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.
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
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