実験報告書様式（一般利用課題・成果公開利用）（ ※本報告書は英語で記述してください。ただし、産業利用課題として採択されている方は日本語で記述していただいても結構です。）

課題番号 Project No.

承認日 Date of Approval 2014/9/3
承認者 Approver Takanori HATTORI
提出日 Date of Report 2014/9/3
装置責任者 Name of Instrument scientist

2014A0004

Takanori Hattori

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）

Low-Temperature and High-Pressure transformation of sulfuric

BL11 PLANET

acid hydrates

実施日 Date of Experiment

Experimental Report

実験責任者名 Name of principal investigator9th-16th June 2014

Helen Maynard-Casely

所属 Affiliation
Bragg Institute, ANSTO試料、実験方法、利用の結果得られた主なデータ、考察、結論等を、記述して下さい。（適宜、図表添付のこと）
Please report your samples, experimental method and results, discussion and conclusions. Please add figures andtables for better explanation.

1. 試料 Name of sample(s) and chemical formula, or compositions including physical form.
During the experiment we attempted four experimental runs.

For each of these sample runs a solution of dueterated

sulfuric acid and dueterated water was sealed with 0.03 g of lead, to act as an internal pressure calibrant, into a TiZr
sealed gasket. This gasket was supported by an aluminimum ring, and the assembly was placed into the Mitopressure cell, mounted onto the PLANET beamline.

The first run, with a sample of 35 wt% D2SO4.D2O solution was

not successful as the gasket did not seal properly at 7 tonnes of load. For runs 2-4, the sample was sealed with 11
tonnes of load, which was sufficent to seal the TiZr gasket but did not apply too much pressure to the sample intially.
For samples 2 to 4 a common experimental temperature and pressure path was followed, designed to maximise thearea of phase space explored, and data collected to chart this. The samples were cooled to 100 K (this was undertakento freeze the sample into an glass/amorphous state) then the sampes were warmed to 180 K to crystallise (thisbehvaiour has been noted in previous studies by the principal investigator).

Upon crystallisation at 180 K the samples

were cooled to 100 K where they were compressed to ~2 GPa. Once reaching this pressure the samples were heatedto 300 K.

The action of heating also increased the pressure, an affect that was expected. Each sample rose to ~3.5GPa upon heating to 300 K.

From this point the load applied to the sample was lowered and data was taken in stages

until the sample melted where each run was finished.

RunSample

First data run #Last data run #Calibration

Emply and Vanadium in

12931

12939

Mito pressure cell

135 wt% D2SO4.D2O

12940

12971

235 wt% D2SO4.D2O

12972

13033

345 wt % D2SO4.D2O

13034

13096

425 wt% D2SO4.D2O

13097

13131

2. 実験方法及び結果 （実験がうまくいかなかった場合、その理由を記述してください。）
Experimental method and results.

If you failed to conduct experiment as planned, please describe reasons.

Aims of the experiment
The aim of the proposed experiment was to establish the high-pressure and low temperature behaviour ofwater-rich sulfuric acid hydrates.

Sulfuric acid hydrates are thought to form readily on the surfaces of the ice

moons of Jupiter; Europa, Ganymede and Callisto.

After forming these materials, which are denser than thesurrounding water ice, would potentially sink into the ice crust of these moons and be subjected to the highpressures of these environments.

Hence, understanding the high-pressure and low temperature behaviour ofsulfuric acid hydrates could vastly impact on the interior models of the icy moons of Jupiter.
Preliminary results from data
The sample crystallised at the expected temperature, 180 K, but not to any known forms of sulfuric acid hydrate.
Hence from the very beginning of the experiment we were probing new behaviour of this planetary ice material.

Figure 1 – Compression of 35 wt. % D2SO4.D2O sample at 100 K during Run 2. The pattern collected at 15 MPa is at this point
belivieved to be a mixture of a new form of sulfruic acid hydrate and a high pressure ice phase. During the collection we undertook a
two measurements in ‘double frame’ mode, which allowed observations of peaks at TOF higer than (4000 micro seconds). As is shownin the Figure, this hydrate underwent a phase transition between 30 MPa and 33 MPa of oli pressure applied to the pressure cell.

