Volatiles in the terrestrial planets - CIDER, 2014 Sujoy Mukhopadhyay University of California, Davis
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Volatiles in the terrestrial planets
Sujoy Mukhopadhyay
University of California, Davis
CIDER, 2014
Atmophiles:
Elements I will talk about
rock-loving iron-loving sulfur-loving
Temperatures in Protoplanetary Disk
1 AU ~= 149,597,870 km
K/Th ratio of the terrestrial planets
Peplowski et al., Science, (2011)
K/Th ratio of the terrestrial planets
Peplowski et al., Science, (2011)
What about the H, C, N, noble gases?
Questions regarding volatiles on the terrestrial
planets that we can answer
• What are the potential volatile sources?
• What processes could have sculpted the volatile
budget?
• When could volatiles be delivered?
Questions regarding volatiles on the terrestrial
planets that we would really like to answer
What are the volatile compositions and budgets?
What are the volatile sources?
What are the processes that sculpted the
volatile budget?
When were the volatiles delivered?
What are the potential volatile sources?
1) Acquiring nebular (solar) volatiles
• Capture of nebular
gases after nebula
disperses, heavier
components of
nebular atmosphere
retained; rocky
mantles equilibrate
with nebular
atmospheres through
a magma ocean.
• Irradiation of grains
with solar radiation.
Lifetime of nebular gas
Mamajek, 2009
Mars accretion timescale
Dauphas and Pourmand, 2011What are the potential volatile sources?
2) Acquiring chondritic volatiles
Planetesimal accretion adds an isotopic signature (e.g., in N,
water and noble gases) that is distinct from the solar nebula.What are the potential volatile sources?
3) Acquisition of volatiles from icy planetesimals
Icy planetesimals may add
volatiles with distinct H
and N isotopic
composition compared to
chondritic and solar
volatilesFeeding zone of terrestrial planets
Raymond et al., 2009Processes that lead to volatile loss during
accretion
• Hydrodynamic escape (produces a mass fractionated
residual atmosphere)Processes that lead to volatile loss during
accretion
• Hydrodynamic escape (produces a mass fractionated
residual atmosphere)
Energy input (EUV flux) into upper
atmosphere drives thermal loss of light
constituent (H2)
Escaping flux of H2 can be high enough to
exert upward drag on heavier species and
lift them out of atm.
Mass dependent process: so fractionating
atm loss processy‐axis = ((iKr/84Kr)sample/(iKr/84Kr)air‐1) X 1000
Pepin & Porcelli 2002Processes that lead to volatile loss during
accretion
• Hydrodynamic escape (produces a mass fractionated
residual atmosphere)
• Impacts
– Giant impacts (isotopes are not mass fractionated;
elements maybe fractionated depending upon their
distribution between atmosphere‐ocean)
– Planetesimal impacts (isotopes are not mass fractionated;
elements maybe fractionated; Schlichting et al., Icarus, in press)Loss Is Important in Planetary Formation
Significant atm loss without
an ocean only in most
energetic impacts
Atmospheric loss with an
ocean likely over the energy
range of planet formation
Loss limited in canonical
moon forming impact
Significant loss possible in
high angular momentum
impacts
Velocities from Raymond et al. 2009Reservoirs can be Fractionated in Impacts Atmosphere lost preferentially compared to an ocean H retained in ocean; Noble gases and N (C?) lost in atmosphere
When could volatiles have been delivered?
The two end‐member cases:
1. During the main phase of accretion; i.e., pre‐Moon forming giant
impact
– Giant impacts can lead to bulk
accretion or erosion of volatiles.
Re‐equilibration of magma ocean
with the new atmosphere.When could volatiles have been delivered?
The two end‐member cases:
1. During the main phase of accretion; i.e., pre‐Moon forming giant
impact
– Giant impacts can lead to bulk
accretion or erosion of volatiles.
Re‐equilibration of magma ocean
with the new atmosphere.
2. Associated with a late veneer
All sorts of combinations within the
end‐member cases are possibleHow do we go about establishing volatile
inventories?Venus composition
Mass spectrometers on Venera 13 and 14 missions and the NASA Pioneer
missionMars composition • Surface compositions and inventories: Viking, Odessey, MSL • Surface and interior compositions: Martian meteorites
Earth composition
Interior inventory from basalts
A vesicular subaerial basalt A gas rich popping glass recovered
from the bottom of the oceanCorrect C/N ratio using rare gas
fractionation
N2/40Ar does not change as a function
of degassing
Increasing degassing
Marty, 199510±5 oceans 1.7±0.3 oceans
Halliday, 2013Halliday, 2013
Comparison of volatile abundance patterns
1e+0
1e-1 Earth
Venus
1e-2 Mars
Sun
1e-3 CI
6 Si)
1e-4
(M/106 Si)/(M/10
1e-5
1e-6
Y Data
1e-7
1e-8
1e-9
1e-10
1e-11
1e-12
1e-13
1e-14
2020Ne
Ne 3636Ar
Ar 8484Kr
Kr
14N
14N 1212C
C
After Halliday, 2013Halliday, 2013
Comparison of volatile abundance patterns
1e+0
1e-1 Earth
Venus
1e-2
(M/106 Si)/(M/106 Si)Sun
Mars
1e-3 CI
1e-4
1e-5
1e-6
Y Data
1e-7
1e-8
1e-9
1e-10
1e-11
1e-12
1e-13
1e-14
2020Ne
Ne 3636Ar
Ar 8484Kr
Kr
14N
14N 1212C
CEvidence for accretion of solar volatiles in deep
mantle
Iceland: Mukhopadhyay, 2012; DM Holland and Ballentine, 2006;
(Adapted from Marty, 2012; Mukhopadhyay et al., in prep).Evidence for hydrodynamic escape? Iceland: Mukhopadhyay, 2012; DM Holland and Ballentine, 2006; (Adapted from Marty, 2012; Mukhopadhyay et al., in prep).
H and N composition of Earth
Earth volatiles: Signature of Solar, comets or chondritic
meteorites?
Marty, 2012Earth’s hydrogen budget: mainly acquired during
main phase of accretion and sculpted by impacts.
Isotopic ratios of H, C, N, Cl are chondritic
Elemental H/N ratio is not
Water may have been
mostly accreted prior to
the last giant impact;
~80% (also see Halliday, 2013).Impacts (large and small) and the different outcomes of impact events shaped early terrestrial atmospheres.
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