Deuterium on Venus: observations from Earth.

Area of Science:

• Planetary Science
• Atmospheric Science
• Spectroscopy

Background:

• The deuterium-to-hydrogen (D/H) ratio in Venus's atmosphere is a key indicator of its atmospheric evolution.
• Previous measurements of the D/H ratio on Venus yielded conflicting results.

Purpose of the Study:

• To accurately measure the D/H ratio in Venus's atmosphere using high-resolution spectroscopy.
• To resolve discrepancies between previous in situ and remote sensing measurements of Venus's D/H ratio.

Main Methods:

• Acquired a high-resolution spectrum of Venus's dark side in the 2.34–2.43 micrometer range.
• Detected absorption lines of HDO (deuterium-substituted water) and H2O (water).
• Sounded the Venusian atmosphere at altitudes between 32 and 42 kilometers.

Main Results:

• The D/H ratio in Venus's atmosphere was determined to be 120 ± 40 times the terrestrial ratio.
• This result unequivocally confirms in situ measurements from the Pioneer Venus mission.
• The findings reconcile apparent conflicts with upper limits derived from International Ultraviolet Explorer spectra.

Conclusions:

• The significant enrichment of D/H on Venus provides a fundamental constraint for models of its atmospheric evolution.
• The study highlights the importance of high-resolution spectroscopy for atmospheric characterization.
• Understanding the D/H ratio is critical for deciphering the history of water on Venus.