AGA 0316
Buscando a vida fora da Terra: Marte Why Mars is important for Astrobiology? • Relative proximity – first planet where we can realistically test in loco for biological potential and life • Mars is in many ways similar to Earth. Rocky, terrestrial planet in the inner part of the Solar system with an atmosphere. Yet it is also very different. • Therefore if life is found there it would be a very strong argument in favor of life being an ubiquitous phenomenum in the galaxy History of Martian “Civilization”
• In 1784 William Herschel (famous for the discovery of Uranus) claimed that Mars has an atmosphere and is therefore probably inhabited. • Giovanni Schiaparelli claimed to see a network of 79 linear channels (canali) in 1877 • Percival Lowell opened Lowell Observatory in Flagstaff, Arizona in 1894. (claimed to see 200 canals) • Lowell suggested that canals were built by an ancient martian civilization. Giovanni Schiaparelli
William Herschel Percival Lowell • In 1965 “Mariner 4” spacecraft send a few dozen good pictures of the Martian surface – no evidence for intelligent life. Mars is in fact a cold and dry planet! 6 7 9
1960’s
1970’s
1990’s
2000’s
Pathfinder & Sojourner
Spirit + Opportunity Mars Fact Sheet Parameter Value Units Diameter 6787 km Average Distance From the Sun 1.524 AU EARTH’S Atm
Average Temperature 210 K (-81 F) CO2 0.04% 3 Mean Density 3.94 g/cm N2 78,1% Rotational Period 24.6229 hours Ar 0.93%
Mean Atmospheric Pressure 0.007 bars H2O 0 – 4 % Surface Gravity 3.63 m/s2 Tilt of Axis 25.2 degrees Orbit period 687 days
Atmospheric Components
Element Symbol Percentage
Carbon Dioxide CO2 95.32 Nitrogen N2 2.7 Argon Ar 1.6
Water H2O 0.03 Earth-Mars Similarities
• Position in the Solar system – Martian orbit is 1.5 A.U.; Earth’s is 1 A.U. but Neptune’s is 30 A.U. • Similar bulk chemical composition – Si-rich crust and mantle and Fe-rich core • Size – Mars is only twice smaller than Earth by radius
• Atmosphere has greenhouse gas (CO2) and some amount of nitrogen • Volcanoes • Similar rotation rate – 24.6 hours • Plenty of water (frozen; subsurface?) Earth-Mars Differences
• Earth has a global-scale plate tectonics, Mars does not. • Earth has global oceans at its surface, Mars has not • Martian atmosphere (0.007 bar) is much thinner than Earth’s ( 1 bar) • Earth has an intrinsic global magnetic field, Mars has not Problems for life on the Martian surface
• Cold (average temperature ~220K); not many known organisms on Earth can grow under these temperatures • Thin atmosphere – open liquid water is unstable • Very small amount of oxygen – no terrestrial-like animal life • Very little ozone – no UV protection • No magnetic field – poor protection from the cosmic rays Problem
Water does not have a liquid phase under current low Martian pressures. Ice sublimates to water vapor directly.
However, there are strong evidence that liquid water was present in the past on the Martian surface Evidence for liquid water on the Martian surface
• Geomorphological evidence: 1) Look for features that are similar in appearance to terrestrial water-formed features 2) Degradation (weathering) of the ancient impact craters (erosion) • Mineralogical evidence MARTIAN SOIL FLOOD TRACES ON CRATER WALLS
Valley network on the ancient terrain of the martian surface. Notice that valleys converge downstream. Individual valleys are about a kilometer across. Flood channel occurring on a relatively young surface. Note the well-defined margins of the channel indicating confined flow and the streamlined, tear-drop- shaped islands where erosional remnants have been left behind obstacles. Even the youngest features on Mars appear to show evidence for liquid water. Gullies have been identified on the walls of canyons, channels and impact craters. Most likely were formed by seepage of water from within the crust.
