the Classroom of the Future program at Wheeling Jesuit University:

http://cotf.edu/ETE/scen/scen.html

Eyes on the Sky, Feet on the Ground, a set of pages of the Web site Using Science and the Internet as Everyday Classroom Tools from the Smithsonian Astrophysical Observatory. Planets are discussed in Chapter 5:

http://hea-www.harvard.edu/ECT/the_book/

The Public Connection Web site of Rice University and the Houston Museum of Natural Science, which features interactive displays of real-time Earth and space science data:

http://space.rice.edu/hmns/

Science Information Infrastructure (SII) of the University of California, Berkeley, is a project that links science museums via the Internet and makes satellite-based observations of the Earth, the planets, and the universe accessible to students, teachers, and the public:

http://www.cea.berkeley.edu/Education/ssi/

Windows to the Universe, an innovative and engaging Web site about the Earth and space sciences:

http://www.windows.umich.edu/

Check out other observations in the Observation of the Week Archive.