An overlooked molecule could solve the Venus water mystery

Sub: Science and tech

Sec: Space sector

Context:

About the study:

More than four billion years ago, Venus had enough water to cover its surface with an ocean 3 km deep. Today, the planet only has enough for this ocean to be 3 cm deep.

What are the reasons for loss of water?

Hellish Atmosphere:

The first is its hellish atmosphere which is a result of its carbon dioxide-rich composition, which causes a strong greenhouse effect.
The planet’s surface is hotter than water’s boiling point, simmering at 450 degrees C. So water can only exist as vapor in Venus’ atmosphere.

Planet’s proximity to the Sun:

The Sun’s heat and ultraviolet radiation combined to shred water molecules into their constituent hydrogen and oxygen atoms in Venus’s ionosphere — the upper region of the atmosphere, where charged atoms, molecules, and their electrons zoom around at high speeds.
The two theories broadly blame thermal and non-thermal processes for the water loss.
The thermal process refers to hydrodynamic escape. As the Sun heated Venus’s outer atmosphere, it expanded, allowing hydrogen gas to leak to space.
This escape lasted until the outer atmosphere sufficiently cooled, by about 2.5 billion years ago.

HCO+ dissociative recombination reaction (DR):

Scientists have known for a while that HCO+ molecules drive hydrogen escape on Mars.
On Venus, the HCO+ dissociative recombination reaction (DR) occurs in bulk at an altitude of about 125 km, above the clouds made of sulphuric acid.
HCO+ is created when a carbon monoxide molecule (CO) loses an electron while absorbing an hydrogen atom.
DR is the reverse reaction: HCO+ absorbs an electron and breaks up into CO and a hydrogen atom. These energetic hydrogen atoms then escape into space.
It was found that the reaction accelerated water decline once the hydrodynamic escape of hydrogen gas ended.
HCO+ DR could have doubled the rate at which Venus lost water by hydrogen escape.
The model predicted that the amount of water on Venus would have stayed roughly the same from nearly 2 billion years ago.
As a non-thermal process, the HCO+ DR reaction would’ve gone on indefinitely and drained all the water.
The thermal process was time-bound because the upper atmosphere returned to thermal equilibrium.

About Venus:

Venus is the second planet from the Sun, and the sixth largest planet.
It’s the hottest planet in our solar system.
Venus is a cloud-swaddled planet named for a love goddess, and often called Earth’s twin.

What are various missions to Venus?

BepiColombo:

BepiColombo is a joint mission of the European Space Agency and the Japan Aerospace Exploration Agency to the planet Mercury.
The mission comprises two satellites launched together: the Mercury Planetary Orbiter and Mio.
Scientists found a signature of carbon ions escaping Venus in data collected by the BepiColombo spacecraft.

NASA’s MAVEN:

MAVEN is a NASA spacecraft orbiting Mars to study the loss of that planet’s atmospheric gasses to space, providing insight into the history of the planet’s climate and water.