Preparation

We have found a number of activities to be very beneficial prior to beginning the Mission to Mars unit. First, we believe in getting a global picture of the children's initial conceptions of the key scientific phenomena involved: solar system, Newton's Laws, physical phenomena as well as biological understanding. Hopefully, you will find the section entitled Pre-Assessment of some value in that area. We have tried to provide both a rationale and a short description of each question. We fully encourage you to photocopy the assessment in the appendix and add your own questions. Secondly, we have developed two "starter units" which have been very helpful in getting the students to think about the project that awaits them.In one activity, the children research what should be the next place that humans try to explore (Solar System Search), and in the second activity models are used to aid the students in appreciating the great distances that separate the planets of our solar system (Scale Model). Both activities are "classic" science education exercises that you may have used before. The difference, we hope, is that these activities are now being placed within a context that will make student learning more rewarding and meaningful.

Pre-Assessment

Rationale

For the past twenty years, researchers and teachers have realized that children come to school (and other formal learning environments) with their own personal ideas about the natural world. These ideas are partially based on experience and observation in social settings where language is used in ways that encourage particular everyday explanations. These ideas, which may, but often do not, coincide with accepted scientific theory, are commonly known as preconceptions. During formal instruction, it is not uncommon for preconceptions to interfere with the acquisition of accepted scientific teaching. These ideas may be very resistant to modification by conventional teaching methods because they appear on the surface to be logical. The first step to facilitate any conceptual change is to develop strategies for discovering what the misconceptions are.

Perhaps the most effective method for uncovering students' preconceptions about scientific phenomena is to set up a one-on-one interview with each student individually. Needless to say, this may be a researcher's modus operandi but it is not practical procedure for a classroom teacher who must juggle numerous responsibilities among 20 - 30 students. Fortunately, a number of effective techniques have been developed to give classroom teachers a fair picture of their students' understanding. Research indicates that there are a limited number of commonly recognized alternative conceptions (or mental models) shared by most students about any particular topic. Because of this fact, uncovering each child's ideas in detail is not as necessary as identifying their preconceptions from a categorical perspective. To facilitate this acquisition, a number of approaches are presented to assist the classroom teacher as well as the resident expert in identifying students' alternative frameworks.

One method that we have adopted is the use of a pre-unit-assessment device, commonly referred to as formative assessment. The purpose of this instrument is to give the classroom teacher a sense of what possible preconceptions the students are bringing into class. We have found that it takes about 10 minutes to administer and perhaps 90 minutes to score and tabulate a class set. Analysis of the results are up to individual teachers to use in whatever way they seem appropriate. For example, results can be used to guide instruction, to indicate which "topics" to emphasize, to provide information as to what potential misconceptions exist, and even as a pre / posttest measure at the start and end of the unit.

Example

As an example of Pre-assessment, please see Appendix 1 in which we present the original formative assessment measure that we administered during the 1994-95 academic school year. This format is known as a Likert scale and the students respond by "how much they agree" with the statement. Thus, there is a 5-response range from "strongly agree" to "strongly disagree." There is currently no computational activity in this instrument since we are attempting to understand the students' conceptual understanding more than their mathematical understanding, but teachers should feel free to modify this instrument to satisfy their own individual practice. We will try to provide a brief rationale for the inclusion of each question in the instrument:

1. The force of gravity on a planet depends on the size of the planet.
We wouldn't expect the children to have much prior knowledge of what factors determine the force of gravity on a planet, but they may have some ideas or intuitions.

2. Earth is the only place in the solar system that can support life.
This would be very hard to predict. Undoubtedly, some children will have been influenced by TV and movies (i.e., Star Trek - the Next Generation) where "other" life is routinely encountered. Other children seem to believe firmly that Earth is the only planet in our solar system that can support life. From those children who have been influenced by "space shows", we would expect to see movement towards agreement with this statement.

