Teachers' Guide

Part 1 Modeling Martian Motion

Engage Ask students to describe differences between stars and planets. Record their answers, and return to them later. Tell students that they are going to become stars and planets, and simulate the relative motions of Mars and Earth about the Sun! Demonstration: Take students to a large open area (a field, school playground, or empty gymnasium). Choose one student (holding large sign) to be the Sun. Using the chalk or spray "fake snow" mark a circle about 20 feet in diameter to represent the orbit of the Earth around the Sun. Next, mark a "twin" (actually an ellipse) about 30 feet in diameter to represent the orbit of Mars. (To accentuate the elliptical orbit of Mars, make sure that the line marking Mars'orbit is at one point approximately twice as distant to the line marking Earth's orbit as on the opposite side.) Choose one student to be the Earth (holding appropriate sign) and another to be Mars (with sign.) Have all the other students form as large an extended group as possible around the sun but well beyond Mars'orbit. Explain that these students represent the distant "fixed stars". Now, have the students who represent Earth and Mars begin to orbit the Sun, one step at a time. Since Earth travels faster around the Sun than Mars, have the student that represents Earth take a large step each time while the student who represents Mars takes a smaller step. Each time the Earth and Mars take a step, have them stop and ask the student who's representing Earth to call out the name of the student in the outer or "fixed star" circle who can be seen (from the position of Earth) to be closest to Mars. Have all students closely observe what's going on, and record raw data and patterns about the relative motions of Earth and Mars. Back in class, have students debrief, and help them conceptualize their experience as a simulation of how Mars appears to move among the fixed stars as seen from Earth as the two planets orbit the sun. Explore/Explain Procedure 1. Distribute copies of Diagram 1 showing the orbits of Earth and Mars to students. 2. Allow time for students to examine diagram. Then ask them to work in small groups to brainstorm and list facts that can be gleaned from the diagram. List facts on chalkboard and discuss. The Earth travels on a closer orbit to the Sun than Mars. The Earth travels in its orbit faster (completing one orbit in 365 days while Mars takes about 687 Earth days to do the same). 3. Explain that stars are much farther away from Earth than Mars and the other planets of our solar system, and challenge students to describe Mars'changing position in Earth's skies as the two planets orbit the sun. 4. Ask students to compare and contrast the diagram on their desk with the physical demonstration they completed outside.

The MarsWatch Project 1996-97 This excerpt from the MarsWatch Web Site gives background and rationale for why NASA wants participation from amateur astronomers and others around the world. To: Friends of Mars From: Jim Bell Re: Mars observing campaign, 1996-97 Dear colleague, I am writing this brief note to solicit potential participation by you or your club or institution in a global network of observations of Mars during the 1996-97 apparition. I think that this is the perfect type of project for small-to moderate-sized telescopes that can obtain good planetary image quality. This project would be very appropriate as a graduate or undergraduate class project, as a "service observing" program carried out by observatory staff, or even as a project organized by skilled amateurs or local astronomy club members. It could also serve as an excellent and timely part of the public outreach and education activity at your institution. The upcoming apparition (9/96 to 9/97) is particularly important because THREE spacecraft will be traveling to Mars beginning late this year: A U.S. Orbiter (Mars Global Surveyor), a U.S. Lander (Mars Pathfinder), and a Russian Orbiter (Mars-96). The Pathfinder lander project is particularly interested in groundbased observations of Mars for two reasons: first, their atmospheric entry profile depends on the atmospheric temperature, which is a critical function of dust and cloud opacity; and second, the lander itself is solar powered, so a substantial amount of dust in the Martian atmosphere will degrade their available power and will affect the lifetime of the mission. Thus, information on the behavior of dust in the Martian atmosphere as a function of time during 1996-97 (such as can be obtained from good multi-color imaging) will be extremely important in the planning and execution of this mission. The project will maintain a WWW home page and archive site at JPL in association with the Mars Pathfinder mission. The goal will be to have participants submit one or more of their images (or entire data sets if they like) to this site for dissemination to NASA Project personnel, professional astronomers, amateur astronomers, news and print media, educators and schoolchildren, and the general public. The 1996-1997 MarsWatch Home Page can be found at the URL http://mpfwww.jpl.nasa.gov/mpf/marswatch.html