The surface of Venus, shrouded in thick clouds, has long been one of the most mysterious and difficult to directly observe environments in the solar system. Only a few landing missions have briefly returned limited data under extreme temperatures and pressures. Now, a new study led by a scientific research team at Sorbonne University shows that even under such sparse data conditions, scientists can still extract important laws about near-surface wind fields, temperature changes and dust transport from scattered observations through precise modeling.
The first author of the paper, Maxence Lefèvre of Sorbonne University, led a team to build a regional numerical model focusing on near-surface wind and dust movement based on the measurement results of previous Venus missions. The goal is to provide a "weather forecast" closer to the real environment for the upcoming new generation of Venus exploration missions. The study divided the surface of Venus into different regions, distinguishing between highlands (mountains) and lowlands (plains), tropical and polar regions, and analyzed their respective temperature change amplitudes, wind direction and speed patterns, and the resulting dust-raising capabilities, instead of treating the entire planet as a uniform environment.
Historical data comes from the "Venera" series of probes that successfully landed on Venus. Its observations show that the wind speed near the surface of Venus is only about 1 meter per second, which is far lower than the typical wind speed of about 20 meters per second on the Earth and even up to 40 meters per second in parts of Mars. However, because the atmosphere of Venus is extremely dense, accelerating such a thick atmosphere to these wind speeds requires a huge amount of energy. Therefore, even if the wind speed is not high, the impact on the surface temperature distribution and dust suspension is still significant.
Research points out that one day and one night on Venus is approximately equivalent to 117 days on Earth. This ultra-long day and night cycle will trigger dramatic but regional differences in the atmosphere. In the low-latitude tropics, highland areas are heated by the sun during the day, and near-surface winds blow upward along the slopes, called "upslope winds" (the technical term is "downslope winds" or "anabatic winds"); at night, after the surface is cooled by infrared radiation, cold air flows downwards along the slopes, forming "downslope winds" ("katabatic winds").
This type of diurnal wind direction reversal not only reshapes the local wind field, but also directly affects surface temperature fluctuations. Calculations in the paper show that in the highlands, affected by the adiabatic compressional warming caused by downslope winds, the temperature difference between day and night is "locked" within less than 1 Kelvin, which greatly offsets the surface cooling effect at night; in contrast, in lowland areas that lack a similar adjustment mechanism, the temperature difference between day and night can reach about 4 Kelvin. This means that in the mountains of Venus, the wind fields act as a "temperature regulator" to some extent.
In areas close to the poles, the pattern is different: there, the near-earth wind field flows almost continuously downhill throughout the year, and the long-term "offset" with the continuous infrared heat dissipation in the polar regions forms another form of temperature stabilization mechanism. The research team pointed out that since a number of future Venus orbiting missions, including the European "EnVision" and the American "VERITAS", will focus on observing the polar regions, this new model provides a key background for understanding the climate and surface characteristics of the polar regions.
More directly related to the landing mission is NASA's Venus atmosphere and surface exploration mission called "DaVINCI". According to the current plan, its landing module will descend near a high plateau called "Alpha Regio" (Alpha Regio), an area located near the equator with significantly undulating terrain. New research results show that about 45% of the Alpha Highlands surface area has wind speeds sufficient to lift "fine sand" with a particle size of about 75 microns, which means that the DaVINCI probe is likely to encounter a continuous fine-particle dust environment during the approach and landing stages, and its intensity will also change with the local day and night cycle. This discovery is regarded as an important early warning for the detector structural design, sensor protection and descent timing scheme.
In order to achieve these analyses, the scientific research team adopted a new regional simulation method. They no longer tried to model the Venus surface as a whole, but divided different terrains and different latitudes into multiple "meteorological units" that can be solved independently to calculate their wind field, temperature and dust characteristics respectively. The paper also admits that there is still room for improvement in the current model. For example, more detailed thermophysical parameters can be introduced based on the albedo and thermal inertia of different surface materials, or the infrared absorption characteristics of gases dominated by carbon dioxide in the Venus atmosphere at different temperatures can be more accurately characterized.
However, the researchers emphasized that the scientific community still has time to iterate and correct the model before future batches of landing and orbiting missions actually arrive at Venus. As missions such as DaVINCI carry out field measurements, these regional wind field simulations will become an important reference for interpreting new data and help explain possible abnormal temperature readings and dust characteristics near the probe's landing site. The relevant results are titled "The effect of near-surface winds on surface temperature and dust transport on Venus" and have been published in the "Journal of Geophysical Research: Planets" sub-issue.