Diatoms of this species, sometimes called "commuter" diatoms, remain burrowed in the sand during high tide, and emerge on the sand surface during the daytime low tide.

这种硅藻，有时被称为“通勤硅藻”，在涨潮时留在沙土中，在白天退潮时出现在沙土表面。

youdao

They then walked twice across the same sand surface while assuming a crouched stance.

然后，他们以假设的蜷曲姿态两次走过同一沙面。

youdao

Hydraulic gradient in sand increases constantly and the maximum is occurred when the bottom of bucket arrives to the sand surface.

砂中水力梯度一直增大，极大值产生在桶底接触砂面时。

youdao

Water in the sand between the two pots evaporates through the surface of the larger pot, where drier outside air is moving.

VOA: special.2009.02.09

And in the chamber, the respiration and the metabolic properties of the surface sand material were measured and we added nutrients and measured the gases that were produced.

NPR: Revisiting the Viking Missions to Mars

But a later mission, Mariner 9, showed in 1971 that the surface had extensive sand dunes, massive craters and huge lava flows.

ECONOMIST: Martian chronicles

In the vacuum, the sharp edges of the lunar soil cling together, leaving a smooth surface much as moist sand does on a beach.

MSN: No hoax: Moon landing stands as NASA's finest hour