ASTR 1420 Lecture 12 Sections 8.1-8.5 Martians? Life on Mars ASTR 1420 Lecture 12 Sections 8.1-8.5

Fantasies of Martian Civilization William Herschel (late 1700s) discoverer of Uranus discovered polar ice caps of Mars discovered the length of the Martian day (24h 37 min) noticed permanent marks on the surface “… inhabitants probably enjoy a situation in many respects similar to our own!” Giovanni Schiaparelli (late 1800s) discovered 79 linear features (“canali”) meaning “channels”, but incorrectly translated as “canals” Then, Percival Lowell… Ground-based image of Mars

He knew that not all astronomers see Schiaparelli’s canals… Percival Lowell (1855-1916) He knew that not all astronomers see Schiaparelli’s canals… He thought that it is due to poor “seeing” On top of Mauna Kea Built an observatory in 1894 at Flagstaff, AZ to observe Mars… Due to the astronomical seeing effect, long exposed pictures get blurry.

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 start attacking with their thermal beam!

Still on-going debate on the Martian canals and cities in 60s Mariner 4 1965 Still on-going debate on the Martian canals and cities in 60s No canal ! (no hint of advanced civilization) 1st Mars mission: 1960 by USSR. Failed + a handful of failed mission by USSR. 1963, Mariner 3 by NASA (wrong orbit…) 1964, Mariner 4 by NASA: First successful Mars mission. Fly-by Mars on Jul 14, 1965.

Viking Landers 1979 Many images over several months… No visible life. 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… Since Viking landers  no Mars mission for ~20 years! Many images over several months… No visible life.

“Face on Mars” and other ancient relics… Mars Global Surveyor 1997 “Face on Mars” in 1976 Viking 1 orbiter Mars Global Surveyor : 1997-2006 When you deal with 100,000 of images, you can always find some odd patterns!

Liquid Water from the Underground. August 1999 September 2005 new deposit (~500m long) : liquid water still flows occasionally… gullies formed when liquid water emerges from beneath the ground. Underground ice got melt and gushes out from the crater walls. Mars Global Surveyor images.

Pathfinder + Sojourner 1997 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? 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. 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… Possible solutions enhanced greenhouse effect by other gases such as methane young Sun was not that dimmer 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? condensed to polar caps chemically bound to surface rocks remain in the atmosphere lost to space Why such a change?  mainly due to its small size!!

Small size of Mars Small size lost internal heat rapidly… outer core solidified weakened magnetic field became vulnerable to solar winds being stripped off It is large enough to have volcanism and outgassing in the beginning… H2O got also dissociated by solar UV radiation: 2H2O  2H2 + O2 H2 got escaped quickly while O2 rusted the rocks and lost to space over time…

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!

Time to search! Mars has Is Mars habitable? chemical elements 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 claims based on Viking lander data from Martian atmosphere studies from Martian meteorites

Viking Experiments Examine the soil of Mars to see if there are any living microbes.  Two Viking landers in 1976 Four experiments carbon assimilation experiment gas exchange experiment labeled release experiment 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 Thermal anneal : 3hours of cooking the soil at 175C  to kill all microbes and destroy other organic materials

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 Thermal anneal : 3hours of cooking the soil at 175C  to kill all microbes and destroy other organic materials * measures the molecular weight of each chemical. It could measure molecules present at a level of only a few parts per billion. However, the GCMS measured no significant amount of organic molecules in the Martian soil. In fact, martian soils were found to contain less carbon than lifeless lunar soils.

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??

Martian Meterite : ALH84001, a magnetite? Magnetobacteria  magnetite is known in similar crystals on Earth only when deposited by bacteria ALH84001: a 1.93kg meteorite found in Allan Hills, Antarctica on December 27, 1984

ALH84001 : nano-fossils

nano-fossils electron micrographs showing tiny structures that look remarkably like microorganisms or microfossils. These are smaller than it was thought free-living terrestrial organisms could be, an objection that has shrunk with the study of nano-bacteria.

nano-fossils

Another microfossil-like structure from ALH84001

Is (was) there life? Occam’s razor?  what’s the verdict? Need more concrete information  more missions Phoenix lander (2007 launched, 2008 landing) Mars Science Laboratory (launched 2011 Nov, arrive in August 2012!!!) Mars sample return (ESA, Aurora) Pathfinder  Spirit/Opportunity  MSL rover “Curiosity” (about a size of a small car, max speed = 90m/hour) : mobility (3-12 miles) for more diverse collection of sample!! Prevent contamination !?!

Phoenix Lander Highlights Lander dug up Martian soil several 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 Important Terms 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 Martian canals ALH84001 nano-fossil Chapter/sections covered in this lecture : 8.1-8.5 Life on Jovian Moons : next class!!