Water on Mars

1. Large floods from groundwater origin?

2. Do impacts affect hydrology?

3. Hydrological effects of cooling of the interior?

4. Were there large oceans?

Michael Manga, UC Berkeley

NASA/JPL/Malin Space Science Systems

Why study water on Mars?

• Climate and habitability (Mars and Earth

were not so different once...)

• Human exploration

• Water and life

• Testing terrestrial science

Water on present-day Mars

1. Atmosphere– But not much! (precipitable m)

2. Polar Caps

3. Mantle

4. Regolith

Water on present-day Mars

1. Atmosphere

2. Polar Caps– N cap equivalent to 9m

global ocean

– S cap has CO2 frost cover

(water beneath)

3. Mantle

4. Regolith

NASA/JPL/MSSS

Water on present-day Mars

1. Atmosphere

2. Polar Caps

3. Mantle (?)– Meteorites contain

hydrous minerals, but these may have formed at the surface

4. Regolith

Water on present-day Mars

1. Atmosphere

2. Polar Caps

3. Mantle

4. Regolith– Mars Odyssey

mission: abundant ground ice at high southern latitudes NASA/JPL/U. Arizona

Water-ice lakes

Water on early Mars

“Valley networks”– Dendritic networks

suggest erosion by surface runoff

– On Noachian-age crust

Viking image of Warrego Valles

50 km

Water on early Mars

“Valley networks”– Evidence for

sustained flow: Fans, meander bends, scroll bars

NASA/JPL/MSSS

Moore et al., GRL 2003; Malin & Edgett, Science 2003

Mars Exploration Rovers (MER)

• Outcrop-scale evidence of water-rich environment in Meridiani Planum (Opportunity)

NASA/JPL/Cornell

Water on early Mars

“Outflow channels”– Large channels originate at

point source

– Q ~100 to 10000 x Mississippi R. (> 106 m3 s-1)

– Spatial association with collapsed terrain suggests subsurface fluid source

– Total Vol ~ 107 km3 (where did it go?)

50 km

150 km

Global hydrogeology,aquifers on Mars?

• North-south gradient in elevation• Lots of craters

Global hydrogeology,aquifers on Mars?

• North-south gradient in elevation• Lots of craters

Clif

ford

and

Par

ker

(200

1)

Water on Mars

1. Large floods from groundwater origin?

2. Do impacts affect hydrology?

3. Hydrological effects of cooling of the interior?

4. Were there large oceans?

Michael Manga, UC Berkeley

NASA/JPL/Malin Space Science Systems

1. Recent (<10 Ma) floods at Cerberus Fossae

Did these floods have a groundwater origin?

1. Recent (<10 Ma) floods at Cerberus Fossae

Did these floods have a groundwater origin?

Murray et al., Science (2005)

Model

Can subsurface aquifers deliver enough water, and deliver it fast enough to make the features we see?

Can subsurface aquifers deliver enough water, and deliver it fast enough to make the features we see?

YES

A groundwater source in a large deep aquifer is plausible if k is large enough

Is k ~ 10-9 m2 reasonable?

Permeability of basalt aquifers: The High Cascades

Cultus River

Quinn River

Useful features

• Nearly constant discharge• Peak discharges lags recharge by 1-6 months

Flow governed by

Response characterized by diffusion time

Conclusion:

A groundwater source in a large deep aquifer is plausible if k is large enough

Is k ~ 10-9 m2 reasonable?

Yes, if aquifers are made of basaltic lava flows, not too much weathering

Compared with Earth, slow hydrological cycling

Geological processes that are • infrequent• slow may be hydrological important

Two examples

• Impacts• Secular cooling of the planet

Shaking from earthquakes • changes pore pressure• increases streamflow• causes liquefaction

2. Impacts and groundwater

Shaking from earthquakes • changes pore pressure• increases streamflow• causes liquefaction

Shaking from earthquakes • changes pore pressure• increases streamflow• causes liquefaction

Connection to earthquakes? Impacts also shake the ground

Distance over which liquefaction occurs, streamflow increases

Empirical upper bound

Wan

g, M

anga

, W

ong,

Ica

rus

(200

5)

Scaling of impact shaking to earthquakes

Size-energy scaling (Melosh, 1978)

Seismic efficiency

Maximum distance for liquefaction

Scaling consistent with observations?