Martian Meteorites
• Meteorites which originated from Mars – impactors hit Martian surface and some small fraction of the ejected rock can arrive on Earth • Although > 31,000 meteorites were found, only 34 have been identified as Martian meteorites How do we know that some meteorites are from Mars? • Age. Almost all martian meteorites are relatively young volcanic rocks (180-1300 Myr) with composition similar to terrestrial basalts • Oxygen isotopes are distinct (16O, 17O, 18O) from terrestrial rocks and group all 34 meteorites together • The isotopic composition of gases trapped in the meteorites is almost identical to the Martian atmosphere (comparison with Viking measurements). The oxygen isotopic compositions of rocks from Earth, Mars, and the asteroid Vesta, the largest asteroid that melted, define three parallel lines on this plot of 17O / 16O vs. 18O / 16O. The lines are parallel because on each body the oxygen isotopes were separated according to their masses, when the rocks formed. Classification of Martian meteorites (SNC: shergottite, nakhlite, and chassigny )
• 1 billion tones of Martian rocks crashed into Earth ! • Shergottite (Shergotty meteorite from India, 1865) - 25 • Nakhlites (Nakhla meteorite from Egypt, 1911) - 7 • Chassignites (Chassigny meteorite from France, 1815) - 2 Evidence of water in SNCs
• Carbonate minerals. Liquid water flows
through fractures in rocks and dissolved CO2 can be precipitated. • Hydrated minerals with martian D/H
Electron Microscope image of clay and carbonate (siderite) vein in Lafayette section. ol olivine. ALH84001
• Shergottite which containes structures that were considered to be the fossilized remains of bacteria-like lifeforms. Viking Mission
• Two orbiters, two landers • Two landers landed on the opposite sides of Mars in 1976 • The Viking 1 Lander touched down at 22.7° N latitude and 48.2° W longitude • The Viking 2 Lander touched down at 48.3° N latitude and 226° W longitude Viking Results • Viking carried 4 instruments designed to detect any sign of biology: • The Labeled Release (LR), Gas Exchange (GEX), and Pyrolytic Release (PR) experiments, all designed to detect existent life on Mars. • The Gas Chromatograph/Mass Spectrometer (GC/MS) was capable of detecting organics at a level of a few parts per billion (ppb) Pyrolytic Release experiment (PR)
• Martian soil was put in a chamber and
exposed to CO2 and CO mixture 14 • CO2 and CO were labeled with C • Idea: “If biota were in the soil it would
incorporate some CO2 or CO and convert it to organic material” • Heat the soil → break organic material → look for release of 14C Gas exchange (GEX)
• Martian soil was put into a chamber and mixed with plenty of different nutrients (amino acids, glucose, salts, vitamins ..)
• Look for H2, N2, O2, CH4, CO2,and Ar, Kr (for calibration) released from the soil (bacteria?). Labeled release (LR)
• Martian soil was put into a chamber and mixed with nutrients (glucose and sulfate) enriched in 14C and 35S • Look for gas release enriched in 14C and/or 35S (released by bacteria?) LR - TSM Biology Package • What the Viking biology experiments found:
Expected Response for Expected heat- Response for heat- sterilized Response for sample w/ sterilized Control Experiments sample Biology control Response
GEX oxygen emitted oxygen emitted oxygen emitted none
LR labeled gas emitted labeled gas emitted none none
PR carbon detected carbon detected carbon detected none
• The GC/MS detected no organics above the 10 ppb level What we expected • This was surprising as each year, 2.4 x 108 grams of reduced (organic) carbon is delivered to Mars each year by meteors, which should have been detectable by the Viking GC/MS. • Even without life, organics were expected. • With regolith mixing to a depth of 1 km, organics should be present at about 500 ppb. Viking Conclusions • It was concluded that the Martian surface is rich in UV-produced oxides and superoxides at the ppm level, which destroy any organics present. • This conclusion reconciles the apparently contradictory results of the other Viking life experiments.
• However . . .(cf. OH-based life) The Atacama desert
• Gonzáles et al. use the oxidizing soil and hyper- arid conditions in the Atacama Desert as an analog for the Martian surface. • They analyzed the Atacaman soil with a GC/MS to compare with Viking results. What they found
• In the most arid sample, both formic acid and benzene were found when pyrolized at 750ºC. • However, Viking pyrolysis temperatures maxed out at 500ºC, so . . . • Using the Viking pyrolysis temperature, the formic acid detected was reduced by a factor of 4 and there was no benzene detected at all.
