It should be emphasized that crushing does not liberate all entrapped gases within the sample and the amount of fl uid released varies with each crush (McMahon et al. Table 2 presents the relative abundances of each gas detected. The sampling and analysis techniques are discussed in great detail in Norman & Moore (1997) Moore et al. Several crushes per sample were performed to obtain some statistical data on the spread of the gas concentration within each sample (the exact number of crushes for each sample is given in Table 2). After shooting, * 0.1 g samples were taken from the shocked regions within the impact craters and from the pre- shot material, crushed and analysed separately using Pfeiffer Prisma quadrupole mass spectrometers at New Mexico Tech. In each case, several grams of pre-shot material were kept to compare gas concentrations within the material before and after the shot.

V p and m are the projectile volume (4.19 × 10 m for a 2 mm diameter sphere 8.18 × 10 − 9 m 3 for a 2.5 mm sphere) and mass (3.24 × 10 − 5 kg for a 2 mm diameter sphere 6.33 × 10 − 5 kg for a 2.5 mm diameter sphere), respectively, C (2600 m s − 1 ) and s (1.62) are the linear shock wave speed parameters for basalt (Melosh 1989) and v is the impact velocity (m s − 1 ). A Horiba LabRam-HR Raman spectrometer was used to determine if serpentinization had occurred in. The grains were then left overnight in a fume cupboard to dry completely before analysis was carried out. This allowed the olivine grains to be quickly separated from the CO 2 and H 2 O ice mixture, ensuring any serpentinization that may have occurred resulted from the impact alone.

The impacted material recovered from each segment of the ECS, control, and the remaining target material within the target container, were placed into separate funnels onto clean fi lter paper and placed inside a fume cupboard. Each segment (labelled ESC 1 – ECS 4) of the ECS collects materials at different angles of ejection (ESC 1: 0 – 25°, ECS 2: 50 – 65°, ECS 3: 65 – 75° and ECS 4: 75 – 85° – see Fig. A four segment ejecta capture system (ECS) was used to collect ejected target material. In each case the targets were impacted by a 2 mm diameter stainless steel sphere at velocities between 3 and 6 km s − 1. Four shots were made in this part of the programme. Spraying the target with HPLC water prevents the target material crumbling when being placed into the horizontal target holder. 2Mg Si O ( OH ) 3Mg SiO + SiO + 4H O Crushed CO 2 (sourced from ‘ BOC special gases ’, UK) and H 2 O ice (made from fi ltered, reverse osmosis water) were mixed with the olivine grains (total mass 100 g, sourced from the Natural History Museum ’ s (London) mineral collection), and the surface sprayed with high performance liquid chromatography grade (HPLC) water before being stored overnight in a freezer at − 30 ☌ prior to the hypervelocity impact. Heating the grains in air at 600 ☌ causes the reaction below (Deer et al. The olivine grains were baked in a furnace at 600 ☌ for 12 h to remove any serpentinization which may have previously occurred. Targets were made-up of a mixture of CO 2, H 2 O (ice) and olivine grains (> 355 μ M in diameter), with a 2 : 2 : 1 weight ratio, respectively. 2012) indicating that there may be reservoirs of methane on Mars from historic impact of organic rich impactors. Additional supporting work has shown that methane can be impregnated, and subsequently trapped, within a porous sandstone target by a hypervelocity impact from an organic-rich impactor (McMahon et al. 2013) into calcite, and have also been observed in iron rich carbonates (Trieman 2003). However, similar globules are produced in shock impacts (see Figure 2 from Lindgren et al.

1996) was supported by the discovery of carbonate globules. For example, the possible identi fi cation of microbiota in ALH84001 (McKay et al. Shock production of either negates the necessity for a biological origin. methane and magnesite (MgCO 3 ) are of astrobiolo- gical signi fi cance (Russell et al.

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