Figure 1 shows the compression of the sample in experimental Run 2 at 100 K.

The first pattern collected in thissequence, it is believed at this time, is a mixed pattern of a new sulfric acid hydrate and a high pressure water ice.
Upon compression,

at a pressure of ~1.5 GPa determined from the internal lead calibrant, the sample underwent atransistion to a further new phase of sulfuric acid hydrate.

The pattern of this new hydrate was distinctly strained,

and co-existed with large broad feature in the pattern, which was interpreted to be a form of amorphous ice.

2. 実験方法及び結果（つづき） Experimental method and results (continued)
On warming the pattern fully amorphised at 200 K, which is very unusual behaviour.

On further warming it

crystallised to a pattern that has been interpreted to be a mixture of a further new sulfruric acid hydrate and Ice
VII.

On decompression at 300 K the high-pressure ice phases did not behave as expected.

Indeed, Ice VII

was observed in Run 2 to transform to ice VI at 1.8 GPa – much higher than the boundary in pure deuterated
water at 0.9 GPa. Additionally on compression it was noted that the ice phases melted at much higher pressuresthan in pure ice. Across the three solutions studied, this effect was very variable and indicates that the presenceof sulfuric acid, as well as forming hydrate phases at high-pressures, also has a sigificant effect on the water ice
phases formed.
Intial conclusions

Figure 2 – Preliminary phase diagram of sulfuric acid hydrates under pressure.

The red arrows indicated that the Ice VI to liquid

and Ice VI to a mixture of High Pressure sulfuric acid hydrates and Ice VII is very dependent on the wt. % of sulfuric acid in thesample.

The dotted lines indicated that, at this stage in the analysis, these boundaries are only for guidance and will be

confirmed at a later stage.

The initial conclusions are summarised in Figure 2, but additionally the following points can be made from theprelimary analysis.
1) Hydrates of sulfuric acid do exist at high-pressure, but are distinctly different from the seven forms thatare observed at ambient pressures. Hence, sulfuirc acid hydrate do have to be considered as materials forthe interors of the ice moons of Jupiter.
2) At present, preliminary data analysis suggests that three new phases of sulfuric acid hydrate wereobserved during the experiment. Of these, the data quality of two is sufficent for indexing and potential

structure solution. It is possible that these patterns (especially those from initial compression at 100 K)
are in fact from two hydrate phases – this will be determined from closer inspection of the data.
3) The full amorphisation of the pattern on warming from 100 K to 300 K at 2.5 GPa is very strange
behaviour in a sytem of this kind. Further study will be needed to investigate this mechanism and to see
if there is a precident for this behaviour in the litereature.
4) The presence of sulfuric acid distinctly changes the melting and phase boundaries of the high-pressure ice
phases VII and VI. For instance Ice VI was observed existing at a much higher pressure (greater than 2GPa) than observed in pure D2O. Charting this modification of phase boundaries as a function ofpressure and acid content is an essential input for interior models of Jupiter’s ice moons.
Further work and publication outlook
To date, because of time contraints and the complexity of the observed behvaiour, only very preliminary analysis
has been undertaken on this data set. However, the data set obtained from this experiment will be the starting
point for the principal investigator’s (Helen Maynard-Casely) JSPS fellowship at Univeristy of Tokyo,
commencing in November 2014. During this three month fellowship Dr Maynard-Casely will be working in
the lab of Assoc/Prof Komatsu and be able to undertake a number of complimentary measurments to the datacollected at the PLANET beamline.
this time.

Hence, an exact plan for publication of this work would be unrealistic atBut, we anticipate that at least two peer-reviewed papers could result from this work and it is hopedthat the work will be presented at the American Geophysical Union conference in 2015.