Martians?Life on Mars

ASTR 1420

Lecture 12

Sections 8.1-8.5

Fantasies of Martian Civilization

• William Herschel (late 1700s)o discoverer of Uranuso discovered polar ice caps of Marso discovered the length of the Martian day

(24h 37 min)o noticed permanent marks on the surface“… inhabitants probably enjoy a situation in

many respects similar to our own!”

• Giovanni Schiaparelli (late 1800s)o discovered 79 linear features (“canali”)

meaning “channels”, but incorrectly translated as “canals”

• Then, Percival Lowell…

Ground-based image of Mars

Percival Lowell(1855-1916)

• He knew that not all astronomers see Schiaparelli’s canals…

• He thought that it is due to poor “seeing”

Built an observatory in 1894 at Flagstaff, AZ to observe Mars… Due to the astronomical seeing effect, long exposed

pictures get blurry.

On top of Mauna Kea

Lowell’s interpretation of Martian surface

• Mapped 200 canals. He knew about Mars being arid and its polar ice caps…• Canals transportation of water from poles to equator cities…• One global network a single nation.

• But, many scientists did not believe his claim (w/o confirmation).• Excepting a couple of large geometrical features, his canals were purely imaginary!• All scientists abandoned Martian canals (by 1910), but the idea of the advanced Martian

civilization persisted among public for a long long time!

Martians’ Attack!

A famous science fiction written by H. G. Wells, “The War of Worlds”.

Orson Welles’s 1938 radio broadcasting…

Intro..

Martians startattacking with their thermal beam!

Mariner 41965

• Still on-going debate on the Martian canals and cities in 60s

• No canal ! (no hint of advanced civilization)

Viking Landers1979

Viking Lander 1 & 2 : 1979

• Two landers within two months landed at nearly opposite sites across the planet.• And two orbiters…• A thin coating of ice on the rocks and

soil…

Many images over several months… No visible life.

“Face on Mars” and other ancient relics…

• When you deal with 100,000 of images, you can always find some odd patterns!

“Face on Mars” in 1976Viking 1 orbiter

Mars Global Surveyor 1997

Liquid Water from the Underground.

August 1999September 2005

Pathfinder + Sojourner1997

• Mars lander, Pathfinder, on July 4, 1997.• Its rover, Sojourner, could travel 10-20m

away from the lander.

Martian Water Today

Mars Odyssey : Hydrogen content of the soil = existence of Water. Blue highest content…

Frozen Sea structure?

on Mars

on Earth

Wet Red Planet!!

• NASA's Mars Reconnaissance Orbiter took images of a fresh, 6 meter wide crater on Mars on Oct. 18, 2008, left, and on Jan. 14. The impact exposed water ice from below the surface.

Climate History of Mars• We saw evidence of liquid water on the Mars.• Why was Mars warmer and wetter in the past?o If Mars had about 400 times more CO2, then it could have liquid water on the

surface via a stronger greenhouse effect and denser atmosphere.o If the composition of outgassed material was the same as Earth’s, then it should

have enough H2O to fill oceans hundreds meters deep.

• However, the Sun was dimmer in the past CO2 alone could not have warmed the ancient Mars’ atmosphere high enough…o Possible solutions

1. enhanced greenhouse effect by other gases such as methane2. young Sun was not that dimmer3. Mars never had an extended period of warmth liquid water only after major impacts…

• It was never Earth-like, but Mars was certainly warmer and wetter!

Where did CO2 go?

• Mars lost significant amount of CO2 where did it go?o condensed to polar capso chemically bound to surface rockso remain in the atmosphereo lost to space

• Why such a change? mainly due to its small size!!

