Venus is third brightest object in our sky, after the sun and the moon. It can be visible in daylight, just like the moon.
Venus will achieve its greatest brilliance this year in early February and is viewable before and during early sun rise. Peak brightness is about February 9; Venus will not be this bright in our sky again until July 2023. Photographers will be stargazing the morning of February 27, when Venus is bright, Mars is faint and the moon a crescent; the three will appear in a nearly vertical line.
Although Venus is approximately the same size as Earth, any similarity between the second and third planets ends there. Venus is a “world of intense heat, crushing atmospheric pressure and clouds of corrosive acid.”
These clouds are about 40 miles (60 kilometers) above the planet surface. On Venus, the clouds are comprised of sulfuric acid particles; on Earth, water droplets or ice crystals. Researchers do not know the “mysterious material that absorbs light at blue and ultraviolet wavelengths” that results in those red-tinted clouds.
In addition, the clouds of Venus circle the planet with hurricane force, blowing to the west, not to the east as they do on Earth.
Mariner 10 acquired the images used to create this newly processed false color composite on 07-08 February 1974. The image on the right is a contrast-enhanced version that causes the cloud cover to be visible in greater detail.
Nearly 50 years after this view was obtained, many fundamental questions about Venus remain unanswered. Did Venus have oceans long ago? How has its atmosphere evolved over time, and when did its runaway greenhouse effect begin? How does Venus lose its heat? How volcanically and tectonically active has Venus been over the last billion years?
Launched on 03 November 1973, Mariner 10 was the first NASA spacecraft sent to study the planet Mercury. While en route, Mariner 10 also studied Venus while using that planet’s gravity to modify its speed and trajectory so it could reach Mercury.
On 05 February 1974, Mariner 10 made its closest flyby to Venus (3,584 miles / 5,768 kilometers) and began sending images of Venus back to Earth; it returned 4,165 photos and scientific data.
After another course correction, Mariner 10 reached Mercury on 16 March 1974. It came within 437 miles (703 kilometers) of the planet on 29 March 1974. It achieved its third flyby on 16 March 1975, coming with about 200 miles (327 kilometers) of the planet.
It would be 30 years before NASA launched another Mercury mission.