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  • (Music)

  • We were looking at these strange features on Mars. They're what we call, 'linear gullies,'

  • because they're long troughs. They can extend up to two kilometers,

  • which is just over a mile and they're really strange because

  • they go down and then they end abruptly in a pit.

  • A lot of features on the Earth that are similar do end in a debris apron

  • because stuff has been moved from the top to the bottom. But these don't have the apron.

  • They just have a pit at the end. And so we were wondering how they could form.

  • Frozen carbon dioxide accumulates on the surface

  • and we think that some of this accumulation will compress down and actually form ice slabs and ice blocks.

  • We bought some frozen carbon dioxide dry ice blocks

  • and we took it out to a dune slope, and we put it down and we saw what happened.

  • Most dune slopes will be at 33 degrees and that's a nice steep slope.

  • And so we did it with a water ice block and the sand got wet and it didn't move.

  • And we did it with a wooden block and, you know, it moved three inches and then it stopped.

  • The dry ice block, we expected it to see a bit more activity,

  • but we didn't expect it to just move and move and move and move and keep moving all the way to the bottom.

  • But even on the other side of the dune, which is more like six degrees -- it's very shallow --

  • we put the block on and we pushed it and it would just slide right down

  • and the only reason it stopped was because it hit the bushes at the bottom.

  • Dry ice, as it heats up, turns into gas that pushes against the sand as it comes out.

  • After a few hours, it's scooped out a nice little area.

  • And so you have a feature that looks like what we see on Mars.

  • They will move down that dune slope and carve out a shallow trough.

  • When the block of ice is on the sand surface, that sand is just a little bit warmer.

  • And so it causes a cushion of air to form. And that lifts that block just a little bit

  • so when it moves forward, it's like its lubricated and it can just slide very easily.

  • And when it got to the bottom, instead of just sitting there,

  • it would disappear as the area heated up and then that could possibly leave a pit.

  • I'm looking forward to the day when astronauts can engage in a whole new area of extreme sports.

  • They could snowboard down these carbon dioxide covered dunes on a cushion of carbon dioxide.

  • They would just shoot right down those slopes. It would be amazing.

(Music)

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B1 中級

乾冰在火星上移動 (Dry Ice Moves on Mars)

  • 558 35
    Bing-Je 發佈於 2021 年 01 月 14 日
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