Reactivity and Survivability of Glycolaldehyde in Simulated Meteorite Impact Experiments

V.P. McCaffrey1*, N.E.B. Zellner2, C.M. Waun1, E.R. Bennett1, and E.K. Earl1

1Department of Chemistry, Albion College, Albion, MI 49224, USA

2Department of Physics, Albion College, Albion, MI 49224, USA

*vmccaffrey@albion.edu, 517-629-0622 (Phone), 517-629-0264 (Fax)

Supplemental Materials and MethodsSupplemental Text

Supplemental FiguresFigure S1 – Shock Experiment TargetsFigure S2 – GC of Neat, Unshocked GLAFigure S3 – Gas chromatogram of GLA/4.6 GPa (shot 3597) Figure S4 – Gas chromatogram of GLA/9.4 GPa (shot 3603)Figure S5 – Mass Spectrum of Glycerol, shocked and referenceFigure S6 – Gas Chromatogram (14.0 – 22.0 min) of GLA/4.6 GPa (shot 3597) with

corresponding MS.Figure S7 – Gas Chromatogram (18.5 – 22.0 min) of GLA/9.4 GPa (shot 3603) with

corresponding MS.Figure S8 – GC of authentic, TMS derivatized D-thresose with corresponding MS and

structures.Figure S9 – GC of authentic, TMS derivatized D-erythrose with corresponding MS and

structures.Figure S10 – Gas Chromatogram (20.5 – 22.0 min) of GLA/clay/4.6 GPa (shot 3598)

with corresponding MS.

Supplemental TablesTable S1 – Summary of shock experimentsTable S2 – Retention times

Supplemental References.

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Supplemental Materials and MethodsMethod: Impact ExperimentsThe generation of a desired shock stress relies on the impact of a flat projectile onto the flat

surface of a target-bearing assembly, ideally with both surfaces parallel. Given the metal

composing the target assembly, both the composition of the projectile and its speed can be used

to control the peak shock stress. The projectile is usually a metal flyer plate set into the front of

a Lexan cylinder, although a projectile without a flyer plate can also be used; flyer plates are

typically 22 mm in diameter and 2 mm thick. The projectile's orientation just before impact is

determined through orthogonally mounted cameras and a high-speed flash unit.

The sample is placed in a shallow well (10 mm in diameter and 0.76 mm deep) and capped by a

thin layer of the desired metal (stainless steel 304). Referring to Figure S1a, the female piece

provides the metal cap; the assembled male and female components are threaded into the

coupling ring, which is then pressed into a receptacle in a massive metal cylinder (Figure S1b).

The sample end of the entire assembly is faced flat on a lathe in stages to prevent overheating of

the sample. At the time of the experiment, the entire sample lies just under the surface at one

end of the cylinder, which is used primarily to trap the momentum of the projectile (thus

minimizing the possibility of damage to the impact chamber by high-speed fragments). It also

serves to confine the shocked sample to a limited volume from which it can be extracted

following the impact.

Following the experiment, the metal cylinder is mounted in a lathe and the impacted end is

machined away very gradually so as to minimize thermal effects from the machining process.

Eventually, after enough material has been removed, the metal covering the sample can be pried

away and the sample extracted.

The shock-reverberation technique provides a means of attaining high shock stresses at relatively

low impact speeds (~2 km s-1). It does so, however, through a series of reflected shocks, a

process that is characterized by a lower entropy production than would be generated by a single

shock of the same peak stress (Gibbons and Ahrens, 1971). Thus, the shock-induced effects

presented and discussed below represent the minimum that would be generated by a single shock

of the same amplitude.

2

As described in Peterson et al. (1997), shocked samples were extracted from the target assembly

as quickly as possible after impact in order to limit continuing chemical reactions that could

result from residual heat in the target assembly. The vacuum chamber was rapidly repressurized

and the target was recovered and machined to provide access to the sample well. During the

milling process, the surface of the target holder and assembly were monitored with a remote,

hand-held thermometer; surface temperatures of the metal did not rise more than a few degrees

above room temperature.

(A) (B)

FIGURE S1. (A) Male (containing the sample well, outlined in black) and female target assembly pieces, which are screwed together via the coupling. (B) Stainless steel target holder, showing the placement of the sample-filled target assembly. The thin gap near the center is typical of the intersection of the flat surface and one of the threads in the coupling.

Control experiments with neat (no mineral matrix added) GLA, a fine-grained white powder

(Aldrich), were performed at three impact pressures (Table S1) to ensure that changes seen were

due to reactions at the clay surface and not to autocatalysis or reactions with the sample chamber.

The GLA was tamped into the sample well and the target assembly was then pressed into the

stainless-steel target holder. For masses used, please see Table S1. For each experiment, the

entire target was then placed into the impact chamber. The chamber was evacuated to a pressure

below 200 mTorr and the target was then impacted by either a Lexan projectile with no flyer

plate, an aluminum (AL 2024) flyer plate, or a stainless steel (SS 304) flyer plate, depending on

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the desired shock stress. Given the composition of the projectiles and the flyer plates, with

velocities averaging ~1.1 km s-1, the samples experienced shock pressures ranging from 4.6 to

>25 GPa (see Table S1).