Origin of “chaotic terrain”?

lateralspreading?

3. Slow processes may be important on Mars:As planet cools, cryosphere gets thicker

Implications for groundwater?

Water pressure increases

Discharge continues until pressure is hydrostatic

Cooling

Cryosphere thickens

Water erupts when pressure becomes lithostatic

A small number (of large) floods may be possible,

4. Paleoshorelines on Mars?

4. Paleoshorelines on Mars?

Carr & Head, JGR 2003

Webb, JGR 2004

Paleoshorelines on Mars?

~300 kmBonneville paleoshoreline, Utah www.geo.cornell.edu

Raw elevations from Carr & Head [2003]

Problem: Shorelines don’t follow an equipotential surface [Head et al., 1999; Carr & Head, 2003]

Interpolation artifacts

[Carr & Head, 2003; Webb, 2004]

Long-wavelength lithospheric deformation

• Loading by H2O (Leverington and Ghent)

• Flexural response to large surface loads

• Dynamic topography (mantle convection)

• True polar wander (TPW)

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TPW + elastic lithosphere spatially non-uniform change in topography

a

Initial Final Difference

( ) ( )1cos32

1cos 2

0,2 −= ηηP

( ) ( ) ( )[ ]θγωψθ coscos3

1, 0,20,2

22 PPa i −=ΛDifference in centrifugal potential determines geometry of sea level response [Mound & Mitrovica 1998]

TPW + elastic lithosphere spatially non-uniform change in topography

a

Topography increases

Topography decreases

Amplitude depends on amount of TPW, elastic thickness of lithosphere, and

internal density structure

( ) ( ) ( )[ ]ff khg

+−Λ

=Δ 1,

,Topoψθ

ψθ

Degree 2 fluid tidal Love numbers

Details of TPW calculations inMatusyama et al. (2006)

Inversion procedure

• Monte Carlo search for best-fit paleopoles for 100 km ≤ Te ≤ 400 km

• Allow constant C to vary freely

• Minimize RMS misfit between S(θ,ψ) and shoreline topography

Approach: use shoreline topography to infer paleopole locations

Displacement (km)

Shoreline

Present pole

Paleopole

Elevation increases

Elevation decreases

Best-fit paleopoles

Te = 200 km

Arabia (older, deeper)

Deuteronilus(younger, shallower)

TPW can explain long-wavelength shoreline topography

Inferred TPW path implies Tharsis would remain at the equator

90°

Best-fit paleopoles

What caused the polar wander?

TPW Implications

Equatorial ocean ~4Ga? Ocean volumes

Arabia, 690 m

Deuteronilus, 150 m

Oceans on Mars: Open questions

• Source of water, ocean formation time?

• Short- and long-term fates of ocean water?

• Independent evidence of oceans?

Oceans are a major uncertainty in Mars’ global water budget

Based on data from Clifford and Parker (2001), Zuber et al. (1998), Smith et al. (1999) and Kass (2001) Clifford & Parker [2001], Zuber et al. [1998], Smith et al. [1999], Kass [2001]; as summarized by Carr & Head [2003]

Arabia Deuteronilus

NorthSouth

0.20.150.10.050

Volume in billions of km3)

Northern oceanplains

Lost to space

Regolith

Polar caps

Collaborators

Chi-Yuen Wang

Martin Saar

Alex Wong

Isamu Matsuyama

Jerry Mitrovica

Taylor Perron QuickTime™ and aTIFF (Uncompressed) decompressor

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Why study water on Mars?

• Climate and habitability (Mars and Earth

were not so different once...)

• Human exploration

• Water and life

• Testing terrestrial science

Lowell’s canals implied intelligent construction – leading to the idea of a desperate civilization… Invasion of Earth by Martians (Wells 1898)

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Percival Lowell’s canals 1895

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Movie 1953

Summary

• Large floods on Mars require lots of water (big aquifers) and high permeability

• Some hydrogeological processes may be important on Mars, but not Earth

(e.g., impacts, slow cooling of the planet)

• Mars may once have had large oceans