Drifting inwards in protoplanetary discs

In previous laboratory experiments, we measured the temperature dependence of sticking forces between micrometer grains chondritic composition. The data showed a decrease in surface energy by factor ~5 with increasing temperature. Here, focus on effect water grains. Under ambient conditions laboratory, multiple layers are present. At low pressure protoplanetary discs and for moderate temperatures, likely only hold monolayer. As dust drifts inwards, even this monolayer eventually evaporates completely higher regions. To account this, tensile strength same material as was prepared under normal our work, but now introducing two new preparation methods: drying cylinders air (dry samples), heating pressed into vacuum (super-dry samples). For all temperatures up to 1000 K, dry samples consistent simple increase force ~10 over wet samples. Up 900 K super-dry behave like However, then exponentially another ~100 at about 1200 K. from extends trend that is known amorphous silicates multimineral mixtures. findings imply aggregate growth boosted small spatial high-temperature region around which might be sweet spot planetesimal formation.