Method: Chemical AnalysesIn all cases, the samples’ organic materials were dissolved in tetrahydrofuran (THF; passed over

molecular sieves and alumina to remove water) prior to derivatization and analysis. With the neat

GLA, approximately 30 mg of the sample were dissolved in THF and sonicated to ensure

complete dissolution. The resulting solution was derivatized with nitrogen-purged BSTFA (N,O-

bis(trimethylsilyl)trifluoroacetamide; Fisher Scientific) to form the trimethylsilyl ethers prior to

analysis by gas chromatography-mass spectrometry (GC/MS).

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Supplemental TextAnalysis of Unshocked Neat GLABefore analysis, the alcohol groups of the GLA were derivatized with trimethylsilyl (TMS)

groups. The resulting silylated compounds have increased volatility and are more easily analyzed

by gas chromatography. TMS ethers of sugars and related compounds also have several common

and diagnostic fragmentation patterns that allow for more facile identification of unknown

compounds. A representative gas chromatogram of the unshocked, silylated GLA in THF is

shown in Figure S2. The predominant component of the sample is the 6-membered ring dimer

(B) at 19.26 min. Also present are peaks representing the monomer (A) at 14.68 min and the 5-

membered ring dimer (C) at 19.32 min. The five- and six- membered ring dimers were identified

by comparison of the MS to published spectra (Novina 1984). Small peaks are present at 13.3

and 15.7 min. These are products from side reactions that occur during the functionalization of

the GLA. The reaction conditions have been optimized for complete silylation of the hydroxyl

groups and no evidence of the mono-silylated GLA dimers was seen.

FIGURE S2. Representative gas chromatogram of neat, silylated GLA showing the three species in equilibrium in THF solution. The peaks correspond to the compounds shown in Figure 1 in the main text. Decane, an internal standard, is marked with a *. All compounds were identified by comparison of their mass spectra to literature mass spectra (Novina 1984).

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Analysis of Shocked Neat GLA: Physical Characteristics

When the neat GLA/4.6 GPa sample was recovered, it was a solid that showed signs of

darkening around the outer edges of the sample, Table S1. When the target assembly from the

shot with GLA/9.4 GPa was opened, the sample was recovered partially as a dark brown liquid

that seeped from the solid sample. The viscous liquid sample was collected using cotton swabs

and stored separately from the solid sample. Before analysis of the samples, it was noted that

they had dried to a solid crust and were no longer viscous. There was no material recovered from

the high pressure shot with GLA/25.6 GPa. Most of what remained was a black crust on the

walls of the container. It was attempted to obtain measurable material by soaking the sample

wells in tetrahydrofuran (THF) before analysis, but no results were obtained.

Shocked Neat GLA: Chemical Analyses

The neat GLA samples at the lowest pressure investigated (4.6 GPa, Figure S3) showed no

significant changes in the composition after derivitization and analysis by GC/MS. New peaks at

retention times between 16 and 18 minutes were seen, but nothing at retention times longer than

20 minutes was detected, indicating that threose and erythrose were not being formed without the

presence of the clay matrix. The new peaks had extremely low abundances and the resulting

mass spectra did not lead to conclusive identification. Briefly, fragments of 73, 105, 135, 147,

and 239 m/z are seen in the EI-MS of each of the five peaks indicated on the GC (Figure S6).

The presence of these fragments suggests that compounds with one or more hydroxyl functional

groups are being synthesized in the impact but as can be seen in the GC, at very low abundances

(Petersson 1969, 1970).

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FIGURE S3. Gas chromatogram of GLA/4.6 GPa (shot 3597). See Figure 1 in the main text for structures of A-C. New compounds are marked with a +.

When the pressure of the shot with neat GLA was increased to 9.6 GPa, however, changes can be

seen in the gas chromatogram at longer retention times (Figure S4). In addition to the GLA

monomer peak at 14.68 min (not shown) and the dimer peaks at 19.2 min, a new peak at 18.84

min, corresponding to glycerol (Figure S5), was seen. Additionally, there are several new peaks

found between 19.75 and 21.25 min labeled with a plus sign (Figure S7). The mass spectra of

each of these peaks show 73, 103, and 117 m/z fragments, suggesting that the newly synthesized

compounds have one or more hydroxyl functional groups in them. However, none of these peaks

had MS or retention times that were consistent with threose or erythrose. Additionally, no peaks

for ethylene glycol were found in this sample either.

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FIGURE S4. Gas chromatogram of GLA/9.4 GPa (shot 3603). For structures of identified peaks, see Figure 1 in the main text. New peaks in the shocked sample are identified with +. Peaks with mass fragments of 147 and 205 m/z are at 19.83, 20.25, and 20.35 min.

