Transcript Slide 1 - BYU Physics and Astronomy

Determining Favorable
Environments for Endolithic
Growth From Physics
Considerations
Doug Archer, Dr. David Allred
Dept. of Physics and Astronomy
Brigham Young University
What’s an Extremophile?
Extremophile’s are
organisms that can
live in extreme
environments
 Examples are
Halophiles,
Thermophiles, and
Endoliths

Limits on Life
 Lack
of Liquid Water
 Temperature extremes
 Ultraviolet Radiation
 Soil toxicity
 Sparse Energy Resources
Mars Had Water in the Past and
Still Has Water Today
Temperature Concerns
 Mars’
Temperature range -123C to
20C
 Once thought a major concern, the
discovery of Extremophiles
metabolically active from -15C to
120C has changed our thinking.
 Active->Dormant cycle
Ultraviolet Radiation
 UVA
= 400-315nm
 UVB = 315-280nm
 UVC = 280-200nm
 Below ~290nm, UV energy is very
damaging to most biological
systems.
 It affects proteins, lipids, and most
importantly, DNA.
UV Flux, Earth vs. Mars
Present
Day Earth
Present
Day Mars
Early
Earth
Early
Mars
UVC and UVA
DNA
B
effective
(W/m^2)
irradiance
1.86
52.81
.1
13.2
41.5
116.4
5.2
34.1
41
4.8
22.3
33.8
The Role of Ozone
The Chapman
Reaction describes
ozone
creation/reaction.
 Ozone absorbs
between 200360nm
 Mars’ ozone layer
is <1% of earths at
maximum

UV Damage
Surviving UV
 There
are three primary methods:
– Avoidance: chemoautotrophs
– Repair: photolyase cuts thymine dimers.
Present in modern branches of ancient
archaebacteria.
– Protection: Matting, Substrate
Production, Physical Environment
Sheltering.
Why Endoliths?
 Endolithic
communities, also known
as cryptoendoliths, could provide
protection from numerous life
limiting conditions.
 We have ready access to endoliths in
the Southern Utah Desert.
Physics Concerns

Which compounds found in common
minerals block UV?
– This is a function of band gap

Is UV light preferentially absorbed or
scattered out of certain materials?
Rayleigh vs. Mie scattering
– Particle size (<1/10 wavelength=Ray.)
– Wavelength Dependence (λ^4 vs λ)
How fast does the intensity drop as a
function of depth and wavelength
 To what extent is color important and how
is it produced?

Martian Minerology
Sample
Na2O
MgO
Al2O3
SiO2
SiO3
K2O
CaO
TiO2
Fe2O3
Near Yogi
3.7
8.1
8.9
46.8
6.3
0.2
5.5
1.4
15.6
Scooby Doo
1.9
6.9
8.9
50.3
5.2
0.5
7.1
1.1
14.5
--
7.4
7.2
44.1
10
0.9
5.9
0.6
18.3
Rocky Flates:crust
Absorption Example
K values for Fe2O3
1.4
1.2
K
1
0.8
0.6
0.4
0.2
0
200
300
400
500
Wavelength (nm)
600
700
800
Correlate and Compare
 Minerals
with Fe203:
– Hematite, Maghemite
 Compare
to Martian minerals using
spectography and terrestrial
analogues.
– USGS Imaging Spectroscopy
– Have found abundant Olivene
(Mg1.6Fe2+0.4(SiO4))
Remaining Questions
 Can
microporosity and capillary
action act to prevent or lessen
dessication of the cryptoendoliths?
 How can we robotically detect the
presence of Endoliths?
Conclusions
Given what we know about the early
history of Earth and Mars, it is not a
stretch to theorize that life appeared
simultaneously. Earth provided a more
successful habitat, but conditions on Mars
do not preclude the continued presence of
life.
 Endolithic habitats provide a refuge from
many of the limiting factors on life as we
know it.