formic acid benzene • All three Viking’s experiments assumed that we would be able to culture potentially present martian organisms. • Even on Earth only 1 in 100 organisms can be cultures at best. • Viking results do not rule out the possibility of life in the martian soil. • Is there another way to discover martian life? Arguments in favor of “life on Mars” from ALH84001 • Presence of polycyclic aromatic hydrocarbons (PAHs). PAHs can form as decay products of microorganisms • Presence of magnetite crystals whose structure is very similar to crystals produced by some terrestrial bacteria • Ovoid structures in carbonate globules similar to terrestrial microbes PAHs Carbonate globules (50-250 m)
Ovoid structures (20-100 nm) Magnetite crystalls
(Fe3O4) History of ALH84001
• Age ~4.5 Gyr old (rock crystallized) • Carbonate globules are ~3.9 Gyr old • Rock remained on the surface of Mars until 16 Myr ago when it was ejected • Meteorite was captured by Earth 13,000 years ago and fell into Antarctica • Covered with snow and ice until 700 years ago • Recovered in 1984 Summary of ALH84001
• Most of the morphological fossils are thought to be too small to represent living organisms • Most of the organics are terrestrial in origin and the martian organics could have been produced by nonbiological processes • The magnetite grains are thought to represent the strongest evidence for life • McKay et al. found fossil like structures in other Martian meteorites (Nakhla 1.3 Gyr and Shergotty 165 Myr)
Can martian biota “hide” in the terrestrial biosphere? • Primitive life is very resilient. Some bacteria can grow under -15 C (and lower). Some bacteria has tolerance to extreme desiccation. Some bacteria are tolerant to UV and ionizing radiation. • Suppose a microorganism from Mars survived a trip to Earth • How would we distinguish between martian and terrestrial bugs? One possible clue is the ability to adapt to environments that could never have happened on Earth. (Pavlov et al., 2006)
Radioresistance – tolerance to ionizing radiation (p.n,-rays)
High radioresistance - totally unnecessary ability on Earth. Why are there bacteria like that on Earth? Why were them selected on Earth? Radioresistance
1. Extremely radioresistant bacteria : Deinococcus radiodurans , Rubrobacter radiotolerance, Rubrobacter xylanophilus, Chroococcidiopsis, Termococcus gammatolerance. Radioresistance is 100-1000 times higher than in other microorganisms 2. High doses of ionizing radiation create a lot of DNA damages and radioresistant bacteria have an unknown and unique mechanism for DNA repair (more 100 double strand breaks) 3. Lethal radiation dose >> dose accumulated during the lifetime of the radioresistant bacteria (by 10 orders of magnitude). Time of accumulation of the lethal doses is 106 – 108 years.
Totally useless on Earth! Hypothesis
• Radioresistant bacteria originated on Earth • Bacteria was transferred to Mars by meteorites • On Mars microorganisms acquired radioresistance ability • Radioresistant bacteria were transferred back to Earth by Martian meteorites
0 -1 -2
lg S lg -3 -4 -5 0 2 4 6 8 10 12 D o s e (k G y )
Gamma radiation survival curves of the Еscherichia coli (rhombus) and Deinococcus radiodurans (squares) (Battista et al, 1999). S – surviving fraction of the bacterial population
1 Gy = 1 J/kg 5 Gy is lethal for humans within two weeks Background radiation on Earth: 0.0005 Gy/year Experiment with Deinococcus Radiodurans at LNLS (Lima et al. 2009) Why Mars? Great oscillations in Martian obliquity (period 1.2x105 years) → oscillations of annual insulation of the polar regions → dramatic regular oscillations of global climate and atmospheric mass → long periods of the “frozen state” for subsurface layers → long periods of the bacterial dormancy
Low atmospheric mass , no magnetic field → Irradiation of cosmic rays in subsurface layers of Mars 100-fold of the terrestrial irradiation → Periods of sublethal doses accumulation 104 years. → Total time of “training process” (100 cycles) 106 years Problem with Martian climate
• Plenty of frozen water in the shallow subsurface (Mars Odyssey) • Evidence of the “open” liquid water on the early Mars (Martian meteorite, Water-formed features) • How did early Mars manage to maintain liquid water on its surface? Hydrogen abundance from Mars Odyssey observations
Global map of Mars in epithermal (intermediate-energy) neutrons. Odyssey mapped the location and concentrations of epithermal neutrons knocked off the Martian surface by incoming cosmic rays. Deep blue areas at the high latitudes mark the lowest levels of neutrons, which scientists have interpreted to indicate the presence of high levels of hydrogen. The hydrogen enrichment, in turn, is suggestive of large reservoirs of water ice below the surface. Challenge for the early warm Mars could be much worse.
CO2 can condense in the polar regions at the ground!
Sink for CO2 – volcanoes cannot compensate. Carbonate silicate feedback breaks down.
30% CO2 Atmosphere would start to condense at 200K (-73 C). Suggested solutions for the early Mars
• Additional greenhouse gas (CH4). But! It is hard to justify high levels of CH4 on Mars. • Water was liquid on Mars only after a strong impact. However, some features required millions of years to form and warming effects from impact can not last that long. • Mystery of the warm and wet early Mars remains unresolved …. Phoenix Scout Mission Overview
• Scouts were designed to be relatively low-cost and innovative complements to NASA’s Mars Exploration Program. (Total cost ended up being about $420 Million) Phoenix’s Descent
Landing ellipse size compared to Earth Science Operations Center
Engineers in the Payload Interoperabilit Testbed testing the rasp technique on Sol 50 Surface Stereo Imager PHOENIX LANDED ON MARS ICE SUBLIMATION ON MARS Robot: Self Portrait First Images Exposing Water Ice Touching and Tasting Mars Working Together SSI & RAC images RA scoop with sample going to the Optical Microscope.
