the era of wet climates on Mars Stratigraphy and paleohydrology of Aeolis Dorsa Edwin Kite Princeton Antoine Lucas U Paris John Armstrong Weber State University Oded ID: 182594
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Slide1
Resolving the era of wet climates on Mars:Stratigraphy and paleohydrology of Aeolis Dorsa
Edwin Kite (Princeton), Antoine Lucas (U. Paris), John Armstrong (Weber State University), Oded Aharonson (Weizmann), Michael Lamb (Caltech), Alan Howard (U. Virginia)
Rationale: River-deposit dimensions constrain Early Mars hydrology, but stratigraphy is essential to constrain Mars climate evolution models Today, use measurements of Early Mars river-deposit dimensions versus stratigraphic elevation to:Constrain intermittency of wet conditionsConstrain climate models.
wavelength
widthSlide2
River deposits record constraintssorely needed for Mars climate evolution models
Environmental scenarios for precipitation-fed runoff on Early Mars
vary widely: e.g. Haberle et al. 2012, Kite et al. Icarus
2013, Mischna et al. 2013, Segura et al. 2012, Urata & Toon 2013, Wordsworth et al. 2013, Andrews-Hanna & Lewis 2011, Kite et al. Nature Geoscience 2014
102
mbar atmosphere needed to suppress evaporitic coolingKey geologic constraint – intermittency of wet conditions: e.g. Burr et al. 2010, Palucis et al. 2014, Irwin et al. 2005, Hoke et al. 2011, Williams et al. 2011, Morgan et al. 2014, Grant & Wilson 2012, Fassett et al.2010, Hobley et al. 2014, Hauber
et al. 2013.
Need
error bars on geologic constraints to avert climate model
overfitting
Intermittent
“One-pass”
“One-pass”
Intermittent
Long timescales
(> 10
6
yr
)
:
Short timescales (< 106)
thick-atmosphere greenhouse; transient high eccentricity
impactcataclysm
impact-triggered metastable wetstates; volcanic forcing
orbital forcingvolcanic forcing
IMPORTANCE OF
INTERMITTENCY
One-pass
Intermittent
Orbital forcing
Volcanic forcing
Impact-triggered
m
etastable wet
states
Impact cataclysm
Thick early greenhouseSlide3
NASA/JPL/MSSSWilliams et al. Science 2013Palucis et al. JGR 2014
ESP_027807_1765PSP_008002_1750
F2
MSL rover
This Talk
)E
longitude
latitude
Tharsis
Hellas
Early Mars water-availability model output (Kite et al
., Icarus 2013a)
Zimbelman
&
Scheidt
, Science 2012
Kite et al., Nature
Geosci
. 2014
Aeolis Dorsa river deposits in global context:
Gale
Aeolis Dorsa
a
lluvial fans
a
lluvial fans
Kite et al.
, in prep.
geosci.uchicago.edu
/~kite/stereo
1 cm
rhythmite
rhythmite
Relatively young,
p
ost-Noachian (?)
0E
360E
60S
60NSlide4
>10
8
yr time gap(embedded craters)
R-2
B20_017548_1739_XI
R-1
Howard PNAS 2009
400m
400m
e.g.
Burr et al
. 2009 & 2010
Kite et al.
2013 & in prep.
Stratigraphic context of river deposits suggests wet-dry alternations
Channel deposits
>3.2 km stratigraphic thickness
rhythmite
a
lluvial
fans
rivers
>400 km E-W extentSlide5
Getting from stereopairs to stratigraphic logsErrors: StratigraphicMeasurementOutcrop varianceMeasurement correlationSlide6
Meander wavelengths tighten upwards
Small meanders rare/absent below
0m, common above 0m
(4-20
) Myr (
Kite et al., Icarus 2013b)
X
t
ransect 1
(153.5ºE)transect 2(155
ºE)t
ransect 3(151ºE)
strat
.
e
rror
1. Meander
wavelengths (
λ
)
p
oor exposureSlide7
Channel widths narrow upwards
Narrow channels rare/absent below
0m, common above 0m
strat
.
