Figure 1. Close-up of the ODC collector surfaces upon opening of the MEEP container. Ram-pointing Tray 1 is to the left and wake-pointing Tray 2 (with handles) is to the right. Horizontal rows were assigned letters A-F (starting on left), while vertical columns were labeled 1-6 (starting from top; see Figure 6). The two largest impact features are seen on Tray 1, tile C04 (towards bottom) and on Tray 2, tile B01 (impinging on left frame-member/hold-down grid). Back View/Download Full Size; 972 x 449; 332 Kbytes

Figure 2. Typical mug shot showing that impact features at scales of 2 mm are easily resolved macroscopically. However, the actual tile shown (B02 from Tray 2) is the most densely cratered aerogel specimen observed, containing a large number of circular pits and tracks of various lengths. Back View/Download Full Size; 700 x 700; 354 Kbytes

Figure 3. Typical morphologies of tracks observed in ODC aerogel specimen: (A) Top view of classical, carrot-shaped track with inserts of the enlarged track-terminus showing a small white dot, the projectile, in the lower right-hand corner, and a side-view of the entire track. (B) Top view of a relatively large track that has a wider entrance hole and cross-section than seen in (a); insert is again an enlarged view of the terminus and associated projectile residue. (C) Top (left) and side (right) views of a stubby track that does not exhibit any obvious impactor residue. Tracks pictured in (A) and (C) are classical track shapes produced in impact simulations, yet the stubby track, presently, does not have an experimental analogue. Back View/Download Full Size; 500 x 925; 346 Kbytes

Figure 4. Top-views of typical pits observed in the aerogel collectors of ODC. (A) Largest impact feature observed on ODC that happened close to the edge of tile 2B01 (see Figure 2), and that is obviously affected by the aluminum hold-down grid and frame. Note the rough interior of this pit and the jagged nature of the rim-area. (B) Typical small pit of modestly irregular plan-view and rough interior, yet lacking radial fractures. (C) Intermediate-sized pit displaying a pronounced relief in the pit interior and modestly developed, radial fractures; the latter do not extend to great depth and are confined to the immediate aerogel surface. Back View/Download Full Size; 501 x 1398; 587 Kbytes

Figure 5. Unusually large flake event in plan- and side view. Note the highly irregular outline and the very shallow depth of penetration. The initial flake actually broke up into a number of pieces with the thickest ones displaying distinctly honey colored hues. Note the highly micro-fractured, feathered walls and bottom of this depression, lacking any fracture system, in spite of the large size impactor. Clearly, most of these characteristics are compatible only with low-velocity impacts. Back

Figure 6. Distribution of tracks, pits, and flake-features > 1 mm, based on macroscopic inspection of all ODC surfaces. Note the preponderance of flakes on Tray 1 and the higher density of classical, carrot-shaped tracks on the rearward-facing surfaces. Detailed microscopic investigation will substantially amend these macroscopic observations (for details refer to Table 1). Also indicated is the direction of the swarm-particles. Back View/Download Full Size; 512 x 318; 86 Kbytes

Figure 7. Detailed microscopic view of tile F01 from Tray 2 illustrating the numerous small tracks of constant orientation and inclination. Such tracks are obviously the result of a single, collisional event, presumably the high-speed ejecta from a relatively local hypervelocity impact on the Mir Station. Back

Figure 8. Typical energy-dispersive X-ray spectrum obtained from the white-flake material illustrated in Figure 5. Back View/Download Full Size; 512 x 372; 37 Kbytes