Water the Ancient Climate of Mars and Life

Water, the Ancient Climate of Mars, and Life Brian Hynek Laboratory for Atmospheric and Space Physics University of Colorado

Current Mars Atmosphere • Predominantly CO 2 (~95%) – minor contributions from N 2, Ar, H 2 O, O 2, CO • Global mean temperature = 220 K • Atm pressure = 0. 6% Earth (6 millibars) – this means that water isn’t stable; even in places where the temp gets greater than the freezing point • ~10 precipitable microns of water in the atm

Evidence for Past Water • The current thin, cold 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) * only one that requires a different climate than at present Viking Orbiter image 10 km 500 km MOLA topography

Main evidence for a “warm and wet” ancient Mars • Valley networks – clear evidence of erosion by water – there has been a long standing debate over the importance of surface runoff vs. groundwater processes – more recent works show that precipitation was required to form many of the features • Widespread highland erosion (up to a km of crust lost) • Recently identified chemically weathered components of the crust (TES and OMEGA instruments) – hematite deposits in limited locales – sulfate deposits seen in many settings on Mars – clays (phyllosilicates) also detected • Mars Exploration Rovers show clear signs of groundwater interaction and possible signs of standing bodies of water

Some really convincing evidence of surface flow NE Holden Crater Delta MOC NA images

Global Distribution of Valley Networks

Amazonian (<3 Ga) Valley Networks Implication: 90% of VNs formed in the 1 st billion years of the planet’s history.

Outflow Channels of Mars • Formed from catastrophic release of groundwater in mid to late martian history.

Did the Northern Lowlands Once Contain an Ocean? Northern plains Tharsis Valles Marineris

Where did all the water go? Venus • Deuterium/hydrogen ratios show that Mars (and Venus) lost most all of their water to space. • For Mars, the remaining water is tied up in the subsurface and polar caps Ref: Owen and Bar-Nun, in R. M. Canup and K. Righter, eds. , Origin of the Earth and Moon (2000), p. 463

Missions Greatly Improve Our Understanding of Mars • New data sets & improved resolution can vastly change our view of the planet’s history. One Example – The “Face” on Mars Viking 1976 MOC 2001

What have we learned about water on ancient Mars from recent missions? Specifically, can we determine the role of groundwater vs. surface runoff from precipitation?

Strahler [1958] stream order classification 1 1 1 downslope 1 2 2 2 1 1 2 1 3 3 * Higher stream order corresponds to more mature drainage systems and more contribution from surface runoff

Demonstration of Technique: Mapping Valley Networks with MOLA 128 pix/deg grid and MOC WA atlas (256 pix/deg) in Arc. GIS (much of this could be done in GRIDVIEW) Start with MOLA gridded data Create MOLA shaded relief

Demonstration of Technique: Mapping Valley Networks with MOLA 128 pix/deg grid and MOCWA atlas (256 pix/deg) in Arc. GIS + MOLA shaded relief Overlay MOC WA mosaic with some transparency

Demonstration of Technique: Mapping Valley Networks with MOLA 128 pix/deg grid and MOCWA atlas (256 pix/deg) in Arc. GIS shaded relief + MOC WA Add a bit of MOLA color

blue = previously recognized valley networks by Carr [1995]

Additional valley networks seen in MGS data

Quantitative comparison of previous and new data for previous figure Carr [1995] This Study # mapped valley segments 44 667 stream order 3 rd 6 th 1, 308 11, 161 7. 6 × 10 -3 6. 5 × 10 -2 * total length of valleys (km) drainage density (km-1) * Typical terrestrial values determined in a similar manner range from 6. 5 × 10 -2 km-1 to 2. 09 × 10 -1 km-1 [Carr & Chuang, 1997]

Comparison of old and new data Viking MDIM and Carr VN MGS data and newly recognized VN

Previously mapped unconnected valleys (blue) are now recognized as an integrated drainage system (yellow). Carr VN on Viking base Newly recognized VN from MGS

Numerous VNs head near divides Centered near 1ºS, 22ºE

Conclusions • Combination of MGS data sets provide vast improvement in image clarity and resolution with the added bonus of topographic information. • Using the same defining characteristics for VN as Carr [1995] our mapping reveals an order of magnitude increase in the number of valleys, total valley length, and drainage density over large sections of the highlands. • MGS data show that many previously mapped unconnected, low order segments, are part of larger integrated, mature drainage networks (multiple >5 th order systems).