error
X
t
ransect 1
(153.5ºE)transect 2(155ºE)transect 3
(151ºE)
2. Channel
widths (
w
)
(4-20)
Myr (
Kite et al.,
Icarus 2013b)
p
oor exposureSlide8
# data points
Stratigraphic elevation (m)
0Also: intermittency at 10m scale (correlatable basinwide using marker bed;Burr et al., 2010)ESP_034189_1740
h
igher channel-depositproportion
lateral-accretion depositsLogs show basin-wide discharge (Q) variability
Wavelength λ (m)
Width
w
(m)Slide9
Constraints on models of post-Noachian Mars climate evolution:Both short term intermittency and long-term intermittency.A thicker atmosphere – and a way of removing it Escape-to-space, or loss-to-ground (carbonate formation)?Stochastic Mars climate evolution model:
Uniform initial conditions: 3.5 Gya, 100 mbar
Liquid water availability model(e.g. Kite et al. Icarus 2013)Supply-limited carbonate weathering in area of H2O(l)
update atmospheric pressure, solar luminosityescape to space scaled using ASPERA-3 datascaled to UV flux of young Sunlike stars
Variable
3.5
Gyr
orbital
forcings
(n = 100)Armstrong et al. 2004Ensemble approach
Obliquitye
ccentricityLs of perihelionSlide10
Obliquity (°) / Patm (mbar)
Obliquity (°) / Patm (mbar)Late bursts of habitability on Mars-like planets: 1
exampleatmosphericpressurenormalized areaof liquid-waterobliquityPreliminary
long, globally-dryintervalpatchily,intermittently wet
a
rea of liquid waterobliquityatmospheric pressure
Metz et al.
2009,
Edgar et al.
2014, Andrews-Hanna & Lewis 2011, Head et al. 2009, Toon et al. 1980 …Dry spells: Aeolian supply/ deflation?(e.g. Kocurek & Bridges, 2012)Wet spells: Cementation? (e.g. Milliken et al., 2014)
Obliquity (°)
/
Patm
(mbar)
Model Age (Gyr)
20 MyrSlide11
Long dry intervals commonLaskar et al. Icarus 2004,
Li & Batygin ApJL 2014Late-stage carbonate drawdown? 100x less carbonate than in Pollack et al. (1987), consistent with SAM δ13C Still need young, voluminous sedimentary reservoir for carbonate
longglobally-dryintervallong, globally- dry intervalPreliminary
Late bursts of habitability on Mars-like planets: 3 different, equally likely scenarios
Obliquity (°)
/ Patm (mbar)wetwetObliquity (°) /
Patm (mbar)
Obliquity (°)
/
Patm (mbar)Slide12
Testing late-stage carbonate drawdown requires an extended Curiositytraverse
MAVEN Test escape-to-space hypothesis
Upper Gale mound - above the sulfates: A representative sampleof the only geochemical reservoiradequate to explain the loss of habitabilityvia carbonate drawdown Test loss-to-ground hypothesis:Slide13
ConclusionsAeolis Dorsa records 1.5-2x reduction in river-deposit
dimensions at or near R-1/R-2 contact - Consistent with 3-4x reduction in peak discharge across the contact. - 200m stratigraphy, (4-20) Myr total
depositional intervalIntermittency at multiple timescales (regional unconformities, river-deposit dimensions, marker beds).Constrains quantitative models linking sed. & strat. to climate evolution e.g. Kite et al., ‘Seasonal melting,’ Icarus 2013, Kite et al., ‘Growth and form …’, Geology 2013, Kite et al., ‘Low paleopressure …,’ Nature Geoscience 2014
With thanks to
:
Devon Burr, Kevin Lewis, Rebecca Williams, Robert Jacobsen, Lynn Carter, Bill Dietrich, Laura Kerber, Frederik Simons, Nicolas Mangold, Ross Irwin, Bill Dietrich, Alexandra Lefort, & Noah Finnegan for discussions, ideas, and inspiration.
More information:
www.astro.princeton.edu
/
~
ekite