Small size of Mars

• It is large enough to have volcanism and outgassing in the beginning…• H2O got also dissociated by solar UV radiation: 2H2O 2H2 + O2

o H2 got escaped quickly while O2 rusted the rocks and lost to space over time…

Small size lost internal heat

rapidly… outer core solidified weakened magnetic

field became vulnerable to

solar winds being stripped off

Short-term climate changes of Mars

After losing its atmosphere and H2O, has the climate of Mars unchanged for the past 2-3 Gyr?

No. The climate had changed with period of hundreds of thousands years!

Ice ages of Earth due to the change of obliquity. 22° - 25° : small range due to the stabilizing effect of the large Moon

Mars does not have a large moon. Closer to Jupiter a much wider range of obliquity change, 0° - 80°

Larger obliquity warm summer pole more CO2 stronger greenhouse effect warmer temperature.

Even with this, average T couldn’t maintain surface liquid water, but high enough to have liquid water just beneath the surface!

Is Mars habitable?• Mars haso chemical elementso energy Sun light + chemical energy(?)

• Current surface of Mars is not habitable due to no liquid water

• However, during the high obliquity periods, Martian surface might have been habitable!

• Subsurface has been habitable throughout the period until now.

Time to search!

Evidence of Life on Mars?

• There are some scientific claims already about the existence of life on Mars

on-going debate!

• Three groups of claims1. based on Viking lander data2. from Martian atmosphere studies3. from Martian meteorites

Viking Experiments

Examine the soil of Mars to see if there are any living microbes. Two Viking landers in 1976

Four experiments1.carbon assimilation

experiment2.gas exchange

experiment3.labeled release

experiment4.gas chromatography

1. Carbon Assimilation Experiment

Mix Martian soil with terrestrial CO2 and CO ( with 14C) : if these gases were used by life, then 14C would get incorporated into the soil

Yes! Some 14C were incorporated!

repeated experiments after 3 hours of cooking the soil at 175°C a hint of 14C assimilation still Must have been a non-biological process of processing Carbon

12C : 98.9%13C : 1.07%14C : <10-12

2. Gas Exchange Experiment

Mix the soil with organic nutrients and check for any released gas (e.g., O2 for terrestrial photosynthesis)

O2 was released!

But, similar result from an experiment with no sunlight!?!

O2 detection even after a thermal treatment of the soil

Non-biological process

3. Labeled release experiment

Mix the soil with organic nutrients that were tagged with radioactive 14C and 35S

if nutrients were used by Martian microbes, byproducts containing 14C and 35S would be detected via radioactivity.

Yes, indeed! Repeated an experiment after cooking

the soil at 160°C then no detection! Evidence of Life??

4. Mass Spectrometer

Measuring the level of organic molecules…

This is the one that made most scientists believe that Martian soil does not have microbes…

What is this experiment??

ALH84001: a 1.93kg meteorite found in Allan Hills, Antarctica on December 27, 1984

Martian Meterite : ALH84001, a magnetite?

Magnetobacteria magnetite is known in similar crystals on Earth only when deposited by bacteria

ALH84001 : nano-fossils

nano-fossils

nano-fossils

Another microfossil-like structure from ALH84001

Is (was) there life?• Occam’s razor? what’s the verdict?

• Need more concrete information more missionso Phoenix lander (2007 launched, 2008 landing)o Mars Science Laboratory (launched 2011 Nov, arrive in August 2012!!!)o Mars sample return (ESA, Aurora)

Prevent contamination !?!

Phoenix Lander Highlights• Lander dug up Martian soilseveral ice blocks were

exposed which were sublimated over 3-4 days

“sol” = Martian day = 24 hrs 39min

Pheonix lander confirmed water ice

In summary…

Important Concepts• Fantasy of Martian Civilization• Characteristics of Mars• Seasons of Mars• Climate history of Mars• Evidences of Water • Reason for Mars climate change• Viking Lander Experiments• Evidence of Life from ALH84001

Important Terms• Martian canals• ALH84001• nano-fossil

Chapter/sections covered in this lecture : 8.1-8.5Life on Jovian Moons : next class!!