Secret of Burning Ice--Methane Hydrate--
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Cassini-Huygens spacecraft and Titan (c) NASA
High Pressure Phase of Mathane Hydrate: MH-III (c) T.Iitaka
MH is also known as an important material for understanding the mystery
of the atmosphere of Titan, the largest satellite of Saturn. The
conventional theory could not explain abundant methane gas in Titan's
atmosphere because MH-I inside Titan was assumed to decompose into ice
and methane around 1 or 2 GPa, and escape to the atmosphere to be
photodecomposed in early stage of Titan's history. To understand this
mystery is one of the goals of the Cassini-Huygens spacecraft, which
started its journey in 1997 and will arrive at Saturn system in 2004}.
Methane hydrate (MH), known as Burning
Ice, is a special class of ice that contains methane molecules
in cages or networks of hydrogen bonded water molecules. Low pressure
phase of methane hydrate (MH-I) forms sI structure of cages. MH-I,
abundant in the deep ocean, has been attracting attention of the
industry as a key material of new energy resource, whose amount is
estimated twice as much as the total fossil fuel reserve.
On the earth, in 2001, Loveday
et al. discovered new phases of MH by X-ray and neutron diffraction
experiments under high pressure: MH-I transforms to MH-II ( sH cage
structure) at 1 GPa, and then to MH-III phase (orthorhombic filled ice
structure) at 2 GPa, which survives at least up to 10 GPa. Other
researchers reported similar high pressure phases. Recently Hirai et
al. reported that MH-III survives up to 42 GPa at room temperature.
et al. have measured the site- and
pressure-dependence of CH- and OH-vibration frequencies in these phases
up to 5.2 GPa. Discovery of these high pressure phases allows us a new
abundant methane gas in Titan's atmosphere: methane gas may be reserved
in thick layers of MH-III under Titan's surface and gradually emit to
the atmosphere from the reservoir. In 1997 NASA and ESA launched
Cassini-Huygens space craft for investigating the Titan's atomosphere,
which will arrive at Titan in January 2005 and provide a large impact
the space materials science.
Other types of hydrates are also important such as H2
hydrate for hydrogen strage, inert gas hydrates with simplest
structure, and CO2 hydrate for preventing green house
We are studying the physical properties of the newly discovered high
pressure phases of methane hydrate by the first principles molecular
Links to Titan
extracts gas from methane hydrate in world first
- J. S. LOVEDAY,
R. J. NELMES, M. GUTHRIE,
S. A. BELMONTE, D. R. ALLAN, D. D. KLUG,
J. S. TSE and Y. P. HANDA,
Stable methane hydrate above 2 GPa and the source of Titan's
atmospheric methane, Nature
410, 661- 663(2001).
- J. S.
Loveday, R. J. Nelmes, M. Guthrie, D. D. Klug, and J. S. Tse, Phys.
Rev. Lett. 87, 215501 (2001).
and T.Ebisuzaki, Methane hydrate under high pressure,
Phys. Rev. B 68, 172105 (2003).
et al., Retention of filled ice structure of methane hydrate up to
42 GPa, Phys. Rev. B68, 172102 (2003).
et al., In situ observations of
high-pressure phase transformations in a synthetic methane
hydrate, J. Phys. Chem. B 106, 30 (2002).
- T.Iitaka and T. Ebisuzaki, The Study of Materials under Extreme
Hydrates and Planetary Ices" (Invited)
- T.Iitaka and T. Ebisuzaki, Joint
- 41th ehprg international conference high pressure science and
(Bordeaux, July 7-11, 2003). T.Iitaka
and T.Ebisuzaki, Filled ice
structure of gas hydrates―a density functional study, J.
Conden. Matt. 16, S1171 (2004). (proceedings)
and K.Terakura, Structural
transformation of methane hydrate from cage clathrate to filled ice
Chem. Phys. 119, 6784 (2003).
Kumazaki et al., Single-crystal
growth of the high-pressure phase II of methane hydrate and its Raman
scattering study, Chem. Phys. Lett. 3888, 18 (2004).
Links to H2 hydrate
Links to Methane hydrate
Links to Silicon Clathrate
- V.V. Struzhkin et al.,
Hydrogen Storage in Molecular Clathrates, Chemical Reviews 207, 4111 (2007).
Schuth, Fuelling the hydrogen economy, Nature 434, 712-713(7
et al., Tuning clathrate hydrates for hydrogen storage, Nature
434, 743-746(7 April 2005)
et al, Structure and Dynamics of Hydrogen Molecules in the Novel
Clathrate Hydrate by High Pressure Neutron Diffraction, Phys. Rev.
Lett. 93, 125503 (2004).
could make hydrogen fuel storage more efficient, practical
et al., Hydrogen Clusters in Clathrate Hydrate, Science 2002 297:
Hydrogen storage in molecular compounds, PNAS
Patchkovskii and JS. Tse , Thermodynamic stability of hydrogen
clathrates, PNAS | December 9, 2003 | vol. 100 | no. 25 | 14645-14650.
hydrogen fuels new storage method
- Takuo OKUCHI