The Science Part
Mercury, Venus, Earth and Mars are called terrestrial planets as these have 'land' to stand-on. We may also add moon to the list. Lunar and Mervury surfaces are highly cratered. These craters were formed about 4 billion years ago when the solar system was just born (about 0.3 byr ago) and taking it's present shape. At that time there were large number of small bodies flying in the solar system and naturally colliding with the other planets.
The gaseous planets like Jupiter, Saturn, Uranus and Neptune simply swallowed these debris. But on terrestrial planets these missiles left their mark in the form of a craters.
On planets like the Earth, Venus and Mars most of these makes were eroded by changing weather on these planets. Whereas Mercury and Moon, which have little atmosphere, have retained their poke marks.
Thus - if one goes exploring planets of other suns and come across a planet which has highly cratered surface then it is quite likely that the planet has little or no atmosphere.
Study of these features on the planets has helped astronomer to get insight into how the surfaces of these planets have evolved over a period of time.
The Fun Part
---->>>> begins from the next step
Step 1: DIY Surface of a Planet Without an Atmosphere
For this project we required
A) Quick setting Plaster of Paris ( POP ) available in the hardware shops. Cost of 5 k.g. POP (about 1 USD).
( POP is a white powder that, when mixed with water to form a paste, will turn hard in a few minutes. POP is made by heating gypsum, a mineral composed of calcium sulfate and water. )
B) A cardboard box tray of 20 x 20 x 5 cm. Normally 8 inch pizza comes in a box of this size. We need only one side of the box
C) 250ml cup - a Styrofoam cup will do.
D) A white sheet of paper (standard wall calendar will do).
E) A vessel to mix POP.
F) A pair of rubber gloves (for every player)
Also a few sheet of newspapers, scotch or paper tape to stick the sides of the pizza box if needed.
Step 2: POP Mix
You may have to make a few trial before arriving at your own formula.
Take two full measures of POP (D) is taken on a sheet of paper. And Three measures of plain water in a big broad pan (E).
Mix POP from (D) into water in (E). This operation has to be carried out quickly. To make smooth paste, while mixing POP to the water one needs to keep stirring the mixture and avoid formation of lumps.
Once all of POP is poured in the water and smooth slurry is make, pour the mixture in the tray (A). It is OK to have a few bubbles in the mixture. These will be the craters.
Step 3: Make Your Own Craters
You may also drop a few larger droplets using a dropper.
Step 4: It Is Done Now
It would help to spray a little amount of water to slow down drying. This will avoid formation of cracks.
After the surface has dried completely take it out of the cardboard box and mounted or placed.
Step 5: What Next - 1
You may add a bit of red or brown colour or rouge (ferric oxide) to POP.
Surface of Mars has ferric oxide on it to get it a reddish hue.
And never mind if your mixture becomes too lumpy.
Here is what you can do -- make some mountains on the planetary surface.
Every child will have his or her own piece of land. You may even ask children to name the features on the planet.
Step 6: What Next - 2
You can ask the students to study the craters and tell you what do the infer?
There are large and small size craters. Some craters on top of the other - indicating those were formed later.
You may also add little extra water to slow down setting of POP and thenuUsing a standard dropper - put drops from different heights.
A drop from higher height will make larger crater. What does that tell us?
How about dropping a small stone -
Variations could be many -
And children love this project - slushy - muddy clay to play with too.