Venus is often called Earth's twin, but its current surface conditions are very different from Earth's and are not suitable for life to exist: not only cannot liquid water exist due to the extreme temperatures and pressures beneath the thick cloud layer, but more importantly, there is almost no water in Venus' atmosphere. Solar Occultation Observatory in Infrared (SOIR) On ESA's Venus Express spacecraftPlanetary researchers have discovered an unexpected increase in the abundance of two variants of the water molecule.2O and HDO, and their ratio HDO/H2O in Venus' mesosphere. This phenomenon calls into question our understanding of Venus' water history and its possible past habitability.
Currently, the temperature on Venus is about 460 degrees Celsius and the pressure is almost 100 times that of Earth.
The atmosphere is extremely dry, covered with thick clouds of sulfuric acid and water droplets, and most of the water resides beneath and within these cloud layers.
However, it is possible that Venus once contained as much water as Earth does.
“Venus is often called Earth's twin planet because its size is similar to Earth's,” says Dr. Hiroki Kario of Tohoku University.
“Despite the similarities between the two planets, their evolutionary processes are different. Unlike Earth, the surface conditions on Venus are extreme.”
Survey of H abundance2O and its deuterated isotope HDO (isotope) reveal insights into the history of water on Venus.
It is generally accepted that Venus and Earth originally had similar HDO/H2O ratio.
However, the ratio observed in Venus' entire atmosphere (below altitude 70 km) was 120 times higher, indicating a significant increase in deuterium over time.
This enrichment occurs primarily when solar radiation breaks down isotopes of water in the upper atmosphere, producing hydrogen (H) and deuterium (D) atoms.
Hydrogen atoms have a small mass and are therefore prone to escaping into space, so HDO/H2The O ratio gradually increases.
To understand how much hydrogen and deuterium has been released into space, it is important to measure the amount of isotopes in water at altitudes where hydrogen and deuterium are broken down by sunlight (above the clouds at altitudes of 70 km or more).
Dr. Caryu et al.2O and HDO increase between 70 and 110 km altitude, and HDO/H2In this range, the O ratio increases by an order of magnitude, reaching levels more than 1,500 times higher than in Earth's oceans.
“The proposed mechanism to explain these findings is the reaction of hydrated sulfuric acid (H2So4) aerosols,” the researchers said.
“These aerosols form just above the clouds, where temperatures drop below the dew point of sulfuric acid water, leading to the formation of deuterium-rich aerosols.”
“These particles rise to high altitudes and evaporate due to rising temperatures, releasing a much higher proportion of HDO compared to non-HDO.2“oh.”
“The steam is then conveyed downwards and the cycle begins again.”
“This study highlights two important points,” they added.
“First, altitude changes play an important role in pinpointing the location of deuterium and hydrogen reservoirs.”
“Second, the increase in HDO/H2The O ratio ultimately increases the release of deuterium, influencing the long-term change in the D/H ratio.”
“These findings encourage us to incorporate highly dependent processes into models to make accurate predictions about the evolution of D/H.”
“Understanding the evolution of Venus' habitability and water history can help us understand what makes a planet habitable and inform how to ensure Earth doesn't follow in its twin's footsteps.”
of result Published in Proceedings of the National Academy of Sciences.
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Arnaud Mahieu others2024. Unexpected increase in deuterium to hydrogen ratio in the Venus mesosphere. PNAS 121 (34): e2401638121; doi: 10.1073/pnas.2401638121
Source: www.sci.news
