Water, the Ancient Climate of Mars, and Life

Brian HynekLaboratory for Atmospheric and Space Physics

University of Colorado

Current Mars Atmosphere

• Predominantly CO2 (~95%)

– minor contributions from N2, Ar, H2O, O2, 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)

10 km

500 km

Viking Orbiter image

MOLA topography

* only one that requires a different climate than at present

Valley Networks (really old)

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 Some really convincing evidence convincing evidence of surface flowof 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 1st 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?

Tharsis

Northern plains

VallesMarineris

Northern plains

Ref: Owen and Bar-Nun, in R. M. Canup and K. Righter, eds., Origin of the Earth and Moon (2000), p. 463

• 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

Venus

Where did all the water go?

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

19761976 20012001VikingMOC

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

11

1

12 22

23

3

* Higher stream order corresponds to more mature drainage systems and more contribution from surface runoff

dow

nslo

pe

Demonstration of Technique: Mapping Valley Networks with MOLA 128 pix/deg grid and MOC WA atlas (256 pix/deg) in

ArcGIS (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 MOC-

WA atlas (256 pix/deg) in ArcGIS

MOLA shaded reliefOverlay MOC WA mosaic with some

transparency

++

Demonstration of Technique: Mapping Valley Networks with MOLA 128 pix/deg grid and MOC-

WA atlas (256 pix/deg) in ArcGIS

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 3rd 6th

total length of valleys (km)

1,308 11,161

drainage density (km-1)

7.6 × 10-3 6.5 × 10-2 *

* 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]

Viking MDIM and Carr VN MGS data and newly recognized VN

Comparison of old and new data

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 near1ºS, 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 >5th 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

older, degraded channel system

older, degraded channel system

differentdifferentflow pathsflow paths

medial ridge

THEMIS day THEMIS day IR + MOLAIR + MOLA

5N, 33E5N, 33E

2003 study meets THEMIS

“undissected” region of the martian highlands

THEMIS shows valleys everywhere!

The jump to THEMIS VIS…

2 rare examples of MOC NA showing highly dissected VNs

Carr and Malin, 2000 (Icarus)

18 km across 11 km across

• 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.

Resolution and Data Sets

Viking MOC WA + MOLA

THEMIS IR + MOLA

few valleys 5-15 times more up to another factor of 2-4

MOC NA

very few more

~240 m/pix~3 m/pix

~100 & ~460 m/pix

~240 & ~460 m/pix

THEMIS

VIS

very few more

~19 m/pix

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

Life can flourish in cold environments too! Example: Lakes under ice in Antarctica

under Lake Hoare

microbial mat

preparing to dive under Lake Hoare

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 Categories of extremophiles Type

Hyperthermophile

Thermophile

Mesophile

Psychrophile

Barophile

Piezophile

Xerophile

Halophile

Alkaliophile

Acidophile

Anaerobe

Miroaerophil

Aerophile

Type

Hyperthermophile

Thermophile

Mesophile

Psychrophile

Barophile

Piezophile

Xerophile

Halophile

Alkaliophile

Acidophile

Anaerobe

Miroaerophil

Aerophile

Examples

Pyrolobus fumarii -113°, Geobacter-121°

Synechococcus lividis

humans

Psychrobacter, insects

D. radiodurans

Shewanella viable at 1600 MPa

Haloarcula, Dunaliella

Spirulina, Bacillus firmus

OF4 (10.5); 12.8??

Cyanidium, Ferroplasma

Methanococcus jannaschii

Clostridium

Homo sapiens

Cyanidium caldarium

tardigrades

Examples

Pyrolobus fumarii -113°, Geobacter-121°

Synechococcus lividis

humans

Psychrobacter, insects

D. radiodurans

Shewanella viable at 1600 MPa

Haloarcula, Dunaliella

Spirulina, Bacillus firmus

OF4 (10.5); 12.8??

Cyanidium, Ferroplasma

Methanococcus jannaschii

Clostridium

Homo sapiens

Cyanidium caldarium

tardigrades

Environment

Temperature

Radiation

Pressure

Desiccation

Salinity

pH

Oxygen tension

Chemical extremes

Vacuum Electricity

Environment

Temperature

Radiation

Pressure

Desiccation

Salinity

pH

Oxygen tension

Chemical extremes

Vacuum Electricity

Definition

growth >80°C

Growth 60-80°C

Growth 15-60°C

Growth <15°C

Weight loving

Pressure loving

Cryptobiotic; anhydrobiotic

Salt loving (2-5 M NaCl)

pH >9

Low pH loving

Cannot tolerate O2

high CO2, arsenic, mercury

Definition

growth >80°C

Growth 60-80°C

Growth 15-60°C

Growth <15°C

Weight loving

Pressure loving

Cryptobiotic; anhydrobiotic

Salt loving (2-5 M NaCl)

pH >9

Low pH loving

Cannot tolerate O2

high CO2, arsenic, mercury

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:

• pH of 2-10, high salinity, various radiation enviros, range of temps, etc

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

The Project: