Thematic Organizer

Perhaps you have heard or read about Martians on Mars. In 1938, the United States was faced with a serious dilemma about the circumstances surrounding Hitler in Europe. The United States was about to embark into World War II. During this year, on October 30^th, Halloween night, Orson Wells performed his radio adaptation of the novel written by H.G. Wells "The War of the Worlds." This broadcast that occurred on Mercury Theater On the Air frightened the listening audience mostly in area surrounding New York and New Jersey. Many listeners believed that Martians were invading the world (see http://www.waroftheworlds.org/Background.htm). What some perceived as facts combined with fiction sparked hysteria throughout the country. Reaction from the public to this broadcast sparked decades of research into the possibility of life beyond Earth. Countless science fiction movies have portrayed men from Mars coming to Earth with various story lines.

Earth and Mars have stimulated conversations over many decades. The "little green men" from Mars has been depicted in novels, radio plays, and in movies. Martians who purportively lived on Mars, and have convinced some of our inhabitants of their visit to our planet, have fascinated people throughout the world. If we are to make comparisons between Earth and Mars we need to investigate the historical "geology" that took place on both of these planets.

Are you aware of any "geological" features on Mars? If so, what are your impressions? Write your thoughts in the Electronic Notebook.

Today we are in a better position to learn more about this Earth and Mars connection. Our satellites and landers are collecting information that may lead to a better understanding of the mystery of the geologic features of Mars: volcanoes, canyons, valley, craters, channels and icecaps. When comparing these surface features of Mars to Earth, we see similarities, but in many Mars has larger physical surface features than Earth. For example, Olympus Mons is one largest volcanoes known in the solar system and the "the Grand Canyon" of Mars, Valles Marinaris, would stretch from New York to California. Branching valley networks and large channel systems suggest that water may have once flowed on the Martian surface. However, the combination of a thin atmosphere and low temperatures make it impossible for water to exist as a liquid on the surface of Mars today. A question that arises is " Did Mars have a warm wet past?"

As you proceed with your case investigation relate what you know to this topic about Water on Mars. Think about research questions you would like to have answered. What are some preliminary ideas that come to mind now? Use the Electronic Notebook to record your present thoughts.

Directions: Read the statements below. Then read the information that follows about the Mars Orbital Laser Altimeter (MOLA) Mission to Mars under Background below. If you agree with the statement place a check mark on the space provided. If you disagree with the statement leave it blank. Be able to give reasons to support whether or not you checked each statement.

Upon completion, discuss your responses to these statements with your teacher and/or other students who are interested in investigating aspects of this case. After your discussion, review your Research Questions that you entered in the Electronic Notebook earlier. Have you narrowed your case investigation with this topic? If so, do you need to restate your Research Questions?

_____ 1. Water on Mars is a relevant topic for investigation.

_____ 2. Martian days differ in length from Earth days.

_____ 3. MOLA measurements give accurate information about Mars’s topography.

http://mars.jpl.nasa.gov/mgs/sci/mola/data1/mola_first.html

_____4. There is agreement among scientists about liquid water on Mars.

http://cmex.arc.nasa.gov/SiteCat/sitecat2/water.htm

http://cmex.arc.nasa.gov/VOViews/CHANNELS.HTM

_____5. It is not important to estimate the volume of the water ice cap.

_____6. Determining if there was water on Mars, while interesting, is not very helpful in determining the Earth’s past or future?

LASER PROVIDES FIRST 3-D VIEW OF MARS' NORTH POLE

Measurements by a laser altimeter instrument orbiting aboard NASA's Mars Global Surveyor spacecraft are providing striking new views of the north pole of the red planet and the processes that have shaped it.

This first three-dimensional picture of Mars' north pole enables scientists to estimate the volume of its water ice cap with unprecedented precision, and to study its surface variations and the heights of clouds in the region for the first time.

The elevation measurements were collected by the Mars Orbiter Laser Altimeter (MOLA) aboard Global Surveyor during the spring and summer of 1998, as the spacecraft orbited Mars in an interim elliptical orbit. MOLA sends laser pulses toward the planet and measures the precise amount of time before the reflected signals are received back at the instrument. From this data, scientists can infer surface and cloud heights.

Approximately 2.6 million of these laser pulse measurements were assembled into a topographic grid of the north pole with a spatial resolution of .6 miles (one kilometer) and a vertical accuracy of 15-90 feet (5-30 meters). A peer-reviewed paper based on the measurements will be published in the Dec. 11 issue of Science magazine.

The topographic map reveals that the ice cap is about 750 miles (1,200 kilometers) across, with a maximum thickness of 1.8 miles (3 kilometers). The cap is cut by canyons and troughs that plunge to as deep as 0.6 miles (1 kilometer) beneath the surface. "Similar features do not occur on any glacial or polar terrain on Earth," said Dr. Maria Zuber of the Massachusetts Institute of Technology and NASA's Goddard Space Flight Center, Greenbelt, MD. "They appear to be carved by wind and evaporation of ice."

The MOLA data also reveal that large areas of the ice cap are extremely smooth, with elevations that vary by only a few feet over many miles. In some areas the ice cap is surrounded by large mounds of ice, tens of miles across and up to half a mile in height. "These structures appear to be remnants of the cap from a time when it was larger than at present," Zuber said. Impact craters surrounding the cap appear to be filled with ice and dust that was either deposited by wind or condensation, or perhaps remains from an earlier period when the ice cap was larger.

The shape of the polar cap indicates that it is composed primarily of water ice, with a volume of 300,000 cubic miles (1.2 million cubic kilometers). The cap has an average thickness of 0.64 miles (1.03 kilometers) and covers an area 1.5 times the size of Texas. For comparison, the volume of the Martian north polar cap is less than half that of the Greenland ice cap, and about four percent of the Antarctic ice sheet.

The estimated volume of the north ice cap is about 10 times less than the minimum volume of an ancient ocean that some scientists believe once existed on Mars. If a large body of water once existed on the red planet, the remainder of the water must presently be stored below the surface and in the much smaller south polar cap, or have been lost to space. But such a large amount of unaccounted-for water is not easily explained by current models of Martian evolution.

During its mapping of the north polar cap, the MOLA instrument also made the first direct measurement of cloud heights on the red planet. Reflections from the atmosphere were obtained at altitudes from just above the surface to more than nine miles (approximately 15 kilometers) on about 80 percent of the laser profiles. Most clouds were observed at high latitudes, at the boundary of the ice cap and surrounding terrain.

Clouds observed over the polar cap are likely composed of carbon dioxide that condenses out of the atmosphere during northern hemisphere winter. Many clouds exhibit dynamic structure probably caused by winds interacting with surface topography, much as occurs on Earth when winds collide with mountains to produce turbulence.

The principal investigator for MOLA is Dr. David E. Smith of Goddard. The MOLA instrument was designed and built by the Laser Remote Sensing Branch of Laboratory for Terrestrial Physics at Goddard. The Mars Global Surveyor Mission is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for the NASA Office of Space Science.

Further information about MOLA and images created from its measurements of the north pole are available on the Internet at the following address: http://ltpwww.gsfc.nasa.gov/tharsis/mola.html

Images of the north pole from the Mars Orbiter Camera (MOC) aboard Mars Global Surveyor can be viewed at: http://www.msss.com/mars/global_surveyor/camera/images/MENUS/poles_list.html

(http://ltpwww.gsfc.nasa.gov/tharsis/agu_f98.html)