From Z to Planets: Phase III - DOE-NNSA grant #DE-NA0003904 (7/1/19- 6/30/22) to Harvard University
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DOE-NNSA grant #DE-NA0003904 (7/1/19-
6/30/22) to Harvard University:
From Z to Planets: Phase III
2021 Stewardship Science Academic Programs (SSAP) Symposium
February 16-18, 2021
Harvard University: Stein Jacobsen, Michail Petaev, Dimitar Sasselov, Li Zeng.
UC Davis: Sarah Stewart, Dylan Spaulding, Bethany Chidester, E. Davies.
Sandia National Laboratory: Patricia Kalita (ZFSP Co-I), Seth Root, Josh Townsend, Thomas
Mattsson, Daniel Dolan, David Bliss, Chris Seagle, Luke Shulenburger, Raymond Clay.
Lawrence Livermore National laboratory: Richard Kraus
Z Fundamental Science Program (ZFSP): Formation and evolution of Earth-like and Super-
Earth planets: Fundamental planetary material property experiments on Z – Phase IV
Sandia National Laboratories is a multi program laboratory managed and operated by Sandia Corporation, a
wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National
Nuclear Security Administration under contract DE-AC04-94AL85000.
.
Objectives: • (i) giant impacts, including To achieve these goals, we
Moon-forming events, continued studies of
Measure the fundamental material
• (ii) early silicate vapor
physical properties atmospheres, properties of major
components of Earth-like and
of the major • (iii) interiors of Earth-like and SuperEarth planets using the
building blocks of Super-Earth planets, unique Z accelerator at SNL.
Earth-like and • (iv) planetary thermal
SuperEarth planets evolution, differentiation,
and core formation, and
in order to develop
• (v) why the most common
better models of: sizes of exoplanets are ~1.5
and 2.3 Earth radii.
Earth-like planets Z measurements of important materials in
rocky planets
Phase II: Measure properties of the BSE with the Z
machine
1) Internal • BSE = Bulk silicate Earth
Finish up work on individual components
structure •
• Fe, O, Si, Mg are 90% of the Earth
Main sequence • Add Ni, Al, Ca for 98%
of planets
2) Planetary Major minerals
• Upper mantle: (Mg,Fe)2SiO4 (olivine)
formation by • Lower mantle: (Mg,Fe)SiO3 (perovskite now
“giant impacts” bridgmanite)
(Mg,Fe)O (magnesiowüstite)
New model: (Mg,Fe)SiO3 (post-perovskite)
synestia • Core: Fe, Ni (5.5 wt%) (iron alloy)
Major Earth end members: Fe, FeO, MgO, SiO2
Exoplanet observations
• Mass and radius, temperature
• Infer interior structure & composition
All will have rock-metal cores
Nebular Condensation: protoplanetary disk of solar
composition at 10-4 bar.
The fraction of condensed rocky Methane Clathrate
matter (>200 K) is calculated with the
GRAINS code
Ammonia Hydrate
This condensation sequence can be
In reality, ices probably exist
approximated as a piecewise as complex mixtures in the
function with 0.5% rock (including interiors of planets. Thus,
metals) condensed above ~200K and exploring the properties of
the mixtures under high
0.5% rock + 0.5% H2O ice condensed
pressure is important.
below ~200 K.
Zeng et al. PNAS 2019
Evidence for cosmic ices in the composition of solar system planets
• Elemental abundance ratios in the atmospheres of Jupiter, Saturn, Uranus and Neptune. “N” in Jupiter
represents values from ammonia (NH3) abundance measurements made by the Galileo probe (mass
spectrometer: [J(M)] and attenuation of probe radio signal: J[R]) and the Juno microwave spectrometer
[J(MWR)], whereas “Ar” values are based on protosolar Ar/H values of Asplund et al. (2009) [J(A)] and Lodders
et al. (2009) [J(L)]. Saturn’s He and N are labeled S. N/H of Saturn is a lower limit, and S/H is highly
questionable. Only C/H is determined for Uranus and Neptune from ground-based CH4 but remains uncertain.
Ref: Atreya et al (2017,2018,2020).
EOS: H2O • Density-Temperature • Isentropes • Isobars • Phase Domains • Phase Gaps • Ionization of Fluid Ref: Zeng & Jacobsen et al. 2021 (in progress) IAPWS
EOS: H2O
• Zoom-out
• Density-Temperature
• Isentropes
• Isobars
• Phase Domains
• Phase Gaps
• Ionization Constants
• Superionic Phases
• NH3 expected to be
similar in the ultra-
compressional regime
Ref:
Zeng & Jacobsen et al. 2021 (in progress)
IAPWS
Mass-Radius log-log plot of
exoplanet candidates (RV)
• The planets’ data were downloaded from
the NASA Exoplanet Archive.
