Impact Crater Lakes and the Impact Crater Lakes and the Astrobiological Exploration Astrobiological Exploration

of Marsof Mars

NASA Astrobiology Institute Mars Focus Group Videocon (01/08/01)

Nathalie A. Cabrol

NASA Ames Research Center

Space Science Division, MS 245-3

Moffett Field, CA 94035-1000

Email: ncabrol@mail.arc.nasa.gov

Phone: (650)604-0312/Fax: (650)604-6779

Criteria for Astrobiology SitesCriteria for Astrobiology Sites

Evidence of waterEvidence of water Presence of mechanisms to concentrate lifePresence of mechanisms to concentrate life Presence of thermal energy sourcePresence of thermal energy source Evidence of rapid burial (water or sediment, Evidence of rapid burial (water or sediment,

lava, ice…)lava, ice…) Excavation or exposure in outcropsExcavation or exposure in outcrops

Science Priorities and Martian Science Priorities and Martian EnvironmentsEnvironments

Geologic HistoryGeologic History

Climate HistoryClimate History

Chemical EvolutionChemical Evolution

Fossil LifeFossil Life

Extant LifeExtant Life

Channels, Valleys, Channels, Valleys, PaleolakesPaleolakes

Channels, Valleys, Polar Channels, Valleys, Polar deposits, deposits, PaleolakesPaleolakes

Deep Hydrothermal Systems, Deep Hydrothermal Systems, PaleolakesPaleolakes

Thermal Springs, Thermal Springs, LakebedsLakebeds

Frozen in ice, Current Frozen in ice, Current Hydrothermal sites, Hydrothermal sites, Caves, Caves, Evaporites, Endoliths, etc...Evaporites, Endoliths, etc...

Table adapted from Farmer and DesMarais, in Landing Site Catalog

Why Lakes in Impact Craters?Why Lakes in Impact Craters?

Well-delimited topography Well-delimited topography

Protected Environments (“Local” Climate);Protected Environments (“Local” Climate);

Unlike most other lakes, they were at some point in Unlike most other lakes, they were at some point in their history associated with a heat source.their history associated with a heat source.

Combining Combining WaterWater and and Energy SourceEnergy Source

A. Declining heat from impact melt sheet;B. Ablation rate of an ice-cover (cm/yr)in a65-km Ø crater with a 200-m thick melt sheet.

C.C.

C. Energy Sources for an impact crater lake. Convective currentsConvective currents related to water temperaturevariations are associated with rotary currents rotary currents relatedto channel flow. (Grin and Cabrol 1997)

10-5

0.0001

0.001

0.01

0.1

1

10

0 5000 1 10 4 1.5 10 4 2 10 4 2.5 10 4

HEAT FLOW (W/M**2)

0

100

200

300

400

500

0 5000 1 10 4 1.5 10 4 2 10 4 2.5 10 4

ICE THICKNESS (meters)

TIME (years)

Charts after Newsom et al., 1996

Melt Material, Central Peak and Ice-cover

1cm/yr

3cm/yr

10cm/yr

A Lake is Defined by:A Lake is Defined by:

• Physical Processes;

• Hydrological Processes;

• Chemical Processes;

• Biological Processes

• Observed and/or can be modeled;•Reconstructed from data;

• Poorly known

• ???

classification based on fluvio-lacustrine systems for Mars.

Closed Lake System: Concentration Closed Lake System: Concentration with Lifetime (ancient) with Lifetime (ancient)

Closed and deep crater Closed and deep crater basin without an outflow. basin without an outflow. Terraces in the channel Terraces in the channel suggest either suggest either there was several episodes there was several episodes ofofflow (sevral lakes) or one flow (sevral lakes) or one major episodes with major episodes with fluctuating levelsfluctuating levelsAfter Cabrol and Grin, 1999 Icarus. After Cabrol and Grin, 1999 Icarus.

Closed Lake/Pond System: Recent?Closed Lake/Pond System: Recent?

Open Lake System: River-DominatedOpen Lake System: River-Dominated

Example of open crater lake system in theExample of open crater lake system in theMemnonia NW region of Mars. Open craterMemnonia NW region of Mars. Open cratersystems may have experienced a “closed” phasesystems may have experienced a “closed” phasebefore channels cut through the rim andbefore channels cut through the rim andoutflow from the basin. This episode might beoutflow from the basin. This episode might befound in deep sedimentary recordfound in deep sedimentary record..

(a) River dominated clastic sediment. The(a) River dominated clastic sediment. Thelake water chemistry is river-dominated.lake water chemistry is river-dominated.Search for parent-rock;Search for parent-rock;(a1) Episodes of flow recorded in varves; (a1) Episodes of flow recorded in varves; layers. Importance of near-inlet shorelinelayers. Importance of near-inlet shorelineto search for life.to search for life.

