|
Mar. 16, 1999:
NASA/Marshall's "Life on the Edge" program is barely a month old but
it's already producing results in some grade school classrooms.
"It was wonderful," says Mrs. Nancy Walters, whose 3rd grade class
recently tried some simple microbiology experiments with yeast.
"The kids felt like they were doing real science, and they couldn't
stop talking about it for days."
Life on the Edge is an educational program that aims to
expose grade school students to some of the
basic principles of astrobiology and to explore the possibilities for life
elsewhere in the Solar System. The program began
just over a month ago when 50 lb of yeast and other microbes
were delivered
to a summit in California's White Mountains. Conditions there present
severe challenges for most forms of life, so it is a good place to
test the response of microbes to extreme environments.
Some of the
microorganisms will remain there for months, and some for longer than a year
before they
are retreived and distributed to classrooms for experimentation.
"Eventually we'll be sending thousands of yeast
packets to schools around the country," says Dr. John Horack,
director of science communications at the NASA/Marshall Space Sciences Lab.
"But even before the microbes are ready to go
we have to develop some simple lab protocols
that kids can use to measure how their samples were affected by exposure.
That's why we're going into classrooms now to test
some of our ideas."
One of these ideas, called "Planets in a Bottle," was field-tested in a 2nd/3rd grade class room
in February.
"'Planets in a Bottle' is a simple way to test the viability of yeast samples,
and a great way to teach young students about conditions on
other planets," explained Dr. Tony Phillips, who is evaluating the
concept in classrooms. "The basic ingredients
for a planet in a bottle are 1 cup of warm water, 3 sugar cubes, a 1/4 oz. packet
of yeast, a half liter plastic water bottle, and a nine inch party balloon.
Simply mix the sugar, water, and yeast in the bottle, and cap the
bottle with the balloon. A healthy sample of yeast will inflate
the balloon to 12 inch circumference in less than an hour."
What happens is this: In the nutrient broth --
warm water containing both dissolved oxygen and sugar --
yeast metabolizes the sugar and produces carbon dioxide.
The rate of carbon dioxide production at any given instant is
proportional
to the number of healthy microbes in the bottle. Because
the yeast are constantly reproducing through cell division the
number of microbes increases exponentially. Likewise, carbon dioxide
production increases. The balloon inflates slowly at first, then
rapidly accelerates.
In practice the balloon inflates to maximum volume in about 45 minutes.
That's when the yeast have consumed all the available nutrient. At
room temperature the cells remain viable for several hours afterward
and then begin to die.
The maximum volume of CO2 and the time required to produce
the gas can be used to estimate the number of healthy microbes in the
original sample.
Click here for a sample
"Planets in a Bottle" lesson plan
"Two weeks ago we visited Mrs. Walter's 3rd grade classroom in Bishop,
CA" continued Dr. Phillips. "The class was divided into seven groups,
each with the basic ingredients for a Planet in a Bottle. Rather
than have every group do the same experiment, we added variations
so that each bottle would represent a different planet. For example,
the Moon has no atmosphere to protect its surface from solar UV radiation.
So, one group exposed their yeast to a UV lamp before adding the microbes
to the nutrient mix, creating a "Moon in a Bottle." Another group
used scalding hot orange juice as a nutrient mix for
'Venus in a Bottle.' Citric acid in the orange juice served as
a substitute for sulfuric acid in Venus's hot atmosphere."
Above: Young scientists
monitor yeast growth in a bottle labelled "Pluto". In this case the yeast were
frozen for weeks before being added to the nutrient mix.
"Clearly we can't reproduce true planetary conditions in a
simple water bottle, nor did we pretend to,
but these excercises have powerful teaching value. Every kid
in Mrs. Walter's class now knows that Venus has acid in its atmosphere
thanks to the orange juice experiment, and they also learned that
weak acids are not deadly to yeast," Phillips said.
"My students were really excited when their balloons began to inflate,"
recalled Mrs. Walters, "but the best part came at the end when we
measured the
sizes of the balloons and held a classroom debate about the results.
We argued about which planet was most congenial to yeast and what the
limitations of our results were. It felt like real science."
Left: Students in Mrs.
Walter's 3rd grade class debate the question: "Which planet is really best for yeast?"
NASA scientists have
a crowded schedule of classroom
visits planned in the months to come, even though the
Life on the Edge yeast container won't be retreived for
some time. The goal is to develop safe and
effective classroom protocols before the yeast
packets are distributed nationally.
"We don't want to spoon feed students with overly-detailed protocols,"
says John Horack," That's not science. But, we do want to give them
a good starting point for their own creative experiments with
extremophiles. The only way to do that is by spending lots of time in
the classroom now, while the microbes are still in the White Mountains."
To view a prototype lesson plan for "Planet in a Bottle"
yeast experiments click here.
Readers are invited to try the experiments
(they are lots of fun) and we welcome comments from
educators and others to improve our procedures.
Please send comments and
suggestions to james.a.phillips@earthlink.net.
 We're
looking for a few good volunteers
Next month we'll be inviting educators, students, and other scientists
to join us as participants in Life on the Edge. If you
have an interest in learning about life in extreme environments,
you'll be able to sign up to receive a sample packet of microbes
returned from the White Mountain summit. What's it cost? Nothing!
We'll simply ask that you try out some of our classroom-safe
lab protocols and give us your feedback. If you're interested
please sign up
for our Partners in Discovery program. |
Life on the Edge is a collaborative educational project being
developed between NASA/Marshall Space Science Laboratory, the
University of California White Mountain Research Station (WMRS)
and the
Center for Astrophysical Research in Antarctica (CARA).
Participants include David Noever, Richard Hoover, Tony Phillips,
John Horack, and Dale Watring of NASA; Dave Trydahl,
Joe Szewczak, and Susan Szewczak of the WMRS.
|
Life on the Edge FAQ
 What is Life on the
Edge? Why study life in extreme environments? How do I become
involved?
The answers to these and many other questions about Life on the
Edge may be found on our Frequently
Asked Questions web page.
|
|
Join our growing list of subscribers
- sign up for our express
news delivery and you will receive a mail message time we post a new story!!!
Headlines