3. The Space Shuttle would be the ideal spacecraft for a trip to the planet Mars.
The Space Shuttle does not have the capability of breaking away from the earth's gravitational pull. We have found that the students consistently reference the Shuttle as the ship of choice in a journey to Mars. No doubt, this is due to the fact that it is the only spaceship with which they have any experience. Nonetheless, comprehending the difference between the capabilities of a spaceship and a space shuttle is essential in understanding the unit. Soon, the students will appreciate the efficiency in design and realize that the shuttle's wings would serve no purpose in the vacuum of space.

4. The planet Mars is always the same distance from the Earth.
Again, this is not true due to the elliptical orbits of both the Earth and Mars. Furthermore, students will need to address the dynamic relationship between the planetary orbits. Students will develop an appreciation for the difference between the closest approach and the most distant approach as they begin to plot out launch date possibilities during the unit.

5. The Earth is always the same distance from the planet Mars.
Same as #4, but asked in a slightly different way. Would hope to see reliability between these two questions.

6. Oxygen is essential for life to exist.
This is not true. Anaerobic life existed on Earth for millions of years, and, in fact, at one point oxygen was actually a deadly poison to the existing anerobic life on Earth. We would like to see a big change on this question from AGREE to STRONGLY DISAGREE upon posttest. Again, as students learn that life can exist without oxygen, they will begin to modify their own definition of "life" and better understand the many varied forms of life that are possible.

7. Gravity helps muscles stay healthy.
A very serious health concern of any extended human mission is what happens to muscle tissue after long periods of reduced gravity. In our experiences, almost 80% of the students either "disagree" or "strongly disagree" to such a statement. As the unit progresses and the students investigate more of the physiological aspects of long-term space flight, responses will change substatially.

8. Once a rocket has reached full speed in space, its engines can be shut off and the rocket will continue at full speed.
This is a test on Newton's First Law of Motion. An object at rest will stay at rest; an object in motion will continue in motion unless acted upon by an outside force. A very difficult concept for children to master, this law of inertia has been fairly resistant to change and is somewhat counter-intuitive to the child's experiences here on earth. Nevertheless, it is tough concepts like this that our unit is trying to tackle.

9. The force of gravity on Earth is dependent on its distance from the sun.
This is false, and the source of a potential misconception. The force of gravity is dependent on the largest body nearby. Therefore, the reason Mars and Earth have different accelerations of gravities is due to the size of each planet and NOT the distance each planet is from the Sun.

10. The force of gravity is dependent on the size of the planet you are on.
This is true. See #9 for details.

11. Mars once had water; therefore, it once had life.
Trying to generate some deductive logic with this question. This question may spur some interest in the students to study the conditions that at one time existed on Mars. Certainly, there is evidence of water on Mars. The question remains, however, if life ever existed as we know it.

12. There is no place on Earth that is similar to the planet Mars.
The hope is that as students study the arctic areas of the Earth (see Isolated Environments Benchmark) they will come to appreciate the similarity that areas of our planet share with areas on Mars.

13. It is much easier to send humans to Mars than satellites.
False Ñ due to all the backup systems and life-support equiment, a satellite is MUCH easier to send. We would hope for movement on this question from Agree to Disagree as the students progress through the unit as they better appreciate the complexities of human space flight.

14. The planets revolve around the Sun in exact circular orbits.
While planets move in elliptical orbits, students often exaggerate the nature of these orbits. In fact, it is due to this exaggeration that misconceptions can be traced to the students' mental models of the reasons for seasonal change. This question attempts to assess the students' initial ideas of Kepler's Law of Planetary Motion as well as identify misconceptions concerning planetary orbit.

15. An object weighing 100 pounds falls to Earth faster than an object weighing 10 pounds.
This is a classic misconception problem. As students complete the unit, they will have a better appreciation of the factors involved in free-fall. We have found the use of CSILE to be most advantageous in probing deeper into students' initial thoughts on this subject. With some guidance, students will come closer to a more acceptable scientific explanation of this phenomena.