IMPACT: MAKING CRATERS
going to travel to the stars again . . . or just to the kitchen . .
. to see how those big holes in moons and planets (including our own)
When you look at the moon, you can tell that it s had more
than a few interstellar encounters over the millennia that
were strong enough to leave their mark: craters. Some large, some (relatively)
small, these craters reveal hints about their origin that scientists
analyze to figure out the shape of what hit the crater (asteroid), at
what angle it was going when it hit, and how big it was.
So let's go to the surface of our own planet. What we'll need
for this experiment is:
Flour, at least five cups, but you may end up using a five-pound bag.
Expect to be covered in flour before we're done, so wear your jeans!
2. A shallow, long tray or box
and a plastic bag to line it with. Something like a litter box would
be perfect, but don't use it if it's not new! Yuck!
3. A rolling pin.
4. Marbles, beans, or just about
any small object you wouldn't mind being covered in flour. No siblings allowed.
5. Contrasting powders. I used
the strawberry and chocolate flavors of milk drinks, but you can certainly
use colored sugar or any other nontoxic powder you wish.
6. A chart (that we'll make).
Now we're going to make a powder layer
cake. Just as the surface of planets have different layers, so will
our cake. Pour in enough flour to line the bottom of the tray and even
out with the rolling pin. Sprinkle a thin layer of chocolate powder,
then another thick layer of flour (evening out again), and finally some
Take a bean and drop it into the powder
from waist level and see what happens. Did you get all the way down
to the bottom layer? Do you see chocolate on the surface now? Does it
help with sound effects (just kidding).
Move to another section and drop another
bean from over your head, and see the difference. Try this with different
heights, different objects, and different angles, writing down your observations as you
go. You can even vary how tightly packed the flour is. You can clearly
see that the pattern in the flour is different for a bean dropped straight
down from waist-high from one flung from the side. How do the other
variables affect the pattern in the flour?
Scientists use a very similar experiment
to reproduce craters, and they can predict what impact an asteroid can
make. The actual crater itself may smooth over timewhich helps
us predict its agebut the mark will always be there, proving an
encounter in the stars.