Although Venus is sometimes referred to as Earth’s twin, its current surface conditions are drastically different, making it inhospitable to life. Not only is liquid water unable to exist due to the extreme temperatures and pressures beneath the thick cloud layer, but more importantly, it is nearly absent from the Venusian atmosphere. Using data from the Solar Occultation in the Infrared (SOIR) instrument on ESA’s Venus Express spacecraft, planetary researchers have discovered an unexpected increase in the abundances of two water molecule variants — H2O and HDO — and their ratio HDO/H2O in the mesosphere of Venus. This phenomenon challenges our understanding of Venus’ water history and the potential that it was habitable in the past.
Venus in real colors, processed from Mariner 10 images. Image credit: Mattias Malmer / NASA.
Currently, Venus has temperatures around 460 degrees Celsius and pressures nearly 100 times higher than Earth.
Its atmosphere, covered by thick clouds of sulfuric acid and water droplets, is extremely dry; most water is found below and within these cloud layers.
However, Venus may have once supported just as much water as Earth.
“Venus is often called Earth’s twin due to its similar size,” said Tohoku University’s Dr. Hiroki Karyu.
“Despite the similarities between the two planets, it has evolved differently. Unlike Earth, Venus has extreme surface conditions.”
Investigating the abundances of H2O and its deuterated counterpart HDO (isotopologues) reveals insights into Venus’ water history.
It is generally accepted that Venus and Earth initially had a similar HDO/H2O ratio.
However, the ratio observed in Venus’ bulk atmosphere (below 70 km) is 120 times higher, indicating significant deuterium enrichment over time.
This enrichment is primarily due to solar radiation breaking down water isotopologues in the upper atmosphere, producing hydrogen (H) and deuterium (D) atoms.
Since hydrogen atoms escape into space more readily due to their lower mass, the HDO/H2O ratio gradually increases.
Source : Breaking Science News