Context: Venus is much drier than Earth, and scientists have been trying to figure out why. They believe that Venus once had a lot of water, but it has since escaped into space.
Venus
- 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.
Water loss mystery from Venus:
- One theory is that the water from Venus was lost due to the Sun's heat and ultraviolet radiation.
- A new study suggests that a chemical reaction involving a molecule called HCO+ may be responsible for some of the water loss. This reaction breaks down water molecules and allows hydrogen atoms to escape into space.
- The study's authors say that this reaction could have doubled the rate at which Venus lost water. They also say that the reaction could have been going on for billions of years.
- However, there is no direct evidence that HCO+ exists in Venus's atmosphere. Hence, future missions to Venus should look for HCO+.
Significance in Planetary Atmospheres:
- Hydrogen Escape Mechanism: The neutral hydrogen atoms produced in this reaction are energetic enough to escape the planet’s gravity, leading to a gradual loss of hydrogen from the atmosphere.
- Water Loss: Since water (H2O) is composed of hydrogen and oxygen, the loss of hydrogen atoms contributes directly to the depletion of water on a planetary scale. (As Oxygen atoms would not have sufficient Hydrogen atoms to combine to form Water)
Facts about Venus:
- Venus has a solid surface by virtue of being one of the 3 inner planets besides Mercury and Earth. It is nearly the same size as the Earth.
- The atmosphere of Venus is composed of 95% carbon dioxide and thus has a high greenhouse effect.
- Surface pressure on Venus is about 90 times that on Earth while surface pressure on Mars is 1/100th of that on Earth.
- NASA’s image data from the Magellan spacecraft's visit to Venus has revealed evidence of volcanic activity on it. Sulphur compounds make up about 0.015% due to volcanic eruptions and thus hot Sulfuric acid clouds that envelop Venus. About 80% of the surface of Venus is composed of flat plains of volcanic origin.
- Its rotation period is longer than its orbital period. (Rotation on its own axis – 243 days, Orbital period around the sun - 224.7 days) The planet has retrograde rotation, meaning it spins in the direction opposite to the direction in which it orbits the Sun.
- Due to the slow rotation of Venus it has no global magnetic field. (Earth’s magnetic field is due to rotation of iron core).
Upcoming Venus missions:
- Shukrayaan (ISRO, India), DAVINCI mission (NASA, USA), VERITAS orbiter (NASA, USA), EnVision mission (European Space Agency).
- Shukrayaan-1 (2024): Expected to be launched in 2028. This orbiter will study the planet's atmosphere, surface, and ionosphere.
- NASA's DAVINCI (Deep Atmosphere Venus Investigations of Noble gases, Chemistry, and Imaging) mission will study Venus from above its clouds down to its surface, investigating how the planet and its dense atmosphere formed and evolved over the past 4.5 billion years. Tentatively scheduled to be launched in June 2029 and would enter the Venusian atmosphere in June 2031.
- VERITAS: NASA's VERITAS (Venus Emissivity, Radio Science, InSAR, and Spectroscopy) mission is expected to be launched in 2031. VERITAS will use a suite of seven instruments to study the surface and atmosphere of Venus.
- EnVision: The European Space Agency (ESA)'s EnVision mission is planned for launch in the early 2030s. EnVision will study the atmosphere, surface, and interior of Venus.