TMT & Observations of giant planets
Junjun Liu
Caltech
TMT
 The Thirty Meter Telescope (TMT) is a
30 m ground based telescope with a
collecting area of 650 m2 .
 It will observe through the atmospheric
windows from 0.31 to 28 μ m.
 Advanced adaptive optics capabilities
will allow highly sensitive, diffractionlimited observations beyond 1 μ m over
most of the sky.
Jupiter’s infrared spectrum
TMT gives unprecedented opportunity to retrieve the abundance of
multiple species simultaneously over a wide spectral range.
Jupiter: Vortices
Fletcher et al. (2010)
 TMT can be used to study the detailed structures of large coherent vortices
on Jupiter, such as the Great Red Spot (GRS) and white ovals, as well as their
temporal variability.
 Highly sensitive and diffraction-limited observations of TMT can increase
the information content and enable better retrieval of temperature,
composition (Ammonia, Phosphine, and para-Hydrogen) and aerosol
structure of vortices.
Jupiter: Atmospheric thermal waves
 Thermal waves are ubiquitous in Jupiter’s
atmosphere, in particular, in the
equatorial region (~ 15 N and ~15 S).
 Better characterization of the thermal
waves would greatly enhance our
understanding about their generation
mechanisms, and their influence to the
atmospheric circulation.
 TMT could be used to investigate the
vertical structure of the waves, as well as
the propagation direction and speed.
Jupiter: Color
 What determines the color of the cloud
bands? NH4SH ice? (Baines et al. 2004)?
 How does the composition couple with
temperature and flow fields?
Jupiter: Global upheaval
 Jupiter’s visible cloud structure undergo a sudden upheaval where belts and
zone change color (e.g., Rogers 1995).
 Measurements of the temperature and composition fields, and the opacity and
vertical distribution of cloud provide direct clues to particulate cloud chemistry
and atmospheric dynamics accompanying the color change.
Jupiter: Low frequency variability
 Jupiter’s stratosphere
undergoes “quasiquadrennial” oscillation
(QQO) with period of 4 ~ 5
years. It is similar with the
QBO in Earth’s atmospheres.
 How does the low-frequency
variability is generated? What
determines its characteristic
time scale?
Observed equatorial temperature
oscillation on Jupiter (Leovy et al.,
1991)
 Is the global upheaval related
to the different phases of
QQO?
Saturn: Low frequency variability
 Saturn’s stratosphere undergoes “quasisemiannual” oscillation with period of 14 ~15
years. It is likely related to Saturn’s seasonal
variation. But how?
NASA (IRTF), Orton et al. 2008
Saturn: Giant storm
 TMT can be used to monitor the onset, develop and decay of the large scale
convective storm.
Saturn: Hexagon polar vortices and
Ribbon-like feature
 TMT can be used to
characterize distinct features
on Saturn: such as the
hexagon polar vortices and
ribbon-like feature.
 Such observation can
constrain the global
circulation model and shed
light on the underlying
dynamics.
Liu et al. 2010
NASA image collection
Uranus: Previous observations
Orton et al. 2012
Photometric (low-resolution) modes of Spitzer Infrared Spectrometer (IRS)
spectroscopy of Uranus.
 The ground-based observations could constrain the bulk composition and the
mean vertical distribution of temperatures and abundance of gases, such as
He/H2 ratio, para-H2 fraction and hydrocarbon abundance (Burgdorf et al.
2006; Hesmann et al. 2006).
Uranus: troposphere and stratosphere
VLT filtered radiometric images of
Uranus at 13.2 μm, sensing
stratospheric emission from C2H2.
VLT filtered radiometric images of Uranus at
18.7 μm, sensitive to tropospheres.
Neptune: observations
 A hot spot near Neptune’s
southern pole was discovered
(Orton et al. 2012).
 The spatial variability is strongly
tied to the atmospheric
dynamics, such as the vertical
propagation of waves from the
troposphere to the
stratosphere.
Image of Neptune in CH4 emission
at 7.9 μm, taken with VISIR at the
VLT.
 The observations would
constrain the properties of the
waves, as well as the
background states for wave
propagation, for instance, the
atmospheric stratification.
Uranus and Neptune: Seasonal cycle
Uranus: 97 degree
obliquity
Conclusions
 TMT gives unprecedented opportunity to retrieve the abundance of
multiple species simultaneously over a wide spectral range.
 TMT can be used to study the detailed structures of the distinctive
features on giant planets, such as the Great Red Spot (GRS) and white
ovals, as well as their temporal variability.
 TMT can be used to monitor and characterize the long term variability
on giant planets.
 The observations from TMT would provide important clues for
understanding the similarities and differences in atmospheric dynamics
and chemistry among the giant planets.