Prof. Christopher T. Russell: A Celebration of a Life in Science
Gullies on Vesta
Gullies on Vesta Jennifer Scully et al., 8th May 2013
Prof. Christopher T. Russell: A Celebration of a Life in Science
Introduction | Linear | Curvilinear | Gullies summary | Water flow | Formation Mechanism | Conclusions
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Take home messages
• Two
Two types of gullies identified on Vesta: curvilinear and types of gullies identified on Vesta: curvilinear and
linear • Curvilinear gullies formed by transient flow of liquid water
• Sourced in subsurface ice‐bearing deposits
• First morphological evidence to suggest that Vesta is not as dry as previously thought Prof. Christopher T. Russell: A Celebration of a Life in Science
Introduction | Linear | Curvilinear | Gullies summary | Water flow | Formation Mechanism | Conclusions
2t
2 types of gullies identified on Vesta
f lli id tifi d V t
• Two types of gullies: different morphologies & network yp
g
p
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geometries • 48 craters containing linear type gullies
• 11 craters containing curvilinear type gullies
• Gullies
Gullies in craters that are relatively young, e.g. Marcia in craters that are relatively young, e.g. Marcia ~60‐
60
150 Ma (Williams et al. 2013)
Prof. Christopher T. Russell: A Celebration of a Life in Science
Introduction | Linear | Curvilinear | Gullies summary | Water flow | Formation Mechanism | Conclusions
Li
Linear gullies example: Fonteia crater
lli
l F t i
t
Prof. Christopher T. Russell: A Celebration of a Life in Science
Introduction | Linear | Curvilinear | Gullies summary | Water flow | Formation Mechanism | Conclusions
Li
Linear gullies in Fonteia: detailed map
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• Originate in alcoves below spurs
below spurs
• Linear, straight channels
• Parallel channels
• Rarely intersect
• Low length to width ratio
width ratio
• Sometimes end in lobate deposits
lobate deposits
• Bounded by levees
Prof. Christopher T. Russell: A Celebration of a Life in Science
Introduction | Linear | Curvilinear | Gullies summary | Water flow | Formation Mechanism | Conclusions
A l
Analogous to lunar gullies
t l
lli
Kumar et al. (2013)
Prof. Christopher T. Russell: A Celebration of a Life in Science
Introduction | Linear | Curvilinear | Gullies summary | Water flow | Formation Mechanism | Conclusions
C ili
Curvilinear gullies example: Cornelia crater
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li
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Note pitted terrain
Prof. Christopher T. Russell: A Celebration of a Life in Science
Introduction | Linear | Curvilinear | Gullies summary | Water flow | Formation Mechanism | Conclusions
C ili
Curvilinear gullies in Cornelia: detailed map
lli i C
li d t il d
Prof. Christopher T. Russell: A Celebration of a Life in Science
Introduction | Linear | Curvilinear | Gullies summary | Water flow | Formation Mechanism | Conclusions
C ili
Curvilinear gullies in Cornelia: detailed map
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li d t il d
• Originate below cliff base/ V‐shaped alcoves • Frequently intersect
• Curvilinear, sinuous channels
• High length to width ratio
• Dendritic to subparallel networks
• Some end in superposing lobate deposits
Prof. Christopher T. Russell: A Celebration of a Life in Science
Introduction | Linear | Curvilinear | Gullies summary | Water flow | Formation Mechanism | Conclusions
A l
Analogous to terrestrial and martian gullies
i l d
i
lli
Malin & Edgett (2000)
Prof. Christopher T. Russell: A Celebration of a Life in Science
Introduction | Linear | Curvilinear | Gullies summary | Water flow | Formation Mechanism | Conclusions
Li
Linear & curvilinear gullies have different morphologies
&
ili
lli h
diff
h l i
Curvilinear gullies gullies
Linear gullies
Linear gullies Prof. Christopher T. Russell: A Celebration of a Life in Science
Introduction | Linear | Curvilinear | Gullies summary | Water flow | Formation Mechanism | Conclusions
Wh t
What processes formed the gullies?
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• Impact melt has been ruled out for both gully types
• Morphologies & network geometries of linear gullies consistent with dry granular flow
i t t ith d
l fl
• Morphologies & network geometries of curvilinear gullies resemble those formed by flow of liquid water
Prof. Christopher T. Russell: A Celebration of a Life in Science
Introduction | Linear | Curvilinear | Gullies summary | Water flow | Formation Mechanism | Conclusions
E id
Evidence for volatiles & water on Vesta f
l til & t
V t
• Pitted terrain: formed by impact‐induced degassing of volatile material (Denevi et al. 2012)
‐> associated with curvilinear gullies
NASA/JPL‐Caltech/UCLA/MPS/DLR/IDA/JHUAPL
Prof. Christopher T. Russell: A Celebration of a Life in Science
Introduction | Linear | Curvilinear | Gullies summary | Water flow | Formation Mechanism | Conclusions
E id
Evidence for volatiles & water on Vesta f
l til & t
V t
• From meteorites: ‐ quartz & other mineral veins => aqueous alteration
(Treiman et al. 2004, Warren et al. 2013)
‐ high OH apatites => water in magmas hi h OH
i
i
(Sarafian et al. 2012)
‐ carbonaceous chondrite clasts (e.g. Herrin et al. 2011)
0.5 mm
• From Dawn data: ‐ dark material is carbonaceous chondrite (Reddy et al. 2012) ‐ areas of OH f OH (De Sanctis et al. 2012)
‐ areas high in H (Prettyman et al. 2012)
Prof. Christopher T. Russell: A Celebration of a Life in Science
Introduction | Linear | Curvilinear | Gullies summary | Water flow | Formation Mechanism | Conclusions
F
Formation mechanism of curvilinear gullies
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h i
f
ili
lli
Prof. Christopher T. Russell: A Celebration of a Life in Science
Introduction | Linear | Curvilinear | Gullies summary | Water flow | Formation Mechanism | Conclusions
C l i
Conclusions & implications
& i li ti
• Curvilinear gullies formed by transient flow of liquid water, sourced in subsurface ice‐bearing deposits
• First morphological evidence to suggest that Vesta is not as dry as previously thought
• Vesta is a diverse, heterogeneous and complex mini‐world with planetary style processes
planetary‐style processes
• Should not be surprised by possible presence of water on other h ld
b
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ibl
f
h
asteroids Prof. Christopher T. Russell: A Celebration of a Life in Science
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Thank you!