• Exoplanets color-coded by their surface T.
• The yellow histogram on the right-hand
side shows the logarithmically-binned
radius distribution of 4433 Kepler planet
candidates, with a hint of bimodality and
a gap at 1.8-2 Earth radii.
•
• The dashed cyan arrows and purple
arrows are growth trajectories for the
addition of H2O-ices, and H2-He gas
respectively.
• The boundaries in radius dividing up
different planet types are from model-
independent survival function analysis of
planet radii, shown as the thick dashed
lines parallel to the mass-axis.Growth Model:
new
classification of
planets
Zeng et al. PNAS 2019Mathematica Tool under development in order to Understand Exoplanet Population • Exoplanet Radius Bi- modal Distribution (aka Gap) Confirmed with new data up to 2021/02/02! • Cosmic Ices (H2O/NH3/CH4) important! • Manipulate Exoplanet Temperature Range • Manipulate Host Stars’ Properties • Comparison with solar system planets Ref: Zeng & Jacobsen et al. 2021 (in progress)
Mathematica Tool under development in order to Understand Exoplanet Population • Exoplanet Radius Bi- modal Distribution (aka Gap) Confirmed with new data up to 2021/02/02! • Cosmic Ices (H2O/NH3/CH4) important! • Manipulate Exoplanet Temperature Range • Manipulate Host Stars’ Properties • Comparison with solar system planets Ref: Zeng & Jacobsen et al. 2021 (in progress)
Mathematica Tool under development in order to Understand Exoplanet Population • Exoplanet Radius Bi- modal Distribution (aka Gap) Confirmed with new data up to 2021/02/02! • Cosmic Ices (H2O/NH3/CH4) very important!!!!! • Manipulate Exoplanet Temperature Range • Manipulate Host Stars’ Properties • Comparison with solar system planets Ref: Zeng & Jacobsen et al. 2021 (in progress)
We divide • i) Rocky worlds (1/4, and possibly more than 1/2, by mass) of H2O-
four main dominated ices in addition to rock.
categories • iii) Transitional planets (4–10 R⊕) are likely to be ice-rich
according to the with substantial gaseous envelopes (~5–10% by mass).
They are typically a few tens of M⊕ forming a bridge
cumulative planet between small exoplanets and gas giants on the mass–
radius distribution radius diagram.
and mass–radius • iv) Gas giants (>10 R⊕) are dominated by H2–He in the bulk
composition and have masses and radii comparable to
diagram Jupiter.Mass-Radius Diagram suggests a peak of planet abundance around 2 Earth radii These Planets are most likely water worlds They are very common around sun-like stars, But our solar system lacks such type of planets
EOS of H2O is well
known
Ices on these Water
worlds are mixtures
(H,O,C,N)
Ammonia (NH3) and
Methane (CH4) are
important components of
water worlds and we are
funded to use Z for such
measurementsThe experiments use the cryogenic liquid cell system, which has been used previously for CO2, xenon, and deuterium experiments (Knudson et al. 2004; Root et al. 2010, 2013) • Schematic view of the flyer-plate impact experiment showing the front and rear sapphire-quartz top-hat assembly. • The flyer approach to the target is measured to high precision using VISAR. • At impact the shock transits into the sapphire window. • When the shock transits into the quartz window, the VISAR begins tracking the shock front as it progresses through the quartz window and into the liquid sample (CO2 in this example) • The shock velocities and thermal emission in the quartz, sample, and rear quartz window are measured directly.
Understanding water worlds evolution and habitability • Water worlds are made up of significant mass fraction of C, N, O, H-bearing ices plus rock, and metals. • Given their composition, these planets are potential candidates for harboring life. • Identifying such exoplanets will rely on recognizing diagnostic characteristics in their atmospheres. Thus, understanding the formation and structure of the mantles oceans and atmospheres of exoplanets is important. • Our calculations suggest a wide range of possible water-content: from super-Earth planets with either shallow global oceans (similar to Earth) or deep global oceans with such high pressures at depth that water transforms into high pressure ice phases.
