Extended Data Fig. 3: RB18-H2 sampling site.
Before (A) and after (B) photograph montages of the sampling site for samples RB18-H2_0, RB18-H2_50, and RB18-H2_100. All three samples are from the base of the flow, which is greater than 4 m thick. RB18-H2_50 and RB18-H2_100 were sampled 50 cm and 100 cm above the base of the flow, respectively. All three samples are from minimally weathered surfaces beneath an overhang, where they were shielded from cosmic rays. In these images, the lighter portion of the outcrop is dry because it is beneath the overhang and therefore less exposed to rainwater. Dashed white lines indicate the approximate ___location of each sample. See the 6 lb. hammer for scale.
