Saw a gorgeous ant pile this morning. Because the soil particles were wet they had cohesion, and as the ants dropped them the normal distance from the hole they did not avalanche down the sides as usual. Instead, they built a vertical wall with an overhang. So fascinating!
Also noticed water droplets glistening on the large Elephant Ear leaves. Some leaves had droplets while others had none at all! I assume the older leaves lose their hydrophobic, waxy coatings so the water runs off, but that’s just a guess. 
Also, check out the shape of the new Elephant Ear leaves as they are just beginning to unfurl. So interesting!
One of the mysteries of lunar soil is *exactly* how does it have so much cohesion? You can see the cohesion in the boot print of @TheRealBuzz. This was an intentional soil mechanics experiment. The imprint has vertical sidewalls despite the soil being bone-dry. That is cohesion.
Some theories for lunar soil cohesion:
1. There’s lots of dust so lots of surface area for Van der Waals force.
2. It is in hard vacuum so the grains lack the typical monolayer of adsorbed water molecules as on Earth, so the Van der Waals force is even stronger.
(cont’d)
1. There’s lots of dust so lots of surface area for Van der Waals force.
2. It is in hard vacuum so the grains lack the typical monolayer of adsorbed water molecules as on Earth, so the Van der Waals force is even stronger.
(cont’d)
3. It’s in low gravity, so cohesion becomes more dominant relative to gravitational weight, making the cohesion more obvious.
4. The lunar soil particles are jagged and interlocking, creating “apparent” cohesion as they chain-up together. (See picture of lunar soil particles.)
4. The lunar soil particles are jagged and interlocking, creating “apparent” cohesion as they chain-up together. (See picture of lunar soil particles.)
5. There may be electrostatic charging of soil particles causing patches of positive and negative charge on their surfaces, so they “chain-up” by the electric force. In vacuum in hard ultraviolet light, directly exposed to solar wind plasma, the charging environment is exotic.
Years ago when I first started working on lunar soil as part of the NASA Space Resources project, the first thing we did was travel to @VirginiaTechCEE to meet Prof. James Mitchell, who was principle investigator of lunar soil mechanics during Apollo 14-17. We wanted to ask...
...”What is the cause of so much cohesion in lunar soil?”
His answer: “I don’t know.” 😄👍
So when we get back to the surface of the Moon, this is one of the things we need to study. It is important for all future activities on the Moon. #Artemis
His answer: “I don’t know.” 😄👍
So when we get back to the surface of the Moon, this is one of the things we need to study. It is important for all future activities on the Moon. #Artemis
8/8 The reason I stopped to photograph the ant pile was because I noticed the vertical sidewalls, which reminded me of @TheRealBuzz’s boot print. For the ant pile, it had cohesion simply because it was wet. For the boot print, we need data from the Moon to find out.
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