Analysis of the GLA/25.6 GPa shot (sample 3596, Table S1) was not possible because no

material was recovered due to decomposition of the sample. Only a black residue was left on the

inside of the target assembly. This material was not recovered or analyzed. This complete loss of

the GLA is consistent with similar studies of amino acids, in which Bertrand et al. showed a

steep decline in the survival of amino acids at pressures > 220 kbar (22 GPa; Bertrand et al.

2009).

After analysis of the shocked neat GLA samples, few changes were seen in the gas

chromatograms. As the pressure of the impact was increased, additional peaks were seen in the

chromatogram but due to their extremely low abundances, conclusive identification of these new

compounds was not possible. Analysis of the mass spectra of the new peaks showed

fragmentation patterns that are consistent with compounds containing OTMS groups in the

derivatized compounds. Current studies in our lab are aimed at elucidating the exact structure of

these new compounds.

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FIGURE S5. A. Mass spectrum of the authentic sample of tri-TMS derivatized glycerol. B. Mass spectrum of 18.95 min peak (Figure S4) from unshocked GLA/clay.

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FIGURE S6: Gas Chromatogram (14.0 – 22.0 min) of GLA/4.6 GPa (shot 3597) with corresponding MS.

16.36 min

16.77 min

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FIGURE S6: cont.

17.44 min

17.54 min

17.91 min

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FIGURE S7: Gas Chromatogram (18.5 – 22.0 min) of GLA/9.4 GPa (shot 3603) with corresponding MS.

19.83 min

20.25 min

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FIGURE S7: cont.

20.35 min

20.50 min

21.25 min

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Figure S8: GC of authentic, TMS derivatized D-thresose with corresponding MS and structures.

20.81 min:

20.88 min:

20.98 min:

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Figure S9: GC of authentic, TMS derivatized D-erythrose with corresponding MS.

20.84 min: impurity

20.90 min: erythrose

21.15 min: erythrose

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FIGURE S9: cont.

21.50 min: impurity

21.79 min: impurity

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Figure S10: GC (20.5 – 22.0 min) of GLA/clay/4.6 GPa (shot 3598) with corresponding MS.

20.81 min assigned to threose

20.88 min assigned to threose

20.91 min assigned to erythrose

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FIGURE S10: cont.

20.97 min

21.16 min assigned to erythrose

21.67 min unidentified

21.83 min unidentified

assigned to keto- form of threose

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Table S1. Summary of shock experiments (August 2011, JSC EIL). ND = not measured.

Shot #

SampleStarting

Mass(g)

Density

Recovered Mass

(g)%

Recovered

v(km/sec)

P(GPa

)

Target/Flyer Plate

3597 GLA 0.062 1.1277 0.06102 98.4 1.113 4.6SS 304/

No flyer plate

3603 GLA 0.0546 0.9931 0.05180 94.9 0.885 9.4 SS 304/Al 2024

3596 GLA 0.0616 1.1205 0 0 1.183 25.6SS 304/SS 304

3598GLA +Clay 0.0903 1.6425 0.0852 94.3 1.127 4.6

SS 304/No flyer plate

3604 GLA +Clay

0.1128 1.7394 0.1160 94.5 1.012 12.2 SS 304/Al 2024

3622GLA +Clay ND ND ND ND 1.163 25.1

SS 304/SS 304

Table S2. Retention times of selected peaks in authentic samples of organic compounds and shocked GLA and GLA/clay mixtures.

Sample RT (min) RT (min) RT (min) RT (min) RT (min)Ethylene Glycol

12.53

Glycolic Acid 15.35Glycerol 18.90D-Threose 20.81, 20.88, 20.98D-Erythrose 20.92, 21.15Shot 3603(GLA only,9.4 GPa)

18.86

Shot 3598(GLA/Clay4.6 GPa)

15.27 18.92 20.81, 20.88, 20.97 20.91, 21.16

Shot 3604(GLA/Clay12.2 GPa)

15.26 18.92 20.81, 20.87, 20.96 20.92, 21.15

Shot 3622(GLA/Clay25.1 GPa)

12.51 20.81, 20.87, 20.97 20.91, 21.15

20

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Supplemental References

Bertrand M, van der Gaast S, Vilas F, Hörz F, Haynes G, Chabin A, Brack A and Westall F (2009) The fate of amino acids during simulated meteoritic impact. Astrobio 9:943-951.

Gibbons RV and Ahrens T J (1971) Shock metamorphism of silicate glasses. J Geophys Res 76:5489-5498.

Novina R (1984) Determination of the structure of glycolaldehyde as their trimethylsilyl derivatives by gas chromatograph – mass spectrometry. Chromatographia 18:96-98.

Peterson E, Hörz F and Chang S (1997) Modification of amino acids at shock pressures of 3.5 to 32 GPa. Geochim Cosmochim Acta 61:3937-3950.

Petersson G (1969) Mass spectrometry of alditols as trimethylsilyl derivatives. Tetrahedron 25:4437-4443.

Petersson G (1970) Mass Spectrometry of aldonic and deoxyaldonic acids as trimethylsilyl derivatives. Tetrahedron 26:3413-3428.

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