Homogeneous Nucleation of Water Vapor Evidenced by Elongated Clouds on Mars
Abstract
It is widely accepted that water vapor forms clouds by heterogeneous nucleation (condensation on pre-existing dry nuclei). Homogeneous nucleation (directly from water vapor, without a pre-existing nuclei) is theoretically possible, but it requires high levels of supersaturation and so it is not considered a viable cloud formation process under real atmospheric conditions. Here, we show that introducing homogeneous nucleation in a meteorological model of Mars allows to successfully reproduce the unique characteristics of the Arsia Mons Elongated Cloud, a remarkable water ice cloud that occurs recurrently on Mars and which had remained impossible to model under conventional cloud microphysics. This finding demonstrates that homogeneous nucleation happens on Mars, provides the first evidence of homogeneous nucleation of water vapor in a planetary atmosphere, and challenges current assumptions about cloud formation processes, which is also relevant for certain clouds on Earth and potentially on other planets.
Versions
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BibTeX
@misc{hernandezbernal2026homogeneous,
title = {{Homogeneous Nucleation of Water Vapor Evidenced by Elongated Clouds on Mars}},
author = {J. Hernandez-Bernal and A. Maattanen and A. Spiga and F. Forget},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.37259},
eprint = {2609.37259},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.37259},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Homogeneous Nucleation of Water Vapor Evidenced by Elongated Clouds on Mars
AU - J. Hernandez-Bernal
AU - A. Maattanen
AU - A. Spiga
AU - F. Forget
PY - 2026
DA - 2026/09/29
PB - arXiv
DO - 10.48550/arxiv.2609.37259
UR - https://arxiv.org/abs/2609.37259
AB - It is widely accepted that water vapor forms clouds by heterogeneous nucleation (condensation on pre-existing dry nuclei). Homogeneous nucleation (directly from water vapor, without a pre-existing nuclei) is theoretically possible, but it requires high levels of supersaturation and so it is not considered a viable cloud formation process under real atmospheric conditions. Here, we show that introducing homogeneous nucleation in a meteorological model of Mars allows to successfully reproduce the unique characteristics of the Arsia Mons Elongated Cloud, a remarkable water ice cloud that occurs recurrently on Mars and which had remained impossible to model under conventional cloud microphysics. This finding demonstrates that homogeneous nucleation happens on Mars, provides the first evidence of homogeneous nucleation of water vapor in a planetary atmosphere, and challenges current assumptions about cloud formation processes, which is also relevant for certain clouds on Earth and potentially on other planets.
ER -