Implications for Early Climate • Newly calculated drainage densities are comparable to terrestrial values derived in a similar manner [Carr and Chuang, 1997]. • Surface runoff is the simplest explanation for: 1) integrated, mature drainage basins 2) valley heads near the top of divides 3) high stream order 4) drainage densities comparable to terrestrial values

The obvious next step: look at higher resolution data (THEMIS and MOC NA)

MOLA grid

MOC WA

THEMIS Day IR

MOLA ~460 m/pix

MOCWA ~230 m/pix

THEMIS IR 100 m/pix

medial ridge older, degraded channel system different flow paths

THEMIS day IR + MOLA 5 N, 33 E

2003 study meets THEMIS

“undissected” region of the martian highlands

THEMIS shows valleys everywhere!

The jump to THEMIS VIS…

Carr and Malin, 2000 (Icarus) 18 km across 11 km across 2 rare examples of MOC NA showing highly dissected VNs

Resolution and Data Sets ~240 & ~460 m/pix ~100 & ~460 m/pix Viking MOC WA + MOLA few valleys 5 -15 times more ~240 m/pix ~19 m/pix ~3 m/pix THEMIS IR + MOLA THEMIS MOC NA up to another factor of 2 -4 very few more VIS very few more • Valley network identification increases up to a point. – Beyond that cutoff (~50 m resolution), few additional valleys are seen. • Why? – 2 choices: Small VNs did not form or they were erased. • Give terrestrial experience, the latter is preferred through resurfacing from impact gardening, mass wasting, aeolian erosion/deposition, volcanic lavas and ash, etc. , have likely obscured or removed many first order segments and tributaries of this scale.

Conclusion: Multiple episodes of precipitation-fed runoff is the only plausible way to explain these features.

Water = life, right?

What about life on Mars? ? ? • Mars has all the necessary ingredients for life (judging from our terrestrial experience) – 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. • Life on Earth is exceptionally tough!

Examples of Extreme Life: Zygogonium sp. Zygogonium is a type of filamentous green algae that lives in really hot, acidic water! (this and the following 3 slides from Lynn Rothschild)

Life can flourish in cold environments too! Example: Lakes under ice in Antarctica under Lake Hoare preparing to dive under Lake Hoare microbial mat layers

Deinococcus radiodurans (Conan the Bacterium) • An example of survival in extreme radiation environment • Can withstand 1, 500, 000 “rads” • 500 rads kill humans!

Categories of extremophiles Environment Type Definition Examples Temperature Hyperthermophile growth >80°C Thermophile Growth 60 -80°C Pyrolobus fumarii -113°, Geobacter 121° Mesophile Growth 15 -60°C Synechococcus lividis Psychrophile Growth <15°C humans Psychrobacter, insects Radiation Pressure D. radiodurans Barophile Weight loving Piezophile Pressure loving Desiccation Xerophile Shewanella viable at 1600 MPa Salinity Halophile Cryptobiotic; anhydrobiotic p. H Alkaliophile Salt loving (2 -5 M Na. Cl) Spirulina, Bacillus firmus Acidophile Oxygen tension Anaerobe Miroaerophil Aerophile p. H >9 Low p. H loving Cannot tolerate O 2 OF 4 (10. 5); 12. 8? ? Cyanidium, Ferroplasma Methanococcus jannaschii Clostridium Homo sapiens Chemical extremes Vacuum Electricity Haloarcula, Dunaliella high CO 2, arsenic, mercury Cyanidium caldarium tardigrades

Extremophile Lab: The Great Sea Monkeys * idea modified from David E. Trilling, Univ. of Arizona

The Amazing Brine Shrimp • Sea Monkey eggs can survive dormant for >20, 000 years without water • Sea Monkeys breathe through their feet • They are born with 1 eye but develop 2 more • They are ideal for testing life’s response to extreme conditions since they can survive (or remain dormant) in a wide variety of conditions: • p. H of 2 -10, high salinity, various radiation enviros, range of temps, etc

The Project: The assignment is the following (see handout): (1) Design a scientific experiment to examine the effects of some kind of extreme conditions on the revival and/or survival of dormant life forms (2) Carry out a scientific experiment following the Scientific Method (3) Discuss the results in terms of their hypothesis (4) Discuss the results in the broader context of astrobiology