Exchange
between
silicate The pressures and temperatures of these
mantles and contact points are much different than those
found in the Solar System, so we must develop
deep oceans new models to determine how volatiles will
exchange between these planetary reservoirs
or ice mantles and how these will affect the habitability of the
planet and its biogeochemical cycles.
must be
consideredHabitability of water worlds • Need to understand both the surface and the interior of such an object. • Requires a clear understanding of the equations of states (EOS) of the mixture of methane (CH4), Ammonia (NH3), and a variety of salts added to H2O, in particular, the melting curve, evaporation curve, and critical points for this multi-component mixture. • This mixture is considered to be the most likely composition of the ocean on these water worlds, based on the abundances of chemical elements that form planets. • We investigate the range of planet models for 2 R⊕ planets. • We will address whether these objects have an ocean or not, and the nature of such oceans in relation to their interior thermal evolution and their distances to their stars.
Accretion and early history of the planets: Evidence from Cratering
• Direct evidence for the former
existence of large bodies comes
from the observation of craters on
planets and satellites.
• Craters of all sizes are present (pits
due to impact of tiny grains to giant
craters over 1000 km in diameter.
• The craters record the previous
existence of now vanished objects,
in this case the planetesimals. A composite photograph of
Phobos, 26 x 18 km, the larger
• Planets grew by accretion of smaller satellite of Mars and an analog
bodies for a planetesimal
Planet Earth is believed to have formed by the accretion of planetesimalsThe Moon is likely the result of a Giant Impact on the proto-Earth Modeling: 1) SPH 2) EOS 3) EOS improved with Z The outcome of such collisions is a disk from which the Moon formed
Schematic single component phase diagram The black curves are phase boundaries The blue curve is the shock Hugoniot, The green lines show decompression paths along isentropes from specific shock states (blue points). In mixed phase regions, the mass fraction of each phase is given by the lever rule, where a parcel at E is a mixture of B and F. The triple point of silicates is similar to an average pressure of the solar nebular at 1 AU, about 10-4 bar. The critical point for silicates is approximately 0.1 bar. The dark blue line shows an example vaporization path at constant pressure.
Water- methane-ammonia EOS mixtures
liquid ammonia
1bar = 100 kPa
EOS equations tables and diagrams are being preparedForsterite (Mg2SiO4) Shock-and-release data are key for robust forsterite EOS model development.
Our team has expanded the capabilities of the ANEOS code
package developed a new model for forsterite using our Z results.
Shock temperatures are too large in previous forsterite ANEOS
models; our new model is a significant improvement (A). Our
calculation of absolute entropy on the forsterite Hugoniot and Z
shock and free surface release to derive (B) temperatures and (C)
densities on the vapor curve with comparisons to previous and
new ANEOS models for forsterite.Thermal profiles through the Earth after a canonical Moon-forming impact event, comparing
two forsterite EOS models for the mantle: ANEOS-G (A) and New ANEOS (B).
Dots show the pressure-entropy
in the midplane (+/-1000 km)
within the Roche radius compared
to the phase boundaries (orange
line: vapor curve from ANEOS-G;
black lines are the melt curve and
vapor curve from New ANEOS.
The highest pressures are at the
core-mantle boundary and the
lowest pressures are in the disk.
The pressure profiles through the
mantle and disk fall above the
forsterite critical point.
T he case thatmuch ofthe Earth's mantle reaches the supercriticalfluid regime during the Moon
-constrained EOS model.Giant Impact time evolution (SPH simulation)
• Earth-mass body impacted by a
20 km/s half mars-mass
projectile.
• Colors in the final panel
represent the core (gray) and
layers of the post impact state
which are mapped to the initial
conditions.
• Material in red is the escaping
material.
• Most of the ejecta comes from
the impact site and the
projectile, making up some of
the most shocked material in
the simulation.
Melting and vaporizationNew Model:
Formation of the
Moon within a
terrestrial synestia.
Test these principles
for water worlds
Earth's mantle reaches the
model.
All the stages are to scale.Challenges • Our solar system planets fit into our new classification of planets. • However, two puzzles remain unsolved: • The compactness of many Kepler planetary systems compared with our own solar system • The lack of planets intermediate in size between Earth and Neptune in our own solar system. • The most common planet (2 R⊕) does not exist in our solar system! • Solving these puzzles may be a key to understanding the unique initial conditions that form our own solar system. • The abundance of these intermediate-size planets (water worlds) in our galaxy challenges us to understand their formation, migration, interior structure, atmosphere, and habitability. • Proper EOS in the form P-T, P-ρ, P-S, T-S diagrams for rock, metal components and water-ammonia methane ices are essential for progress. • The case that much of the Earth's mantle reaches the supercritical fluid regime during the Moon forming giant impact is much more robust with our new experimentally- constrained EOS model.
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