Deliveries to OM, WCL, and door open for next TEGA What Phoenix discovered? • TEGA (Thermal and Evolved Gas Analyzer) – Carbonates on Mars! – Can’t quantify this yet, but we definitely saw carbonates, which has implications for past climate and perhaps liquid water. Very high probability of Calcite, possibly other carbonates as well. – Much less sulfur than we expected. Can’t explain this yet. • Weather (MET and SSI) – Snow on Mars! – Saw dust devils in Martian arctic. – Frost formation and fog – Water ice clouds and dust storms – Martian arctic temperatures and pressures for ~150 days • Soil Properties – Very sticky – Very cloddy in some areas What Phoenix discovered? • General – confirmed the hypothesis based on orbital data that there is shallow subsurface water ice on Mars! • Two different types of ice within ~1m. Why? • WCL (Wet Chemistry Laboratory) - – Found perchlorate (ClO4 ) in the Martian soil. Totally unexpected. Perchlorate is harmful to humans, but is used as a source of energy by some microbes. – Also found other chemicals used by life (K, Na, etc.) – Slightly alkaline pH (exact number still being worked on – a little higher than 7) CURIOSITY: amarrissagem em 06/08/2012 CURIOSITY: 1ª foto CURIOSITY em testes CURIOSITY DESCENDO SOBRE MARTE CURIOSITY local da descida: cratera GALE CURIOSITY: esquema de descida Curiosity results* Ancient Mars could have the right chemistry to have supported life. Carbon, hydrogen, oxygen, phosphorus and sulfur found in many rocks that formed in water. Clay minerals and not too much salt suggests fresh water in the past. Evidence of ancient streambed. Smooth and rounded rocks that likely rolled downstream for at least a few kilometers. Structures that are layers of exposed bedrock made of smaller fragments cemented together, suggesting a steady stream of flowing water about half meter deep. High radiation levels during the trip to Mars. They exceed the NASA's career limit for astronauts. Need of protecting against radiation during missions to be safe for human explorers. Lack of Methane. Given that living organisms produce methane, its presence could be a biosignature. Major richness and diversity of soil and rock types. At Gale Crater, there are gravels, streambed deposits, an unusual type of possibly volcanic rock, water-transported sand dunes, mudstones, and cracks filled with mineral veins. All of these are clues to Mars' watery past.
http://mars.jpl.nasa.gov/msl/mission/science/results/
Cratera Garni
Descoberta água líquida em Marte! (28/9/2015)
EXOMARS (ESA, 2016) InSight (NASA, 2018) Perseverance (NASA, 2020)
Cratera Jezero
Ingenuity (helicóptero)
The War of the Worlds (1898)
A Ética do Cosmos
Six Trends The Better Angels of Our Nature, Steven Pinker
• Pacification Process (~3.000 B.C- ) • Civilizing Process (13rd century- ) • Humanitarian Revolution (17th century- ) • Long Peace (1945- 1989) • New Peace (1989- ) • Rights Revolutions (1948- ) ET rights
Sept 21, 2003
1967 UN. Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, Including the Moon and Other Celestial Bodies Europa Mergulho da Galileo em Júpiter 21 de setembro de 2003 Titan Mergulho da Cassini em Saturno 15 de setembro de 2017 MARTE The Martian Chronicles (1950) Ray Bradbury Como podem me tocar estas fantasias de maneira tão íntima?
Prólogo a Crónicas Marcianas de Ray Bradbury Jorge Luis Borges (outono de 1954) Acaso La tercera expedición es la historia más alarmante de este volumen. Su horror (sospecho) es metafisico: la incertidumbre sobre la identidad de los huéspedes del capitán John Black insinua incómodamente que tampoco sabemos quiénes somos ni cómo es, para Dios, nuestra cara. Quiero asimismo destacar el episodio titulado El marciano, que encierra uma patética variación del mito de Proteo. Los marcianos, que al principio del libro son espantosos, merecen su piedade cuando la aniquilación los alcanza. Vencen los hombres y el autor no se alegra de su victoria. Anuncia com tristeza y com desengaño la futura expansíon del linaje humano sobre el planeta rojo...
O PIQUINIQUE DE UM MILHÃO DE ANOS
“Eu sempre quis ver um Marciano”, disse Michael. “Onde eles estão, Pai? Você prometeu.” “Eles estão ali”, disse Papai, e ele tirou Michael do seu ombro e apontou para baixo. Os Marcianos estavam ali. Timothy começou a tremer. Os Marcianos estavam ali – no canal – refletidos na água. Timothy e Michael e Mamãe e Papai. Os Marcianos olharam-se a si mesmos por longo, longo silencioso tempo na água ondulante...