Transcript The Origin and Evolution of Life on Earth

Happy Halloween!
Homework #6
Due 6:00 pm today
Exam #2 on Wednesday
Could Mars once have been warm and soggy?
And could Mars have/had life?
Much has been learned from
orbiters/rovers that are active today
Orbiters:
Mars Reconnaissance Orbiter
Mars Express
Rovers:
Spirit
Opportunity
Early Mars was similar to Earth
Evidence of past water flows
• The current thin, cold
Viking Orbiter image
atmosphere prohibits
liquid water from being
stable on the surface.
• However, there is ample
evidence for past water
• 3 flavors of flowing
surface water:
1) Valley Networks (really old)
2) Outflow Channels (pretty
old)
3) Gullies (really young)
10 km
500 km
MOLA topography
Outflow Channels
• Formed from catastrophic
release of groundwater in
mid to late Martian
history.
older,
degraded
channel
system
different
flow paths
Orbital photos from
Mars Express
show features
similar to ice
patterns seen in
Antarctica: dust
covered “frozen
sea”?
Sedimentary rocks
Main evidence for a “warm and wet” ancient Mars
• Valley networks
• Widespread highland erosion (up to a km of crust
lost)
• Chemically weathered components of the crust
• Mars Exploration Rovers show clear signs of
groundwater interaction and possible signs of
standing bodies of water
Did the Northern Lowlands Once Contain an
Ocean?
Northern plains
Northern plains
Tharsis
Valles
Marineris
It is quite possible!
Evidence of current water flows
Martian gullies are the
best evidence for liquid
water on Mars today.
These fresh-cut
features are found on
the inner walls of some
craters and the old
runoff channels.
For water to produce
these features, it must
have been released in
a torrent, for a slow
trickle will not suffice.
This image shows
recent gullies in a
crater wall.
Gullies
Where did the water go to?
• Mars (and Venus) lost most of their water
to space.
• For Mars, frozen water is tied up in the
subsurface and polar caps
• Mars’ geologic history was once
warmer and wetter than now.
Climate History
• Atmosphere warmer in the past
– Greenhouse effect due to CO2 and some CH4
• Loss of CO2 to space
–
–
–
–
Polar caps insufficient to account for missing CO2
No good evidence for carbonates
Loss via impacts
Loss via the solar wind, which is not well deflected
because of weaker magnetic field (core cools faster)
• Loss of H2O
– Loss via impacts
– UV breaks up H2O and H2 escapes easily
Life on Mars???
• Based upon our understanding of biology, Mars
has all the necessary ingredients for life
– Water, an energy source, and the basic elements and
compounds required make life.
• Mars likely had a very different climate in the past
that was more hospitable to life.
• Life on Earth is exceptionally tough (lives and
survives under extreme conditions)!
Meteorite from Mars
• ALH84001
– possible
evidence of
fossil microbes
from Mars?
Life on Mars? Martian Meteorite.
Fossil
Life?
If this is life it is very small in size. Too small?
Some scientists are convinced it is life.
Most are still unsure.
Life on Mars?
It has been proven there is water ice on Mars.
Probably below the surface today but a large
ocean in the past.
Water  reasonable possibility of life
but is it extinct, dormant or alive?
Life on Mars today?
Direct search by space probes
1976 Viking probes - inconclusive
2003 Beagle II – crashed on landing
Methane & Water!
Data obtained by the Mars Express probe show that water
vapor and methane gas are concentrated in the same regions
of the Martian atmosphere.
Methane & Water!
Data obtained by the Mars Express probe show that
water vapor and methane gas are concentrated in
the same regions of the Martian atmosphere.
 Must be recently made!
 Methane only lasts about 100 years (UV light destroys it)
 Life (micro-organisms) or volcanoes?
 If microbes are making methane in the Martian atmosphere
as part of their living process, they would rely on water.