1 00:00:07,310 --> 00:00:04,289 that's what we call I so chemical 2 00:00:09,630 --> 00:00:07,320 weathering what happens there is that 3 00:00:11,940 --> 00:00:09,640 you have this acidic vapor that's 4 00:00:14,730 --> 00:00:11,950 altering the rock and if there's enough 5 00:00:17,250 --> 00:00:14,740 acidity there too and water to alter the 6 00:00:19,110 --> 00:00:17,260 rock to a bunch of other minerals not 7 00:00:22,430 --> 00:00:19,120 enough water to wash it anything away 8 00:00:24,780 --> 00:00:22,440 and so basically what happens is that 9 00:00:26,580 --> 00:00:24,790 you're altering the rock inside you're 10 00:00:28,290 --> 00:00:26,590 altering the entire rock to the extent 11 00:00:29,790 --> 00:00:28,300 that water does wick to the surface and 12 00:00:31,140 --> 00:00:29,800 evaporate you form a crust on the 13 00:00:33,120 --> 00:00:31,150 outside that's actually a little more 14 00:00:34,560 --> 00:00:33,130 resistant because it's got that salt 15 00:00:36,810 --> 00:00:34,570 component its evaporated and 16 00:00:38,459 --> 00:00:36,820 precipitated so you end up with this 17 00:00:40,139 --> 00:00:38,469 rock that's completely altered its 18 00:00:41,790 --> 00:00:40,149 softer on the inside than on the surface 19 00:00:44,279 --> 00:00:41,800 and then as you see as it starts to fall 20 00:00:46,049 --> 00:00:44,289 apart you see the soft inside that 21 00:00:49,079 --> 00:00:46,059 crusty surface forming that interesting 22 00:00:50,970 --> 00:00:49,089 pattern that we see these on Mars we 23 00:00:52,950 --> 00:00:50,980 found them and it's evidence that you've 24 00:00:55,049 --> 00:00:52,960 had water activity but at a very low 25 00:00:56,579 --> 00:00:55,059 abundance of water just enough to alter 26 00:00:58,380 --> 00:00:56,589 this stuff but not to carry away the 27 00:01:01,349 --> 00:00:58,390 more soluble things that have been 28 00:01:03,000 --> 00:01:01,359 formed in the alteration process and you 29 00:01:04,680 --> 00:01:03,010 see that a lot of Death Valley to it's