After Cabrol and Grin, 1999 Icarus.

Lake Chain System: Fractioning Lake Chain System: Fractioning of Evaporitesof Evaporites

Chain of impact cratersChain of impact cratersconnected by a channel, withconnected by a channel, with3 open components. 3 open components. Fractioning of evaporites,Fractioning of evaporites,and clasts, from C1 to C3.and clasts, from C1 to C3.

The degree of concentrationThe degree of concentrationis predicted to be higher foris predicted to be higher forcrater lake chain supportedcrater lake chain supportedby long-lived runoffs thanby long-lived runoffs thanfor short outburst of outflows.for short outburst of outflows.

The degree of salinity and evaporiteThe degree of salinity and evaporitefractioning will vary depending if the fractioning will vary depending if the system ends by a closed or an opensystem ends by a closed or an openbasin.basin.

Lacustrine Deltas in Impact Craters

Deltas provide vertical facies succession, with indication of climate and Deltas provide vertical facies succession, with indication of climate and atmosphere (composition, thickness, and grain-size of sediment; hydrological atmosphere (composition, thickness, and grain-size of sediment; hydrological regime; geologic history in sequence. regime; geologic history in sequence. Sites to search for fossils.Sites to search for fossils.

Terraces and Layered Sedimentary Deposits

Lacustrine TerracesLacustrine Terraces

Open window on hydrogeological variations during the lake lifetimeOpen window on hydrogeological variations during the lake lifetime. . Lacustrine Terraces, and Structural Terraces provide access to Lacustrine Terraces, and Structural Terraces provide access to ancient crust material and subsequent sedimentary and geologic ancient crust material and subsequent sedimentary and geologic history. Climate accessible by morphologic analysis and sediment history. Climate accessible by morphologic analysis and sediment mineralogical composition. mineralogical composition. Sites to search for fossils.Sites to search for fossils.

• Shorelines, Mounds, EvaporitesShorelines, Mounds, Evaporites

Margin of deposits and traces ofMargin of deposits and traces ofwaning waning

Mounds associated with Mounds associated with shorelineshoreline They could be either relics of ancient They could be either relics of ancient sedimentary deposits or tufas towers as sedimentary deposits or tufas towers as suggested in recent works.suggested in recent works.

Tufas Tower: Tufas Tower: sites for diversified sites for diversified commu-commu-nities of bacterias. They are observed near nities of bacterias. They are observed near shore.shore. EvaporitesEvaporites

- Climate, regional envir.- Climate, regional envir.- Chemistry of the basin- Chemistry of the basin- Lifetime of crater lake- Lifetime of crater lake- Can host microorganisms- Can host microorganisms

After Cabrol and Grin, 1999 Icarus.After Cabrol and Grin, 1999 Icarus.

What Environments for Life in Martian What Environments for Life in Martian Impact Crater LakesImpact Crater Lakes

Water:Water:prerequisite for Lifeprerequisite for Life Evaporites Evaporites (carbonates, sulfates...)(carbonates, sulfates...): : Halophiles...Halophiles... Caves Caves (dissolution, thermokarst, cracks): Troglodytes(dissolution, thermokarst, cracks): Troglodytes Sediments: Sediments: Endoliths,chasmoendoliths, Endoliths,chasmoendoliths,

Chemolithoautotrophic organisms, etc...Chemolithoautotrophic organisms, etc... Hydrothermal Systems: Hydrothermal Systems: Thermophilic BacteriasThermophilic Bacterias Ice:Ice: algae... algae...

FossilsFossils in Layers, Terraces. Possibly at surface if excavated by in Layers, Terraces. Possibly at surface if excavated by young impactsyoung impacts

Some Favorites: 2003 and BeyondSome Favorites: 2003 and Beyond

• ~ 180 Impact Crater Lakes at Viking Resolution~ 180 Impact Crater Lakes at Viking Resolution

• Probably thousands will be discovered at MOC and M-Ex Res.Probably thousands will be discovered at MOC and M-Ex Res.

• Latitudes should not be a constraint for studies as it varies with Latitudes should not be a constraint for studies as it varies with mission windows of opportunities and landing precision will be mission windows of opportunities and landing precision will be improved with future technologies.improved with future technologies.

- Gusev (2003?)- Gusev (2003?)

- Gale (2003?)- Gale (2003?)

- Schiaparelli (2003)- Schiaparelli (2003)

- 7-km crater in Newton- 7-km crater in Newton

- Many others (Holden, Galle, Pollack, etc…)- Many others (Holden, Galle, Pollack, etc…)

GusevGusev

GaleGale

SchiaparelliSchiaparelli

C-NewtonC-Newton C-NewtonC-Newton