Transcript Slide 1

ActivityYour
3.3
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Get the Signature!
Focus Question: What is a
biosignature?
A biosignature is a sign of
present or past life.
•Fossils
•Tracks
•Burrows
•Chemicals
Focus Question 2: How does the study of biosignatures
help scientists search for life on Mars?
By studying
biosignatures here
on earth, scientists
can train themselves
to recognize the
signs of Martin life
Linda Jahnke
Microbiologist
NASA Ames Research Center
Microbial Mats
• Layers of
microorganisms
• Believed to be among
the first forms of life
• May have been on Mars
in the ancient lakes or
oceans
Microbial Mats
Jahnke and fellow
researchers:
• grow and analyze the
living mats at Ames
Research Center.
• develop methods to look
for the chemical
biosignatures of ancient
microbial mats on Earth and
Mars
Using Chemical Biosignatures of Microbial Mats
• show modern microbial mats are
similar to those that existed billions
of years ago on earth
• someday compare Earth’s
microbial mats with mats from Mars
Chromatography* is used to determine
the specific chemicals found in
microbial mats.
* A process in which a chemical mixture is
passed through a material that separates it
into is parts. This leaves a unique chemical
signature
Activity 3.3 Get the Signature! Objectives
• Use chromatography to analyze biosignatures
• Compare biosignatures from different life forms
• Draw conclusions about how biosignature
scientists search for life on Mars
Teacher Preparation Chromatography Paper
• Tape each paper strip to the middle of a
Popsicle stick
•With a pencil and ruler, draw a line across
each paper 2 cm form the bottom
•Store in a zip-lock bag
Teacher Preparation
Pigment extraction
Carrots – Boil carrots for
25 minutes, crush them,
add 5ml to a petri dish for
each group
Spinach – Using a garlic
press, crush fresh spinach.
Put 5 ml of crushed spinach
into a petri dish for each
group
• Dip a toothpick into the crushed
spinach -paint a green line over
the pencil line
•Allow the strip to dry - paint a
second green line
• Repeat with cooked crushed
carrot
Chromatography Paper
Student Activity
Chromatography Paper
Student Activity
• Place strip into the cup –
submerged in about 1 cm deep
of isopropyl alcohol
• Wait 15 min, or until alcohol
travels most of the way up strip
• Remove the paper strips and
allow to dry
Chromatography Paper
Student Activity
• Observe bands of color
• Each band of color represents a
different pigment that is present in
the spinach or carrot
• These patterns the chromatograms
- or chemical biosignatures
Observations/Conclusions
Families of pigments
•Carotenes
•Chlorophylls
•Xanthophylls
For Further Exploration
Calculate the retention factor (Rf) for each pigment –
Rf = Distance a component travels (Dx)
Distance a solvent travels (Ds)
Thin Layer Chromatography (TLC)– greater speed,
sensitivity and resolving power over paper.
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