!
2, H. Y. McSween
3, C. T. Russell
C
TR
ll1, A. Yin
A Yi 1, R. Jaumann
R J
H YM S
C. A. Raymond4, V. Reddy5, 6, L. Le Corre5, 7.
1Department of Earth and Space Sciences, University of California, Los Angeles, California 90095‐1567, USA.
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it f C lif i L A l C lif i 90095 1567 USA
2DLR, Institute of Planetary Research, Berlin, Germany.
3
Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN, 37996‐1410, USA.
4Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA.
5Max Planck Institute, Katlenburg‐Lindau, Germany.
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6University of North Dakota, Grand Forks, ND, USA.
7Planetary Science Institute, Tucson, AZ, USA. We thank B.W. Denevi, K. Otto and D.P. O’Brien. We also thank the Dawn team for the development, cruise, orbital insertion and operations of the Dawn spacecraft at Vesta
the Dawn spacecraft at Vesta. Prof. Christopher T. Russell: A Celebration of a Life in Science
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Thank you!
!
Dawn team at G ld t
Goldstone Deep Space D
S
Network,
January 2011 Prof. Christopher T. Russell: A Celebration of a Life in Science
Additi
Additional slides
l lid
Prof. Christopher T. Russell: A Celebration of a Life in Science
R l
Relevant basic facts about Vesta
tb i f t b tV t
1. Average radius: 262 km (Russell et al. 2012)
2. Differentiated: iron core, olivine mantle & basaltic crust Russell et al (2012) & Ermakov (in prep )
Russell et al. (2012) & Ermakov (in prep.) 3. Parent body of howardite, eucrite & diogenite (HED) meteorites t it (Russell et al. 2012, De Sanctis et al. 2012, Prettyman et al. 2012)
4. Little impact melt is anticipated or observed (Williams et al. 2013)
4. Little impact melt is anticipated or observed (Williams et al. 2013)
5. Dark material is exogenous (carbonaceous chondrite) & bright material is endogenous (freshly exposed) (Reddy et al. 2012, McCord et al. 2012) Prof. Christopher T. Russell: A Celebration of a Life in Science
Introduction | Linear | Curvilinear | Gullies summary | Water flow | Formation Mechanism | Conclusions
Li
Linear & curvilinear gullies have different morphologies
&
ili
lli h
diff
h l i
Curvilinear gullies
Linear gullies
Originate below base of cliffs/ in Originate in alcoves below spurs
V‐shaped alcoves
Curvilinear, sinuous channels
Linear, straight channels
Subparallel to dendritic Parallel networks
networks
t
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Rarely intersect
Frequently intersect
L length to width ratio
Low
l th t idth ti
Hi h length to width ratio
High
l th t idth ti
Sometimes end in larger lobate
Sometimes end in smaller deposits & bounded by levees
deposits & bounded by levees
lobate deposits covered by lobate deposits,
covered by
pitted terrain
Prof. Christopher T. Russell: A Celebration of a Life in Science
M h l i
Morphologies consistent with sapping
i t t ith
i
Characteristic
Typical for curvilinear gullies?
1. Constant channel width
Yes: 50±10 m
2. Dendritic network geometry
Yes
3. Long main valleys & short, stubby tributaries
Yes
4 High tributary junction angles
4. High tributary junction angles
Yes
5. Sapping below permeable layer
Yes
6 Plots of of characteristics of 6. Pl t f f h
t i ti
f
Y
Yes
sapping channels on Earth
• Groundwater/
Groundwater/ aquifer origin has been suggested for some aquifer origin has been suggested for some
Martian gullies (e.g. Malin & Edgett 2000, Heldmann et al. 2007)
Prof. Christopher T. Russell: A Celebration of a Life in Science
F
Forming the curvilinear gullies
i th
ili
lli
• Morphologies of curvilinear gullies are consistent with groundwater sapping => probable formation mechanism
Cross section view of one Cross
section view of one
side of crater:
Curvilinear gullies formed by sapping
Impermeable Impermeable
layer
Water
Impermeable layer
p
y
Adapted from Luo (2000)
Prof. Christopher T. Russell: A Celebration of a Life in Science
F
Formation mechanism of curvilinear gullies
ti
h i
f
ili
lli
• Pressure‐temperature diagram for H2O ~145 K
Prof. Christopher T. Russell: A Celebration of a Life in Science
F
Formation mechanism of curvilinear gullies
ti
h i
f
ili
lli
• Water is stable as a gas on Vesta’s surface, however, • Water will not all instantaneously evaporate
Water will not all instantaneously evaporate
• Top
Top layers will evaporate while sub
layers will evaporate while sub‐layers
layers are protected are protected
and can flow [experiments soon!] • Evaporation takes at least ~97 hrs
• Gullies can be carved in ≥22 minutes
G lli
b
d i ≥22 i t