| Abstrakt: |
Dust dynamics influence planetary atmospheres. However, the settling velocity of dust—and thus its residence time in the atmosphere—is often mispredicted. Challenging, indirect experiments involving few ideal particles revealed that dust settling velocity deviates from Stokes' law under rarefied atmospheres. While useful, such experiments are inadequate to simulate more complex scenarios, including variable particles sizes and shapes. Here, we present direct measurements of settling velocity for spherical particles under Earth‐to‐Mars atmospheric pressures using time‐resolved particle image velocimetry (TR‐PIV), and validate their robustness with existing models. Our results demonstrate that TR‐PIV provides a relatively simple approach to quantifying dust settling velocity from direct observations of over 10,000 particles, enabling systematic investigations of dust settling under realistic scenarios. Such experiments will have significant implications for our understanding of Mars' past, present, and future ‐ from providing a tool to decipher its sedimentary record to enhancing predictive capabilities of atmospheric models. Plain Language Summary: Airborne dust strongly affects the environments and atmospheres of Earth and Mars. Knowing the speed at which dust settles is critical because it controls the time dust stays in the atmosphere. However, it is a difficult quantity to measure, and as a result, it is often poorly predicted by existing models. These models were built from experiments that did not match real‐world conditions and typically only considered few, idealized particles. Here, we propose a relatively simple approach to make direct measurements of dust settling under Earth‐to‐Mars atmospheric pressures. This technique, time‐resolved particle image velocimetry, allows us to directly measure the speed of over 10,000 particles. Using ideal particles, we show that our measurements align well with results from previously published models, validating the robustness of our procedure. The same experimental setup can be used to investigate dust settling under more realistic conditions, for example, varying the size distribution of dust particles, their shape, or dust concentration. Such measurements are a stepping stone toward accurate interpretations and predictions of dust dynamics on Earth and Mars. Key Points: Dust settling velocity controls residence time of dust in the atmosphere but is challenging to measure under low atmospheric densityWe measure dust settling velocity under Earth‐to‐Mars‐like conditions using time‐resolved particle image velocimetry (TR‐PIV)TR‐PIV enables systematic studies of dust settling on Mars and other bodies using realistic particles and varying dust concentrations [ABSTRACT FROM AUTHOR] |
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